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Traffic loads induce cyclic loading under influence of environmental factors, and is affected by the variation of moisture content and suction (s). These parameters are difficult to quantify, and the methods for determination are cumbersome. This paper presents extensive experimental studies used to obtain the resilient modulus-suction (M R -s) relationship of the treated subgrade soil. An optimum design of bentonite‑magnesium-alkalinization (BMA) was used an additive. The cyclic Triaxial frame with ELDYN system was employed to measure M R values and the suction was estimated using the filter paper test. A bimodal soil water characteristic curve (SWCC) was observed for treated soil with unheated BMA additive and pre-treatment at heated (BMAH) conditions due to the presence of cementitious products. The M R -s relationship was also developed for the stabilized soil using a normalized model. Results showed that the BMAH samples had a significant level of improvement of M R at higher suction levels as compared to BMA samples but this behaviour of BMAH didn't sustain under fully saturated condition. The change in moisture contents under seasonal variation affects the subgrade performance. This study shows the soil additive can effectively improve the mechanical properties of the soil under various moisture contents. The M R for the treated soil can be estimated using the normalized model under the worst-case scenario of a subgrade when the soil is at a fully saturated condition • Silty sand subgrade soil is treated with bentonite-magnesium-alkalinization (BMA) • Resilient modulus-suction (M R -s) relationship of the treated subgrade soil is presented • A bimodal soil water characteristic curve (SWCC) is observed for treated soil with unheated BMA additive • The MR-s relationship is also developed for the stabilized soil using a normalized model [ABSTRACT FROM AUTHOR]

The engineering properties of marine clays are closely related to its depositional environment. However, the correlation between the chemical properties and depositional environment and their effect on engineering properties of upper Shanghai marine clay are still pending. The sedimentary processes of upper Shanghai marine clays from the Quaternary transgression, the correlation between the chemical properties and its depositional history are investigated in this study based on a series of laboratory experiments. The distribution of chemical indicators (e.g., pH value, oxidation-reduction potential and salt content) with depth showed that the depositional environment directly affected the chemical properties of the soil layer. The correlation of salt content with sensitivity, liquid limit and liquidity index in upper Shanghai layers represents a unique two-stage distribution, with the boundary at the bottom of the Layer-4 clay. The two-stage distribution is caused by the Quaternary transgression and regression, which is confirmed to have different effects on the salt content, sensitivity, liquid limit and liquidity index. The quantitative approaches used to evaluate the correlation between depositional environment, chemical and mechanical properties can provide valuable references for investigating the engineering properties of soft clays. [ABSTRACT FROM AUTHOR]

In several locations along Sweden's northern Baltic coast there are deposits of contaminated fibrous sediments that are known as fiberbanks. Historically, these anthropogenic fiberbanks and associated contaminants were formed outside pulp and paper factories because of unregulated waste discharges. Some of the fiberbanks are located on seafloor slopes that are unstable and may fail, which could result in large amounts of fiber and contaminant dispersion. Hydroacoustic surveys have revealed that some parts of the fiberbanks have been dispersed to a wider area by submarine landslides. However, the unusual nature of these cellulose-rich sediments makes it difficult to apply conventional techniques for assessing submarine slope stability. Therefore, a combination of investigation techniques and interpretation methods was tested to assess the stability and triggering mechanisms for submarine slope failure identified in fiberbanks from the Ångermanälven river estuary on the Baltic sea coast. The integration of bathymetric data, sediment lithology and geotechnical characteristics from in-situ and laboratory measurements, enabled the characterisation of underlying natural sediments and the fiberbanks at two sites. Despite low densities, which indicate that the fiberbank material is near the buoyancy level, the fiberbank deposits seem to be relatively stable. Our results indicate the underlying natural sediments are also stable and would require an external triggering mechanism to generate the observed slope failures. We suggest that pore water pressure, potentially related to groundwater table fluctuations, may be an important trigger for submarine landslides in the study area. Management of fiberbanks and associated fiber-rich sediments, which are numerous along Sweden's north east coast, requires that sites are risk assessed and prioritized for remediation. To do so, under water slope stability should be considered as a possible dispersion pathway and therefore needs to be investigated. The study illustrates the value of using a combination of geophysical and geotechnical field and laboratory methods, together with empirical relationships, to assess relevant input parameters for slope stability calculations for this type of sediment. • A multi-faceted offshore site investigation of contaminated fibrous sediments. • The stability of fiberbank sediments were tested with a tipping box. • Stability of underlying slopes could be compromised by small excess pore water pressures. [ABSTRACT FROM AUTHOR]

The Kahramanmaraş seismic sequence of February 6th, 2023, caused extreme damage and a significant number of casualties across a large region of Turkey and Syria. The paper reports on the survey activities carried out by the authors in the city of Gölbaşı, where extensive liquefaction took place. The damage to the built environment caused by liquefaction differs from that caused by typical inertial seismic actions, with quasi-rigid body displacement mechanisms, resulting in extreme settlements, tilts, and, in some cases, complete overturning. After a brief introduction to the geological features of the Gölbaşı area and a discussion of the seismic effects on the area, the paper reports and comments on the damage observed in one part of the city and provides some statistical interpretations. • For the Gölbaşı district, the proposed seismic motion estimation methodology yields a max = 0.25 g for the Mw = 7.8 event. • The w/B and q values from the maximum deformation curve indicate significant liquefaction in Gölbaşı. • Taller buildings suffered the most due to higher load transfer and lower initial bearing capacity safety factors. • Larger foundation areas resulted in lower damage for a given number of floors. [ABSTRACT FROM AUTHOR]

The stress state of a fault plane influences the mode of sliding and characteristics of slide behaviour. Existing researchers have mainly focused on studying the effect of shear stiffness on fault behaviour under the constant normal load (CNL) boundary conditions. However, the impact of the normal stiffness effect of deep faults on fault sliding stability and seismic source parameters remains uncertain. Addressing the issue, this paper conducts friction tests on granite-simulated faults under the constant normal stiffness (CNS) boundary conditions. It analyzes the impact of normal stiffness on the mechanical behaviour of fault sliding. The results of this paper demonstrate the following findings: (1) Under both normal boundary conditions, various sliding modes occur, including creep-slip, chaotic stick-slip, regular inclusion chaotic stick-slip, and regular stick-slip. (2) The normal stiffness effect reduces the duration of creep-slip and chaotic stick-slip behaviour and decreases the frequency of regular inclusion chaotic stick-slip behaviour. (3) Shear stress and normal stress of the regular stick-slip mode exhibit periodic changes under the CNS boundary conditions. (4) Compared to the CNL boundary conditions, the CNS boundary conditions show a larger shear stress drop and a positive correlation between the normal stress drop and normal stiffness. (5) The CNS boundary conditions result in larger shear stiffness, the absolute value of stick-slip stiffness, characteristic sliding displacement, and fracture energy compared to the relevant seismic source parameters of the CNL boundary conditions. These parameters display positive correlations with normal stiffness. The stick-slip period and normal stiffness initially decrease and then increase, while the normal displacement drop and normal stiffness display a negative correlation trend. These analyses provide comprehensive insights into the mechanical characteristics of fault-slip behaviour and can contribute to improving models and predictions related to fault-sliding behaviour and seismic activity. • We discover a new fault-slip pattern known as regular inclusion chaotic stick-slip. • The normal stiffness effect shortens the duration of fault-slip behaviour. • Under CNS condition, the shear and normal stress exhibit synchronous changes. • The values of seismic source parameters tend to be larger for the CNS condition. [ABSTRACT FROM AUTHOR]

The "regional advantage" hypothesizes that inference uncertainty/prediction error of geotechnical or geological properties at a target site (a site contains a group of records measured from different locations/depths using a variety of tests) can be smaller if we use a quasi-regional cluster (includes two or more database sites with geotechnical or geological properties similar to the target site) instead of the entire database. A tailored clustering enabled regionalization (TCER) framework has been proposed to verify this "regional advantage" hypothesis. TCER requires the target site should not be an outlier site relative to the database. However, it remains a challenge on how to detect an outlier site (or data group) from a database. In this paper, we modify the original TCER by introducing a novel outlier site detection step called maximum site similarity (MSS) into the original TCER. The capability of MSS is verified using synthetic and real examples. Additionally, three inference methods [e.g., probabilistic multiple regression (PMR), classical Bayesian model (CBM), and hierarchical Bayesian model (HBM)] are studied for the purpose of determining the optimal inference method for the modified TCER in terms of achieving the minimum inference uncertainty/prediction error with reasonable computational time. It is shown that the modified TCER with CBM outperforms other inference methods for the examples shown in this paper. • An efficient method that addresses a non-traditional class of outlier site detection problems is proposed. • The proposed outlier detection method is added to the original TCER framework for screening appropriate database. • A Shenzhen clay database named SZ-CLAY/7/3426 is compiled to validate the modified TCER framework. • Three inference methods are applied in the modified TCER framework and their inference uncertainties are compared. [ABSTRACT FROM AUTHOR]

