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The understanding of the initial ground stress field in a deep and long tunnel can help to optimize the support structure design and reduce the occurrence of collapse and other failures in tunnel construction and operation periods. Daxiangling Tunnel is a deep and long tunnel under multiple faults condition, many collapses, rock bursts, and large deformations occurring during construction. This paper presents a study of initial ground stress field regression analysis in Daxiangling Tunnel. A three-dimensional geomechanical model with faults is established first, which satisfies the deformation compatibility equation at the fault location. Then, according to the superposition principle, the distribution of regional stress field under the fault condition is obtained by the method of partition inversion. The results show that the distribution of the ground stress field in the Daxiangling Tunnel areas is mainly tectonic stress. The horizontal stress in the area is greater than the vertical stress, and the extreme value appears at the maximum excavation depth. Owing to fault extrusion shear, the stress relaxation exists in the stratum near the fault. The regression analysis results are generally consistent with the measured results, and the relative error is controlled within 10%. However, owing to the boundary effect of the finite element model, the regression stress values near the tunnel entrance and exit are distorted. This can be corrected by applying a mathematical statistical method to obtain the initial stress field of the Daxiangling tunnels with higher applicability.

Investigation into natural fractures is extremely important for the exploration and development of low-permeability reservoirs. Previous studies have proven that abundant oil resources are present in the Upper Triassic Yanchang Formation Chang 7 oil-bearing layer of the Ordos Basin, which are accumulated in typical low-permeability shale reservoirs. Natural fractures are important storage spaces and flow pathways for shale oil. In this study, characteristics of natural fractures in the Chang 7 oil-bearing layer are first analyzed. The results indicate that most fractures are shear fractures in the Heshui region, which are characterized by high-angle, unfilled, and ENE-WSW-trending strike. Subsequently, natural fracture distributions in the Yanchang Formation Chang 7 oil-bearing layer of the study area are predicted based on the R/S analysis approach. Logs of AC, CAL, ILD, LL8, and DEN are selected and used for fracture prediction in this study, and the R(n)/S(n) curves of each log are calculated. The quadratic derivatives are calculated to identify the concave points in the R(n)/S(n) curve, indicating the location where natural fracture develops. Considering the difference in sensitivity of each log to natural fracture, gray prediction analysis is used to construct a new parameter, fracture prediction indicator K, to quantitatively predict fracture development. In addition, fracture development among different wells is compared. The results show that parameter K responds well to fracture development. Some minor errors may probably be caused by the heterogeneity of the reservoir, limitation of core range and fracture size, dip angle, filling minerals, etc.

Tectonic fracturing of the Mesozoic and Cenozoic structures was studied in the Northern Priokhotie (Magadan region). The cataclastic analysis method and the statistical method of fracture density analysis were used to reconstruct their state of stress. It is revealed that the folded structures of the Arman’-Viliga synclinorium are subjected to horizontal shearing; the axis of maximum compression is sublatitudinal (azimuth 67°, angle 12°); extension is submeridional (azimuth 161°, angle 19°). In the Uda-Murgal volcanic arc, horizontal extension with shear takes place; the compression axis is directed to NW (azimuth 259°, angle 29°), and the extension axis to NE (azimuth 152°, angle 26°). In the Okhotsk-Chukotka volcanogenic belt, volcanic structures are in the field of varying tectonic stresses, from predominant horizontal extension to horizontal shear. The Cenozoic intermontane depressions of the Miocene – Pliocene ages are subjected to horizontal shear; the compression axis is directed to NE (azimuth 214°, angle 29°), and the extension axis to NW (azimuth 121°, angle 4°). The results of the comparative analysis of the stress states in the above-mentioned areas reliably show that the diversity of the stress state types is statistically related to the structural positions of the studies sites. Such diversity cannot be explained by an influence of active faults, or by any consecutive superposition of deformations at different stages, despite the fact that the deformations have complicated the observed pattern of the stress states. We conclude that each subsequent geodynamic stage only introduced additional elements into the previous structure, but did not completely transform it.

A single-pass large-deformation rolling method was used to study the effect of cold rolling degree on the microstructure, microtextural evolution, and grain orientation during the cold rolling of pure nickel N6. The results show that the microstructure evolves from micro-bands to lamellar-bands with the increase of cold rolling reduction, and the fraction of coincidence site lattice boundaries always decreases. Starting from an initially low imposed strain (20% of the cold rolling reduction), the deformed microstructure is mainly composed of Goss, rotated Goss, P, and Brass orientations. When cold rolling reduction exceeds 50%, the shear textures appear and other textures remain but their intensities decrease. The strong shear stress on the surface of the rolled plate causes the normal cold-rolled texture dominated by Cu{112} , S{123} , Brass{011} to rotate around the transverse direction to form a shear texture composed of shear4{112} and {110}∥RD fiber textures.

The derivation of geomechanical properties from petrophysical/geophysical data is not only of great importance in the oil industry but also in mining, geothermal projects and tunnelling, for reduction of costs and to improve security. For the oil industry and geothermal sector, it is mainly important for drilling rate and the stability of the borehole and, as a result, the economic factor. A key issue is that geomechanical properties, which can support a better planning of a project, cannot be measured in the borehole or on the surface directly. In this study, the focus is put on anisotropic effects on the correlation between static and dynamic properties, which is neglected in most studies but important because values can vary extremely. Therefore, measurements in the geotechnical laboratory of compressional and shear wave velocity during uniaxial compression strength test were taken. Additionally, typical properties like bulk and grain density as well as porosity were determined too. Different samples (carbonate–silica schist, marble and phyllite) from the "Zentrum am Berg"-research tunnelling centre at the "Erzberg" in Austria were used. Shown are correlations between uniaxial compression strength and compressional wave velocity as well as for static and dynamic Young’s modulus including their anisotropic effect. The results are promising and provide an opportunity for further applications on log data.

