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The seismic stability assessment of anthropogenic cavities is a challenging issue for land and urban planning, particularly in areas of possible interaction with surface structures and infrastructures. The paper proposes a novel methodology for the preliminary assessment at urban scale of the safety level against roof collapse of underground cavities under seismic actions through seismic stability charts, SSCs. The SSCs are the result of extensive parametric two-dimensional FEM analyses focused on cavities excavated in soft rock, as it is frequent in many inhabited areas all over the world. The study is mainly oriented to the instability of shallow cavities, includingthe effects at the ground surface. The SSCs allow evaluation of stability conditions of a generic cavity through a factor of safety, calculated as the minimum ratio between the resistant and loading bending moment of the critical sections of the cavity roof during the whole earthquake duration. The method is applied to the case study of Sant'Agata de' Goti, a historical center in Southern Italy, rising on top of a volcanic tuff ridge. • Methodology to preliminary screen the seismic stability of underground cavities at urban scale. • Parametric 2D FEM analyses to calculate the cavity factor of safety during earthquake. • Analytical interpretation of cavity response under a seismic pseudo-static action. [ABSTRACT FROM AUTHOR]

Abstract A high-fill slope located in Zhenxiong County, Yunnan Province, China, was designed for building placement on its top platform. A reinforcement system consisting of a geogrid, front stability piles (FSPs), retaining sheets, prestressed anchors, and rear deeply buried piles (DBPs) has been used to stabilize the slope. Two typical slope sections were selected to study the high-fill slope stability and retaining mechanism of the reinforcement system. Field measurements of the horizontal displacement and strain in the piles, as well as the anchor working load, were collected and analyzed. In addition, a series of two-dimensional finite element method (FEM) analyses combined with a strength reduction technique was conducted to analyze two selected cross sections. The results show that the retaining structure behavior is closely related to the fill construction process of a high-fill slope. The deflection of the stabilizing pile increases almost linearly with the filling height in the initial stage of fill construction. The variation in the working load of the prestressed anchor shows an offset between prestress loss and increasing fill pressure. The FEM results can provide insight into the pile-soil interaction mechanism and its contribution to fill slope stabilization. The FSPs shift the sliding surface from through the slope toe to through the top of the FSPs. The anchors can reduce the bending moment by supplying additional bearing points. The DBPs can share a portion of the sliding thrust and effectively enhance the safety factor. This paper provides a reference for reinforcement system design for similar engineering projects considering high-fill slopes. Highlights • A case of reinforcement and monitoring for a high-fill slope is presented. • The reinforcement system includes two rows of piles, retaining sheets and anchors. • The behavior of the reinforcement system is investigated through field measurements. • The reinforcement mechanism is analyzed by FEM combined with monitoring. • This study provides a reference for the design of similar high-fill slopes. [ABSTRACT FROM AUTHOR]

Abstract A drainage layer can easily cause clogging during rainfall, and a retained seeper may cause a strong uplifted-floating effect on the overlying soil layer, thereby inducing serious disasters. This paper proposes two failure modes (i.e., direct-slip failure and uplifted-floating failure) that may be encountered simultaneously by the cover soil layer of landfills. Corresponding analytical models and computing methods are established. Results demonstrate that both failure modes can potentially occur on the cover system but exhibit different performance levels. The immersion ratio (λ) of the drainage layer is an important factor influencing the safety factor (FS) of both failure modes. By increasing the λ-value , the Fs-values of both failure modes decrease evidently, but the decrease rates are vastly different. Moreover, the effects of other parameters such as slope length and slope angle on the FS of the two failure modes are also discussed in this study. Results indicate that these parameters exhibit different effect degrees on the occurrence of the two failure modes. Finally, the Fs-values of the direct-slip failure calculated in this study are compared with the results of others', and indicated that the reliability of this study is high. The results of this study can optimize the design parameters of the landfill final cover system and render its stability evaluation more accurate. Highlights • Uplifted-floating failure may be encountered by the cover soil layer when the drainage layer was water-logged. • Combining the two failure models can make the stability evaluation of landfill cover system more accurate and comprehensive. • The parameters including L, β, h, c, φ, c 0 and δ all influence the Fs-values of both failure modes to different extents. [ABSTRACT FROM AUTHOR]