This study investigates the influence of freeze-thaw (FT) cycles on the (i) microstructure, (ii) soil water characteristics, and (iii) sensitivity of the volumetric strain and mechanical properties to moisture content for a compacted clay. The mechanical properties herein include resilient modulus (M R), unconfined compression strength (q u), and reloading modulus (E 1%) and stress (S u1%) at 1% strain. Specimens were compacted at optimum moisture content and subjected to different FT cycles (i.e. 0, 1, 3, and 10 cycles). Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were performed to reveal the evolution of the microstructure during FT cycles. Specimens were then wetted or dried to different suction (s) and degree of saturation (S r) values to obtain the (i) soil water characteristics using filter paper method and (ii) M R , q u , E 1% , and S u1% using cyclic and static triaxial tests. Experimental results demonstrate that FT cycles induce cracks that are tens of microns in dimension, which reduce specimens' water retention capacity and the volumetric strain upon wetting and drying. Mechanical properties also reduce significantly and become less sensitive to the s and S r after FT cycles. A model was used to predict the variation of the M R , q u , E 1% and S u1% with s and S r for specimens subjected to different FT cycles. An attenuation coefficient χ FT was proposed to describe the FT-induced degradation in the q u , E 1% , S u1% , and M R. It was found that the χ FT for different mechanical properties are consistent. The evolution of their χ FT with FT cycles can be described by a uniform empirical equation. The study presented in this paper is useful for the rational understanding and prediction of the hydromechanical behaviors of compacted clay taking account of the influence of FT cycles. • Freeze-thaw (FT) cycles generate cracks that are tens of microns in dimension. • FT cycles reduce soils' water retention capacity and mechanical properties. • Mechanical properties are less sensitive to moisture changes after FT cycles. • Models were proposed to predict mechanical properties considering FT influences. [ABSTRACT FROM AUTHOR]

This paper presents the slope dynamic response of jointed rock slopes containing three groups of typical joints and analyzes the effect of input harmonic frequency and joint density on the peak horizontal acceleration (PGA) of the slope surface under vertically impinging SV wave (shear vertical wave) excitation. First, the dynamic response of the slope surface of the bedding slope was investigated with a large-scale shaking table test, and the reliability of the numerical model was verified by the physical modeling. Then, a series of jointed rock slope models with different joint densities were established based on the three-dimensional discrete element software 3DEC. It is found that the natural frequency f n of the jointed slope decreases with the increase of joint density. The effect of excitation frequency f on the slope surface dynamic response of the jointed slope is stronger than that of joint density. The closer the f is to the f n , the stronger the slope surface and slope crest dynamic response is. Notably, taking f n as the critical value of f , the slope surface dynamic amplification mode of jointed slope can be divided into two types: when f ≤ f n , the acceleration amplification factor of X-direction (AAF-X) of the slope surface amplifies monotonically with increasing elevation; when f > f n , the AAF-X of the slope surface shows a fluctuated amplification pattern with the increase of elevation. The results of this paper show that in the seismic design of slope engineering, the influence of site conditions on the frequency spectrum characteristics of ground motion should be considered, and then the optimal design should be carried out. • Input frequency mainly controls the amplification effect on the slope surface. • Increase in joint density causes a decrease of the natural frequency of the slope. • Input frequency near the natural frequency makes the amplification effect strongest. • Input frequency divides seismic response of a jointed slope surface into two forms. [ABSTRACT FROM AUTHOR]

The longevity prediction and analysis of landslide dams are significant for evaluating the failure risks and formulating emergency plans. However, owing to the large range of landslide dam longevity (from "minutes" to "millennia"), both the analysis of influencing factors within different longevity ranges and a reliable longevity prediction model are still challenging. Based on 1045 landslide dam cases, the statistical analysis of the available data and longevity records is conducted. The landslide dam longevity is classified into seven categories (L1: <1 h, L2: 1 h to 1 day, L3: 1 day to 1 week, L4: 1 week to 1 month, L5: 1 month to 6 months, L6: 6 months to 1 year, and L7: >1 year). The k-Nearest Neighbor algorithm is used to impute the missing data for each longevity category. Based on geometric parameters (dam height, length, width, and volume), hydrological parameters (dammed lake volume and upstream catchment area), triggers, and dam materials, a longevity category classification model and a longevity numeric regression model are developed. The former is established for estimating the longevity range of landslide dams with an accuracy of 91%, and the latter is constructed with an R2 value of 0.95 for predicting precise longevity. Furthermore, the application of longevity prediction models proposed in this paper is verified by three landslide dam cases with reliable recorded data in the recent few years, while their predictive performance is also compared with that of conventional statistical models. Based on the SHapley Additive exPlanations attribution theory, the importance of geometric/hydrological parameters, triggers, and dam materials in determining the longevity of landslide dams in each longevity category is demonstrated using the complete database. Additionally, the influence level of each input variable on the prediction results is analyzed by examining the specific cases. The results indicate that the models proposed in this paper are superior to conventional statistical models in applicability and prediction accuracy. Notably, geometric parameters serve as the most important factor in each longevity category. Generally, the hydrological parameters can be regarded as the second most important factor in terms of influencing the longevity of landslide dams, while dam material demonstrates the lowest impact. The impact of triggers is more significant for landslide dams with a longevity of < 1 day. For landslide dams with a longevity exceeding one month, the importance of hydrological parameters is more prominent. Analyzing the impact of input variables on the prediction results of the specific landslide dams can facilitate the identification of key factors and provide some preliminary guidance for emergency rescue efforts. • Two longevity prediction models of landslide dams are proposed. • Models are applicable to cases with missing data and imprecise longevity records. • The application of the models is verified by three recent landslide dam cases. [ABSTRACT FROM AUTHOR]

Geotechnical testing serves to assess the strength and stiffness of in-situ soils, for purposes such as informing foundation design. Despite its importance, time constraints, financial considerations, and site-specific limitations often restrict testing to isolated locations with limited horizontal resolution. Therefore, this paper presents a novel hybrid generative deep learning model designed to approximate soil properties across sites based on sparsely sampled geotechnical data. The model uses geological subsurface samples derived from random field theory as 'a priori' data for a conditional variational auto-encoder (CVAE) model. By doing so, it attempts to map the relationship between in-situ data and the corresponding spatial coordinates, as well as the inherent link between in-situ data and spatial distribution. Then, in the post-processing phase, a Kriging model interpolates minor discrepancies between the measured and predicted values. To demonstrate its practical application, this paper focuses on cone penetration testing (CPT) as the geotechnical test method. The model's development is thoroughly discussed, followed by the validation using in-situ data and an analysis conducted with synthetic data. It is shown that the uncertainty associated with CVAE-Kriging depends upon both the distance from the sample point and the site's inherent complexity. The proposed methodology not only offers refined subsurface modeling but also expands the understanding of uncertainty in geotechnical testing. Practically, it can assist geotechnical engineers with insights during the survey phase. • A hybrid deep generative method for geological subsurface modeling is proposed. • Substantial 'prior' information is incorporated to guide subsurface modeling. • Validation is performed using multiple non-stationary cases and various methods. • The CVAE's uncertainty correlates with the complexity inherent to the site itself. [ABSTRACT FROM AUTHOR]

The French National Agency for Radioactive Waste Management (ANDRA) has been constructing an Underground Research Laboratory (URL) in Meuse/Haute-Marne since 2000 to determine the viability and protection of deep geological formation for hosting industrial nuclear waste repositories. The purpose of this URL is to describe the in situ properties and behavior of the Callovo-Oxfordian (COx) claystone. At the same time, various types of computational models have been developed to reproduce the in situ phenomena. This paper presents an elastoviscoplastic model called SC2D: Swelling, Creep, Diagenesis, with anisotropic Damage, taking into account in situ measurements. This phenomenological model was developed to contribute to the understanding of the short- and long-term behavior of the COx claystone around the excavated drift. The model parameters are calibrated using in situ measurements and observations. The model assumes that intact COx claystone (around from the excavated drift) exhibits elastic behavior with anisotropic damage in extension as macropores are occupied by calcite fibers. The short-term behavior of damaged COx claystone (near the excavated drift) is also characterized by an elastic mechanism with anisotropic damage. Sampling causes hydromechanical unloading that breaks the calcite fibers. Upon reloading the sample to site mean pressure, the damaged COx claystone first presents elastic behavior and then elastoplastic behavior depending on the load surface. Triaxial tests in axial compression and axial extension are conducted to validate this model with satisfactory results. Its long-term behavior follows an elastoviscoplastic mechanism. • Intact claystone has elastic behavior as macropores are occupied by calcite fibers. • Sampling induces hydromechanical unloading causing calcite fibers rupture. • Short-term behavior of damaged claystone is elastic with anisotropic damage. • Calibration of model parameters to the in situ measurements. • An elastoviscoplastic mechanism describes the long-term behavior of claystone. [ABSTRACT FROM AUTHOR]