[Abstract This work examines the mode of basal to substrate interaction, and flow dynamics of recurrent mass wasting events from a high‐quality 3D seismic reflection data. The Taranaki Basin, offshore New Zealand offers a unique environment to understand these processes, as the Neogene succession of the area preserves vertical stacks of mass transport deposits (MTDs) from the Miocene to Pliocene. The approach used here combines seismic interpretation of the basal shear zones (BSZs) of the MTD, seismic attribute analyses and colour rendering of both RMS amplitude and energy gradient maps. The five mass transport deposits are characterized into blocky‐MTDs consisting of moderate to high amplitude and variably deformed rafted blocks, and chaotic masses composed of slides and debris flow deposits. Classic examples of kinematic indicators at the BSZ of the MTDs akin to free‐slip flow processes such as liquefaction, hydroplaning and shear wetting are convolute flow fabrics and basal shear zone cut‐offs (fractures). Striations, grooves, mega scours, U‐ and V‐shaped scours, substrate erosion, monkey fingers (peel backs), substrate deformation and shearing are associated with no‐slip flows, suggesting that the mass movements efficiently interacted with the underlying substrate. Importantly, the intersection of different kinematic indicators along the BSZs of all the MTDs suggests an overlap of flow regimes, flow overprinting and transformation during mass movement. Although basal tooling by rafted blocks seems dominant during remobilization of the blocky MTDs, the presence of other kinematic indicators signifies combined mechanisms involving both free‐flow and no‐slip processes during their translation. The classification scheme evaluated here innovatively shows mass movements habitually occur through a combination of flow mechanisms rather than an independent flow regime., Panel a: Conceptual classification of mass movements into free‐flow and no‐slip flow (redrawn after Sobiesiak et al., 2018). Panel b: Kinematic indicators observed in the study area include variably oriented convolute fabrics, basal shear zone fractures (cut‐offs or cracks), striations, grooves and monkey fingers (responsible for peeling back of the BSZs). Panel c‐ Classification of the five interpreted mass transport deposits into those with free flow and no‐slip flow. The BSZ for MTD 1, 3, 4 and 5 is marked using blue, green, pink and orange lines. ]

The development and construction of offshore wind farms requires the correct estimation of the friction that can be mobilised at the rock/grout interface. In conventional studies, the shear behaviour of a joint is usually investigated with laboratory tests under constant normal load/stress (CNL), however, in engineering practice, direct shear testing under constant normal stiffness (CNS) has been proved to be more realistic in the assessment of the development of the side shear resistance in rock grouted pile design. In this work, an extensive experimental campaign on the shear response of a weak carbonate rock (limestone) interface with grout is presented, in the frame of offshore wind turbines. First, basic mechanical testing is performed on the two interface materials in order to evaluate their mechanical properties. The output of these tests reveals not only the contrasting properties of the two interacting materials, but also the decreased response of the limestone in the presence of water. A series of monotonic shear tests (both under CNL and CNS conditions) on wet rough limestone/grout interfaces reveal the high impact of adhesion between the two materials to the mechanical response. Based on the monotonic results, a number of CNS shear tests under cyclic loading takes place, where different failure modes are observed dilatant and contractant response. The variability of the failure mode is strongly related not only to the adhesion created with the cast grout, but also to the limestone’s micro-structural heterogeneity that manifests already after consolidation. The post-shear morphological state of the interface is analysed, while the variability of the failure surface and the presence of water gouge creation do not allow a clear correlation of the morphologfy to the mechanical response. Overall, the response of this type of weak rock interface where the properties of the grout are significantly higher, is governed by the behaviour of the rock.

To clarify the sliding mechanism of a landslide, the shear behavior characteristics of slip zone soil are always vital. In the Northwest of China, thousands of landslides generally develop in three main types of slip zone soil, i.e., Quaternary loess, weathered Mesozoic-Cenozoic mudstone, and weathered Mesozoic-Paleozoic phyllite. In the present study, the shear behavior characteristics of these three kinds of slip zone soil were investigated through direct shear tests and their implications for the sliding mechanisms of landslide were also discussed. It was found that, in general, an abrupt failure of loess landslide could be related to the strong strain-softening behavior of loess in the direct shear test, while the ductile shear behavior of weathered mudstone and phyllite coincided with the creep deformation of the corresponding landslides. The residual friction angle of slip zone soil varied with the soil type and its mineral composition, and the lowest residual friction angle about 11.5° could be found in weathered phyllite (SET) with graphite. Compared with the previous research, it is interesting to find that the residual friction angles of mudstone and phyllite in the present study accorded reasonably with the empirical correlations proposed by Wen et al. (2007) for weak rocks in the Three Gorges area, China.

Rock joints have obvious acoustic emission (AE) Kaiser effect and Felicity effect under multilevel cyclic shear conditions. The TFD-20H/50J rock shear apparatus was used to carry out cyclic loading and unloading joint shear tests, and the acoustic emission parameters and frequency spectrum characteristics of the whole shearing process were analyzed. The results show that, under the cyclic loading, the shear stress-displacement curve forms several cyclic hysteresis loops, and the number of loops increases with the increase of normal stress. With the cycles increase, the shear damage gradually increases, and the Felicity ratio gradually decreases. The Felicity ratio at the final shear failure moment is about 0.94~0.99. The ratio of the RA value (rise time/amplitude) and the average frequency value (RA-AF) is used to classify the cracking mode of the joint sample. There are two AE crack signal types (tensile type and shear type) during shear damage. The peak frequency is displayed as high, medium, and low three frequency bands, which are distributed in the range of 0~35 kHz, 35~122 kHz, and 122~300 kHz, respectively. Both low-frequency and high-frequency signals account for less than 10%, and medium-frequency signals account for more than 90%. The research of the AE monitoring signals of multilevel shear behaviors can help understand the shear-friction mechanisms of rock joints.

The tunnel crossing active fault is severely damaged under the action of fault dislocation. Considering the “economic and safety” principle in engineering design, the tunnel damage should be effectively reduced. In this work, a two-level design method for fault dislocation was proposed and the Urumqi subway tunnel in China was chosen as a typical model to deeply investigate its application feasibility. Based on the definition of the design events of different levels and corresponding design goals, three-dimensional finite element soil-tunnel models were established to estimate the response of tunnel. Meanwhile, the rationality of soil-tunnel model was judged by tunnel deformation and internal forces distribution characteristics analysis, and the two-level design goals were evaluated by comparing tunnel damage degree and volumes. The results suggest that under the condition of fault dislocation, the tunnel without disaster mitigation method suffers severely shear, tensile-crack, and compressive damage, which may eventually induce the tunnel collapse. The tunnel damage is reduced significantly by adopting the method of flexible joint. For Urumqi subway tunnel with flexible joints, both of the two-level design goals are effectively realized.