Previous determinations of the optimal stabilizing pile location have generally been based on the idealized assumption of arc-shaped sliding surfaces. This assumption, however, may be inconsistent with the actual situation of most common irregular shapes, such as the step shape; as a result, determinations based on this assumption tend to involve considerable error. This paper presents a strategy, termed the local safety partitioning (LSP) methodology, for accurately determining optimal pile locations for step-shaped configurations. Instead of assuming the sliding surface to be arc-shaped, this strategy considers the actual sliding shapes. A new index termed the local safety factor is introduced for measuring the stabilities of local landslide masses, and this method employs the Swedish slice method to calculate the value of the index. The LSP methodology consists of four procedures: slicing the landslide mass into blocks, calculating the local safety factor of each sliced block, dividing the landslide mass into local partitions based on the previous step, and identifying the optimum pile position using previously identified partitions. The performance of the presented methodology is illustrated using the Jinle No. 2 landslide case for well-rounded demonstration and using the Yancun landslide case for additional validation. The results indicate that analysis of a reinforced landslide employing the LSP methodology acquires the largest safety factor and smallest deflection, shear force and bending moment on the pile body compared with any other case from a series of positions that incorporate traditional positions for arc-shaped sliding surfaces. The presented methodology provides a simple but accurate determination of the optimal stabilizing pile location for stepped sliding surfaces, although it may involve errors and unexpected limitations when applied to arc shapes and peculiar scenarios. [ABSTRACT FROM AUTHOR]

Assessing the influence of the impact pressure exerted on surrounding rock mass by potential debris flows is one of the challenges in a mountain tunnel construction project. This paper proposes an effective mathematical model for the assessment of impact pressure exerted by debris flows on obstacles. The characteristics of the new model are analyzed, and the parameters determination method for the new model are deduced. Also, a new method for dynamic reliability analysis of the rock mass surrounding tunnels is proposed and is constituted into three key steps. First, by inputting impact pressure of debris flows generated by the aforementioned new model, the FLAC3D is used as the dynamic analysis engine to obtain the time-varying stress distribution of surrounding rock mass during the impact of debris flow. Second, the factor of safety (FOS) contours of surrounding rock mass are generated based on element states using the maximum tensile stress criterion and the Mohr-Coulomb yield criterion. Third, by using the time-varying contours of the FOS, a failure probability and a reliability index are obtained from a reliability perspective. A case study shows the complete analysis process and confirms the effectiveness of the above methodology. In sum, this paper provides new ideas, new methods, and a reference example for evaluating the influence of dynamic impact exerted by debris flows on the rock mass surrounding tunnels. • A novel mathematical model is proposed for the assessment of impact pressure exerted by debris flows on obstacles. • A new method is proposed for dynamic reliability analysis of the rock mass surrounding tunnels. • The instantaneous factor of safety (FOS) of each element of the rock mass surrounding tunnels is applied based on the maximum tensile stress criterion and the Mohr-Coulomb yield criterion. • The failure probability and the reliability index of the rock mass surrounding tunnels are obtained based on space-time-varied stress fields. [ABSTRACT FROM AUTHOR]

Pore pressure changes play a major role in the stability of natural slopes, whose safety factor value is usually much smaller than that generally accepted in any other geotechnical problem. Correct assessment of potential seasonal pore pressure distributions is therefore a crucial issue in slope stability analysis. Based on long-term monitoring of some natural slopes, this paper compares the pore pressure distribution recorded in saturated fine-grained deposits and in shallow unsaturated granular covers, both monitored in southern Italy. In spite of the expected differences, the soils display some common features. In particular, from December to mid-May (wet period) in all examined cases the pore water pressures are quite constant over a monthly scale. Thus an essentially steady-state pore pressure condition establishes. It is in this phase, which is characterised by an essentially downward flux, that the safety factor drops to its lowest yearly value. Finally, a simplified method is adopted to model the steady-state pore pressure during the wet period and to calculate the average rain infiltration in equilibrium with the steady-state condition; the results thereby obtained are compared with the findings of an advanced approach, based on the hydrological balance. [ABSTRACT FROM AUTHOR]