Loess, a Quaternary wind-blown deposit, is a problem soil that gives rise to frequent geohazards such as landslides and water-induced subsidence. The behaviour of loess is controlled by its microstructure, consisting of silt-sized skeleton particles and complex bonding structures formed by clay-sized particles. Achieving a deep understanding and precise modelling of loess behaviour necessitates comprehensive knowledge of the realistic 3D microstructure. In this paper, a correlative investigation of the 3D loess microstructure is performed using X-ray micro-computed tomography (μXCT) and focused ion beam scanning electron microscope (FIB-SEM). Details of clay structures in loess, such as clay coatings, clay bridges and clay buttresses, are visualized and characterized in 3D based on FIB-SEM images with a voxel size of 10 × 10 × 10 nm3. The clay structures exhibit a diverse degree of complexity and their impact on the mechanical properties of loess is highlighted. Statistical analysis of the skeleton particles, including size, shape and orientation, are derived from μXCT images with a voxel size of 0.7 × 0.7 × 0.7 μm3. The findings provide insights into the collapse mechanism and particle-scale modelling of loess. The combination of μXCT and FIB-SEM proves to be a powerful approach for characterizing the intricate micro-structures of loess, as well as other geomaterials. • Innovative 3D analysis of loess microstructure using μXCT and FIB-SEM. • Detailed visualization of clay coatings, bridges, and buttresses in loess. • Impact of clay structures on loess geomechanical properties and collapse. • Comprehensive characterization of loess particles' size, shape, and orientation. [ABSTRACT FROM AUTHOR]

As a typical mechanism of internal erosion, suffusion has led to geological disasters in engineering structures worldwide. A slight deviation in soil structures, also known as the spatial randomness of soil parameters, determines the significant differences in this erosion process. However, owing to the lack of absolute quantitative prediction models for suffusion, this issue has not been effectively evaluated. This paper introduces initial random fields of soil properties into a hydromechanical model to quantitatively predict the possibility of suffusion, considering the random deviations in soil gradation, porosity, and permeability. Through the prediction of 50 sets of random fields, certain trends and uncertain deviations of suffusion are discovered. This certainty and uncertainty constitute the possible range of suffusion, which surrounds the prediction of the homogeneous model and will be temporally widened to larger deviations, indicating the unpredictability of the later stage of suffusion. Statistical analysis revealed that soils with more compacted porosity, more movable particles and less permeability at the seepage outlet are prone to suffusion, and this advantage gradually increases to form the upper envelope of the possible range. This phenomenon is attributed to the larger additional forces acting on the movable particles and the abundant movable particles. The hydromechanics-based model of random soil structures can theoretically estimate the possible development of suffusion and effectively assess the uncertainty of internal erosion risk in hydraulic engineering. • A hydromechanics based prediction of suffusion is proposed for cohesionless soils. • Spatially random fields in soil gradation, porosity and permeability are applied in suffusion model. • Possible range of suffusion is predicted and analyzed by the random structure model. • Certainty and uncertainty of suffusion are summarized within the hydromechanical interpretations. [ABSTRACT FROM AUTHOR]

Wildfires striking vegetated hillslopes appear to increase the hazard towards rainfall-induced landslides. One mechanism little investigated in the literature consists in the formation of Wooden Embers Cover (WEC) following the wildfire. This layer has very peculiar thermohydraulic properties and may affect the interaction between the atmosphere and the subsoil. The paper presents an experiment conducted in an outdoor lysimeter filled with pyroclastic silt (SILT) up to 75 cm covered with 5 cm of WEC. Water storage in the SILT layer, soil water content, suction, and temperature were recorded for several years, initially under bare (no-WEC) condition (4 years), then vegetated (no-WEC) condition (5 years) and, finally, with a WEC placed on the top of the SILT (SILT+WEC condition; 3 years). The hydrological effect of the WEC was assessed by comparing the response of the SILT+WEC with the SILT under bare or vegetated conditions. The WEC reduces water losses by evaporation, thus increasing the average water content in the underlying SILT, an effect that is detrimental to slope stability. To discriminate whether the barrier effect was associated with the lower thermal or hydraulic conductivity of the WEC, a numerical simulation was carried out by considering the case of a WEC with its real thermal and hydraulic properties and the case of a fictitious top layer placed on the top of the SILT having the same hydraulic properties of the WEC but the thermal properties of the SILT. It is concluded that the barrier effect of the WEC is mainly associated with its hydraulic properties, i.e. the WEC acts as a capillary barrier. To demonstrate the practical implications of this findings, a case study of rainfall-induced landslide has been reanalysed by simulating the presence of a WEC layer having the same thermohydraulic properties as the material characterised in this study. It is shown that a WEC can substantially reduce the severity of the triggering rainfall event, thus increasing the vulnerability of the slope to rainfall-induced failure. • The post-fire Wooden Embers Cover (WEC) reduces evaporative fluxes in a silty slope. • The WEC acts as thermal barrier due to lower thermal conductivity. • The WEC acts as hydraulic barrier due to lower unsaturated hydraulic conductivity. • The WEC may have negative consequences on rainfall-induced instability. [ABSTRACT FROM AUTHOR]

Erosion and entrainment significantly increase the volume and destructive potential of high-speed long-runout landslides. Previous studies seldom quantitatively address these effects, and even fewer incorporate the extent of slope weathering into the analysis of landslide dynamics. This study addressed this gap by developing a framework for dynamic analysis, combining Finite Element Method-Smoothed Particle Hydrodynamics-Finite Discrete Element Method (FEM-SPH-FDEM), and applying it to the Shuicheng landslide. Simulation results closely matched field data, revealing substantial sliding mass deviation and velocity variations influenced by rocky ridges and valleys. According to the simulation, the weathering degree of rock slope significantly affects landslide dynamic processes. The interparticle friction coefficient is crucial for accurately modeling these processes using the SPH-FDEM method. Additionally, by incorporating landslide erosion behavior into the framework, the case study indicates that the volume of landslides in Shuicheng County increased by approximately 0.6 times. Three stages of evolution mechanisms of high-altitude landslide-induced erosion behavior are proposed in this paper, highlighting the effectiveness of this framework in understanding landslide mechanisms and providing information for prevention strategies in high-altitude, highly weathered areas. • FEM-SPH-FDEM accurately capture landslide scraping and entrainment effects. • Rock slope weathering considerably enhances scraping and entrainment effects. • Significant landslide volume increase by scraping and entrainment is quantified. • Terrain and friction coefficients underscore the need for landslide modeling. [ABSTRACT FROM AUTHOR]

The computation of boundary frictional interaction between debris-flow and rough channel beds is crucial for simulating debris-flow dynamic behavior, owing to its impact on the resulting flow velocity and deposition area. Until now, some boundary treatment methods have been proposed in the Smoothed-Particle-Hydrodynamics (SPH) method, such as the conventional Dynamic-Boundary-Conditions (DBC) and Boundary-Critical-Layer (BCL) methods, which are limited in the effective consideration of boundary friction over complex topography. In this paper, instead of the fixed and predefined boundary critical layers in conventional methods, a concept of particlized frictional influence domain is defined, and a novel centroid aggregation-based boundary detection algorithm (CA-BD) embedded in the 3D-SPH framework is proposed. The algorithm captures the diverse interaction forms and computes mutual penetration between debris-flow particles and rough boundary particles, so that the frictional forces exerting on the debris-flow particles can be determined. Additionally, to enhance the computational efficiency, a CPU-OpenMP parallel acceleration framework is implemented. To validate the proposed model, a well-documented dam-break flow experiment and a debris-flow flume experiment are simulated, wherein the proposed model better reproduces the flow behavior compared to the DBC and BCL methods as observed in the experiments. Comparison on the computational efficiency indicates that the proposed model attains a 2.9 times acceleration factor than the CPU serial solution. Sensitivity analysis also reveals that the predefined length of the frictional influence domain l f has a significant influence and the value equating to the particle smoothing length h is suggested. • A novel centroid aggregation-based boundary detection algorithm (CA-BD) is proposed. • The CA-BD algorithm is embedded in 3D-SPH to simulate debris-flow frictional dynamics. • A CPU-OpenMP parallel is implemented to enhance computational efficiency. • A dam-break flow experiment and the USGS flume case are used to validate the model. [ABSTRACT FROM AUTHOR]

This study introduces the Energy Method Upper-bound (abbreviated as EMU), originally proposed by Donald and Chen (1997), for calculating bearing capacities with a focus on earthquake loadings affecting layered geological strata. The theoretical components of this study consist of (1) an extension of Prandtl's solution for bearing capacity analysis to inclined surface loads, (2) a mathematical demonstration of the theoretical congruence between EMU and the Prandtl-Reissner solution, and (3) a validation of the numerical outcomes through four illustrative bearing capacity examples with known closed-form solutions. This innovative approach eliminates the semi-empirical coefficients typically required in conventional bearing capacity evaluations, thus enhancing its relevance to seismic analysis for stratified geological formation that can hardly be evaluated with empirical coefficients accurately. The study also discusses various technical aspects such as seismic load determination, the use of undrained shear strength, and specifications for allowable safety factors under seismic conditions. With these methodologies, the paper assesses the seismic bearing capacities of two different buildings, with different scales and footing types. Additionally, a computer program, BEARING-IWHR, featuring an Excel interface and open-source coding, is available online. This method provides a theoretically sound and practically feasible framework for addressing seismic bearing capacity on stratified foundations. • Presentation of an upper-bound numerical method capable of evaluating seismic bearing capacity on layered geological strata, eliminating the reliance on semi-empirical coefficients. • The theoretical foundation of this method has been extensively validated through analytical formulations and comparisons with established closed-form solutions, derived from the slip-line field theory. • The practical applicability of this method has been appraised by two case studies involving multilayer stratum by the spread sheet software BEARING-IWHR that is downloadable at the web, facilitating widespread accessibility and utilization. [ABSTRACT FROM AUTHOR]

