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En aquest treball es va seguir el flux d'estudi d'un bloc que es percep com de risc, anomenat Oliver ubicat al massís de Montserrat, al quilòmetre 3+000 de la carretera BP-1103. Es va estudiar l'estabilitat del bloc front a bolcada i lliscament, mitjançant equilibri límit, es va instrumentar i monitoritzar per un període proper a un any i es va finalitzar l'estudi amb una modelació de les trajectòries de caiguda tenint en compte la vegetació present al vessant. L'estudi de l'estabilitat no va poder anar més enllà del que es considera una aproximació o estudi esquemàtic pel fet que les equacions usades simplifiquen la complexitat del bloc en figures geomètriques perfectes; una altra limitant va ser la incertesa sobre la unió entre el bloc i el massís rocós, així com la naturalesa de la diàclasa que els uneix. La monitorització va donar resultats prometedors en definir un rang de variació diari de 0,003° i un canvi en la inclinació mesurada a l'eix B de 0,3° durant la temporada càlida de l'any. La modelació de les trajectòries inicialment es va realitzar sense contemplar la vegetació, això va donar una simulació de gran propagació al llarg del vessant. A partir d’un despreniment anterior a la mateixa zona, es va poder introduir adequadament l’efecte de la vegetació, amb la consequent significativa reducció de l’abast dels blocs produits per l’eventual despreniment de la llastra ‘Oliver’, reduint-se dràsticament el perill que l’event pot significar per la carretera BP-1103. A la discussió de resultats i a les conclusions s'assenyalen les àrees d'incertesa i les dades que s'haurien d'investigar amb més profunditat per millorar aquest tipus d'anàlisi a l'entorn del massís de Montserrat, En este trabajo se siguió el flujo de estudio de un bloque que se percibe como de riesgo, denominado “Oliver” ubicado en el macizo de Montserrat, en el kilómetro 3+000 de la carretera BP-1103. Se estudió la estabilidad del bloque frente a vuelco y deslizamiento, mediante equilibrio límite, se instrumentó y monitorizó por un periodo cercano a un año y se finalizó el estudio con una modelación de las trayectorias de caída tomando en cuenta la vegetación presente en la ladera. El estudio de la estabilidad no pudo ir más allá de lo que se considera como una aproximación o estudio esquemático debido a que las ecuaciones usadas simplifican la complejidad del bloque en figuras geométricas perfectas; otra limitante fue la incertidumbre sobre la unión entre el bloque y el macizo rocoso, así como la naturaleza de la diaclasa que los une. La monitorización dio resultados prometedores al definir un rango de variación diario de 0,003° y un cambio en la inclinación medida en el eje B de 0,3° durante la temporada cálida del año. La modelación de las trayectorias inicialmente se realizó sin contemplar la vegetación, esto dio una simulación de gran propagación a lo largo de la ladera. A partir de un desprendimiento anterior en la misma zona, se pudo introducir adecuadamente el efecto de la vegetación, y con ello se redujo significativamente el alcance de los bloques en la simulación del desprendimiento de la laja “Oliver”, reduciéndose drásticamente el peligro que este evento podría significar para la carretera BP-1103. En la discusión de resultados y en las conclusiones se señalan las áreas de incertidumbre y los datos que se deberían investigar con mayor profundidad para mejorar este tipo de análisis en el entorno del macizo de Montserrat., In this project, the workflow of a block that is perceived as risky was followed, the block is called “Oliver”. The block is located in the Montserrat massif, at kilometer 3+000 of the BP-1103 highway. The stability of the block, to overturning and sliding, was studied through limit equilibrium methods. It was instrumented and monitored for a period of almost a year. The study was completed with modeling of the rock fall trajectories taking into account the vegetation present on the slope. The stability study could not go beyond what is considered an approximation or schematic study because the equations used simplify the complexity of the block into geometric figures. Another limitation was the uncertainty about the union between the block and the rock mass, as well as the nature of the joint that between them. The monitoring gave promising results by defining a daily variation range of 0.003° and a change in the inclination measured on the B axis of 0.3° during the warm season of the year. The modeling of the trajectories was initially carried out without considering the vegetation, this gave a simulation of great propagation along the slope. Once the effect of this was introduced, the extension of the blocks was significantly reduced and the danger that these blocks represent to the road was completely eliminated. In the discussion of results and in the conclusions, the areas of uncertainty and the data that should be investigated in greater depth are pointed out to improve this type of analysis in the area of the Montserrat massif.

Point cloud modeling of rock slopes using LIDAR and Structure-from-Motion digital stereophotogrammetry provides,at a minimum, thousands of facets and facet normals that can be used to identify the densities of orientations of rock massdiscontinuities, the geometries of potentially removable blocks, and the character of the excavation face. As part of the EngineeringGeology graduate curriculum at the Civil and Environmental Engineering program at the University of California, Berkeley we teachgraduate students an integrated methodology for [a] gathering point cloud information be laser or camera; [b] computing facets andfacet normals form point clouds for stereonet presentation and geometric analysis of block dimension; [c] extract rock massdiscontinuities from stereonet data to analyze key blocks, assess discontinuous deformation analysis (DDA) behavior, and modelrock slope stability. These new methods require a suite of different software tools discussed in the paper to move through the workflowprocess. Computational rock mechanics provides data sets that are orders of magnitude richer in detail and result in betterunderstanding of rock slope and tunnel key block behavior. Full application of computational rock mechanics methods should reducethe cost of bolting by identifying critical support orientations and design loads.

Pre-existing fractures in rock engineering significantly affect the entire structural stability. To deepen the understanding of the fracture mechanism of fractured rocks under shear loading, a numerical study based on the distinct element method was conducted to investigate the shear behaviors of rock fractures. A discrete element model with fractures of Barton's ten standard profiles was established, and shear simulations under different normal stresses and joint roughness coefficient (JRC) were carried out. The simulation results show that the shear stress–displacement curve can be divided into three stages: elastic loading stage, inelastic stage and stress drop stage. The shear strength, internal friction angle and cohesion increase with the increase of normal stress and JRC. These macroscopic mechanical characteristics are consistent with the results of previous experimental studies. Most of the microcracks generated during the shearing process are tensile microcracks, which are first formed at the steep position of the fracture profile line, and the proportion of shear microcracks is less than 10%. In addition, the contact force between particles is mainly compressive stress, which is greater in magnitude and density than tensile stress. As the shear proceeds, the displacement of the particles gradually changes from non-uniform distribution to uniform distribution., QC 20240625

To comprehend the stress state and response characteristics of materials under complex conditions, researchers have decomposed stress states into fundamental paths and investigated diverse path combinations. To ensure comparability, four identical samples were carefully selected from a pool of 100 samples using ultrasonic tests based on the wave speed and waveform characteristics. These samples underwent specially designed stress paths to analyze the combined effects of linear loading and perturbation. Our result analysis centred on the perturbation amplitude and stress levels during composite action, revealing intricate relationships between the stress levels, strain, and nonlinear/linear energy evolution under complex stress paths. Simultaneously, 3D surface fractures were precisely reconstructed using the YOLOv5 and FAST feature point detection algorithms, elucidating the evolving patterns of the fractures. As a result of our study, the rotation trend of the main fracture was validated by integrating mechanics and P-wave reflection rules. Notably, our experimental results closely aligned with the theoretical predictions, showing the reliability of our study. These findings can significantly contribute to guiding safety protocols in the field of underground engineering. The combined effects of the stress paths under linear loading and perturbation conditions were investigated via a comprehensive analysis of the experimental results integrating mechanical theory and prior research findings.The YOLOV5 and FAST feature point detection algorithms were used for three-dimensional crack reconstruction, providing insights into the fracture morphology of the experimental specimens and showing the crack propagation patterns on the specimen surfaces.The energy evolution trend was explored, revealing a notable linear trend in the cumulative values. The stiffness evolution trend under compound paths was examined, elucidating the change mechanism through integration with establ

This study focuses on determination of the temperature effect on uniaxial compressive strength of different rock types. For our laboratory tests, we chose local greywacke from the Kobeřice quarry which is situated 10 km south of Prostějov. For comparison, datasets representing other rock types have been gathered from the literature cited. As shown in this study, the rock type structure, composition or the processes that formed the rock can influence how the compressive strength changes across the temperature range. Results of similar analyses can be utilized during the design of underground constructions or for assessment of the fire damage on a rock-based constructions.

Aquest treball aborda l'estudi de la fragmentació de blocs en despreniments rocosos des d'un punt de vista experimental mitjançant assajos de caiguda (“drop tests”) en laboratori. Els nostres objectius primordials ha estat, d'una banda, observar si existeix un llindar d'energia cinètica, de força d'impacte i/o de la pressió d'impacte per a l'inici de la fragmentació i si el grau de fragmentació varia amb l'augment de l'energia i de la força de l’impacte i, d'altra banda, observar si la forma en la qual impacten els blocs influeix en aquests llindars i en el grau de fragmentació., Este trabajo aborda el estudio de la fragmentación de bloques en desprendimientos rocosos desde un punto de vista experimental mediante ensayos de caída (“drop tests”) en laboratorio. Nuestros objetivos primordiales son, por un lado, observar si existe un umbral de energía cinética, de fuerza de impacto y/o de la presión de impacto para el inicio de la fragmentación y si el grado de fragmentación varía con el aumento de la energía, de la fuerza o de la presión y, por otro lado, observar si la forma en la que impactan los bloques influye en estos umbrales y en el grado de fragmentación., This work deals with the study of block fragmentation in rock falls from an experimental point of view by means of drop tests in the laboratory. Our main objectives are, on the one hand, to observe whether there is a threshold of kinetic energy, impact force and/or impact pressure for the onset of fragmentation and whether the degree of fragmentation varies with increasing energy, force or pressure and, on the other hand, to observe whether the way in which the blocks impact influences these thresholds and the degree of fragmentation.