Based on the Spencer's method, this paper presents a simplified approach to assess the stability of three-dimensional (3D) asymmetrical slopes. The approach allows for satisfaction of the force equilibrium in all three directions and the moment equilibrium about two co-ordinate axes. A unique direction of sliding is involved here to calculate the factor of safety. The direction of sliding (DOS) is always parallel to the plane of symmetry for symmetrical slopes. However, the DOS in asymmetrical slopes could deviate from the symmetrical plane and affect the stability assessments. Through two simple asymmetrical examples, the calculated results demonstrate that the deviation of the sliding from the symmetry could destabilize the slopes and cause failures. Neglecting the DOS in 3D asymmetrical slopes will overestimate their stability. Application of the presented approach into complex asymmetrical problems is straightforward. [ABSTRACT FROM AUTHOR]

Due to a limited number of boreholes commonly available in geotechnical practice, the subsurface strata interpreted from borehole data unavoidably contain uncertainty, which can affect the subsequent geotechnical analysis, such as slope stability analysis. This paper proposes an integrated framework to quantify the stratigraphic boundary uncertainty (SBU) from limited borehole data and to investigate its effect on slope stability analysis. The fundamental principles and detail steps of the proposed framework are explained for the SBU quantification and simulation and the subsequent SBU-based slope stability analysis. The framework is illustrated and validated by real data from a real estate project site and a slope site from literature. Then, the effect of borehole number on SBU and slope stability analysis are examined using the framework. Results show that the mean value of factor of safety (FS) of the slope approaches gradually to the real FS value with the increase of borehole number, while the standard deviation of FS decreases as the number of boreholes increases. • Stratigraphic boundary uncertainty (SBU) is quantified by an integrated framework. • The proposed framework is illustrated by data from two real project sites. • Effects of borehole number and location on SBU and slope analysis are examined. • Statistics of factor of safety converge gradually as increasing the borehole number. • A quantitative guideline is proposed to optimize additional boreholes locations. [ABSTRACT FROM AUTHOR]

Energy piles provide clean energy in lieu of non-renewable energy resources such as petroleum and coal. The current geotechnical design of energy piles is merely realized through enlarging the factor of safety. The factor of safety used for energy piles is at least twice that used for traditional piles, which can lead to considerable additional costs and inconsistent levels of safety. Although the performance of existing energy pile technology is satisfactory and recent investigators have significantly advanced the understanding of the load-transfer mechanisms of energy piles, it is still necessary to quantify the uncertainty in the thermal–mechanical analysis and to develop reliability-based designs for energy piles. This paper presents a pioneering probabilistic study on the geotechnical design of energy piles. The critical soil parameters for ultimate limit state (ULS) and serviceability limit state (SLS) are identified through sensitivity study. The point estimate method is adopted to understand the uncertainty propagation and to estimate the probability of ULS failure and the probability of SLS failure. The adverse effects of thermal loading in the geotechnical design of energy piles are explicitly demonstrated through a case study. [ABSTRACT FROM AUTHOR]