The geometric distribution of initial damages has a great influence on the strength and progressive failure characteristics of the fractured rock mass. Initial damages of the fractured rock were simplified as parallel cracks in different geometric distributions, and then, the progressive failure and acoustic emission (AE) characteristics of specimens under the uniaxial compression loading were analyzed. The red sandstone (brittle materials) specimens with the parallel preexisting cracks by water jet were used in the tests. The energy peak and stress attenuation induced by the energy release of crack initiation were intuitively observed in the test process. Besides, three modes of rock bridge coalescence were obtained, and wing crack was the main crack propagation mode. The wing crack and other cracks were initiated in different loading stages, which were closely related to the energy level of crack initiation. The propagation of wing crack (stable crack) consumed a large amount of energy, and then, the propagation of shear crack, secondary crack, and anti-wing crack (unstable crack) was inhibited. The relationship between the crack propagation mode and the geometric distribution of existing cracks in the specimen was revealed. Meanwhile, the strength characteristic and failure mode of fractured rock with the different geometric distributions of preexisting crack were also investigated. The energy evolution characteristics and crack propagation were also analyzed by numerical modeling (PFC2D).

Analyzing the shear resistance of a potential sliding surface based on discontinuity persistence usually does not consider the number of coplanar rock bridges. To examine the effect of the dispersion/number of rock bridges on the shear strength and rock slope stability, direct shear tests and large-scale rockslide simulations were conducted employing the 2D particle flow code (PFC2D). The shear strength of rock bridges under different configurations and the same discontinuity persistence was analyzed based on both the shear behavior controlled by the stress response and crack propagation. The results at both the laboratory and slope scales indicate that the shear resistance decreases with increasing dispersion/number of rock bridges due to multiple rock bridges breaking separately, the mechanism of which is that the rock bridge system more easily experiences initial failure with increasing dispersion/number of rock bridges. On this basis, a function of the strength reduction coefficient with the number of rock bridges was established considering the laboratory-scale numerical simulation results. A feasible stability analysis method, i.e., the improved limit equilibrium method based on the strength reduction coefficient, was proposed to consider the effect of the dispersion/number of rock bridges on the slope stability, which is a useful innovation to ensure that the stability analysis method of potential rockslides, including coplanar rock bridges, is more realistic and accurate.

There were many gently inclined shallow landslides along the soil-bedrock interface at a depth of 3–5 m in Nanjiang County, Sichuan Province, China. To explain why slope failure occurs at the soil-bedrock interface at a depth of 3–5 m, we conducted ring shear tests on samples of the slip zone soils, slip zone soil-to-the smooth bedrock, slip zone soil-to-the natural bedrock, and slip zone soil-to-the rough bedrock interfaces under various normal stresses. Twelve specimens of the slip zone soils and the slip zone soil-to-the bedrock of the gently inclined shallow landslides were tested by means of a ring shear apparatus. The results show that the peak shear strength and residual strength of the slip zone soils were larger than those of the slip zone soil-to-bedrock interface under a normal stress of 60–100 kPa. Thus, the slope slides along the slip zone soil-bedrock interface at a depth of 3–5 m. This can explain why the slope fails along the slip zone soil-bedrock interface at a depth of 3–5 m. The peak shear strength and residual strength of the slip zone soil-to-bedrock were larger than those of the slip zone soils under a normal stress of more than 100 kPa. Thus, the slope slides along the slip zone at a depth of more than 5 m. This can explain why the slope does not fail along the interface between the slip zone soils and the bedrock at a depth of more than 5 m.

This study examines the shear-relative rainfall spatial distribution of tropical cyclones (TCs) during landfall based on the 19-year (1998–2016) TRMM satellite 3B42 rainfall estimate dataset and investigates the role of upper-tropospheric troughs on the rainfall intensity and distribution after TCs make a landfall over the six basins of Atlantic (ATL), eastern and central Pacific (EPA), northwestern Pacific (NWP), northern Indian Ocean (NIO), southern Indian Ocean (SIO), and South Pacific (SPA). The results show that the wavenumber 1 perturbation can contribute ∼ 50% of the total perturbation energy of total TC rainfall. Wavenumber 1 rainfall asymmetry presents the downshear-left maxima in the deep-layer vertical wind shear between 200 and 850 hPa for all the six basins prior to making a landfall. In general, wavenumber 1 rainfall tends to decrease less if there is an interaction between TCs and upper-level troughs located at the upstream of TCs over land. The maximum TC rain rate distributions tend to be located at the downshear-left (downshear) quadrant under the high (low)-potential vorticity conditions.

Moment tensor analyses suggest that shear microfractures dominate the compressive characteristics of most rock materials. However, the microfracture sizes estimated by the traditional shear model are unrealistically large. This paper presents a novel shear model for microfracture size estimation in sandstone specimens based on AE measurements. The sizes of 342 microfractures were estimated via the proposed model; most are found to range from 0.0022 to 1.80 mm with an average microfracture size slightly smaller than the average grain size. The microfracture size distribution characteristics observed here are similar to those observed by microscope for stressed sandstone, suggesting that more realistic microfracture sizes can be obtained with the proposed model than the traditional shear model.

Wet granular materials develop both shear stresses and normal stresses during simple shear. Over a certain range of shear rate levels, both the shear stress and the normal stress that develop are l...

Flow speed past the measuring probe is definitely needed for the estimation of the turbulent kinetic energy dissipation rates ε and temperature dissipation rates χ based on the Taylor frozen hypothesis. This speed is usually measured with current instruments. Occasional failed work of these instruments may lead to unsuccessful speed measurement. For example, low concentration of suspended particles in water could make the observed speed invalid when using acoustic measuring instruments. In this study, we propose an alternative approach for quantifying the flow speeds by only using the microstructure shear or temperature data, according to the spectral theories of the inertial and dissipation subranges. A dataset of the microstructure profiler, vertical microstructure profiler (VMP), collected in the South China Sea (SCS) during 2017, is used to describe this approach, and the inferred speeds are compared with the actual passing-probe speeds, i.e., the falling speeds of the VMP. Probability density functions (PDFs) of the speed ratios, i.e., the ratios of the speeds respectively inferred from the inertial and dissipation subranges of the shear and temperature spectra to the actual speeds, follow the lognormal distribution, with corresponding mean values of 1.32, 1.03, 1.56, and 1.43, respectively. This result indicates that the present approach for quantifying the flow speeds is valid, and the speeds inferred from the dissipation subrange of shear spectrum agree much better with the actual ones than those from the inertial subrange of shear spectrum and the inertial and dissipation subranges of temperature spectrum. The present approach may be complementary and useful in the evaluation of turbulent mixing when the directly observed speeds are unavailable.