Uranium isotopic signatures in the rock record are utilized as a proxy for past redox conditions on Earth. However, these signatures display significant variability that complicates the interpretation of specific redox conditions. Using the model uranium-reducing bacterium, Shewanella oneidensis MR-1, we show that the abundance of electron donors (e.g., labile organic carbon) controls uranium isotope fractionation, such that high electron fluxes suppress fractionation. Further, by purifying a key uranium-reducing enzyme, MtrC, we show that the magnitude of fractionation is explicitly controlled by the protein redox state. Finally, using a mathematical framework, we demonstrate that these differences in fractionation arise from the propensity for back-reaction throughout the multi-step reduction of hexavalent uranium. To improve interpretations of observed fractionations in natural environments, these findings suggest that a variable intrinsic fractionation factor should be incorporated into models of uranium isotope systematics to account for differences in electron flux caused by organic carbon availability.

The paper describes the development of a high-pressure isotropic cell for studying the environmental degradation of low porosity clayey rocks. Air permeability measurements are used in this device as a tool to evaluate rock degradation in unsaturated rock specimens caused by mechanical, hydraulic and chemical paths. A modified equation, based on the air pressure decay method proposed by Yoshimi and Osterberg (1963), is presented. The proposed method is applied to an Australian clayey shale. Estimated values of air permeability are compared against those calculated using the original method which, in the case of low porosity rocks, seems to provide unrealistic values when the air pressure in the vessel decays beyond 50%., Postprint (published version)

En este trabajo se ha realizado un estudio del contenido tierras raras (TR) en los depósitos minerales de la Faja estannífera de Bolivia. El yacimiento más ampliamente tratado es el de Llallagua en la región de Potosí, también se han obtenido análisis de los depósitos de Poopó y Japo que encuentran dentro de la faja estannífera. También se ha estudiado el contenido de dos yacimientos de placeres en la cordillera de Apolobamba un yacimiento ja que en unos estudios de la zona se encontró una elevada cantidad de TR, y se quería evaluar si existía ese elevado contenido de tierras raras a lo largo de la cordillera o si fue un resultado puntual. En este trabajo se ha realizado muestreos in situ en los yacimientos, sus escombreras (arenas y limos) y también en la planta Catavi durante todo el proceso de tratamiento. Las muestras han sido analizadas químicamente para determinar la concentración de TR (1) en laboratorios acreditados mediante ICP y (2) mediante fluorescencia de rayos X portátil. En el caso de los resultados a la hora de evaluar las tierras raras mediante el análisis FRX portátil y comparando con uno análisis realizados mediante FRX convencional, se observa que para los óxidos no se encuentran muchas variaciones pero por el contrario para la evaluación de tierras raras en las únicas que se pueden tomar como buenas son las composiciones del neodimio y cerio ya que en ambos estudios son mu parecidos, pero en el caso del lantano el FRX portátil no lo cuantifica y por el contrario con el terbio y el gadolinio los cuantifica con unas cantidades demasiado elevadas. En Llallagua se han analizado diferentes lugares de los residuos de procesamientos anteriores que forman grandes volúmenes que actualmente se están reprocesando, lo que ha demostrado que éstos tienen bastante homogeneidad y leyes de Sn de alrededor de 0.3 %. El Cerio presenta valores de alrededor de 100 ppm. En el caso de la planta de tratamiento de Catavi se ha observado según los análisis, donde se encu, In this work, a study of the rare earth (RE) content in the mineral deposits of the Central Bolivian Tin Belt has been carried out. The most widely treated deposit is the Llallagua deposit in the Potosí department, but analyses have also been obtained for the Poopó and Japo deposits. The content of two placer deposits in the Apolobamba mountain range also have been studied, one of them was a deposit that in previous studies a high amount of TR was found, and it was necessary to evaluate whether this high content was common in this type of deposits or whether it was a one-off result. In this work, in situ sampling has been carried out at the deposits, their dumps (sands and silts) and also at the Catavi plant during the entire treatment process. The samples have been chemically analysed for TR concentration (1) in accredited laboratories by ICP and (2) by portable X-ray fluorescence. In the case of the results when evaluating the rare earths by means of portable XRF analysis and comparing with one analysis carried out by conventional XRF, it is observed that for the oxides there are not many variations but on the contrary for the evaluation of rare earths the only ones that can be taken as good are the compositions of neodymium and cerium as in both studies they are very similar, but in the case of lanthanum the portable XRF does not quantify it and on the contrary with terbium and gadolinium it quantifies them with quantities that are too high. At Llallagua, different locations of the tailings and dumps from previous processing have been analysed, they represent large volumes that are currently being reprocessed. The present study shows that they are quite homogeneous and have Sn grades of around 0.3 %. Cerium has values of around 100 ppm. In the case of the Catavi treatment plant, it has been observed, according to the analyses, that the highest amount of TR is found in the concentrates, that is to say that these TR are found together with tin, in order to obtain t

The stability of rock engineering projects is tightly related to the mechanical behaviour of rock discontinuities. Although the mechanical behaviour of a discontinuity is often associated with shearing (sliding), experimental data have shown that it can be accompanied by more complex phenomena such as dilation and post-peak strength reduction. Numerous researchers have contributed to the understanding and modelling of discontinuities behaviour. However, many of the constitutive models available in the literature are questionable when applied in practice either because they are highly empirical with parameters that are hardly determined or because they oversimplify the examined behaviour. Moreover, the models are often proposed for a certain range of stresses and specific stress paths, which makes numerical implementation difficult for large-scale engineering applications. This dissertation aims to evaluate the capabilities and the limitations of different constitutive models for rock discontinuity in the context of both numerical implementation and simulation of the mechanical behaviour of rock discontinuity. The first part of the research project investigates the main features of the existing models in the literature. From the investigated models, the two models highly adopted in research and engineering practice, namely the Coulomb’s model and Barton-Bandis’s model, are extensively investigated. Some enhancements and modifications are made to these two models to improve their modelling capabilities and ensure the numerical stability of numerical implementation. Regarding the Coulomb model, the adopted modifications include the reformulation of the model within the framework of strain softening providing a rigorous implemented version that describes the post-peak behaviour of a discontinuity adopting a linear reduction of the strength. Additionally, the employed modifications to the Barton-Bandis model provide a robust version of the model applying reformulations t, Geo-Engineering

A general discrete element method-based model is proposed to investigate the cyclic freezing-thawing induced damage of fractured rocks. A set of cracks is defined as an assembly of interparticle pores that are interconnected due to self-definition (pre-existing) or contact breaking (external force induced). During the freezing-thawing simulation, only the rock grains surrounding the cracks are subjected to frost heave pressure, which are expected to cause contact breaking and crack propagation. In this sense, most of the pores that do not form cracks in the numerical model will not participate in the calculation, so the computational cost and time are substantially reduced. The cracks connected to the atmosphere, i.e. the model boundaries, are classified as inactive cracks and their frost heave pressures are removed accordingly. Therefore, model convergence is recognized when all cracks are converted to inactive. Parametric analysis is further performed to show the influence of some important input parameters, including the unfrozen water content, calibration factor of frost heave pressure, crack density and dip. Finally, the freezing-thawing damage of rocks is quantified by the reduction in uniaxial compressive strength after a prescribed number of freezing-thawing cycles. The results are validated with an analytical solution. It is shown that the rock strength degradation, crack evolution, heave and settlement can be well simulated by the proposed model. This methodology can be extended to large-scale problems such as glacier slope instability or landslides.

The level of advancement in the understanding of the mechanical properties of volcanic rocks is comparatively lower than that of sedimentary rocks. As part of the SUCCEED Project (Synergetic Utilisation of CO2 Storage Coupled with Geothermal Energy Deployment), which aims to investigate the feasibility of injecting captured and produced CO2 into the reservoirs to enhance geothermal production and achieve permanent CO2 storage at the Hellisheiði Geothermal Field in Iceland, this experimental research provides significant insights into the petrophysical and mechanical properties of the volcanic rocks collected from surface outcrops. The subsurface in Hellisheiði is mainly built up of hyaloclastite formations and interglacial basaltic lavas. During a field campaign samples were collected in different outcrops, ensuring that the samples were of high quality and sufficiently diverse to enable comprehensive analysis. Four samples per block and rock type have been prepared from the collected blocks, and they have been subjected to different laboratory tests to evaluate their petrophysical properties, such as porosity, density, and permeability, and their geomechanical behavior, using Unconfined Compression Test (UCS), Active-Source Acoustic Test, and Splitting Tensile Strength Test. Additionally, laboratory experiments have been conducted to investigate the impact of rapid cooling on rock damage due to thermal fracturing. The results show that there are interdependent relationships between porosity, bulk density, ultimate strength, Young's modulus, and wave velocities that can be observed when considering average values per rock. The rocks studied showed a negative correlation between porosity and other parameters and a direct correlation between ultimate strength and Young's Modulus. When examining individual rock samples, no significant correlations were observed between porosity and other parameters, however, those correlations where evident when comparing between diffe, SUCCEED Project, Applied Earth Sciences

In geotechnical engineering practice related to mining, tunnelling, and oil exploration, a set of discontinuities might affect the overall strength and stability of rock mass. To address this issue, a good deal of research has been conducted in the past decades to study the behaviour of jointed rocks under different loading conditions. However, most of previous studies have been conducted on rock-like materials such as concrete or plaster, while only limited research has been done on natural rocks. This study seeks to bridge this knowledge gap and (1) to investigate the effects of discontinuity on the engineering properties of common rocks from South East Queensland, and (2) to develop a numerical model that can accurately estimate the strength of jointed rocks. A series of unconfined compression tests on natural rocks of different geological origins (three types of sandstone, argillite, and basalt) were performed to better understand the effect of crack length (1 cm and 2 cm long) and infill material (sand or clay) on rock strength. In addition, a series of shear tests were conducted on jointed specimens of two types of sandstone with different infill thicknesses, ranging from 1mm to 3mm. The obtained results from the laboratory tests were used to improve the current methods of rock shear strength predictions, which were initially designed to estimate the strength of artificial rock-like material. Also, a new numerical method was proposed to accurately estimate the unconfined compressive strength of rock specimens with pre-existing discontinuities filled with either clay or sand. This numerical model provided valuable insight into the failure mechanism of jointed rocks, which agreed with the data obtained in the laboratory. By combining the experimental and numerical investigations, the mechanism of rock failure with different pre-existing cracks and infill material can be studied. The UCS values estimated by the numerical model and the damage model were able to es, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, Full Text