Semi-empirical models used for liquefaction potential evaluation are often developed based on lumping data from different regions around the world. The accuracy of a semi-empirical model developed in such a way may vary from one region to another, which has been seldom studied previously. Thus, in this paper, a probabilistic method is suggested to characterize the inter-region variability of the model bias factor of a semi-empirical model for liquefaction potential evaluation. As an illustration, the proposed approach is used to characterize the inter-region variability of the model bias factor of the Robertson and Wride model (called RW model for short herein). It is found that substantial inter-region variability exists in the model bias factor of the RW model. For a region not in the calibration database, the uncertainty associated with the model bias factor is significantly larger than that of a region in the calibration database. For regions in the calibration database, the uncertainty associated with the model bias factor in a region also changes with the amount and the type of the calibration data available in that region. It is thus important to collect region-specific performance data for model calibration to achieve accurate liquefaction potential evaluation. For ease of practical application, equations are provided for estimating the liquefaction probability based on the factor of safety (FOS) computed with the RW model for different regions. The suggested method can also be used to characterize the inter-region variability of other semi-empirical models and to derive region-specific relationships between FOS and liquefaction probability for these models. [ABSTRACT FROM AUTHOR]

Using the movability analysis in block theory, one can easily determine all movable blocks. However, only for a movable block with no more than two structural surfaces, called the statically determinate block, can the factor of safety be determined by the static analysis, which limits more extensive application of key block theory. In order to analyze general movable blocks with multiple structural planes, an optimization model for solving the safety factor of blocks is built in this paper. In the model, the safety factor as well as the normal stress on the slip surface is taken as independent variables; and the objective function is specified as the safety factor alone. The statically admissible conditions include the system of equilibrium equations, non-negativity of both normal stress on the slip surface and thrust inside the block. Since the objective function is linear and the constraint functions are polynomials of no more than degree-2, it is weak in nonlinearity and can be solved by those conventional optimization techniques, and disadvantages of the conventional block theory are overcome. After some typical examples are tested, the stability of the left bank rock slope of Jinping-I Hydropower Station is conducted in detail, and the stability evolution due to excavation is systematically studied by this method. [ABSTRACT FROM AUTHOR]

Rainfall is among the most relevant triggering factors of landslides. With the aim of defining a model of the influence of rainfall on deep landslides, this paper presents data of a long-term monitoring of pore water pressures in a clayey earthflow, and the results of many field permeability tests carried out with several procedures. Pore water pressures are being monitored in the Costa della Gaveta slope since 2005. In the last years, new instruments have been installed and permeability tests have been carried out in the stable formation, in the landslide body and in the slip zone. The hydraulic conductivities of the three different zones of the subsoil have been evaluated by two types of field tests: falling head tests (by Casagrande piezometers and test wells), and localized constant head tests (by a permeameter ad hoc designed). The experimental data show that: a) pore water pressures along the slip zone respond to rain more than in the landslide body and in the stable formation, even at about 25 m depth; b) the hydraulic conductivity k sz of the slip zone is much higher than that of the landslide body, k l , in turn higher than the hydraulic conductivity of the stable formation, k f. The numerical 3D modelling of steady-state reference conditions and of transient processes caused by the historical rainfall series shows that the occurrence of k sz higher than k l and k f determines an overall drainage effect which makes the global limit equilibrium safety factor SF greater than that evaluable for other possible conditions. On the other side, even the lowest measured hydraulic conductivity k sz provides seasonal rain effects on water pressures along the slip surface such to determine significant SF variations in phase with the observed seasonal displacement rates. • Pore water pressures along the slip zone of a clayey earthflow respond to rain more than in the landslide body and in the stable formation. • The hydraulic conductivity k sz of the slip zone is much higher than those of the landslide body and of the stable formation. • High k sz causes an overall drainage effect and seasonal changes in pore water pressures along the slip zone influencing SF and displacement rates. [ABSTRACT FROM AUTHOR]

In geological engineering, the unsaturation and non-uniformity of soil have significant influence on slope stability. However, they were common neglected in published literature. Based on the three-dimensional (3D) rotational failure mechanism, this paper introduces a method that combines the gravity increase method and the upper bound theorem, to evaluate the factor of safety (FS) of 3D stepped slope in non-uniform and unsaturated soils. The soil cohesion increases linearly with depth, and three nonlinear unsaturated shear strength models are adopted in this study. After the calculations of internal energy dissipation rate and external work rate, the analytical formula of FS is derived, and the lowest FS value is obtained through optimization. To prove the validity of the proposed method, the present results are compared with previously published solutions. A parametric study is carried out, and the influences of a number of factors on FS are discussed. For non-uniform and unsaturated soils, the new formula for calculating the FS of 3D two-stage slopes is presented for practical use in geological engineering. • New formula for calculating the FS of 3D two-stage slopes is derived. • GIM is introduced to evaluate FS of 3D stepped slopes in inhomogeneous and unsaturated soils. • Validity of the analytical solutions obtained in this study is verified. [ABSTRACT FROM AUTHOR]