Surface moisture has recently been reported to be used in regional-scale landslide early warning. Nevertheless, near-surface multi-depth hydrothermal measurements as a hillslope scale are often less concerned and rarely linked to landslide kinematics. In this paper, we selected two neighboring landslides with different deformation mechanisms as case studies. Using in-situ multi-source sensors, we monitored real-time soil temperature and moisture at specific depths within approximately 1.5 m. The measurements span two complete monsoon seasons, representing concurrent dry and wet hydrological extremes. Statistical Pearson correlation analysis was employed to quantify the relationships between landslide activity and environmental variables such as soil temperature and moisture content. The results indicate that the near-surface soil temperatures and moisture contents contribute to a better understanding of the factors controlling landslide activity, in which variations synergistically reflect hydrothermal interaction and potential deformation mechanisms. These soil temperatures and moisture contents at certain depths (specifically at 20, 50, and even 100 cm) show moderate to strong correlations (with Pearson correlation coefficient values ranging from 0.4 to 0.8) with landslide deformation. In cases where discrete daily rainfall data exhibited unsatisfactory correlations due to their data attributes, soil temperature and moisture effectively served as alternative indicators for rainfall inputs, aiding in the analysis. Overall, this work emphasizes the critical influence of soil moisture and temperature on landslide dynamics. This study also highlights the need for comprehensive monitoring and forecasting strategies that consider a wide range of environmental factors to mitigate landslide risks associated with climate change, particularly in the context of intensified extreme weather events. • Acquiring real-time, in-situ soil temperature and moisture at specific depths within approximately 1.5 m using multi-source sensors. • Identifying the extreme rainfall and heatwave events during the year of 2012–2023. • Quantifying the correlation between landslide activity and soil temperature and moisture. • Measurements of ground temperature and moisture contribute to understanding of deformation mechanisms and triggers of landslides. [ABSTRACT FROM AUTHOR]

Extraction of physical quantities such as flow depth and velocities, is one of the major purposes of geophysical flow numerical modeling and critical for estimating consequent impact forces and sediment entrainment. It is simple in nature for mesh-based models but presenting challenges in three-dimensional smoothed particle hydrodynamics (SPH) schemes. The difficulties lie in the substantial number of particles and their uneven spatial-temporal distribution, particularly over complex topography. Inspired by our previous surface cell (SC) -based approach, we propose a novel topography-based and vectorized algorithm that significantly enhances the ability to extract physical quantities over complex topography. In the proposed algorithm, geomorphologic characteristics are mathematically represented by topographical normal vectors. The correlations of physical quantities with distinct coordinate descriptions are established through the vectorization concept, ultimately leading to effective extraction of physical quantities in SPH form over complex topography. This algorithm provides an important tool to incorporate topography-linked physical models within discretized frameworks. To validate its effectiveness, we employed the algorithm to integrate the debris-flow entrainment law with our previous HBP-SPH model, utilizing the 2010 Yohutagawa debris-flow event in Japan as a case study. The results demonstrate a good agreement between the numerical simulation and on-site observation. Discussion regarding the applicability and limitation of the algorithm concludes the paper. • A novel topography-linked algorithm in 3D-SPH form is proposed to extract debris flow dynamics. • The PCA technique is used to represent complex bed surface by topographical normal vectors. • Vectorized operation is adopt to extract quantities in distinct coordinates, with CLL technique to organize data. • Two physic-based laws are integrated to simulate debris-flow entrainment over complex topography. • The 2010 Yohutagawa event is used to validate the effectiveness and applicability of the proposed algorithm. [ABSTRACT FROM AUTHOR]

For deep large underground cavern projects under complex geological conditions, the determination of rock mass mechanical parameters and stability analysis is fraught with a great deal of uncertainty. This paper proposes a set of methods for estimating rock mass mechanical parameters and probabilistic stability assessment suitable for construction characteristics of large underground caverns. On the one hand, according to the Hoek-Brown criterion and Monte Carlo simulation, a dynamic estimation method for rock mass mechanical parameters is proposed by using Rock Mass Rating (RMR), the uniaxial compressive strength (UCS) of intact rock, and the material constant (m b) as input parameters. On the other hand, considering the uncertainty of rock mass mechanical parameters, a probabilistic evaluation method applicable to the unloading response characteristics of rock mass (including displacement and fracturing zones) around the large cavern is put forward, combining the point estimation method and numerical simulation. The proposed methods were applied to an underground powerhouse, with an excavation span of 34 m and height of 88.7 m, at the Baihetan hydropower station in the southwest of China. Based on extensive field investigations and tests, the probability distributions of key rock mass mechanical parameters were obtained. Furthermore, the high sensitivity of input parameters in the H-B criterion for estimating rock mass mechanical parameters were revealed. Through dynamic simulation, the probability distributions of the displacement and fracturing zones in surrounding rock during the layer-by-layer excavation of the cavern were presented. Comprehensive on-site tests showed that the simulated results were in basic agreement with the actual unloading response behavior during the cavern excavation, validating the correctness and applicability of the proposed methods. The study provides a relatively comprehensive approach for estimating rock mass mechanical parameters and stability evaluation in similar underground engineering projects, and also has guiding significance for predicting and preventing engineering rock mass hazards. • Estimation method rock mass mechanical parameters of the underground cavern reflecting geological variability is proposed; • A method for evaluating excavation unloading response of large caverns considering parameters uncertainty is determined; • The displacement and fracturing depth of the surrounding rock during the cavern excavation can be dynamically calculated; • Input parameters in H-B criterion with high sensitivity to the estimation of rock mass mechanical parameters are identified; [ABSTRACT FROM AUTHOR]

The natural stratigraphic distribution is uncertain due to the geological tectonic movements and sedimentation. It is a challenge for traditional deterministic models to capture geological uncertainty. The objective of this study is to develop an improved three-dimensional coupled Markov chain (ICMC3D) model based on limited boreholes. The proposed method enhances the traditional three-dimensional coupled Markov chain model by modifying the transition probability equation for predicting unknown elements. The dip data is added to estimate the transition probability matrix with the borehole information. On this basis, a back analysis method is proposed for estimating the horizontal transition probability matrics. The method makes the predicted results more suitable for the possible stratigraphic distribution. The accuracy of the proposed method is verified through some applications. In this paper, an improved three-dimensional coupled Markov chain model and transition probability matrix estimation method are illustrated by the borehole data collected from a tunnel project in Qingdao. The results show that the presented method can reflect the asymmetry, continuity and anisotropy of the three-dimensional stratum. The exceedance probability is proposed to predict the fault zone development range in order to reduce the geological uncertainty. • A modification is made to the traditional coupled Markov chain model in 3D. • Propose the method for estimating the 3D horizontal transition probability matrix. • Propose the method to predict the fault zones development range based on exceedance probability. [ABSTRACT FROM AUTHOR]

Developing a robust numerical method to model earthquake-induced landslides has long been a persistent challenge in the field of computational geotechnical engineering. Recently, the meshless methods based on nonlocal theory have piqued the interest of researchers. However, the application of nonlocal theory in seismic analysis is currently limited. This paper proposed a numerical framework based on the updated Lagrangian nonlocal general particle dynamics (UL-NGPD) method to analyze earthquake-induced landslide problems. The UL-NGPD method benefiting from the update support domain can capture the whole process of slope run-out induced by earthquakes. To enhance the numerical stability of the proposed method, several optimizing strategies are proposed. In the current framework, the seismic waves are input through the proposed boundary treatments of nonlocal form. Besides, a nonlocal friction model with velocity-weakening is proposed to accurately simulate the movement process of soils on a rocky sliding bed. The proposed framework is validated by the simulations of several classic problems, including the collapse of sand and the shake table test. The performance of the proposed approach is further demonstrated through simulating the landslides induced by earthquakes. The numerical results consistent with recorded data indicate that the UL-NGPD method has an excellent capacity to deal with earthquake-induced landslide problems. • A novel nonlocal theory-based UL-NGPD framework is established to analyze earthquake-induced landslides. • The boundary treatments in the UL-NGPD are introduced. • A nonlocal friction model with velocity-weakening is proposed to accurately simulate the movement process of soils. • Several numerical examples demonstrate the UL-NGPD framework's capability in handling complex landslide problems. [ABSTRACT FROM AUTHOR]