Toppling of individual rock blocks resting on an inclined surface has often been observed in nature. This instability mechanism has typically been analysed for simple block geometries, considering the contact between the block and the base where it lies is a planar surface. In this study, the authors analyse the case where this contact is a regularly rough surface. To do that, the authors resort to analytical limit equilibrium formulations, laboratory physical models and discrete element methods. All these approaches show a consistent trend of behaviour, where roughness does affect the toppling response. Regularly rough surfaces are studied in detail and a general analytical formulation able to show the potential influence of roughness on the block toppling response is derived. Additionally, some considerations are provided regarding the combined effects of rough bases and rounded corners on toppling stability. The authors show how under particular circumstances, roughness can control the potential failure mechanism of a block to produce toppling instead of sliding, and they eventually discuss the impact of rough bases on the toppling response of natural rock blocks., Peer Reviewed, Postprint (published version)

In numerical modelling, selection of the constitutive model is a critical factor in predicting the actual response of a geomaterial. The use of oversimplified or inadequate models may not be sufficient to reproduce the actual geomaterial behaviour. That selection is especially relevant in the case of anisotropic rocks, and particularly for shales and slates, whose behaviour may be affected, e.g. well stability in geothermal or oil and gas production operations. In this paper, an alternative anisotropic constitutive model has been implemented in the finite element method software CODE_BRIGHT, which is able to account for the anisotropy of shales and slates in terms of both deformability and strength. For this purpose, a transversely isotropic version of the generalised Hooke's law is adopted to represent the stiffness anisotropy, while a nonuniform scaling of the stress tensor is introduced in the plastic model to represent the strength anisotropy. Furthermore, a detailed approach has been proposed to determine the model parameters based on the stress–strain results of laboratory tests. Moreover, numerical analyses are performed to model uniaxial and triaxial tests on Vaca Muerta shale, Bossier shale and slate from the northwest of Spain (NW Spain slate). The experimental data have been recovered from the literature in the case of the shale and, in the case of the slate, performed by the authors in terms of stress-strain curves and strengths. A good agreement can be generally observed between numerical and experimental results, hence showing the potential applicability of the approach to actual case studies. Therefore, the presented constitutive model may be a promising approach for analysing the anisotropic behaviour of rocks and its impact on well stability or other relevant geomechanical problems in anisotropic rocks., The experimental part of the slate in this work was funded by REPSOL S.A. The numerical part of this work was supported by the CODE_BRIGHT Project (International Centre for Numerical Methods in Engineering). The work of the second and fourth authors was possible thanks to the Spanish Ministry of Science and Innovation, who funded the project, awarded under Contract Reference No. RTI 2018-093563-B-I00, partially financed by means of the European regional development fund (ERDF) funds from the European Union (EU)., Peer Reviewed, Postprint (published version)

As part of a seismic monitoring project in a geothermal field, where the feasibility of re-injection and storage of produced CO2 is being investigated, a P- and S-wave seismic velocity characterisation study was carried out. The effect of axial and radial (up to 42 MPa) stress, pore pressure (up to 17 MPa), pore fluid (100% brine or supercritical CO2) and temperature (21–100 °C) on seismic properties were studied in the laboratory for the two main reservoir formations at the Kızıldere geothermal reservoir. Each (un)confined compressive strength test performed revealed a similar trend: rapidly increasing velocity at low stresses followed by a more moderate increase at higher stresses. The data implied that the stress-dependency of the velocity increased with temperature. Increasing temperatures resulted in decreasing P-wave velocities due to mineral thermal expansion. This temperature-dependency increased with reducing stress levels. The S-wave velocity seems to be more sensitive to changes in pore pressure than the P-wave velocity. On the other hand, the S-wave velocity is less affected by an increasing axial stress compared to the P-wave velocity. By performing multiple nonlinear regression on the velocity dataset, related to a brine-saturated fractured marble, second-degree polynomial trends were found for the P- and S-wave velocity, as a function of temperature, axial stress, and pore pressure, that can potentially be used for predicting velocities at Kızıldere, or other similar, geothermal site(s). For distinguishing between a 100% brine-saturated versus a fully supercritical CO2-saturated fracture, the arrival times of the first arrivals were too close to each other to allow their utilization. The fracture aperture was too small compared to the wavelength of the source signal. However, differences in P- and S-wave amplitudes of the first arrivals were seen, where the supercritical CO2-saturated crack revealed consi, Applied Geophysics and Petrophysics

The closure behavior of rock fractures subject to normal loading is essential for deformation analysis of fractured rock masses and the modeling of associated coupled processes. Previous studies have mainly focused on characterizing the closure behavior of mated fractures, and the applicability of existing models to unmated fractures and characteristics of involved parameters have not been comprehensively investigated. We conducted normal loading tests on three tensile granite fractures with different mating degrees by dislocating the fracture surfaces with three offsets. A high-resolution contact model was used to simulate the fracture closure behavior, which was validated by comparing the simulated closure curves and the surface damage areas with experimental measurements. After that, it was applied to simulate the closure behavior for nine numerically generated surfaces with different surface roughness characteristics. The experimental and numerical results exhibit a downward bending trend in the stiffness versus stress curves, which existing models cannot accommodate. An extended hyperbolic model was established by introducing an exponent parameter into the classical Barton–Bandis hyperbolic model, which can better represent the experimental data than previous models. Via regression analysis, we found that the exponent parameter has an approximately constant value of 0.3. The maximum normal displacement is about two times of the mean aperture. The initial stiffness is positively correlated with the elastic modulus and the correlation length and negatively correlated with the mean aperture. Parameters involved in the extended model have precise physical meanings, and they are mathematically predictable based on measurable mechanical and geometrical properties of the rock fractures., QC 20221222

Grout curtains are commonly constructed under dams to reduce the seepage through the rock foundation. In the design of grout curtains, empirical methods have mainly been used since the introduction of dam foundation grouting. Although empirical methods have been used with success in several projects, they have their limitations, such as poor control of the grout spread, only an indirect consideration of the threat of internal erosion of fracture infillings in the grouted zones, and the risk of hydraulic jacking. This paper presents a theory-based design methodology for grout curtains under dams founded on rock. In the design methodology, the grout curtain is designed as a structural component of the dam. The risk of erosion of fracture infilling material is explicitly accounted for along with the reduction of the hydraulic conductivity of the rock mass, and an optimization of the total uplift force. By applying the proposed design methodology, engineers can create a design better adapted to the prevailing geological and hydrogeological conditions in the rock mass, resulting in more durable grout curtains. The proposed methodology also enables cost and time estimates to be calculated for the grout curtain’s construction. Applying the principles of the observational method during the grouting execution also allows the design to be modified via predefined measures if the initial design is found to be unsuitable., QC 20220603

An anisotropic damage model is employed in order to simulate the fracture pattern of Bohus granite under quasi-static (Q-S) spherical indentation loading. The chosen damage description is added to the previously employed Drucker–Prager (DP) plasticity model with variable dilation angle. The resulting constitutive model is implemented to simulate the behavior of Bohus granite under indentation up to the load capacity of the material. The initial fragmentation, corresponding to the first small load-drop in the force–penetration curve, is likely due to the high radial tensile stress state at or close to the contact boundary. Both predicted fracture pattern and force–penetration results from the numerical simulation are compared to experimental data and a good agreement is found. The variability in tensile strength of the material is included in the chosen damage model by taking advantage of Weibull statistics. In this work, it is suggested that indentation test results by themselves may be used to calibrate the statistical distribution of tensile strength at small size scales such as in indentation applications., QC 20220609

The final publication is available at Springer via http://dx.doi.org/10.1007/s10064-022-02927-1., The bearing characteristics of random lumpiness gangue formed by rock fragmentation in gob roofs are important to ensure roadway stability in the new nonpillar mining approach. In this paper, the bearing characteristics of gangue are divided into bulking and compaction characteristics. Bulking characteristics mainly depend on the lumpiness and bulking coefficient of randomly lumpy gangue (KRAFT). This paper proposes a method to invert KRAFT of gangue samples with a small amount of lumpiness, and a random subset of 30% of an experimental sample of broken rocks is selected for analysis. The lumpiness distributions of the subset of samples and all the samples are normal, and the average lumpiness error of the subset is 0.54–2.86%. The ratio of average lumpiness to rock before breakage (KASB) is introduced as a parameter for analysis. The results show that KASB and KRAFT have a log-normal functional relationship, and KASB can be used to infer KRAFT from laboratory and field monitoring data. Compaction characteristics show that the relationship between KRAFT and the supporting force of gangue (sGB) is a power function, and sGB in gangue during different stages of compression in a gob can be obtained from the value of KRAFT obtained from experiments or field monitoring., This work is supported by the Open-end Research Fund of State Key Laboratory for Geomechanics and Deep Underground Engineering (SKLGDUEK2024), the National Key R&D Program (No. 2016YFC0600900), the National Natural Science Foundation of China (No. 52074295, 52074299, 41941018, 52074300), the Excellent Youth Fund of the Education Department of Hunan Province (21B0487) and China Scholarship Council (CSC NO. 202006430081), which are gratefully acknowledged., Peer Reviewed, Postprint (author's final draft)