Capturing the failure mechanisms responsible for static liquefaction is a challenging task for the zoning of landslide susceptibility. While geomechanical models accounting for solid-fluid coupling can identify locations prone to flowslides, their performance in regional settings is impacted by the lack of procedures to replicate accurately stratigraphic heterogeneities. To mitigate this inconvenience, this paper discusses the performance of a spatially-distributed model aimed at capturing distinct landslide triggering mechanisms in layered deposits. The model relies on the simultaneous computation of multiple factors of safety associated with the triggering of frictional slips and liquefaction-induced flowslides. In addition, the spatiotemporal variation of such indices is retrieved from a vectorized finite element platform solving pore pressure transients in stratified unsaturated soils. Such features enable the model to take into account the vertical heterogeneity of individual slope units, while dramatically reducing the computational cost of regional-scale analyses. For illustrative purposes, the model is used to analyze a series of documented shallow landslides that occurred in Campania (Italy) following heavy rainstorms. A comparison of model predictions with and without stratigraphic heterogeneity is provided, showing that the incorporation of site heterogeneity leads to a substantial improvement of the model's spatiotemporal performance, as well as of its ability to identify different modes of failure. Furthermore, the model is applied to four municipalities across the region of interest, each characterized by different representative stratigraphic settings. Despite some mismatches, often linked to the scarcity of site-specific information, the numerical results obtained on the basis of the available dataset shows that the proposed methodology is a robust and effective tool for landslide susceptibility mapping in stratified deposits. • Coexistence of frictional slips and liquefaction induced flowslides can be captured at regional scale. • The vertical heterogeneity of soil deposits was considered in shallow landslide hazard assessment. • Use of stratigraphic data leads to substantial improvements of the spatiotemporal model performance. • Application of the model to multiple sites with different stratigraphic conditions led to satisfactory results. [ABSTRACT FROM AUTHOR]

The importance of the geological model in a geotechnical engineering project has long been recognized. However, the uncertainty associated with the geological model has rarely been quantified and explicitly considered in the geotechnical design. This paper explores the role of the geological model uncertainty and the benefit of reducing such uncertainty in a geotechnical design. To this end, the landslide that occurred on 25 April 2010 at 3.3 K of Freeway No. 3 in Northern Taiwan, referred to herein as NH-3 Slope, is re-analyzed with an assumed geological model (a dip-slope model in this case) under various uncertainty scenarios. Traditionally, the design (i.e., a choice of design parameters such as slope height, slope angle, and supporting anchors) of a rock slope seeks to satisfy a target factor of safety (FS). In the case of NH-3 Slope, the apparent dip angle of the slip surface along the dip direction of slope constitutes the geological model of concern. Different survey techniques produce data with varying degrees of error (or uncertainty) in the measured apparent dip angle. For example, data from a Regional Geological Map (RGM) typically yields an estimate of the bedding plane attitude with a significant level of uncertainty due primarily to low data density. In contrast, LiDAR can significantly reduce the uncertainty of the derived bedding plane attitudes. By lowering this uncertainty, the variation (or uncertainty) in the computed FS may be reduced, which tends to yield a lower failure probability (P f), given other conditions being the same. The benefit of lowering the geological model uncertainty in a geotechnical design is demonstrated through a retrospective analysis of the NH-3 Slope. • We explored the role of geological uncertainty on a dip slope failure in Taiwan. • We treated bedding attitudes as the main geological uncertainty in the stability analysis. • We found the use of LiDAR can lower the uncertainty of derived bedding attitudes. • We demonstrated the engineering benefit of reducing geological uncertainty. [ABSTRACT FROM AUTHOR]