This paper improves a simplified soil hysteresis model for one-dimensional fully coupled effective stress analysis of site seismic response that addresses the limitations of existing hyperbolic soi...

In recent years, the studies on producing data on physical and mechanical properties of Malaysian timber specimens have evolved from small clear specimen to structural size specimen, where most of the research method was based on the American Standard Testing Manual ASTM D198. Numerous data regarding mechanical properties on structural size specimen have been produced through this method, such as bending and compression test. Unfortunately, studies on shear properties on structural size timber are very scarce. It has reviewed that the global timber researchers are focusing to produce data on shear properties of European timber species such as Oak, Spruce and Pine where both shear strength and shear modulus data were obtained from bending and torsion test. Furthermore, from the review of the existing literature, it is clear that there is no proper studies focusing on development of shear properties of Malaysian tropical timber, especially torsion test in accordance with EN 408:2010. Therefore, the aim of this study is to investigate the shear properties (shear strength and shear modulus) of Malaysian Tropical Timber in large size.

μ topologically close-packed phase commonly forms in superalloys and its intrinsic deformation is critical for their performance. Atomic configurations of planar defects in μ phase have been investigated by aberration-corrected scanning transmission electron microscopy and geometrical structure analysis. It is found that the basal slip in μ phase is accomplished by synchroshear inside Laves triple-layers, whereas shear deformations on non-basal planes are associated with long-range diffusions or local atomic rearrangements. Distinct from that on (1 1 ¯ 02) pyramidal planes, displacement vectors of planar faults on ( 1 ¯ 101) pyramidal planes deviate from the slip plane, leading to the contraction or dilation faulted regions.

Earthquakes with magnitudes Mw = 6.4 and Mw = 7.1 occurred in July 2019, one after the other with an interval of 34 hours, several kilometers apart, near the town of Ridgecrest, Kern County, California, USA. There was a moderate shock with a magnitude of Mw = 5.8 in 1995 in the immediate vicinity of the epicenters of the future earthquakes. A strong earthquake with Mw = 7.4 occurred about a hundred kilometers to the north in 1872. To study the seismic deformation process in connection with these events, data from continuous GPS observations at 51 station were used, with a daily recording interval. The initial observation epoch was 13 years prior to the latest events (July 2006), and the final epoch was about a month (August 2019) after those. The study area has a diameter of about 250 km and includes the epicenters of modern and historical earthquakes. Digital models of the distribution of horizontal, total shear and dilatation deformations were obtained for each day of observations. Incorporation of the time sequence of the obtained models into an accelerated kinematic visualization of the seismic deformation process ( https://www.researchgate.net/publication/343577013_Ridgecrest_total_shear_strain_and_seismicity_evolution ) revealed some interesting features. The onset of shear deformation extremum was close to the time of the moderate earthquake (Mw = 5.2), which occurred 10 years before the events of 2019, about 70 km from it, and which presumably initiated the trigger mechanism of the future seismic rupture with the beginning of the development of a weakened elongated zone in the area of the Coso volcanic field. The area of anomalous shear spread in the direction of the future events and reached their epicenters at the time of the main shocks. An analysis of the space-time distribution of the length of the surface displacement vectors showed the possibility of determining the location of a future strong event based on long-term continuous GPS observations in seismic areas.

Rock elastic properties play an important role in the geological characteristics of reservoirs. The analysis of these properties is normally based physical experiments on rocks. However, such conventional physical experiments cannot meet actual requirements when the rock is fragile or has complex composition. With the development of computer technology and the application of micro-computed tomography scanning technology, digital rock physics technologies came into existence. In this work, micro-computed tomography was applied to obtain high-quality three-dimensional images of coal samples. Next, the image multi-threshold segmentation method was used to divide the grayscale image into three reasonable components, including mineral, organic matrix, and pores. Digital rock models with different gas saturations were established using mathematical morphology based methods. Five volume samples were selected from the original large digital rock model under different conditions of porosity, mineral, and gas saturation. Based on these three-dimensional digital cores and the finite element method, the effective elastic moduli of coal rock mass were simulated and the compressional wave velocity and shear wave velocity were computed. Results show that, in the absence of filled minerals, both bulk and shear moduli decrease with rising porosity; compressional and shear wave velocities decline, and the ratio of compressional wave velocity to shear wave velocity increases. However, a more realistic study considering filled minerals demonstrates decreasing shear wave velocity and counterintuitively rising compressional wave velocity when the porosity increases. Gas saturation only affects the compressional wave velocity. The obtained results improve our understanding of rock elastic behaviors in the coalbed. Cited as : Andhumoudine, A. B., Nie, X., Zhou, Q., Yu, J., Kane, O. I., Jin, L., Djaroun, R. R. Investigation of coal elastic properties based on digital core technology and finite element method. Advances in Geo-Energy Research, 2021, 5(1): 53-63, doi: 10.46690/ager.2021.01.06

Finite elemen model for the structural behaviours of bi-directional (2D) FG porous microbeams based on a quasi-3D theory and the modified strain gradient theory (MSGT) is presented. As the main novelty of this study, in order to capture accurately the size effects, the MSGT is employed with three material length scale parameters (MLSPs) rather than the modifed couple stress theory (MCST) with only one MLSP. The material properties including three MLSPs are varied in both the axial and thickness directions as well as porosity. By using a quasi-3D theory, which inludes normal and shear deformations, the governing equations for static, vibration and buckling analysis are derived and solved by Hermite-cubic beam element for various boundary conditions. Through numerical examples, effects of variable MLSP and porosity as well as gradient index in two directions on the deflections, natural frequencies and buckling loads of 2D FG porous microbeams are examined.