This paper presents a novel, cost-effective method for a rapid and quantitative characterization of discontinuities in fractured rock cliffs using Unmanned Aerial Vehicle-derived Digital Outcrop Models (DOMs). The proposed workflow combines manual extraction of discontinuity data from the DOM with a kinematic analysis using an automated algorithm (ROKA), which upgrades and renews the traditional Markland's test. The case study, a designed railway tunnel portal in NW Italy (Finale Ligure) demonstrates the advantages and limitations of this approach compared to current methods. Manual mapping is compared with (semi-)automatic extraction of discontinuity data from the DOM and validated with field-based scan lines. The results show that in complex geological settings, manual mapping provides more statistically robust and geologically reliable measurements of discontinuity orientation, validated by the user's expertise. Traditional stereographic approaches in kinematic analysis are limited in characterizing spatially variable slopes and discontinuity networks, providing only generic estimations of unstable slope surfaces and discontinuity intersections. This limitation is overcome by new algorithms that incorporate 3D spatial relationships of both the discontinuity network and the rock slope, resulting in a more accurate and site-specific kinematic characterization of the rock cliff, emphasized by 3D visualizations of the critical planes and potential rock failure volumes. The new approach significantly impacts the time, effort, and cost of the engineering projects, allowing to quantitatively define the potential unstable areas with a fast analysis. The Authors stress the importance of integrating digital workflows with comprehensive field-based characterizations of the local litho-stratigraphic and structural setting to effectively utilize large datasets and partially automated procedures. [Display omitted] • A strong field understanding improves the kinematic analysis based on a 3D model. • Manual fractures mapping is more effective in complex geological settings. • Automatic fractures mapping could be effective for low deformed and clean rock slopes. • Traditional kinematic analyses cannot depict the complex 3D geometry of rock slopes. • ROKA algorithm localizes in 3D the critical slope areas and discontinuities. [ABSTRACT FROM AUTHOR]

Sensitive clays, when subjected to large strains, exhibit a unique strain-softening behavior, transforming into a remolded liquid with remarkably low shear strength. When a slope fails, this behavior leads to the remolded clay moving away from its original position, triggering subsequent failures and catastrophic outcomes. To accurately predict such scenarios, it is crucial to incorporate realistic strain-softening characteristics into the constitutive soil model. This paper presents a novel yet practical strain-softening law developed by the authors that effectively captures the post-peak behavior of sensitive clays down to their remolded strength. The softening law is implemented in an elastoplastic Mohr-Coulomb model and incorporated into Anura3D, an open-source software that uses the Material Point Method to simulate large deformations. The constitutive model is calibrated by simulating the stress-strain behavior through direct shear tests conducted at three sensitive clay landslide locations. The accuracy of the overall numerical framework is assessed by predicting the post-failure movements of these landslides. Notably, two of the landslides, Sainte-Monique (1994) and Saint-Jude (2010), have previously been analyzed using other numerical tools, allowing for a comparative analysis with the method presented here. The third landslide, the Saint-Luc-de-Vincennes landslide, representing a composite flow slide and spread, has been numerically simulated for the first time. The post-failure behavior observed in the landslide events is compared with field observations and other numerical analyses. The results show that the MPM models with the proposed strain-softening law can reasonably predict post-failure retrogression and runout distance, which are crucial parameters for determining the risk of landslides in sensitive clays. • A new strain-softening law for sensitive clays in the MPM framework accurately simulates stress-strain behavior. • The new softening law allows for the prediction of large strain parameters without rigorous back analysis. • The numerical framework successfully captures post-failure behavior of prehistoric retrogressive failures. • Comparing simulation results with field observations shows that the softening law produces reasonable outcomes. • The Saint-Luc-de-Vincennes landslide is numerically modeled for the first time. [ABSTRACT FROM AUTHOR]

Designing high mine waste rock piles for long-term behavior requires material mechanical characterization over a large range of stresses and variable environmental conditions. However, representative coarse samples cannot be handled by standard testing devices and the common approach is to test small-scaled samples at the laboratory, which might be affected by particle size effects when compared to the field material. Several reported results indicate that coarser samples present higher amount of particle crushing than small-scaled samples, thus lower dilatancy and higher compressibility. However, specific studies of size effects on time-dependent deformation are lacking. The aim of this paper is to identify the effects of particle size and suction on stress-deformation mechanism of partially saturated mine waste rock. Oedometric compression tests on two parallel graded samples are presented: the gravelly fraction (d max =50 mm) and the sandy fraction (d max =2.36 mm). Each stress increment triggers « instantaneous » and delayed strains. The results reveal the combined effects of particle size and humidity on the mechanical behavior. Coarser samples exhibit higher total compressibility and creep deformation, which also increases with the material humidity. The results give empirical support for the development of scaling laws and suggest that total deformation can be decoupled considering a suction dependent index for creep deformation. • Experimental tests reveal the combined effects of particle size and humidity on the compressibility of mine waste rock. • Coarser samples exhibit higher particle breakage and higher total compressibility. • Time-dependent deformation increases with humidity. • Particle size effect in creep strains is verified. [ABSTRACT FROM AUTHOR]

Earthquake-induced landslides are associated with significant risks to human lives and infrastructure. Spatially distributed infrastructure systems, such as pipelines, power lines, and transportation networks, are at particular risk to seismic landslides due to their large spatial extent. To conduct a comprehensive seismic landslide risk assessment for these systems, there is the need to evaluate the seismic landslide characteristics (i.e., location, size, displacement, direction) on a broad, regional scale. This paper presents a framework for seismic landslide analysis that provides this information for subsequent risk assessments. The approach computes seismic landslide displacements using a sliding block approach while accounting for the uncertainties in the input variables and displacement models using a logic tree. The computed displacements are then aggregated based on geomorphic landforms to define landslide zones. For each landslide zone, the statistical distributions of landslide features, such as landslide size, displacement level, and direction of movement, are defined. These attributes are presented in a format that can be integrated with fragility models for distributed infrastructure systems to quantify risk on a regional scale. The application of the approach is demonstrated through assessments for gas pipeline networks across the state of California in the United States. • A framework for regional seismic landslide risk assessment is described. • A sliding block approach with a logic tree accounts for uncertainties. • Geomorphic landforms (slope units) are integrated to define landslide zones. • Distributions of landslide attributes are defined for input into fragility models. • Results are shown for a region of southern California. [ABSTRACT FROM AUTHOR]

This paper focuses on the microscopic roughness of silica sand grain, and its morphological evolution (contact maturing) under a constant load. The surface topology with rich texture is obtained by Atomic Force Microscopy and various roughness parameters are investigated by statistical approaches. The surface profiles in the same contact region before and after being subjected to sustained loading are both measured to identify time-dependent morphological changes on the contact surface. The two congruent surface topologies, initial and mature surfaces, not only show the delayed fracturing of contact asperities, but also present quantitative differences in the spatial roughness parameters over time. These differences are intensified with consideration of upper profiles only, indicating that asperities with higher elevations are susceptible to the contact maturing process. With the geometric information obtained from the same region at two different measurement times, the Greenwood and Williamson asperity model of rough surface is used to estimate contact proximity, real area of the load-bearing contacts, and the number of contact spots. The model results of the post-loaded surface incorporated with true surface profiles show an increased number of contact points as well as the true contact area under constant loading. It is expected that subcritical fracturing of contact asperities leads to closer proximity of contact entities when loaded by prolonged loading, resulting in firmer and stiffer intergranular contact. This may very well be the reason for time effects in sand assemblies. • Surface profiles of sand grains were obtained by AFM and statistically analyzed. • Surface profiles before and after prolonged load were both measured and compared. • Time-dependent morphological evolution on contact surface was identified. • Information of grain surfaces was directly used for contact probability function. • Greenwood–Williamson model was used to estimate the contact properties' change. [ABSTRACT FROM AUTHOR]

A rational rheology model is critical for the numerical simulation of debris-flow behavior. The Bingham model commonly used in many current studies has failed to simulate the shear thickening and thinning phenomenon in experiments. We report an alternative solution by incorporating the Herschel-Bulkley-Papanastasiou (HBP) model with the smoothed particle hydrodynamic (SPH) method. The SPH simulation is based on the open-source DualSPHysics scheme, upon which we built a development by the Bingham-based rheology model in our previous study. In this paper, a straightforward improvement is made such that the HBP model is incorporated to describe the constitutive law between particles, extending the compatibility of the simulation to dilatant and pseudoplastic fluids. To illustrate the performance of the HBP-based SPH method, first, a sensitivity analysis was performed to investigate the influence of important rheological coefficients. The proposed method was then verified by a dam-break experiment of water-clay mixtures and the case study of the 2010 Yohutagawa debris-flow event in Japan. The results indicate a good accordance between simulation and observation. A discussion regarding the potential and limitations of the current method concludes the paper. • An HBP-based SPH method is proposed for numerical simulation of debris flows. • Shear thickening and thinning phenomenon of debris-flow mixture can be simulated. • A sensitivity analysis on the HBP rheological model is conducted. • The performance of the proposed method has been verified by experiment and case study. [ABSTRACT FROM AUTHOR]

Abstract This paper describes case studies of debris flow and related events in the Republic of Korea and their causes before considering the actions that are desirable in terms of management and mitigation. The paper also considers the obstacles to progress, and, in particular, discusses issues surrounding the governance of land and infrastructure. Experience of other events that occurred in the recent past, including those that have occurred in rural and urban environments is drawn upon. It is concluded that many landslides can be attributed to poor understanding of geomorphological, geological and geotechnical issue and that the causes of debris flows can frequently be attributed to anthropogenic factors. The needs for improved regulations for slope construction and maintenance in mountainous areas of Korea, and for an integrated slope management system are presented. Highlights • 1728 landslide fatalities in the Republic of Korea for the period 1970–2017. • Property damage due to landslides is valued at US$500 M to US$1000 M per annum. • Different owners of source/initiation area and elements at risk (infrastructure, buildings). • Specific mitigation measures recommended in the context of land ownership. • New system of landslide governance system recommended for the Republic of Korea. [ABSTRACT FROM AUTHOR]