This paper presents an update of the Hyperbolic Function (HBF) method to evaluate the liquefaction potential of sandy soils. The HBF method was created after the 1999 Chi-Chi, Taiwan Earthquake (M w = 7.6) using the database of case histories developed based on field observations and in situ and laboratory tests in areas affected by the 1999 event. The updated HBF method reported herein reflects the 20-year efforts of research and practice in Taiwan after the 1999 event. Here, the original database created by Hwang and his co-workers was first re-examined and updated. The updated Chi-Chi database was supplemented with the cases derived from the 2016 Meinong, Taiwan Earthquake, and some selected data from other parts of the world. This new database was then used to update the parameters of the HBF model through rigorous statistical methods. The HBF model is unbiased (as it corresponds to a probability of 50%). The updated HBF method, a deterministic model, is further extended into a probabilistic version through rigorous statistical calibration. This probabilistic version is expressed as a mapping function that relates the factor of safety (F S) against liquefaction to the probability of liquefaction (P L). The design recommendation for engineering practice in Taiwan is provided based on the calibrated P L - FS mapping function. The updated HBF method is demonstrated through examples to be an easy-to-use procedure for liquefaction potential evaluation. Use of Bayes' theorem for updating the liquefaction probability and the new concept of liquefaction likelihood ratio are also discussed. • An updated database of liquefaction and non-liquefaction cases from Taiwan is created. • An easy-to-use HBF model for liquefaction evaluation is presented, which emerged from two decades of research in Taiwan. • Procedures for the calibration of empirical models for liquefaction evaluation are introduced and illustrated. • The concept of the liquefaction likelihood ratio (LR) is presented with a graph of LR contour curves for Bayesian updating. [ABSTRACT FROM AUTHOR]

This paper details development of a numerical modelling approach that has been employed to forecast the long-term performance of a cut slope formed in high plasticity clay. It links hydrological and mechanical behaviour in a coupled saturated and unsaturated model. This is used to investigate the influence of combined dissipation of excavation-generated excess pore water pressures and seasonal weather-driven near-surface cyclic pore water pressures. Deterioration of slope performance is defined in terms of both slope deformations (i.e. service) and factor of safety against shear failure (i.e. safety). Uniquely, the modelling approach has been validated using 16 years of measured pore water pressure data from multiple locations in a London Clay cut slope. Slope deterioration was shown to be a function of both construction-induced pore water pressure dissipation and seasonal weather-driven pore water pressure cycles. These lead to both transient and permanent changes in factor of safety due to effective stress variation and mobilisation of post-peak strength reduction over time, respectively, ultimately causing shallow first-time progressive failure. It is demonstrated that this long-term (90 year) deterioration in slope performance is governed by the hydrological processes in the weathered near surface soil zone that forms following slope excavation. • A numerical modelling approach has been developed to forecast long-term deterioration of cut slopes • Prolonged wet periods and elevated pore pressure trigger larger seasonal ratcheting movements • The ratcheting mechanism causes a shallow softening zone which can trigger slope failure • The developed approach can be used to forecast the deterioration of infrastructure cut slopes. [ABSTRACT FROM AUTHOR]