When modelling rock masses that behave anisotropically and in addition present a time dependent behaviour, it is relevant to select a constitutive model able to represent their actual behaviour realistically. This article presents an alternative anisotropic time-dependent constitutive model able to predict the coupling between anisotropic behaviour and time-dependent (or viscous) behaviour. The viscous behaviour is simulated with the Burgers model and all elastic springs and viscous dashpots are considered to exhibit transversely isotropic properties. The proposed constitutive model has been implemented in the finite element method software CODE_BRIGHT. To verify the basic anisotropic elastic solution, it has been compared with that of PLAXIS results. And to verify the isotropic viscoelastic solution, it has been compared with analytical solutions. Furthermore, the proposed constitutive model has been used to predict the behaviour of samples from laboratory tests. Finally, parametric analyses have been carried out to investigate the influence of different factors on tunnelling responses, including the selection of different constitutive models, anisotropy of initial stresses and anisotropy of material properties. The proposed model provides an alternative method for the preliminary design of geotechnical engineering works involving geomaterials that exhibit anisotropic time-dependent behaviour., Peer Reviewed, Postprint (published version)

The version of record of this article, first published in Natural Hazards is available online at Publisher's webside: https://doi.org/10.1007/s11069-022-05282-2, The fragmentation phenomenon has a significant effect on rockfall risk assessment. This information is difficult to obtain, but it is key to improving rockfall modelling. For this reason, the RockModels team has gathered data on the fragmentation of several natural events since 2014 that nowadays wants to share them with professionals, academics and stakeholders. The best way for the dissemination of this information is the use of standard or data specifications in order to be interoperable. A fragmentation rockfall database has been created using all the gathered information, according to the INSPIRE Natural Hazard Area Data Specification currently in force. However, new tables have had to be added, since this specification does not consider fragmentation data. There are currently 6000 records of geometries of source areas, envelopes, deposits and mostly individual blocks. A web mapping application, with an automatic function for coordinate reference system transformation, has been created to facilitate access to the spatial database information. All that was developed on open-source software such as OpenLayers JavaScript library, database (PostGre-PostGIS) and the map generating Web Map Service (GeoServer). As more data are collected, the database can be easily updated and the new information will be published. Moreover, to improve data interpretation, a future task is to incorporate 3D models on the web application. The existence of this public database will facilitate research and advance in knowledge of this kind of natural hazards., Peer Reviewed, Postprint (published version)

The design, manufacture and testing of a small-size down-the-hole hammer PNB76 with a drill bit KNB76 for rotary-percussion drilling of long straight directional holes in rocks with strengths of up to 120 MPa are described. A trial KNB76 model was tested on a brassboard, and the pressure in the chambers in the main line, in the power stroke chamber and in the idle stroke chamber were recorded under a compressed-air driving pressure of 0.6 MPa. Three KNB76 hammers have been delivered to Berezovskaya coal mine in Russia for further trials and operation of an SBR400 drill machine including use for drilling straight service holes of lengths in excess of 130 m in 120-MPa strength rocks., The design, manufacture and testing of a small-size down-the-hole hammer PNB76 with a drill bit KNB76 for rotary-percussion drilling of long straight directional holes in rocks with strengths of up to 120 MPa are described. A trial KNB76 model was tested on a brassboard, and the pressure in the chambers in the main line, in the power stroke chamber and in the idle stroke chamber were recorded under a compressed-air driving pressure of 0.6 MPa. Three KNB76 hammers have been delivered to Berezovskaya coal mine in Russia for further trials and operation of an SBR400 drill machine including use for drilling straight service holes of lengths in excess of 130 m in 120-MPa strength rocks.

The rock plate (RP) method can be used to identify the size and location of potentially dangerous bed separation space (BSS) in coal mines. The RP method is performed in three steps: rock strata above the coal seam is simplified as a composite plate calculation model; the deflection of rock strata is expressed as a double trigonometric series and obtained using the energy method; and the internal-forces and deformation of the RP are solved to determine the size and location of the BSS based on elasticity and a BSS identification process. This requires that the BSS is unbroken, and the BSS upper rock stratum is an aquifer. The RP method has been used at the Yuanzigou coal mine (Shanxi, China) to determine the size and location of BSS water (BSS-W) above the coal goaf of the working face. BSS-W at the mine exists between conglomerate and mudstone formations. Results predicted that when the working face advances 350 m, the third BSS will break, allowing BSS-W to flood into the goaf. These results were verified by borehole video observation. Two control methods were used: inclined drainage holes drilled from the roadway and spaced holes drilled from the surface in areas with abundant water., The rock plate (RP) method can be used to identify the size and location of potentially dangerous bed separation space (BSS) in coal mines. The RP method is performed in three steps: rock strata above the coal seam is simplified as a composite plate calculation model; the deflection of rock strata is expressed as a double trigonometric series and obtained using the energy method; and the internal-forces and deformation of the RP are solved to determine the size and location of the BSS based on elasticity and a BSS identification process. This requires that the BSS is unbroken, and the BSS upper rock stratum is an aquifer. The RP method has been used at the Yuanzigou coal mine (Shanxi, China) to determine the size and location of BSS water (BSS-W) above the coal goaf of the working face. BSS-W at the mine exists between conglomerate and mudstone formations. Results predicted that when the working face advances 350 m, the third BSS will break, allowing BSS-W to flood into the goaf. These results were verified by borehole video observation. Two control methods were used: inclined drainage holes drilled from the roadway and spaced holes drilled from the surface in areas with abundant water.

Rock deformation and failure mechanisms, overburden bearing structures, and working characteristics of supports at the no. 120210 working face of the Zaoquan coal mine (Shaanxi, China) have been studied using physical simulations, field tests, and theoretical analysis. Overburden rock movement has distinct regional characteristics, with a large caving height (to the main roof layer) in the upper area, and lower caving height (to the lower main roof) in the lower area. Support loading is regional and unbalanced along the inclined direction. The critical layer of overlying strata migrates, and bearing structures formed by breaking the critical layer exhibit cross-layer generalisation along the inclination. The upper region has a cantilever beam structure in the basic roof rock layer; the lower region has an inclined masonry structure with multistage ladders in the breakage basic roof rock layer. Application of a false-inclined working face layout with the tailgate ahead of the headgate and an arc arrangement (radius 28.65 m, arc length 10-20 m) in variable angle areas, and regional control of support working resistance and top-coal caving amounts, control regional failure overburden. Safe and efficient mining was achieved, with monthly production and recovery rates reaching 344,900 t and 85.86%, respectively. The results could expand the scope of fully mechanised top caving mining., Rock deformation and failure mechanisms, overburden bearing structures, and working characteristics of supports at the no. 120210 working face of the Zaoquan coal mine (Shaanxi, China) have been studied using physical simulations, field tests, and theoretical analysis. Overburden rock movement has distinct regional characteristics, with a large caving height (to the main roof layer) in the upper area, and lower caving height (to the lower main roof) in the lower area. Support loading is regional and unbalanced along the inclined direction. The critical layer of overlying strata migrates, and bearing structures formed by breaking the critical layer exhibit cross-layer generalisation along the inclination. The upper region has a cantilever beam structure in the basic roof rock layer; the lower region has an inclined masonry structure with multistage ladders in the breakage basic roof rock layer. Application of a false-inclined working face layout with the tailgate ahead of the headgate and an arc arrangement (radius 28.65 m, arc length 10-20 m) in variable angle areas, and regional control of support working resistance and top-coal caving amounts, control regional failure overburden. Safe and efficient mining was achieved, with monthly production and recovery rates reaching 344,900 t and 85.86%, respectively. The results could expand the scope of fully mechanised top caving mining.

High boulder yield can occur due to the mismatching of explosive and rock wave impedance. A study has been carried out of methods of measuring rock wave impedance, rock strength point loading, and detonation wave velocity to obtain more accurate input parameters. An intelligent acoustic monitoring multipurpose instrument (DYF-2) was installed at the Dexing open cast copper mine (Jianxi, China) to monitor longitudinal blast wave velocity. Image processing was carried out to enhance the contrast of the image of muck accumulation, and the ratio of different particle sizes was calculated. The crushing degree and characteristics of a rock mound were compared, and the parameters that could reflect the basic characteristics of crushing distribution were determined. The results suggested that, combined with watershed image segmentation technology, Rosin-Rammler and Gates-Gaudin-Schuhmann distribution functions are effective methods to analyse the distribution of rock fragmentation. A support vector machine regression model can be used to predict and control the blasting effect. The blasting effect was found to be the most efficient when the rock wave impedance and the explosive wave impedance were both 2.51., High boulder yield can occur due to the mismatching of explosive and rock wave impedance. A study has been carried out of methods of measuring rock wave impedance, rock strength point loading, and detonation wave velocity to obtain more accurate input parameters. An intelligent acoustic monitoring multipurpose instrument (DYF-2) was installed at the Dexing open cast copper mine (Jianxi, China) to monitor longitudinal blast wave velocity. Image processing was carried out to enhance the contrast of the image of muck accumulation, and the ratio of different particle sizes was calculated. The crushing degree and characteristics of a rock mound were compared, and the parameters that could reflect the basic characteristics of crushing distribution were determined. The results suggested that, combined with watershed image segmentation technology, Rosin-Rammler and Gates-Gaudin-Schuhmann distribution functions are effective methods to analyse the distribution of rock fragmentation. A support vector machine regression model can be used to predict and control the blasting effect. The blasting effect was found to be the most efficient when the rock wave impedance and the explosive wave impedance were both 2.51.

Discussion is presented of a model to characterise the mechanical behaviour of cable bolts under axial loading and subjected to different boundary conditions (including constant confining pressure and constant normal stiffness). The model is based on the modified Mohr-Coulomb failure criterion as well as a newly proposed non-linear dilation formulae for the development of governing equations. The cone shaped failure mode of grout due to the axial movement of cable bolt is considered as a widely observable failure mode at the cable bolt to the grout interface. The load carrying capacity of the cable bolt under axial loading is significantly affected by both the progressive reduction in the volume of failed cone zone of grout annulus and the continuous degradation of dilation angle at the cable bolt to the grout interface. The full load-displacement performance of different cable bolts under axial loading subjected to both constant confining pressure and constant normal stiffness are simulated. Experimental data from Garfold bulbed, Nutcased, Australian Megabolt and Birdcaged cable bolts were used to calibrate the proposed model under constant confining pressure. An acceptable agreement between the simulations and experimental data confirms the proposed model is suitable for predicting the mechanical behaviour of different cable bolts under axial loading., Discussion is presented of a model to characterise the mechanical behaviour of cable bolts under axial loading and subjected to different boundary conditions (including constant confining pressure and constant normal stiffness). The model is based on the modified Mohr-Coulomb failure criterion as well as a newly proposed non-linear dilation formulae for the development of governing equations. The cone shaped failure mode of grout due to the axial movement of cable bolt is considered as a widely observable failure mode at the cable bolt to the grout interface. The load carrying capacity of the cable bolt under axial loading is significantly affected by both the progressive reduction in the volume of failed cone zone of grout annulus and the continuous degradation of dilation angle at the cable bolt to the grout interface. The full load-displacement performance of different cable bolts under axial loading subjected to both constant confining pressure and constant normal stiffness are simulated. Experimental data from Garfold bulbed, Nutcased, Australian Megabolt and Birdcaged cable bolts were used to calibrate the proposed model under constant confining pressure. An acceptable agreement between the simulations and experimental data confirms the proposed model is suitable for predicting the mechanical behaviour of different cable bolts under axial loading.