Aging causes deleterious changes in resting conduit artery shear patterns and reduced blood flow during exercise partially attributable to reduced nitric oxide (NO). Inorganic nitrate increases circulating NO bioavailability and may, therefore, improve age-associated changes in shear rate as well as exercise hyperemia. Ten older adults (age: 67 ± 3 yr) consumed 4.03 mmol nitrate and 0.29 mmol nitrite (active) or devoid of both (placebo) daily for 4 wk in a randomized, double-blinded, crossover fashion. Brachial artery diameter (D) and blood velocity (V

The double notched shear test specimen has been redesigned to test wood in structural component scale using a compression test setup. A parametric finite element method (FEM) study was performed to obtain the best specimen shape within a domain of geometrically feasible layouts. Several criteria of stress state assessment were considered to characterize the shear zone. Experiments employing DIC (Digital Image Correlation) were performed on the optimized specimens both for RL (Radial-Longitudinal) and TL (Tangential-Longitudinal) material orientation of shear fracture surfaces for the wood of Norway spruce. Two series of specimens with different notch end shapes were tested. Fracture surfaces were 3D laser scanned post-failure, and the actual areas were determined. Shear moduli, nominal and real shear strengths, as well as fracture surface orientations were evaluated. The deformation fields were fitted to the analytical fracture mechanics solutions to identify the intensity of the opening and shearing modes at the notch. The resulting shear strengths were compared with the existing clear wood specimen test results of Norway spruce using fracture surface composition obtained from 3D scan analyses. The estimated shear moduli are on the same level for both specimen designs, G = 1020 MPa. The shear strengths differ considerably, which is correlated positively to the intensity of the opening deformation mode at the notch. The analysis of fracture surface scans reveals the superposition of shear strengths in RL and TL.

Plane strain (2D) finite element models are used to examine factors contributing to basin effects observed for multiple seismic events at sites in the Thorndon basin of Wellington, New Zealand. The models consider linear elastic soil and rock response when subjected to vertically-propagating shear waves. Depth-dependent shear wave velocities are considered in the soil layers, and the effects of random variations of soil velocity within layers are modelled. Various rock shear wave velocity configurations are considered to evaluate their effect on the modelled surficial response. It is shown that these simple 2D models are able to capture basin reverberations and compare more favourably to observations from strong motion recordings than conventional 1D site response models. It is also shown that consideration of a horizontal impedance contrast across the Wellington Fault affects spectral response and amplification at longer periods, suggesting the importance of this feature in future ground motion modelling studies in the Wellington region.

Cemented Paste Backfill (CPB) technology has been effective in using the tailings to refill the underground cavities. The wet or dry rock surface can significantly affect the stability of the CPB-Rock interface, and the shear load-bearing capacity of CPB-Rock interface always reflects the overall stability of the filled underground cavities. Therefore, clear understanding on the shear behavior of the CPB-Rock interface with wet or dry rock surface is very important. To investigate the shear behavior of CPB-Rock interface with different rock surfaces (wet and dry), an apparatus for shear tests at CPB-Rock interface was constructed by modifying the servo-controlled GCTS (Geotechnical Consulting & Testing System) loading frame. Over 72 CPB-Rock samples with dry and wet rock surfaces were tested under four confining pressures (0, 50, 100 and 150 kPa) and different curing time (1, 3, 7 days). The findings show that, under the same confining pressure and curing time, the shear strength of the CPB-Rock interface with the dry rock surface is much larger than that of the wet one. Furthermore, with the increase of the curing time under a same confining pressure, the increase of shear strength on the dry rock surface is also larger than that of the wet one due to the presence of water film on the wet rock surface. The shear strength is enhanced with the increase of confining pressure. Further, the testing results were analyzed within the framework of the Mohr-Coulomb criterion, which comply with the corresponding theoretical curve. It is concluded that the dry rock surface is essential to the stability of the filled underground cavities. In case of wet environment for the underground cavities, it is important to find ways to dry the rock surface before carrying out back filling using CPB method.

SUMMARY The Eastern Mediterranean is the most seismically active region in Europe due to the complex interactions of the Arabian, African, and Eurasian tectonic plates. Deformation is achieved by faulting in the brittle crust, distributed flow in the viscoelastic lower-crust and mantle, and Hellenic subduction, but the long-term partitioning of these mechanisms is still unknown. We exploit an extensive suite of geodetic observations to build a kinematic model connecting strike-slip deformation, extension, subduction, and shear localization across Anatolia and the Aegean Sea by mapping the distribution of slip and strain accumulation on major active geological structures. We find that tectonic escape is facilitated by a plate-boundary-like, trans-lithospheric shear zone extending from the Gulf of Evia to the Turkish-Iranian Plateau that underlies the surface trace of the North Anatolian Fault. Additional deformation in Anatolia is taken up by a series of smaller-scale conjugate shear zones that reach the upper mantle, the largest of which is located beneath the East Anatolian Fault. Rapid north–south extension in the western part of the system, driven primarily by Hellenic Trench retreat, is accommodated by rotation and broadening of the North Anatolian mantle shear zone from the Sea of Marmara across the north Aegean Sea, and by a system of distributed transform faults and rifts including the rapidly extending Gulf of Corinth in central Greece and the active grabens of western Turkey. Africa–Eurasia convergence along the Hellenic Arc occurs at a median rate of 49.8 mm yr–1 in a largely trench-normal direction except near eastern Crete where variably oriented slip on the megathrust coincides with mixed-mode and strike-slip deformation in the overlying accretionary wedge near the Ptolemy–Pliny–Strabo trenches. Our kinematic model illustrates the competing roles the North Anatolian mantle shear zone, Hellenic Trench, overlying mantle wedge, and active crustal faults play in accommodating tectonic indentation, slab rollback and associated Aegean extension. Viscoelastic flow in the lower crust and upper mantle dominate the surface velocity field across much of Anatolia and a clear transition to megathrust-related slab pull occurs in western Turkey, the Aegean Sea and Greece. Crustal scale faults and the Hellenic wedge contribute only a minor amount to the large-scale, regional pattern of Eastern Mediterranean interseismic surface deformation.

The microstructure characteristics of slip zone soils and the variation law of microstructural parameters during shearing are the focus of the study of landslide mechanism, which is of great import...

A series of undrained cyclic axial-torsional shear tests on saturated coral sand and quartz sand under linear, circular, and heart stress paths are performed. The test results show significant diff...