Abstract There are typically three types of models involved in a geotechnical analysis, i.e., the geologic model, the ground model, and the geotechnical model, each of which may be associated with uncertainty to a different extent. However, in a typical geotechnical analysis the geological uncertainty is seldom characterized and considered explicitly. In this paper, we discuss the probabilistic tools developed in the geotechnical profession for tasks such as uncertainty characterization, assessment of impact of uncertainties, uncertainty reduction, and evaluation of the value of uncertainty reduction. We postulate that the same tools may be used for a unified treatment of various types of uncertainties in a geotechnical analysis, which would necessitate the collaboration of the engineering geologists and the geotechnical engineers to comprehensively characterize these uncertainties consistently. To this end, the probabilistic tools or methods that are widely used in geotechnical engineering are examined to determine their applicability in the evaluation of geological uncertainties. Examples are provided to illustrate various concepts introduced in this paper. Highlights • The uncertainties associated with geologic, ground and geotechnical models are discussed • Probabilistic methods can be used to characterize these uncertainties • Reliability methods can be used to consider the effect of these uncertainties • The Bayesian method can be used for uncertainty reduction • The value of uncertainty reduction can be assessed through decision analysis [ABSTRACT FROM AUTHOR]

Abstract Using the major land-creation project 'to bulldoze mountains to build cities' implemented in the city of Yan'an as an example, the collapse potential, microscopic observations, quantitative analyses and qualitative characterization of the microstructures of loess sampled from Yan'an were investigated to probe the fundamental mechanisms of loess collapsibility at the micro scale. The results show that loess in Yan'an exhibits a severe degree of collapse potential, as indicated by its maximum collapse index of 8.10% at a vertical stress value of 600 kPa. From a compositional and microstructural perspective, a large proportion of loosely arranged skeletal particles are widely separated by variants of clay fabric, forming a metastable structure with a high pore area ratio of 32.67% and demonstrating an unstable contact between particles in natural loess. These intrinsic microstructural features, with a high degree of collapse potential, act synergistically to augment collapse. When loess is saturated under a certain load, the initially high stiffness provided by the delicate clay fabric can be destroyed by its softening, dispersion or disruption. Unsupported skeletal particles are then rearranged significantly into a more stable structure. At the same time, pores larger than 60 μm create favorable spatial conditions for wetting deformation, thereby spurring an abrupt reduction in pore size and area. Particles reorganize into a closely packed structure. More interlocking pores of <20 μm are subsequently generated. A greater understanding of soil microstructures and compositions can improve loess performance predictions and facilitate the remediation of collapsible loess for large projects. This paper provides a method of relating microstructure parameters to the mechanisms of loess collapsibility. The pore and particle information presented in this paper can also be used to build models for simulating loess behaviors. However, the applicability of the conclusions to other soils still requires verification, which will be performed in future studies. Highlights • A systematic and successful experimental program for characterizing soil microstructural information is developed. • A method of relating microstructure parameters to loess collapse is presented. • A new method of characterizing particle orientation using the publicly available software program ArcGIS 9.0 is proposed. [ABSTRACT FROM AUTHOR]

Time-delayed spalling is proposed to describe the time-dependent splitting failure near the tunnel periphery, which occurs in several days or several months after excavation. This kind of failure has been frequently encountered in a deep TBM tunnel, endangering workers' security and delaying the construction schedule. In this paper, two typical time-delayed spalling cases were systematically introduced, including geological and supporting conditions. Based on field observation, microseismic monitoring and laboratory creep tests, the characteristics and mechanism of time-delayed spalling were investigated. Results showed that time-delayed spalling is a stress-induced time-dependent failure in the vicinity of tunnel surface and appears as flake or plate-like splitting fracture subparallel to the free surface. Although the failure region where time-delayed spalling happened is intact, discontinuities are scattered in the peripheral region. Time-delayed spalling is sensitive to boundary conditions and timely support is an essential method for preventing time-dependent spalling. This research is helpful to the tunnel excavation under similar geological conditions and provides foundations for the prevention of time-delayed spalling. • This paper makes an all-around introduction to the evolution process and mechanism of time-delayed spalling. • The spatial-temporal characteristics of fracture activities of time-delayed spalling were investigated. • The fundamental drivers of time-delayed spalling and the effective prevention method were analysed. [ABSTRACT FROM AUTHOR]

The heat released from the disposal of High-Heat-Generating Waste (HHGW) in a Geological Disposal Facility (GDF) will result in an increase in temperature, and therefore thermal expansion of both the engineering materials and surrounding rocks. The changes to the stress state arising from the thermal expansion of these materials, restrained by the surrounding rock mass, could affect several of the Thermal, Hydraulic, and Mechanical (THM) processes that operate after closure of a GDF. In this paper a methodology is described which suggests how the influence of thermal stress on fracture aperture around a GDF can be evaluated. A set of calculations on an illustrative Discrete Fracture Network (DFN) are reported. These calculations estimate the responses of the fractures to changes in rock stress, considering changes in fracture aperture and the resultant changes to effective intrinsic permeability. • This paper provides a methodology to describe the influence of thermal stress on fracture aperture. • It uses a, realistic, but illustrative 3D fracture network involving several million finite elements. • Fracture apertures were found to be reduced in a region around and beneath the GDF due to compressive stresses. • The maximum decrease in fracture apertures in the vicinity of the GDF was by a factor of about 2. • The changes in fracture aperture led to a modified effective permeability of the rock mass. [ABSTRACT FROM AUTHOR]

Deep geological nuclear waste repositories use the multi-layer Engineered Barrier System (EBS) to isolate nuclear waste from the environment. The key component of the barrier is densely compacted bentonite, closely resembling claystone. Therefore, to ensure safety, we need a numerical model for the bentonite and the barrier that predicts EBS behaviour during transient thermal, hydraulic, mechanical and chemical conditions. The paper identifies key mechanisms and processes affecting the bentonite in the barrier due to temperature changes (thermal couplings) based on advanced fully-coupled Finite Element Method simulations. The paper investigates 1) non-isothermal infiltration experiment on FEBEX bentonite (Villar and Gomez-Espina, 2009) and, 2) Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (Ciemat) test (Martin et al., 2006), presenting 10 simulation configurations that are set up by inactivating one thermal coupling/variable at a time. The difference between these simulations and the baseline model results, examined in terms of the net mean stress (swelling pressure), suction and fluid flow, give insights into the significance of investigated coupling. Results suggest that thermal couplings related to vapour density, viscosity, water retention curve, and molecular diffusivity are among the most influential. The study additionally highlights the importance of water transport as liquid and gas, and water evaporation and condensation. • Analyse thermal coupling effects on bentonite hydration and swelling characteristics • Saturated vapour density-temperature curve majorly affects the stress state • Assumed viscosity–temperature curve is key for the water flow prediction • Temperature effect on the bentonite water retention curve is critical • Identification of phenomena affecting swelling pressure in a repository [ABSTRACT FROM AUTHOR]

Marine geohazards related to geological features and processes in coastal and offshore environments can cause damage to health, environment, field installations, or loss of life and assets. Given increasing human activities in marine environments and population density on coasts, threats to society from marine geohazards are serious. However, the understanding and awareness of marine geohazards are still severely limited. This paper is aimed to highlight the advances and challenges on marine geohazards. Here, we present an overview of marine geohazard research to discuss the past, present, and future of marine geohazards based on bibliometric analysis and our understanding from an engineering geologist's perspective. This paper summarizes marine geohazard research in the development phase, geographic authorship distribution, related areas and disciplines, keywords, and subjects of focused interest. Trends of significance are synopsized from past events (over the last three decades), present processes, and future (foretelling) marine geohazards. Finally, we provide three recommendations from scientific research and safeguarding society perspectives: (1) intense involvement of engineering geologists, (2) integrated multidisciplinary marine geohazard research, and (3) collaborative efforts in marine geohazard mitigation. There is still a long way to go in protecting the public and infrastructure from marine geohazards. • A global review of marine geohazards is presented by the support of bibliometric results. • Trends of significance are synopsized from past events, present processes, and future marine geohazards. • Prominent themes are submarine landslide, sediment, gas hydrate, earthquake, coastal geohazard, climate change and evolution. • The possible contribution of engineering geologists to marine geohazard research is suggested. [ABSTRACT FROM AUTHOR]