Rock quality designation (RQD), weighted joint density (WJD) and block quality designation (BQD) can be used to survey joints in boreholes; each has its own advantages and disadvantages. WJD and BQD have been combined to use the positive features of both, leading to the definition of an improved BQD (BQDI). Joint surveys were carried out on cores drilled in the Kulikosh marble quarry, Iran, which contains oolitic limestones on a bed of shale, sandstone and conglomerates. Surface observations suggested that a number of faults were present in the area. Linear regressions validated by statistical tests showed that BQD was less dependent on the drilling direction than the rock quality designation RQD. An empirical equation was obtained which allows for the estimation of the value of BQDI by measuring the original BQD. Taking into account the joint orientations, BQDI is logically closer to reality whereby mining engineers can assess block productivity of stone quarries more accurately., Rock quality designation (RQD), weighted joint density (WJD) and block quality designation (BQD) can be used to survey joints in boreholes; each has its own advantages and disadvantages. WJD and BQD have been combined to use the positive features of both, leading to the definition of an improved BQD (BQDI). Joint surveys were carried out on cores drilled in the Kulikosh marble quarry, Iran, which contains oolitic limestones on a bed of shale, sandstone and conglomerates. Surface observations suggested that a number of faults were present in the area. Linear regressions validated by statistical tests showed that BQD was less dependent on the drilling direction than the rock quality designation RQD. An empirical equation was obtained which allows for the estimation of the value of BQDI by measuring the original BQD. Taking into account the joint orientations, BQDI is logically closer to reality whereby mining engineers can assess block productivity of stone quarries more accurately.

A roof fall hazard assessment has been carried out for mines in the Legnica-Glogow Copper District in Poland. The key factors of roof deterioration were determined and divided into four groups: geological, mining, technical and monitoring. It was demonstrated that only regular roof monitoring can ensure the proper rock fall hazard assessment. An artificial neural network was created; several dozen simulations were conducted and two dimensionless indices were developed. The first shows predisposition of a part of the rock mass to destruction, dislocation and deformation (Coefficient of Roof Fall - predisposition) and the second represents predisposition and possibility of maintaining of the working (Coefficient of Roof Fall - maintenance). Roof fall details and roof observations allowed for categorisation of the values of both indices, providing information on roof stability and necessary measures and solutions for monitoring the roof rocks. Both indices allow for a reliable roof fall hazard assessment by comprehensively combining information from monitoring, observations and investigations., A roof fall hazard assessment has been carried out for mines in the Legnica-Glogow Copper District in Poland. The key factors of roof deterioration were determined and divided into four groups: geological, mining, technical and monitoring. It was demonstrated that only regular roof monitoring can ensure the proper rock fall hazard assessment. An artificial neural network was created; several dozen simulations were conducted and two dimensionless indices were developed. The first shows predisposition of a part of the rock mass to destruction, dislocation and deformation (Coefficient of Roof Fall - predisposition) and the second represents predisposition and possibility of maintaining of the working (Coefficient of Roof Fall - maintenance). Roof fall details and roof observations allowed for categorisation of the values of both indices, providing information on roof stability and necessary measures and solutions for monitoring the roof rocks. Both indices allow for a reliable roof fall hazard assessment by comprehensively combining information from monitoring, observations and investigations.

Studies have been carried out of the influence of strain rate and bedding angle on dynamic coal failure. Coupled biaxial static and dynamic tests were conducted on coal specimens with bedding orientations of 0, 30, 45, 60, and 90 degrees with respect to the direction of loading. Mechanical behaviour, including stress-strain curves and peak stresses, were analysed under a series of impact velocities. Real-time coal fracturing was recorded by two high-speed cameras, and full-field deformation and ejection velocities were identified by 3-D digital image correlation. Results showed that at similar strain rates, the peak stress against bedding orientation shows a “U” shape with the lowest value at an orientation of 60 degrees. The peak stress increased with increasing impact velocity. Coal ejection velocities were positively rate-dependent, with the highest ejection velocity between bedding orientations 45 to 90 degrees increasing with increasing impact velocity. The average fragment size of coal specimens was negatively related to impact velocities and energy absorption, with the smallest fragments at bedding orientation around 45 degrees. It is concluded that dynamic behaviour of coal under biaxial pre-stresses are dependent on bedding structures and strain rates, with the bedding effect becoming weaker as strain rate increases., Studies have been carried out of the influence of strain rate and bedding angle on dynamic coal failure. Coupled biaxial static and dynamic tests were conducted on coal specimens with bedding orientations of 0, 30, 45, 60, and 90 degrees with respect to the direction of loading. Mechanical behaviour, including stress-strain curves and peak stresses, were analysed under a series of impact velocities. Real-time coal fracturing was recorded by two high-speed cameras, and full-field deformation and ejection velocities were identified by 3-D digital image correlation. Results showed that at similar strain rates, the peak stress against bedding orientation shows a “U” shape with the lowest value at an orientation of 60 degrees. The peak stress increased with increasing impact velocity. Coal ejection velocities were positively rate-dependent, with the highest ejection velocity between bedding orientations 45 to 90 degrees increasing with increasing impact velocity. The average fragment size of coal specimens was negatively related to impact velocities and energy absorption, with the smallest fragments at bedding orientation around 45 degrees. It is concluded that dynamic behaviour of coal under biaxial pre-stresses are dependent on bedding structures and strain rates, with the bedding effect becoming weaker as strain rate increases.

The purpose of the CUED method is to increase productivity, optimise costs, improve safety, and diminish instability in underground excavations by predicting instability conditions and potential failure modes. The method is based on rock mass characterisation, ground behaviour and failure modes, design analysis to manage ground conditions, and construction and field observation. A procedure for each step is defined by determination of input data, processing data and output data. It is suggested that rock mass composition provides sufficient information for the diagnosis of ground behaviour. Case studies of projects in Iran are used to discuss various aspects of the CUED method: ground characterisation of underground tunnels and caverns at a hydropower project and at a road tunnel through the Alborz Mountains; ground behaviour and possible failure modes in the main caverns in basaltic layers at the hydropower project; design of ground control and management in these caverns; ground control and management at an underground bauxite mine in the Shemshak formation; and construction and field observations at the hydropower project. It is concluded that use of CUED at the sites discussed would reduce the occurrence of instability and therefore improve safety and give reduced costs., The purpose of the CUED method is to increase productivity, optimise costs, improve safety, and diminish instability in underground excavations by predicting instability conditions and potential failure modes. The method is based on rock mass characterisation, ground behaviour and failure modes, design analysis to manage ground conditions, and construction and field observation. A procedure for each step is defined by determination of input data, processing data and output data. It is suggested that rock mass composition provides sufficient information for the diagnosis of ground behaviour. Case studies of projects in Iran are used to discuss various aspects of the CUED method: ground characterisation of underground tunnels and caverns at a hydropower project and at a road tunnel through the Alborz Mountains; ground behaviour and possible failure modes in the main caverns in basaltic layers at the hydropower project; design of ground control and management in these caverns; ground control and management at an underground bauxite mine in the Shemshak formation; and construction and field observations at the hydropower project. It is concluded that use of CUED at the sites discussed would reduce the occurrence of instability and therefore improve safety and give reduced costs.

The proposed intelligent prediction model is based on blast-induced rock movement (BIRM) monitoring tests at the Husab uranium mine (Namibia) and the Phoenix gold-silver mine (Nevada, USA). Variables were used in dimensional analysis to study explosives characteristics, rock mechanics factors, location, gravitational acceleration, burden, and induced rock movement. The artificial neural network technique (ANN) was used to develop an accurate prediction model, and a metaheuristic algorithm (the Equilibrium Optimiser algorithm) was applied to search the optimal hyper-parameter combination. For comparison, a linear model and a non-linear regression model were also performed. The results show that the hybrid ANN-based model can yield better prediction performance. It is concluded that the intelligent model discussed has the potential to predict BIRM during bench blasting, and that the analysis method and modelling process described can provide a reference for solving other engineering problems., The proposed intelligent prediction model is based on blast-induced rock movement (BIRM) monitoring tests at the Husab uranium mine (Namibia) and the Phoenix gold-silver mine (Nevada, USA). Variables were used in dimensional analysis to study explosives characteristics, rock mechanics factors, location, gravitational acceleration, burden, and induced rock movement. The artificial neural network technique (ANN) was used to develop an accurate prediction model, and a metaheuristic algorithm (the Equilibrium Optimiser algorithm) was applied to search the optimal hyper-parameter combination. For comparison, a linear model and a non-linear regression model were also performed. The results show that the hybrid ANN-based model can yield better prediction performance. It is concluded that the intelligent model discussed has the potential to predict BIRM during bench blasting, and that the analysis method and modelling process described can provide a reference for solving other engineering problems.