The allowable safety factors of slope stability for rockfill dams in Chinese design codes are defined irrespective of dam heights and are mainly based on the engineering experiences with respect to the rockfill dams which are lower than 200 m. It is well known that safety margins for different structures are not comparable when safety factors are taken as the measure of safety margin. Thus whether the current allowable safety factors are applicable to the rockfill dams with heights of over 200 m has been controversial in the engineering and academic field. Reliability is well known as a unified measure of safety margin for different structures. Therefore, the slope safety margins of rockfill dams with different heights can be compared in terms of slope reliability indices derived from probabilistic methods. Based on the statistical analysis of nonlinear shear strength parameters of rockfills from 14 Chinese dams, the slope reliabilities of fictitious rockfill dams of different heights designed with equal allowable safety factor are calculated and compared in this paper. It is shown that the slope failure risk of higher dams is larger than that of lower dams if the dams are designed with equal allowable safety factor rather than equal reliability. Therefore, from the perspective of maintaining consistent slope reliability levels among rockfill dams with different heights, the allowable safety factors should be prescribed in terms of dam height, i.e. the allowable safety factor for higher dams should be larger than that for lower dams. • Slope stability analysis of high rockfill dams using fixed allowable safety factor may induce misleading assessment. • Safety margins for rockfill dams designed with fixed allowable safety factor are not identical in terms of reliability. • The allowable safety factors should be prescribed in terms of dam height. [ABSTRACT FROM AUTHOR]

• Use of multi-stage triaxial tests to investigate the post-cyclic behaviour of liquefied sand. • Derivation of instability curves for assessment of post-cyclic deformation of liquefied sloping grounds. • Demonstration of use of instability curves through real case study of post-liquefaction failure of Lower San Fernando Dam. The paper presents a simplified approach to determine the post-cyclic deformation of liquefied sloping grounds. The approach uses instability curves derived from undrained multi-stage (cyclic + monotonic) triaxial tests. It is shown that the salient aspects of the post-liquefaction deformation can be expressed as a function of the state parameter ψ , defined as the void ratio difference between the current state of the soil and its critical state at the same mean stress level, and amplitude of accumulated cyclic strain. As the proposed approach predicts deformations, rather than residual strength or factor of safety, the method can be used for the definition of the performance criteria following a performance-based design approach. The application of the proposed method is illustrated through a real case study. [ABSTRACT FROM AUTHOR]

• DSDM is proposed to analyze the stability of jointed rock slopes by coupling SRM. • A statistics-based criterion for terminating the DEM iterative process was proposed. • A statistics-based criterion for determining the FOS of a rock slope was proposed. • A high-steep bedding rock slope was analyzed using the proposed DSDM method. • Numerical simulation results were consistent with actual field observations. The stability of jointed rock slopes can be effectively analyzed using the discrete element method (DEM). However, the criteria for terminating the DEM iterative calculation process and determining the factor of safety (FOS) are not well defined. In this paper, a displacement-statistics-based discrete element modeling method (DSDM) is proposed to analyze the stability of jointed rock slopes by coupling with the shear strength reduction method (SRM). In the presented DSDM, two important criteria are defined: (1) a statistics-based criterion for terminating the iterative calculation process of the DEM modeling in the stability analysis of jointed rock slopes, and (2) a statistics-based criterion for determining the FOS of a jointed rock slope when coupling DEM and SRM. The novelty of the proposed DSDM is that statistical information of the global displacements around the potential slip surface of the jointed slope, rather than the local displacements of several characteristic points, are utilized to define the criteria for terminating the DEM iterative calculation process and determining the FOS. To verify the effectiveness of the proposed DSDM, the FOS of a simplified jointed rock slope is first calculated using the proposed DSDM, and then compared with the FOS obtained using the finite difference method (FDM). Moreover, the proposed DSDM is applied to analyze the stability of a real high-steep bedding rock slope. The numerical simulation results for the real rock slope are consistent with the in-situ observations. The proposed DSDM is thus capable of effectively analyzing the stability of jointed slopes with potential slip surfaces. [ABSTRACT FROM AUTHOR]