Affected by the disturbance of blasting activities, deformation instability and rock dynamic disasters are prone to occur in deep hard rock roadways. Thus, it is particularly necessary to understand the failure behavior of rocks and roadways under dynamic loads. In this study, a series of impact loading tests were carried out on sandstone samples with and without a circular cavity by a modified split Hopkinson pressure bar (SHPB) test system. The mechanical properties and energy evolution of the samples were systematically investigated, and the effect of cavity size was analyzed. The results showed that the presence of the cavity in the samples weakens the dynamic compressive strength by more than 10%, and the peak strain and brittleness are also reduced to varying degrees. Under dynamic loading, spalling cracks occur first on the roof and floor of the cavity, and then different numbers of shear cracks are formed on the sample diagonals. The eventual shear failure mode is the result of the connection of the shear cracks and the cavity. As the cavity radius increases, the dissipated energy density and fractal dimension both grow accordingly, leading to smaller and smaller rock fragments. The dynamic failure behavior of the circular cavity can be well explained based on the dynamic stress distribution law. Overall, this study can provide a reference for the study of the mechanism of rock burst in deep roadways.

Based on the research background of the damage of high-temperature jointed rock masses, this paper studies the mechanical properties of jointed granite under high-temperature conditions and analyzes the failure law of jointed rock masses with increasing temperature, decreasing temperature and types of joints. The results have important scientific and engineering value. The main research results are as follows: (1) high-temperature conditions change the mechanical properties of granite, especially when the temperature is higher than 400 °C, and the peak stress of granite decreases sharply; the change rate of the mechanical parameters of granite under the condition of water cooling is higher than that under the condition of natural cooling. (2) The uniaxial compressive strength of jointed granite increases with increasing angle α between the joint and the maximum principal plane, and the peak strength of intact granite is higher than that of jointed granite with either conjugate or echelon joints (referred to as conjugate or echelon jointed granite here). (3) The conjugate jointed granite exhibits three failure modes, in which the fractures are all tensile fractures; the echelon jointed granite exhibits three failure modes, most of which include tensile and shear fracturing.

This study employs time domain reflectometry (TDR) technology for the automatic monitoring of a landslide area to explore rock deformation mechanism in comparison with rock cores and to estimate the location of a potential sliding surface and the amount of the sliding. Comparing to the data from the TDR monitoring and rock cores in Lushan landslide area in Taiwan, sliding surfaces of the landslide area occurred mainly at two locations of rock formations. One was located at an interface between colluvium and weathered rock; the other’s location was a buckling type of rock structures associated with slope creeping. Using a regression equation of the relation between TDR reflection coefficients and shear displacements, the magnitude of a TDR-cable deformation in the field can be determined. Resulting from field TDR monitoring, rock mass creep increased from 0 to 0.67 cm at 13.4-, 57.9- and 70.6-m depths of T3 borehole in the landslide area from September 2018 to May 2019. Overall, the TDR technology is practically used for a real-time and automatic slope monitoring system to detect the location and magnitude of sliding surfaces in the landslide area.

Indonesian territory which consists of several islands, both large and large and small, is an area that has a level of vulnerability. In this case heard and witnessed through the media various events from natural phenomena, namely earthquakes in recent years that hit several regions in Indonesia. The potential for natural phenomena to occur is very large because the position of the Indonesian archipelago is at the confluence of the Australian plate, the Pacific plate, and the Eurasian plate. This condition causes the need to comply with the principles of planning and implementing an earthquake resistant system in every building structure to be built in the territory of Indonesia, especially for areas that have a moderate to high level of earthquake risk or vulnerability. Research on the main structure of the LPMP office building with 8 floors aims to determine the behavior of the structure in response to static earthquake loads and dynamic earthquake loads. The method suitable for building design involving earthquake loads in the calculation is the equivalent static. This method is only intended for regular horizontal and vertical SNI 1726(2012)buildings. One of the characteristics of a regular bulding is that the building’s height is less than 40 meters and 10 levels as seen from the building pedestal so that the building tends to be rigid and the building is low. Along with the development of the times, many software that can be used to facilitate an earthquake resistant building design in Indonesia have been revised to SNI-1726(2012). In earthquake SNI 03-1726-2012 article 7.1.3 it is stated that : the final value of the dynamic response of the building structure to the nominal earthquake loading due to the effect of a planned earthquake in a certain direction, should not be taken less than 85 % of the value of the first variety response. If the dynamic response of the building structure is expressed in nominal basic shear force V, where the value of the oh the nominal base shear for each static earthquake in the x direction is 0.867622 and the y direction is 0.975368 where the bigger the dynamic earthquake in the x direction is 3425.624 and the y direction amounting to 3550.92 so that the structural seismicity review shows the result that meet the seismic requirements stipulated in the SNI, starting from the building period, the mass participation ratio, the basic shear force of structural deviations.

The satellite geodesy contribution is decisive for active tectonics determination, as it provides both qualitative and quantitative evidence of a tectonically active region. North Aegean Sea is characterized by intense tectonic, and hence, seismic activity. To estimate the tectonic regime, 7-year primary raw geodetic datasets are implemented, deriving from 32 permanent GPS/GNSS stations. After applying a 30-s sampling rate and ETRF2000 as reference frame, the data are processed using the triangulation methodology, i.e. setting three GPS/GNSS stations each time as the three triangle vertices, from which the barycentre is determined. On each of the 404 barycentres, four-strain quantities are calculated: MAXIMUM and Minimum Horizontal Extension (MaxHE), Total Velocity (TV), Maximum Shear Strain (MaxSS), and Area Strain (AS). The parameterized barycentres are geostatistically processed by applying the Kriging interpolation technique to visualize the pattern of each strain quantity. The results reveal intense crustal deformation in the northern Aegean, directly associated with tectonic activity and, furthermore, plate tectonics. The prevailing shear along with the most dominating tectonic structure of the North Aegean Sea, i.e. the western continuation of the North Anatolian Fault (NAF) in the form of the North Aegean Trough and Basin (NAT and NAB, respectively), is consistent with all the previous geodetic, tectonic and seismological results.

Grouting is a common method used to fill rock joints to improve the stability and integrity of rock mass in geotechnical engineering, and the filling has been observed to have an effect on crack behavior and mechanical property. To investigate this topic, a numerical study of crack behavior and mechanical property of rock samples with two parallel open flaws or infilled flaws under uniaxial compression was conducted in this research. The smooth joint model was proved to be suitable to simulate the interface between rock material and grout material. The occurrence of shear cracks at the interface between rock material and grout material as well as the occurrence of tensile cracks in the grouting material has been successfully simulated in this research. Numerical results indicate that grouting can reduce the tensile force near the flaws, suppress the generation of tensile cracks, and improve the initiation stress of the sample. The tensile force in the specimens with infilled flaws is smaller than that with open flaws, which lead to the improvement of the peak strength of the sample. Moreover, crack development and mechanical properties of samples are affected by bridge inclination angle and flaw inclination angle.