Floor rock strata at the Chenghe mining area (China) is either hard rock (sandstone, limestone, siltstone) or soft rock (bauxitic rock and mudstone). A numerical analysis model of the different floor aquifuges was established to analyse the influence of the lithological combinations of floor type. Fluid-solid coupling numerical simulation software was used to study floor water-blocking performance. It was found that mining failure depth was the shallowest and water-blocking capacity was the best for the soft-hard-soft type of floor, followed by two interbeds of soft and hard type floors, while the mining failure depth was the deepest and the water-blocking capacity the worst for the hard-soft-hard type of floor. These conclusions were applied to guide the floor grouting reconstruction project at the 22,507 working face in the Dongjiahe coal mine. The hard-soft-hard type of floor was transformed into an interbedded soft and hard type of floor with a better water-blocking capacity, avoiding blind grouting, reducing grouting costs and the risk of water inrush, and allowing safe mining above the confined aquifer., Floor rock strata at the Chenghe mining area (China) is either hard rock (sandstone, limestone, siltstone) or soft rock (bauxitic rock and mudstone). A numerical analysis model of the different floor aquifuges was established to analyse the influence of the lithological combinations of floor type. Fluid-solid coupling numerical simulation software was used to study floor water-blocking performance. It was found that mining failure depth was the shallowest and water-blocking capacity was the best for the soft-hard-soft type of floor, followed by two interbeds of soft and hard type floors, while the mining failure depth was the deepest and the water-blocking capacity the worst for the hard-soft-hard type of floor. These conclusions were applied to guide the floor grouting reconstruction project at the 22,507 working face in the Dongjiahe coal mine. The hard-soft-hard type of floor was transformed into an interbedded soft and hard type of floor with a better water-blocking capacity, avoiding blind grouting, reducing grouting costs and the risk of water inrush, and allowing safe mining above the confined aquifer.

The Aznalcollar dyke failed in 1998 and released much of its stored, saturated pyritic tailings after a process of progressive failure in the foundation clay. 1 500 000 m3 of tailings and 5 500 000 m3 of acidic water were rapidly discharged from the pond. The paper reviews the main geotechnical aspects that contributed to the development of a sliding surface under the dyke: its downward construction procedure, the brittle nature of the over-consolidated, high plasticity foundation clay, and the prevalent high pore pressures in the clay. The downward construction method created a wave of high stress ratios under the advancing toe of the dyke capable of taking the strength from peak to residual values. The brittleness of the foundation clay is very significant because of its high plasticity and the presence of montmorillonite among its mineralogical constituents. The high pore pressures are a consequence of the high density tailings (3.1 g/cc), the low permeability of the clay, and the consolidation process in a dominant upward direction. Also discussed are the dynamics of the dam failure (displacement, velocity, and acceleration). The geometry of the dyke, in plan view, and its relationship with the direction and dip of the clay layers explains the position of the failure. (Authors.), The Aznalcollar dyke failed in 1998 and released much of its stored, saturated pyritic tailings after a process of progressive failure in the foundation clay. 1 500 000 m3 of tailings and 5 500 000 m3 of acidic water were rapidly discharged from the pond. The paper reviews the main geotechnical aspects that contributed to the development of a sliding surface under the dyke: its downward construction procedure, the brittle nature of the over-consolidated, high plasticity foundation clay, and the prevalent high pore pressures in the clay. The downward construction method created a wave of high stress ratios under the advancing toe of the dyke capable of taking the strength from peak to residual values. The brittleness of the foundation clay is very significant because of its high plasticity and the presence of montmorillonite among its mineralogical constituents. The high pore pressures are a consequence of the high density tailings (3.1 g/cc), the low permeability of the clay, and the consolidation process in a dominant upward direction. Also discussed are the dynamics of the dam failure (displacement, velocity, and acceleration). The geometry of the dyke, in plan view, and its relationship with the direction and dip of the clay layers explains the position of the failure. (Authors.)

Qualitative and quantitative analysis of fibre-optic sensing of instability in a water-resisting rock group has been carried out using distributed optical fibre sensing technology (BOTDA) and fibre Bragg grating (FBG) technology. The 12 101 working face of the shallow Ha-la ditch coal mine in northern Shaanxi Province, China, is used as an example. Results showed that in shallow coal seams (60-67 m overburden) the water-conducting fractured zone develops up to the ground surface, with cracks in the middle of the key strata becoming the main seepage channel. It was found that the location of the fracture line in the overburden could be predicted using optical fibre sensing. The threshold value of breaking limit strain in the water-resistant key strata was found, based on the optical fibre monitoring. It was found that the FBG sensor can accurately monitor deformation of the rock mass at a specific location. The strain variation rate of key strata was positive before fracture and negative after fracturing. The detection of the instability position of the water-resistant key strata was basically consistent with the actual observation and distributed fibre-optic results., Qualitative and quantitative analysis of fibre-optic sensing of instability in a water-resisting rock group has been carried out using distributed optical fibre sensing technology (BOTDA) and fibre Bragg grating (FBG) technology. The 12 101 working face of the shallow Ha-la ditch coal mine in northern Shaanxi Province, China, is used as an example. Results showed that in shallow coal seams (60-67 m overburden) the water-conducting fractured zone develops up to the ground surface, with cracks in the middle of the key strata becoming the main seepage channel. It was found that the location of the fracture line in the overburden could be predicted using optical fibre sensing. The threshold value of breaking limit strain in the water-resistant key strata was found, based on the optical fibre monitoring. It was found that the FBG sensor can accurately monitor deformation of the rock mass at a specific location. The strain variation rate of key strata was positive before fracture and negative after fracturing. The detection of the instability position of the water-resistant key strata was basically consistent with the actual observation and distributed fibre-optic results.

The PRACLAY long-term in-situ heating test in the Boom Clay started in 2014 at the HADES underground research facility in Mol (Belgium). The test will study the thermo-hydro-mechanical behaviour of the clay both within the excavation damaged zone and in the heated gallery of the high level waste storage chamber. Results after four years of heating at 80 degrees C at the gallery lining/Boom Clay interface show that the zone in which the temperature is affected by heating extends to about 20 m and is growing slowly. The pore water pressures also evolved smoothly, reaching 2.8 MPa in the backfilled part of the heated gallery and a maximum of 3MPa in the Boom Clay. Changes of pore water pressure were seen up to 22 m away from the axis of the heated gallery while the temperature had still not increased at this location. The initial observations confirm the results of smaller scale experiments, particularly that the effects of the mechanical anisotropic properties of the clay affect the pore water pressure. It is concluded that after four years of heating at the lining-clay interface, the conditions in and around the test behaved as expected and the Boom clay can withstand the thermal load., The PRACLAY long-term in-situ heating test in the Boom Clay started in 2014 at the HADES underground research facility in Mol (Belgium). The test will study the thermo-hydro-mechanical behaviour of the clay both within the excavation damaged zone and in the heated gallery of the high level waste storage chamber. Results after four years of heating at 80 degrees C at the gallery lining/Boom Clay interface show that the zone in which the temperature is affected by heating extends to about 20 m and is growing slowly. The pore water pressures also evolved smoothly, reaching 2.8 MPa in the backfilled part of the heated gallery and a maximum of 3MPa in the Boom Clay. Changes of pore water pressure were seen up to 22 m away from the axis of the heated gallery while the temperature had still not increased at this location. The initial observations confirm the results of smaller scale experiments, particularly that the effects of the mechanical anisotropic properties of the clay affect the pore water pressure. It is concluded that after four years of heating at the lining-clay interface, the conditions in and around the test behaved as expected and the Boom clay can withstand the thermal load.

Understanding the mechanical properties of oil rocks is important for exploration and production, especially for hydraulic fracturing. Combined laboratory experiments and computational calculations were applied to specimens from the Bakken Formation (North Dakota, USA) to examine the mechanical properties of the unconventional petroleum resource in different scales. Multistage compressive tests were conducted on core plugs with several loading-unloading cycles under different confining pressures. Microscale nanoindentation mechanical tests were performed to measure microscale elastic properties. A comparative study was also carried out using homogenisation upscaling methods to model the modulus of the macro-scale sample from nanoindentation measurements and rock mineralogy. Results from the triaxial compressive tests showed nonlinear behaviour for all samples and pronounced plastic deformation was observed during loading-unloading cycles when lower confining pressures were employed. Young's modulus increased with increasing confining pressures. The ultrasonic P- and S-wave velocities were sensitive to the changes of confining and differential stresses, which might be due to the open and closure of microcracks. Three mechanical phases were found, and the average microscale Young's modulus obtained from nanoindentation tests showed a positive relationship with the theoretical results., Understanding the mechanical properties of oil rocks is important for exploration and production, especially for hydraulic fracturing. Combined laboratory experiments and computational calculations were applied to specimens from the Bakken Formation (North Dakota, USA) to examine the mechanical properties of the unconventional petroleum resource in different scales. Multistage compressive tests were conducted on core plugs with several loading-unloading cycles under different confining pressures. Microscale nanoindentation mechanical tests were performed to measure microscale elastic properties. A comparative study was also carried out using homogenisation upscaling methods to model the modulus of the macro-scale sample from nanoindentation measurements and rock mineralogy. Results from the triaxial compressive tests showed nonlinear behaviour for all samples and pronounced plastic deformation was observed during loading-unloading cycles when lower confining pressures were employed. Young's modulus increased with increasing confining pressures. The ultrasonic P- and S-wave velocities were sensitive to the changes of confining and differential stresses, which might be due to the open and closure of microcracks. Three mechanical phases were found, and the average microscale Young's modulus obtained from nanoindentation tests showed a positive relationship with the theoretical results.