In the alpine environment, rainfall-induced shallow landslides can involve thin covers of colluvial soil (50–300 cm) on terraced belts that were formed as a result of fill-and-cut sedimentary processes that followed the deglaciation of the alpine valleys. Notably, research on shallow slope failures involving alpine terraces consisting of a near-flat upper ground surface ("tread") and a moderately steep scarp ("riser") is lacking in the literature. This paper describes the engineering geological characteristics and failure mechanisms of a large number of shallow landslides (soil slips or slide-debris flows) that were activated on alpine stratified colluvial terraces due to a rainstorm that hit the mountain area of the Friuli Venezia Giulia Region (NE Italy) on 21–22 June 1996. The paper reports data on the geomorphological and engineering geological characteristics of the soil slips acquired through extensive fieldwork and shows the outcomes of some two-dimensional seepage and slope stability analyses that were carried out in order to investigate the critical hydrological conditions and mechanisms that were responsible for the soil slip activation during and after rainfall. The soil slip activation can occur at two different stages during the infiltration process, based on the interacting water flows through the terrace tread and riser. The first critical stability condition is reached during the phases of greater precipitation intensity or at the end of the rainstorm because of the saturation of the top soil layer on the terrace riser and the subsequent formation of an ephemeral water table accompanied by a seepage sub-parallel to the slope face. The second critical condition is achieved some hours after the end of rainfall as a result of a tread-to-riser water outflow that is supplied by the water amount stored within the near-flat terrace tread during the peak rainfall stages (reservoir-like effect). This study also shows that a critical value of rainfall intensity of about 40–45 mm/h can cause the activation of soil slips in mountain basins characterised by a humid continental climate and by the occurrence of colluvial deposits with a high content of fine fraction. This critical value of rainfall intensity should be considered as a rainfall threshold for a basin-scale under geomorphological and geological conditions similar to those investigated in this paper. • This work describes rainfall-induced shallow landslides on alpine colluvial terraces. • Soil slips were activated by intense (I > 40–45 mm/h) and short (D = 1–6 h) rainfall. • A seepage–slope stability analysis was carried out to study the soil slip activation. • A first stage of slope instability occurs during phases of greater rainfall intensity. • A second critical condition is achieved some hours after the rainfall ends. [ABSTRACT FROM AUTHOR]

There are an increasing number of mega engineering projects of removing the top of hills to fill in the valley for new land creation in the Loess Plateau of China, which significantly changes the hydrological and geological equilibrium state of the site. The formation of a new hydrological equilibrium state is associated with the water movement in the compacted and intact loess layers. Most disasters occurring in the loess area are related to water. The soil-water retention curve (SWRC) is the key to the implementation of unsaturated soil mechanics in engineering practice and is required to numerically model the movement of water in the soil. In this study, the SWRCs and microstructure of intact and compacted specimens from Lanzhou and Yan'an, two typical cities that have new land creation projects, are investigated. The SWRC is obtained using the filter paper method. The mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) techniques are used to explore the microstructure. The results highlight that the intact loess has a higher air occlusion value (AOV) and a similar slope of SWRC in the transition zone compared with the remolded specimens that compacted at the natural water content. The normalized SWRC (i.e., degree of saturation versus suction/AVO) of the intact specimen is approximately the same as the remolded specimens compacted at the natural water content. The difference in the microstructure between intact and compacted specimens originates from different existing states of the clay particles and further contributes to the variation of the SWRC. • The intact loess has a larger air occlusion value (AOV) and a similar slope of the SWRC compared with compacted specimens. • The normalized SWRCs are approximately the same for the intact and compacted specimens. • The difference between the intact and compacted specimens in the microstructure is attributed to clay particles. [ABSTRACT FROM AUTHOR]

Abstract Prominent characteristics of rock fracturing can be described mainly by crack opening displacement (COD), fracture process zone (FPZ) and fracture energy. In view of lack of real-time and comprehensive measurement techniques for characterizing rock fracturing in field applications, this paper developed a characterizing method of rock fracturing by utilizing and integrating Fiber Bragg Grating (FBG), Digital Imaging Correlation (DIC) and Acoustic Emission (AE). In this paper, mode I fracturing test was performed on sandstone using three-point bending, and the fracturing process was simultaneously detected and recorded by FBG, DIC and AE. The experimental results showed that (1) DIC-based measurement of horizontal displacements across the fracture presented a localized discontinuity, in accordance with FBG-based real-time measurement. At the onset of traction-free zone formation (peak load), the critical COD (δ c) was found to be 76 μm as identified by DIC and FBG. (2) Moreover, the dissipated energy distribution and cohesive crack profile in FPZ characterized by the integrated measurement, indicated that 70%–90% of AE energy (dissipated energy) populated in the FPZ, little AE energy concentrated in the traction-free zone, and the position of δ c delineated a boundary for specifying FPZ. The length of fully developed FPZ was 20 mm (±2 mm) in length. (3) The integrated measurement delineated the cohesive crack, which was not available previously. The integrated measurement revealed the softening curve followed a straight line; the relationship between FPZ length and crack tip opening displacement (CTOD) was linear, and the relationship between dissipated energy and FPZ length was quadratic. Based on the interrelations of cohesive crack characteristics identified by the integrated measurements, real-time fracturing can be captured by one technique (e.g. FBG) in field application. Highlights • An integrated method of characterizing rock fracturing was proposed by combining FBG, DIC and AE. • COD, FPZ and fracture energy are determined in real time with the comprehensive method. • The cohesive crack was delineated with the integrated method. [ABSTRACT FROM AUTHOR]

Abstract Intact rock bridges have been recognised as of critical importance in the stability of rock slopes but still remain a poorly understood and challenging engineering problem both in respect to their measurement and their incorporation into design analyses. The objective of this paper is not to provide conclusive answers as to the definition and measurement of rock bridges, and the manner that they can be accounted for in rock slope stability analysis. Rather, we highlight important and as yet unanswered questions to allow review of fundamental rock bridge concepts and then proceed to provide new insight into how rock bridges may be incorporated into slope stability analysis. Early definitions of what constitute a rock bridge are somewhat limited, and the authors suggest that they could be improved by including important constraints such as " block forming potential " and " block kinematics ". In this context, this paper introduces an improved terminology (RB ij) commonly used by the discrete fracture network (DFN) community to define rock bridge intensity relative to the sampling region. In rock engineering, the measurement of rock bridges is exacerbated by the fact that rock bridges are not visible unless the rock mass is exposed by human activities or by natural events such as rockfalls. This constitutes a major problem for engineering design scenarios, since it would not be possible to validate any assumption made with respect to extent of rock bridges without performing some form of field testing or back-analysis. The results of a of the Finite-Discrete numerical analysis are presented to support our conclusions with respect to the limitations current methods used to characterise rock bridge strength. The role of scale effects, block theory, kinematics and what we term "negative rock bridges" in stability analysis is discussed. Highlights • Rock slope stability is controlled by rock bridges. • Rock bridges defined as a portion of intact rock separating joint surfaces. • Direct quantification of rock bridges is possible only post-slope failure. • A new RBij system to define and measure rock bridges • Limitations of 2D stability analysis incorporating rock bridge strength [ABSTRACT FROM AUTHOR]

Abstract This paper represents a predictive model for the earthquake-induced displacement of slopes using a coupled stick-slip-rotation approach recently proposed by the authors in a preceding paper. A collection of 1363 strong motion records associated with 25 worldwide earthquakes was used to generate the model on the basis of results of sliding block analyses. The proposed model predicts sliding displacement in terms of yield acceleration coefficient ratio (k y /k max), period ratio (T s /T m), and slip length (L). The regression analysis indicates that dividing the results into the smaller intervals of period ratio can provide a noticeable higher degree of accuracy. Probable bias of the residuals versus the input variables is examined in detail. Predictions of the developed equation are compared with some available sliding block equations which similarly assumed a flexible sliding mass. The proposed model can be simply used to estimate landslide hazard in seismic prone regions. Highlights • We presented a predictive model for seismic sliding displacement of earth slopes. • The model was developed based on the results of coupled stick-slip-rotation analyses. • Numerous earthquake records with a variety of effective parameters were incorporated. • Comparison was made with available models recently proposed for sliding displacement. [ABSTRACT FROM AUTHOR]

Abstract A method of backanalysis was used for the assessment of pipe-jacking forces from three pipe-jacking drives in laminated shale and interbedded lithological units of metagraywacke, siltstone, greywacke and phyllite found in the highly weathered and fractured lithologies of the Tuang Formation (Malaysia). Direct shear tests were conducted on reconstituted tunneling rock spoils sampled from three pipe-jacking sites. The direct shear test results were initially assessed using the Mohr-Coulomb failure criterion, which demonstrated severe shortcomings in capturing the nonlinear shear strength behavior of the reconstituted tunneling rock spoils. Subsequently, a simple power law function was proposed together with the generalized tangential method to obtain useful equivalent tangential cohesion, c' t,p and friction angle, ϕ’ t,p for the assessment of pipe-jacking forces in fractured lithologies. The outcomes from this study show that the tangential Mohr-Coulomb strength parameters can be used to backanalyze the frictional coefficient, μ avg and the vertical stress at the tunnel crown, σ EV. These backanalyzed values were successfully related back to the measured jacking forces and jacking speeds for pipe-jacking drives in various geological conditions and lubrication efforts. The use of the backanalyzed parameters c' t,p , ϕ’ t,p , μ avg and σ EV in the assessment of pipe-jacking forces from highly weathered rocks comprising of laminated and interbedded lithological units could lead to the prediction of jacking forces using numerical models. A companion paper to this study has also been produced to evaluate the reliability and suitability of these backanalyzed parameters for assessing pipe-jacking forces using the finite element method. Graphical abstract Unlabelled Image Highlights • Three pipe-jacking drives traversed the highly fractured Tuang Formation. • The jacking forces were measured and backanalyzed using direct shear tests. • Equivalent tangential rock strength parameters, c' t,p and ϕ’ t,p were developed. • The jacking forces were successfully backanalyzed using c' t,p and ϕ’ t,p. • Using finite element method, a companion paper shows the parameters to be reliable. [ABSTRACT FROM AUTHOR]