Due to the role of geological structure, the underground rock contains a large number of holes. In order to study the influence of the hole on the mechanical characteristics of the rock failure, the numerical simulation analysis of the intact rock and the rock with three shapes holes(circle, square, triangle) are carried out by using PFC2D. The results show that the rock strength varies with the shape of the hole. Circular holes have the least impact on strength and triangles have the greatest impact. At the same time, different holes shapes have different failure morphology, the intact rock sample forms a penetrating fracture zone inclined by 60°. For the circular hole, forms a through-fracture zone along the upper left and lower right corners. The square hole sample forms an "X"-shaped fracture zone along the four corners. For the triangular holes sample, the damage occurs first at the two positions of the left and right foot of the hole, and then the fracture zone is formed along the upper right corner and the two feet of the sample. Finally, theoretical analysis of stress distribution characteristics around the rock with circular holes is carried out. The compressive stress concentration occurs on the left and right sides of the circular hole, the tensile stress concentration occurs at the top and bottom boundary of the hole. And the tensile crack occurs at the top and bottom of the hole, tensile and shear mixed cracks appear on the left and right sides of the hole from numerical simulation. The crack distribution of numerical simulation is consistent with the theoretical stress analysis results.

Fluid percolation conditions in fault zones are often inferred in geologic studies, but the porosity and permeability of rocks are rarely tested during mineral exploration drilling. Routine permeability and porosity tests on drill core, with adequate detection limits and accuracy, can provide new insights into present- and paleo-fluid flow processes and deposit formation in sedimentary basins and permeable fault zones (e.g. uranium deposits, sub-sea hydrothermal ore deposits). In this study, geological and hydrogeological observations were combined with results of over a thousand permeability tests at spot-on unconfined drill core, extracted along transects through the Gryphon U deposit and fault zone, using a pressure-decay N2 gas probe with adequate seal to the rock surface. The new seal method allowed a wide range of permeability determinations under field conditions (over 5 × 10–20 to 10–12 m2). The penetrative macropore networks were observed directly from gas discharge patterns on drill core surfaces. For the tested crystalline basement rocks below the Athabasca Basin, we inferred that the matrix permeability and porosity distribution appear to be preserved since the late Paleoproterozoic/Mesoproterozoic, under the cover of a sedimentary basin. The permeability values at the present time, and the patterns of rock alteration and deformation, offer insights to paleo-hydrogeological conditions. The gneissic and pegmatitic host rocks have relatively low permeability at present time, except fractured (discrete flow channels) and/or intensely altered to a more porous rock. The alternating zones of silicification and desilicification appear to pre-date the intense argillic alteration, and it may have been a result of earlier hydrothermal activity. The Gryphon U deposit occurs in elongated narrow “lenses” along several fault strands of a fault zone (below the unconformity surface and within basement rocks). U-ore is a cementing mineral in fault-related fractures and fault rocks, but remnant flow channels in fractures in U-ore are still preserved. The most permeable and porous fault rocks are coarse gouges (~ 40% porosity, ~ 10–15 m2 permeability) with approximately three orders of magnitude higher rock matrix permeability than the gneissic host rocks. Such fault rocks locally contain carbonaceous matter, and similar fault rocks may have been preferentially mineralized by U to form the U ore lenses, but the role of brittle-ductile and ductile fault and shear zone rocks in U mineralization is not yet clear at Gryphon. Our review of U–Pb uraninite ages at Gryphon suggests a protracted faulting and U-mineralization history. In response to numerous episodic events of brittle deformation and hydrothermal alteration, the permeability and porosity of the host rocks and U-ores have evolved, as observed by multiple cross-cutting reaction fronts. We inferred from the test results and the alteration halo at the U deposit, affecting a wide part of the fault zone, that the permeability and porosity increased by the downward ingress of U-rich acidic basinal brine that percolated into the basement-hosted (rooted) shear/fault zone and nearby crystalline basement rocks. However, the younger prominent U roll/redox-fronts caused local-scale reduction in porosity and permeability by hematite cementation.

The ground motion intensity of an earthquake is significantly changed when seismic waves propagate from the bedrock to the near-surface soft geological materials. The ground where the shear wave velocity (Vs) exists greater than 760 m/s is generally considered as bedrock. As a common practice in the last three decades, the surface ground motion of a soil site is estimated by multiplying the bedrock motion with the site coefficient that is empirically determined from the time-averaged shear wave velocity in the top 30 m (Vs30) of the site. The site coefficient is defined as the ratio of the ground motion intensity at the ground surface to that of the bedrock. If the bedrock of a site exists at a depth of greater than 30 m, the site effect from the depth of 30 m to the bedrock is not accounted in the Vs30-based site coefficient. In Dhaka City, the minimum depth of the bedrock is approximately 175 m. Therefore, the use of the Vs30-based site coefficient to estimate the surface ground motion is not appropriate for the soft and deep sedimentary deposits of this city. In this study, site response analysis using the Vs30-based site coefficient, linear, equivalent-linear, and nonlinear approaches has been performed to estimate the surface ground motion at different sites of Dhaka City and to compare the results of different approaches. It is observed that the surface ground motion is decreased with increasing the depth of the bedrock due to low shear strain and viscous damping in the soft sedimentary deposits.

Summary Wells are sometimes deformed due to geomechanical shear slip, which occurs on a localized slip surface, such as a bedding plane, fault, or natural fracture. This can occur in the overburden above a conventional reservoir (during production) or within an unconventional reservoir (during completion operations). Shear slip will usually deform the casing into a recognizable shape, with lateral offset and two opposite-trending bends, and ovalized cross sections. Multifinger casing caliper tools have a recognizable response to this shape and are especially useful for diagnosing well shear. Certain other tools can also provide evidence for shear deformation. Shear deformations above a depleting, compacting reservoir are usually due to slip on bedding planes. They usually occur at multiple depths and are driven by overburden bending in response to reservoir differential compaction. Shear deformations in unconventional reservoirs, for the examples studied, have been found to be caused by slip on bedding planes and natural fractures. In both cases, models, field data, and physical reasoning suggest that slip occurs primarily due to fluid pressurization of the interface. In the case of bedding plane slip, fracturing pressure greater than the vertical stress (in regions where the vertical stress is the intermediate stress) could lead to propagation of a horizontal fracture, which then slips in shear.