Worn-out drill bits and rock from highway tunnels in Turkey were used to study the relationships between drill bit lifetime and mechanics, drillability, and abrasive properties of rocks. Regression analyses were employed to derive models for estimating the bit lifetime. Results indicated that the bit lifetime values decrease with increases in the uniaxial compressive strength, point load index, Brazilian tensile strength, Schmidt hardness (L-type and N-type) and Cerchar abrasivity index. However, the drill bit lifetimes increased with increasing Micro Deval abrasion, brittleness values, Sievers' J-miniature drill, and excavation volume values. The statistical results showed that the most important parameters on the drill bit lifetimes were uniaxial compressive strength, Schmidt hammer, Sievers’ J-miniature drill, and excavation volume. Cracking of the bit body and failure of the bit rod were also investigated., Worn-out drill bits and rock from highway tunnels in Turkey were used to study the relationships between drill bit lifetime and mechanics, drillability, and abrasive properties of rocks. Regression analyses were employed to derive models for estimating the bit lifetime. Results indicated that the bit lifetime values decrease with increases in the uniaxial compressive strength, point load index, Brazilian tensile strength, Schmidt hardness (L-type and N-type) and Cerchar abrasivity index. However, the drill bit lifetimes increased with increasing Micro Deval abrasion, brittleness values, Sievers' J-miniature drill, and excavation volume values. The statistical results showed that the most important parameters on the drill bit lifetimes were uniaxial compressive strength, Schmidt hammer, Sievers’ J-miniature drill, and excavation volume. Cracking of the bit body and failure of the bit rod were also investigated.

Reduction in the strength and durability of construction stones occurs due to weathering, erosion and degradation, possibly causing splitting and fragmentation. The physical and mechanical properties of six bioclastic and micritic limestones from quarries in the East Anatolian region of Turkey were investigated after thermal shock (T-S) and freeze thaw (F-T) effects. Properties studied were porosity, mass loss, roughness, gloss, Schmidt hardness, P-wave velocities, and uniaxial compressive strength (UCS). SEM analysis was performed on the rocks with the worst and best properties at room temperature. The results show that as the number of T-S and F-T cycles increase, the degradation of the internal structure of the rocks increases and resistance to physical and mechanical effects significantly reduces. The F-T effect was found to negatively affect the internal structure of the carbonate rocks more than the T-S effect. It was determined that the UCS of the carbonate rocks decreased between 16.14-28.65% after 50 T-S cycles and between 22.96-45.66% after 50 F-T cycles. As the rock sample from Tamara Bej had the fewest flaws in the internal structure, it was identified to be more favourable for decorative use in buildings., Reduction in the strength and durability of construction stones occurs due to weathering, erosion and degradation, possibly causing splitting and fragmentation. The physical and mechanical properties of six bioclastic and micritic limestones from quarries in the East Anatolian region of Turkey were investigated after thermal shock (T-S) and freeze thaw (F-T) effects. Properties studied were porosity, mass loss, roughness, gloss, Schmidt hardness, P-wave velocities, and uniaxial compressive strength (UCS). SEM analysis was performed on the rocks with the worst and best properties at room temperature. The results show that as the number of T-S and F-T cycles increase, the degradation of the internal structure of the rocks increases and resistance to physical and mechanical effects significantly reduces. The F-T effect was found to negatively affect the internal structure of the carbonate rocks more than the T-S effect. It was determined that the UCS of the carbonate rocks decreased between 16.14-28.65% after 50 T-S cycles and between 22.96-45.66% after 50 F-T cycles. As the rock sample from Tamara Bej had the fewest flaws in the internal structure, it was identified to be more favourable for decorative use in buildings.

A modified rock mass classification system for TBM tunnels is proposed based on the hydropower rock mass classification (HC) method used in China. Rock mass properties and TBM performance data from three tunnelling projects were used for regression analysis. The proposed method considers the rock mass boreability and stability, and estimates the penetration per revolution, utilisation, and advance rate of a TBM under various rock mass conditions. The influence of adverse geological conditions (rockbursts, squeezing, faults, highly abrasive rock, and water inrush) on TBM performance is also considered. The classification system can be used to evaluate the feasibility of TBM construction and serve as the basis for selection of TBM types and design parameters in the pre-construction phase. It can also be applied to estimate TBM performance and guide tunnel support for a given ground condition in the design phase, and to optimise TBM operational parameters during the construction phase. A 7.9 m diameter section of the YE water conveyance tunnel, which was driven through granite in Xinjiang, is used to illustrate the application of the modified rock mass classification system., A modified rock mass classification system for TBM tunnels is proposed based on the hydropower rock mass classification (HC) method used in China. Rock mass properties and TBM performance data from three tunnelling projects were used for regression analysis. The proposed method considers the rock mass boreability and stability, and estimates the penetration per revolution, utilisation, and advance rate of a TBM under various rock mass conditions. The influence of adverse geological conditions (rockbursts, squeezing, faults, highly abrasive rock, and water inrush) on TBM performance is also considered. The classification system can be used to evaluate the feasibility of TBM construction and serve as the basis for selection of TBM types and design parameters in the pre-construction phase. It can also be applied to estimate TBM performance and guide tunnel support for a given ground condition in the design phase, and to optimise TBM operational parameters during the construction phase. A 7.9 m diameter section of the YE water conveyance tunnel, which was driven through granite in Xinjiang, is used to illustrate the application of the modified rock mass classification system.

Sandstones from a roadway 985 m below the surface of a coal mine in Huainan (Anhui, China) were used to investigate the influence of weakly filled joint angles on the dynamic mechanical properties and fracture evolution mechanism of sandstone. Dynamic uniaxial compression tests were performed at 15 degree intervals on specimens with joint angles of 0-90 degrees under different strain rates. The dynamic stress-strain relationship, dynamic strength, dynamic peak strain, energy characteristic, failure mode, typical failure progress, crack coalescence category, fracture micro-mechanism, and theoretical analysis were examined. The results indicated that both the dynamic compressive strength and peak strain of jointed sandstone first decreased and then increased with increasing joint angle. Specimens with joint angles below 45 degrees exhibited considerable plastic deformation capacity, whereas those above this were more likely to show brittle failure. The ultimate failure patterns of the jointed specimens were found to be controlled by the joint angle and strain rate. Four types of crack coalescence behaviours were identified which were compared with the crack coalescence categories of jointed specimens under static loading. The variable tendency of the dynamic compressive strength of jointed specimens based on experimental results agreed with theoretical analysis., Sandstones from a roadway 985 m below the surface of a coal mine in Huainan (Anhui, China) were used to investigate the influence of weakly filled joint angles on the dynamic mechanical properties and fracture evolution mechanism of sandstone. Dynamic uniaxial compression tests were performed at 15 degree intervals on specimens with joint angles of 0-90 degrees under different strain rates. The dynamic stress-strain relationship, dynamic strength, dynamic peak strain, energy characteristic, failure mode, typical failure progress, crack coalescence category, fracture micro-mechanism, and theoretical analysis were examined. The results indicated that both the dynamic compressive strength and peak strain of jointed sandstone first decreased and then increased with increasing joint angle. Specimens with joint angles below 45 degrees exhibited considerable plastic deformation capacity, whereas those above this were more likely to show brittle failure. The ultimate failure patterns of the jointed specimens were found to be controlled by the joint angle and strain rate. Four types of crack coalescence behaviours were identified which were compared with the crack coalescence categories of jointed specimens under static loading. The variable tendency of the dynamic compressive strength of jointed specimens based on experimental results agreed with theoretical analysis.

Laboratory simulation results of rock creep in areas with excavation disturbance showed that the long-term rock strength was significantly lower than in areas without excavation disturbance. Samples from a depth of 2 400 m from the traffic tunnel of the Jinping Underground Laboratory (China) were used for step-loading triaxial creep and associated acoustic emission (AE) tests using a single-stage loading time of 5 days and a total loading time of approximately 50 days. Results show that with an increase in stress level, the transient strain of the deep rock increases nearly linearly, while the axial creep strain rate increases exponentially. Results showed that multistage AE data can be used to determine the long-term strength of rock. With an increase in the stress level, the microcracks of the deep rock under excavation disturbance changed from closed primary microcracks to initiating, propagating and coalescence secondary microcracks, which ultimately leads to macroscopic shear failure. It is suggested that these results can provide a reference for deep resource exploitation and stability evaluation., Laboratory simulation results of rock creep in areas with excavation disturbance showed that the long-term rock strength was significantly lower than in areas without excavation disturbance. Samples from a depth of 2 400 m from the traffic tunnel of the Jinping Underground Laboratory (China) were used for step-loading triaxial creep and associated acoustic emission (AE) tests using a single-stage loading time of 5 days and a total loading time of approximately 50 days. Results show that with an increase in stress level, the transient strain of the deep rock increases nearly linearly, while the axial creep strain rate increases exponentially. Results showed that multistage AE data can be used to determine the long-term strength of rock. With an increase in the stress level, the microcracks of the deep rock under excavation disturbance changed from closed primary microcracks to initiating, propagating and coalescence secondary microcracks, which ultimately leads to macroscopic shear failure. It is suggested that these results can provide a reference for deep resource exploitation and stability evaluation.

The constant-resistance-large-deformation (CRLD) yielding bolt consists of a cone, a sleeve, a face pallet, and a tightening nut installed on a bolt shank which is fixed in rock through the anchored end. A method has been developed to predict the resistance of the CRLD bolt under high geostress conditions or in squeezing ground during soft rock tunnelling in western China. The method can be used to consider the effect of surrounding rock pressure, and the effects of compression between the sleeve and the cone on the resistance. The solution incorporates two novel developments: the constant resistance based on the thin-walled circle ring theory with the consideration of surrounding rock pressure; and an analysis of the interaction between the sleeve and the cone considering both the friction force and compression force. The results show that the constant resistance increases linearly with an increase in surrounding rock pressure. As the half cone angle and friction coefficient increase, the contribution of the surrounding rock pressure increases. It is concluded that, compared with the classical theoretical solution, the new method is better for analysing and predicting the resistance behaviour of the CRLD bolt under high geostress conditions., The constant-resistance-large-deformation (CRLD) yielding bolt consists of a cone, a sleeve, a face pallet, and a tightening nut installed on a bolt shank which is fixed in rock through the anchored end. A method has been developed to predict the resistance of the CRLD bolt under high geostress conditions or in squeezing ground during soft rock tunnelling in western China. The method can be used to consider the effect of surrounding rock pressure, and the effects of compression between the sleeve and the cone on the resistance. The solution incorporates two novel developments: the constant resistance based on the thin-walled circle ring theory with the consideration of surrounding rock pressure; and an analysis of the interaction between the sleeve and the cone considering both the friction force and compression force. The results show that the constant resistance increases linearly with an increase in surrounding rock pressure. As the half cone angle and friction coefficient increase, the contribution of the surrounding rock pressure increases. It is concluded that, compared with the classical theoretical solution, the new method is better for analysing and predicting the resistance behaviour of the CRLD bolt under high geostress conditions.