In this paper, we explore the mechanical performance of colloidal silica grout to assess its potential for ground stabilisation and hydraulic barrier formation during decommissioning of major industrially contaminated sites. We consider two colloidal silica -soil systems: sand grouted with colloidal silica and kaolin clay mixed with colloidal silica. The aims of the paper are to evaluate the drained stress-strain behaviour (1-D compression and shear resistance) of colloidal silica-soil systems and to determine the particle interactions between soil and colloidal silica at a micron-scale so as to provide an understanding of the macroscopic mechanical behaviour. Two different colloidal silica-soil interaction mechanisms have been found: formation of a solid, cohesive matrix for the case of grouted sand, and increase of the clustering of clay particles for the case of clay mixtures. This paper illustrates for the first time that even under drained conditions colloidal silica can provide mechanical improvement. Colloidal silica-grouted sand showed an increased stiffness and enhanced peak friction angle, while still having a very low hydraulic conductivity (~10 −10  m/s), typical of intact clay. Similarly, clay-colloidal silica mixtures showed reduced volumetric deformation, increased stiffness for low values of stress (~100 kPa), and increases in both the peak and the ultimate shear strength. Our results show that colloidal silica could be deployed in environments where not only hydraulic containment is critical, but where reduced deformation and enhanced resistance to shearing would be beneficial, for example in landfill capping or in the outer fill layers of embankments designed to minimise internal seepage and infiltration. [ABSTRACT FROM AUTHOR]

In order to achieve higher fidelity (i.e., higher accuracy) in the model predictions, the solution models employed in geological and/or geotechnical engineering are becoming complex and sophisticated. However, simple and robust models are preferred by engineers in practice. Thus, a dilemma exists between the choice of a complex model for fidelity and that of a simple model for high robustness (i.e., lower variation in the discrepancy between model prediction and observation). This issue becomes more profound when model parameters exhibit uncertainty, which is quite common in geological and geotechnical problems. In this paper, we examine the issue of model selection in the face of uncertainty with three problems: the selection of the order of polynomial fit (i.e., lower order vs. higher order) in the development of data-driven empirical model, the selection of the level of sophistication (i.e., random variable vs. random field) in the probabilistic characterization of the detrended soil property, and the selection of the level of complexity (i.e., simple vs. complex) of the soil constitutive model in numerical modelling. The results illustrate that although the complex and sophisticated models could yield predictions that are more accurate, the simple models might yield predictions that are more robust. This paper provides an insight regarding the question, “Does a complex model always outperform a simple model?” [ABSTRACT FROM AUTHOR]

Most glaciotectonically deformed deposits, including varved clays and glacial tills, are characterised by cracks and fissures. This paper presents a method for describing the yield criteria for glacitectonically deformed cohesive deposits using a model of cracked geomaterial with isotropic or anisotropic matrix. The general representation of the limit conditions for anisotropic materials in plane-strain is used to determine the yield criterion. The yield criterion represents a convex, piece-wise surface in the three-dimensional stress space revealing explicitly global, plastic properties of the materials considered. An example of using proposed yield criteria to solve a bearing capacity problem of a strip foundation constructed on a glaciotectonically cracked layer is presented. The lower and upper-bound estimates of limit loads on the strip footing are given. The limit state analysis presented in this paper can be used to solve many other geotechnical engineering problems, for example, the stability of slopes and reinforced walls or the bearing capacity of pile foundations. [ABSTRACT FROM AUTHOR]

The paper reports on the results of 1D and 2D site response analyses carried out in the Kathmandu Valley, Nepal, in order to investigate how site effects influenced the seismic response during the 2015 Mw 7.8 Gorkha earthquake sequence. The mainshock and a Mw 6.6 aftershock, for which recordings at both rock and soil sites are available, were considered. First, 1D analyses were carried out for the Pulchowk soft soil site, where a borehole was drilled. The shear wave velocity profile was defined using several 2D seismic array surveys carried out in the valley and constrained by noise measurements at Pulchowk site; the nonlinear soil behavior was characterized by means of cyclic simple shear tests carried out on undisturbed soil samples. Both equivalent and nonlinear approaches were adopted in the 1D analyses. Overall, the 1D model was capable to capture some relevant features shown by mainshock recordings such as the de-amplification of medium-to-high frequencies. On the contrary, the unusual high spectral amplification at long periods (3–6 s) recorded during the mainshock was better captured by the 2D finite element analyses carried out on a 20 km-large cross section of the entire valley, thus supporting the hypothesis of the occurrence of basin effects. The paper contributes to the understanding of site effects in Kathmandu Valley for the implementation of seismic risk mitigation strategies in the area. [ABSTRACT FROM AUTHOR]

In recent years public concern about earthquakes induced by gas production has increased in the Netherlands. This has mainly been caused by numerous seismic events related to gas depletion in the Groningen gas field, the largest gas field in Western Europe. Induced seismicity has also been observed in 31 smaller gas fields located on land (onshore) or in the area close to the Dutch coast. Earthquakes with magnitudes as high as M L  = 3.5 have occurred in Roswinkel and Bergermeer causing damage to buildings. In 2016 State Supervision of Mines (SSM), with input from the geological survey of the Netherlands (TNO) and the onshore operators, proposed a guideline for a qualitative seismic risk analysis for depletion induced seismicity arising from gas production in the small fields in the Netherlands. The guideline follows international practices for risk assessment using a risk matrix approach. This paper elaborates the seismic risk guideline and reports on the application of the guideline to the gas fields in the Netherlands. Risk is a combination of hazard and consequences. The result of the seismic risk analysis is qualitative and gives a relative scoring of the producing gas fields in the Netherlands in terms of risk. In order to obtain more information on the quantitative assessment of the risk, more detailed studies are needed. The Groningen gas field clearly poses a much larger seismic risk than that obtained for the other, smaller gas fields, most of which fall into the lowest risk category. Because of the large difference in risk between the Groningen field and the other smaller gas fields, the guideline of SodM deems it sufficient to carry out a qualitative risk analysis for the other gas fields in the Netherlands, as performed in this paper. Based on the combination of the hazards and consequences, the risk can be further interpreted and, if necessary, appropriate measures can be implemented. [ABSTRACT FROM AUTHOR]

Mining processes fracture the surrounding strata and may modify the flow of groundwater by inducing new fractures or changing the permeability of existing defects. The result of mining-induced permeability changes can be disturbance to aquifers or other surface or sub-surface water bodies. Traditional methods for predicting mining-induced fracture connectivity and enhanced permeability based on empirical strain-based criteria may not satisfy modern regulatory demands, nor adequately reflect local geological, geotechnical and hydrogeological conditions. Standard continuum numerical methods may indirectly estimate permeability enhancement from plastic strains however they are not able to track aperture on flow paths or predict fracture connectivity. This paper presents a numerical approach that is demonstrated to be capable of representing longwall mining induced fracturing in sedimentary rock masses. By initiating and propagating fractures, determining connectivity and calculating aperture in a piecewise manner on flow paths, we have estimated permeability enhancement from first principles. Fracture intensity and porosity metrics are calculated and identify the height of the enhanced permeability fractured zone above a longwall goaf. Permeability within the overburden is estimated from the Kozeny-Carman permeability–porosity equation. At a mine site studied in detail in this paper a permeability increase from the in situ state is predicted to range from approximately eight orders-of-magnitude in the caved zone to one to two orders-of-magnitude in the strata above the fractured zone. Realistically simulating cracking, fracturing and crushing of rock strata remains numerically intensive and challenging at the scale of a longwall panel. It is demonstrated in this paper and provides valuable insights into the rockmass response to mining. [ABSTRACT FROM AUTHOR]

Due to the inherent spatial variation of the site information and the limited number of boreholes which could be afforded in a specified project, the geotechnical and geological information at a site could not be fully characterized, which imposes a significant challenge to the analysis, design and construction of the geotechnical system of concern. Indeed, the issue of site characterization has long puzzled engineers. This paper presents a three-dimensional site characterization in the urban area of Suzhou where plenty of borehole explorations have been undertaken. With the borehole database established, the relationship between the shear-wave velocity and the depth is analyzed, this relationship can be captured by regression-based models; and then, a sequence extrapolation method that is based upon the linear relationship between the time average shear-wave velocities is developed for the prediction of the shear-wave velocity along the depth. Next, a three-dimensional characterization and visualization of the stratigraphic model in the urban area of Suzhou are presented. The characterization of the stratigraphic model, in this paper, is realized through the characterization of the elevations of the interfaces between adjacent strata in the sequence stratigraphic structure. The sequence stratigraphic structure is derived with a method that is based upon the one-by-one comparison and updating of the borehole data; and then, the best unbiased estimator of the elevations of the interfaces between adjacent strata at the concerned site is predicted with the Kriging-based interpolation method. With the aid of ArcGIS Engine, a three-dimensional visualization of the characterized stratigraphic model is made possible. [ABSTRACT FROM AUTHOR]