The paper applies the observation cycle to rock fracturing processes. Specifically, it repeats the observation cycle by going from the large (field) scale to increasingly detailed laboratory scales. With this, it is possible to determine that what appear to be tensile or shear fractures on the large scale are produced through a combination of tensile and shear mechanisms on the smaller scale. This involves observations with a variety of techniques that are briefly described. What is also emphasized is that observation has to go hand in hand with abstraction, i.e., modeling to help understand the observed phenomena. The paper, therefore, makes two contributions—a better understanding of rock fracturing processes and showing the importance of the observation cycle in a scientific process.

The effects of dip angles and thicknesses of bedding layers at the interaction line in between the planes of a normal fault and bedding layers are numerically studied by a discrete element modelling technics. The calibration of the numerical method is accomplished by using an inverse-modelling approach. The laboratory results of Brazilian tensile tests may be used to measure the micro-mechanical parameters of the intact rocks. The shear test results are also performed on the rock joints to determine the micro-mechanical parameters of the bedding interfaces in the present simulation work. The numerical simulation of the shear behaviour of normal fault is performed by making box models with dimensions of 100 mm × 72 mm to represent the bedding layers with different dips and thicknesses. The bedding plane dip angles change from 0° to 165° with an increment of 15° and the thicknesses of these layers change from 6 mm to 12 mm with an increment of 6 mm. The shear testing conditions are exposed to these models to form the normal faults for the numerical modelling of the physical problem under a lateral pressure of 2 MPa. The numerical modelling results show that the shear cracks initiate from all of the bedding interfaces. In this numerical modelling, three major oriented parallel tensile bands are developed and one vertical tensile fracture also propagates through the shear band so that the model is failed. As the bedding layers’ dips are increased, the angle in between the shear bands and the bedding layers is decreased, and as the bedding thickness is decreased, the lengths of shear bands are increased. However, when the bedding angles are 120° and 135° the minimum shear strength of the model is occurred.

In this study, the micro-failure process and failure mechanism of a typical brittle rock under uniaxial compression are investigated via continuous real-time measurement of wave velocities. The experimental results indicate that the evolutions of wave velocities became progressively anisotropic under uniaxial loading due to the direction-dependent development of micro-damage. A wave velocity model considering the inner anisotropic crack evolution is proposed to accurately describe the variations of wave velocities during uniaxial compression testing. Based on which, the effective elastic parameters are inferred by a transverse isotropic constitutive model, and the evolutions of the crack density are inversed using a self-consistent damage model. It is found that the propagation of axial cracks dominates the failure process of brittle rock under uniaxial loading and oblique shear cracks develop with the appearance of macrocrack.

Understanding the stress regime that develops in the vicinity of reinforcements in reinforced soil masses may prove crucial to understanding, quantifying, and modeling the behavior of a reinforced soil structures. This paper presents analyses conducted to describe the evolution of stress and strain fields in a reinforced soil unit cell, which occur as shear stresses are induced at the soil-reinforcement interface. The analyses were carried out based on thorough measurements obtained when conducting soil-reinforcement interaction tests using a new large-scale device developed to specifically assess geosynthetic-reinforced soil behavior considering varying reinforcement vertical spacings. These experiments involved testing a geosynthetic-reinforced mass with three reinforcement layers: an actively tensioned layer and two passively tensioned neighboring layers. Shear stresses from the actively tensioned reinforcement were conveyed to the passively tensioned reinforcement layers through the intermediate soil medium. The experimental measurements considered in the analyses presented herein include tensile strains developed in the reinforcement layers and the displacement field of soil particles adjacent to the reinforcement layers. The analyses provided insights into the lateral confining effect of geosynthetic reinforcements on reinforced soils. It was concluded that the change in the lateral earth pressure increases with increasing reinforcement tensile strain and reinforcement vertical spacing, and it decreases with increasing vertical stress.

Very limited attention was paid on the micro–response of sand as it interacts with geomembrane and the effect of surface hardness on the interaction at the microscopic level. In this study, a coupled finite difference–discrete model was adopted with which to analyze the shear behavior of sand–smooth geomembrane interface. The model was validated using published experimental data. The numerical results show that the effects of normal stress and surface hardness on the interface strength depend on the shear mechanism (sliding or plowing) at the interface. There exists a critical normal stress at which the mechanism transforms from predominant sliding to predominant plowing. There is a high level of coupling effect between normal stress and surface hardness on the interface strength. Micro–topographical analysis of geomembrane provides clear insights into the shear mechanism at the interface, supporting the results obtained from interface shear tests. No shear band is formed during shearing for a sand–smooth geomembrane interface. The shear resistance of sand–smooth geomembrane interface relies on interface indentations and characteristics rather than on the formation of shear band.

The impact of vertical wind shear (VWS) on tropical cyclogenesis is examined from the synoptic to mesoscales using airborne Doppler radar observations of predepression Hagupit during the Tropical Cyclone Structure 2008 (TCS08)/THORPEX Pacific Area Regional Campaign (T-PARC) field campaigns. The high temporal and spatial resolution observations reveal complex localized convective and vortical characteristics of a predepression in a sheared environment. Predepression Hagupit interacted with an upper-tropospheric trough during the observation period. The strong deep-layer VWS (>20 m s−1) had a negative impact on the development through misalignment of the low- and midlevel circulations and dry air intrusion. However, the low-level circulation persisted, and the system ultimately formed into a tropical cyclone after it left the high-shear zone. Here we propose that a key process that enabled the predepression to survive through the upper-tropospheric trough interaction was persistent vorticity amplification on the meso-γ scale that was aggregated on the meso-α scale within the wave pouch. Multi-Doppler wind analysis indicates that cumulus congestus tilted the low-level horizontal vorticity into the vertical in the early stage of convective life cycle, followed by stretching from maturing deep convection. Variations in low-level VWS on the meso-β scale affect convective organization and horizontal vorticity generation. The results provide new insights into multiscale processes during TC genesis and the interactions of a predepression with VWS at various spatial scales.