The historical development from the 1950s of simple closed-form elastic and elastoplastic analytical design methods – which have subsequently been incorporated into finite element programmes – and some limitations of their application are reviewed. The validity of the various approximations used to simplify the analysis and of the assumption of elastic and plastic characteristics is discussed. The development of the New Austrian Tunnelling Method (NATM) and the American Arch Rib Method (AARM) is described. A summary of US government-commissioned studies of plastic design methods by the University of Illinois conducted in connection with the expansion of the transportation networks and the excavation of nuclear bunkers and Minuteman silos in the USA is provided., The historical development from the 1950s of simple closed-form elastic and elastoplastic analytical design methods – which have subsequently been incorporated into finite element programmes – and some limitations of their application are reviewed. The validity of the various approximations used to simplify the analysis and of the assumption of elastic and plastic characteristics is discussed. The development of the New Austrian Tunnelling Method (NATM) and the American Arch Rib Method (AARM) is described. A summary of US government-commissioned studies of plastic design methods by the University of Illinois conducted in connection with the expansion of the transportation networks and the excavation of nuclear bunkers and Minuteman silos in the USA is provided.

Understanding processes and conditions that lead to rockfalls during and after a wildfire in different geological contexts is crucial since this phenomenon is one of the major hazards in mountainous regions across Europe. Spain is one of the European countries with the highest rate of wildfires, and rockfalls cause high economic and social impact, with many fatalities every year. The increase of rockfalls during and after wildfires is connected with the merging of different factors, not only in the detached area but also in the propagation and potentially affected area. When wildfire occurred, many actions take place: changes in the mechanical conditions of the rocks, the loss of protective capacity from vegetation, the effect induced by firefighting activities and/or the impact by the high temperatures in the adopted protective measures. After the wildfire, there is an increase in frequency and intensity of rockfalls in the burned area, causing a major impact of rockfalls on not only road networks and built-up areas but also people living. Additionally, the removal of vegetation by wildfires causes an increase in the risk perception, related not only to detached blocks but also to the general appearance of the rock mass. In this review, the main factors that influence the occurrence of rockfalls after a wildfire are analyzed, and three actual case studies in Spain are presented to support the variety of conclusions obtained.

At ten percent of sedimentary rocks, limestones are common geo-energy reservoirs. Being highly soluble, limestones are prone to fluid-assisted deformation and their mechanical behaviour likely susceptible to fluid chemistry. In this study, we saturated limestone samples with 0.4 M MgSO4 or 0.4 M Na2SO4 CaCO3-saturated solutions (naturally present in many reservoirs) or a reference CaCO3-saturated solution for 1, 50 or 200 days prior to mechanical testing. Triaxial deformation tests were then performed at 7, 30, and 70 MPa of confining pressure room temperature, under drained conditions. Our results show that exposure to one different cation impacts the strength of this rock (up to [Formula presented] of dry rock strength) and its failure dynamics, associated with different microstructural damage distribution. A 200 day exposure to MgSO4 promotes strengthening whilst similar exposure to Na2SO4 leads to weakening. We posit that these strength changes may be related to changes in surface charges on the mineral surfaces. More data on fluid–rock interaction will be key to fully understand fracture propagation in natural carbonate formations., Applied Geophysics and Petrophysics

The mechanical behaviour of natural, unfilled rock joints is influenced by the interaction between surface roughness and matedness of the contact surfaces. In the field, natural rock joints normally exhibit a mismatch between the contact surfaces, mainly due to different geological processes such as weathering or deformations. Various attempts have been made to estimate how matedness of rock joints influences their peak shear strength. However, the proposed methodologies imply certain difficulties since they are intended to estimate the matedness of rock joints based mainly on visual inspection, and by relating an initial shear displacement to the length of the analysed sample or by relating the opening of saw-tooth and two-dimensional joint profiles with the degree of interlocking. Therefore, a tested peak shear strength criterion for natural, unfilled rock joints that realistically accounts for the influence of matedness on their peak shear strength is still lacking. This paper presents a methodology where objective measurements of the average aperture of natural, unfilled rock joints are used to estimate their matedness as a step in the prediction of the peak shear strength. This measured average aperture is based on high-resolution optical scanning of the surface roughness. The proposed relationship between measured average aperture and matedness of natural rock joints has been included in a further developed peak shear strength criterion. The verification against ten natural rock joint samples of coarse-grained granite showed that the revised criterion can predict the peak shear strength considering rock joint matedness., QC 20210423

The natural rock masses are situated in various complex geological conditions. Quantitative description of the deformation and failure behaviors of rock fractures under these conditions is of fundamental importance for the studies related to their mechanical behaviors. In this study, the unconfined compression tests and the elastic-plastic contact numerical simulations are implemented to study the compressive deformation and failure behavior of two kinds of rock fractures under dry and saturated conditions, together with acoustic emission detection and analysis. The results show that the normal stress-displacement curves and the plastic failure areas obtained from the experiment and the numerical simulation agree well with each other, which verifies the reliability of the contact method. The mean increment of plastic deformation decreases nonlinearly with the increasing normal stress with a decreasing rate, and a fitting formula is established using mechanical and geometric parameters. The position of acoustic emission (AE) sources matches with the damage area obtained from the experiment and the numerical simulation. Both the AE ringing count and the cumulative count are higher in dry rocks than those in saturated rocks. The AE ringing count and the mean increment of plastic deformation follow an identical changing trend. These results reveal the controlling role played by the fundamental mechanical parameters and geometric properties in the deformation and failure behaviors of rock fractures., QC 20220613

Los desprendimientos rocosos constituyen fenómenos de movimientos de rocas que ocurren debido a una combinación de parámetros internos y factores externos que potencian la inestabilidad de la masa rocosa en zonas montañosas. Entre las consecuencias directas se encuentran el daño parcial o total de infraestructuras, interrupciones en la circulación del tránsito, lesiones y hasta potenciales muertes de los usuarios. La complejidad de los procesos involucrados entorno a los desprendimientos rocosos obliga a establecer metodologías que permitan realizar una evaluación objetiva y veraz del riesgo frente a estos fenómenos. Por este motivo, el presente estudio del riesgo establece una metodología objetiva de evaluación cuantitativa del riesgo de estructuras lineales como carreteras frente a los eventos de caídas de rocas en el ámbito de uso de un Sistema de Información Geográfica, implementando las técnicas propuestas al caso particular de la carretera LV-9124, de gran interés técnico, social y político. El riesgo de caída de rocas se define a partir de los componentes de frecuencia, probabilidad de alcance, exposición y vulnerabilidad, determinados a partir de la fotointerpretación de depósitos utilizando ortofotografías históricas, la simulación de trayectorias de bloques en el programa RockGIS; características particulares de los diferentes elementos expuestos y escenarios planteados, y la intensidad de los daños en términos económicos o número de muertes respectivamente. Los valores de riesgo resultantes se presentan para los diferentes elementos expuestos y se visualiza en forma de mapas donde resulta una tramificación de la carretera en función de los niveles de riesgo calculados, y que servirá de instrumento para la adopción de medidas preventivas y de mitigación., Rockfalls are rock movement phenomena that occur due to a combination of internal parameters and external factors that enhance rock mass instability in mountainous areas. Direct consequences include partial or total damage to infrastructure, traffic disruptions, injuries and even potential user deaths. The complexity of the processes involved in rockfalls requires the establishment of methodologies that allow an objective and truthful evaluation of the risk to these phenomena. For this reason, this risk study establishes an objective methodology for the quantitative evaluation of the risk of linear structures such as roads in the event of rockfalls in the context of the use of a Geographic Information System, implementing the techniques proposed to the particular case of the LV-9124 road, of great technical, social and political interest. Rockfall risk is defined from the frequency, range probability, exposure and vulnerability components determined from the photointerpretation of deposits using historical orthophotographs, the simulation of block trajectories in the RockGIS program; particular characteristics of the different elements exposed and given scenarios, and the intensity of damage in economic terms or number of deaths respectively. The resulting risk values are presented for the different elements exposed and are displayed in the form of maps which result in road tramification according to the calculated risk levels, and which will serve as a tool for preventive and mitigation measures., Els despreniments rocosos constitueixen fenòmens de moviments de roques que ocorren a causa d'una combinació de paràmetres interns i factors externs que potencien la inestabilitat de la massa rocosa en zones muntanyenques. Entre les conseqüències directes es troben l'afectació parcial o total d'infraestructures, interrupcions en la circulació del trànsit, lesions i fins a potencials morts dels usuaris. La complexitat dels processos involucrats entorn als despreniments rocosos obliga a establir metodologies que permetin realitzar una avaluació objectiva i veraç del risc enfront d'aquests fenòmens. Per aquest motiu, el present estudi del risc estableix una metodologia objectiva d'avaluació quantitativa del risc d'estructures lineals com a carreteres enfront dels esdeveniments de caigudes de roques en l'àmbit d'ús d'un Sistema d'Informació Geogràfica, implementant les tècniques proposades al cas particular de la carretera LV-9124, de gran interès tècnic, social i polític. El risc de caiguda de roques es defineix a partir dels components de freqüència, probabilitat d'abast, exposició i vulnerabilitat, determinats a partir de la fotointerpretació de dipòsits utilitzant ortofotografies històriques, la simulació de trajectòries de blocs en el programa RockGIS; característiques particulars dels diferents elements exposats i en els escenaris plantejats i la intensitat dels danys en termes econòmics o nombre de morts respectivament. Els valors de risc resultants es presenten per als diferents elements exposats i es visualitza en forma de mapes on resulta una tramificació de la carretera en funció dels nivells de risc calculats, i que servirà d'instrument per a l'adopció de mesures preventives i de mitigació.