• Two theoretical models for block-flexure toppling failure were proposed. • Detailed damage information of the joints during block-flexure was studied. • Effects of cross joint spacing on block-flexure were discussed. Block-flexure toppling failure is frequently encountered in rock slopes. In this paper, we first proposed two theoretical models to calculate the factor of safety against block-flexure toppling, namely, step by step analysis model (LEM-SSAM) and overall analysis model (LEM-OAM). Then, we developed two special MATLAB codes for a quick stability estimation based on the proposed methods, respectively. Next, the universal distinct element code (UDEC) was used to study the failure mechanisms of block-flexure toppling. In order to realistically simulate the excavation of slope and obtain the detailed damage information of joints, we developed two FISH functions in UDEC. Finally, we conducted a comparative analysis of the limit equilibrium method and the numerical simulations through twelve theoretical models. The results show that many aspects of block-flexure toppling failure have been captured using UDEC combined with the developed FISH functions. The LEM-OAM and UDEC agree well while a larger factor of safety is obtained using the LEM-SSAM. It is found that the dip angles and friction angles of the joints dipping steeply into face have a great influence on block-flexure toppling failure while the influence of the cross joint spacing is less significant. [ABSTRACT FROM AUTHOR]

Slope failure or landslide is a common and severe geo-hazard which may cause significant casualties and economic losses. Casualties and economic losses caused by soil slope failure are often determined by volume of sliding soil mass and influence zone during post-failure process. It is therefore of great importance to study both slope failure probability and post-failure behavior. Estimation of failure probability has attracted much research attention, but assessment of post-failure behavior, especially the influence zone, is relatively rare. This probably dues to the difficulty in simulating the whole process of slope failure (e.g., initiation of the slope failure, transportation and final deposition of the sliding mass). For example, the factor of safety and critical slip surface obtained from the commonly-used limit equilibrium method only correspond to initiation of the slope failure; while finite element/difference methods may suffer from grid distortion problems when simulating large soil deformation that occurs during slope failure. To properly assess the post-failure behavior of soil slopes, this paper proposed a Monte Carlo simulation (MCS) based method, called random smoothed particle hydrodynamics (RSPH), in which random field theory is used together with a particle-based mesh-free numerical method, called smoothed particle hydrodynamics (SPH). The proposed approach is able to simulate the whole process of soil slope failure and provide reasonable estimations of failure probability, influence zone and volume of sliding mass during post-failure process. • A Monte Carlo simulation based method is proposed for probabilistic analysis of post-failure behavior of soil slopes. • The whole process of a soil slope failure is simulated. • Both failure probability and post-failure behavior of slopes are quantified. • Effects of the definition of slope failure on failure probability are discussed. [ABSTRACT FROM AUTHOR]

Bi-planar failure is the commonest type of failure in steep and high footwall slopes. This paper presents an investigation of the bi-planar failure mechanism and a stability analysis model for footwall slopes based on the study of eleven diabase mines in Hunyuan County, Shanxi Province, China. First, a detailed investigation of the site and tests were carried out to obtain a geological model and calculation parameters for the slope. Then, the failure process in footwall slopes was investigated by a trigon approach performed using the Universal Distinct Element Code (UDEC) software package. A mechanism was then obtained for bi-planar compression–shear failure by combining the results obtained for the stress, displacement, and crack development. Subsequently, based on the limit equilibrium and frictional plasticity theories, a new columnar mechanical model was proposed for bi-planar footwall slope failure. The results demonstrate that the UDEC trigon approach was well suited to simulating bi-planar failure in steep and high footwall slopes. Employing this approach, a sliding failure surface that initiates, develops, and propagates in the discontinuity and intact rock could be correctly captured and the evolution of the damage in the toe of the slope could be quantitatively investigated. The results also indicate that shear failure first occurs at persistent discontinuities and then compression–shear failure occurs in the intact rocks. In addition, the failure surface of the rock emanates from the toe of the slope, is oriented upwards at an angle to the persistent discontinuity thus forming the through sliding surface (this angle can be determined using frictional plasticity theory). The critical heights and safety factors of footwall slopes could be readily obtained by employing this new columnar mechanical model giving results that are consistent with the results of numerical simulations. Furthermore, the results of a parameter-sensitivity analysis show that the dip angle of the toe breakout surface increases as the slope angle increases. However, the angle between the toe breakout and internal shear surfaces remains unchanged as the slope angle increases. Moreover, the critical height of the footwall slope decreases linearly as the slope angle increases. The method proposed provides theoretical guidance for the stability analysis of steep and high footwall slopes. The results produced should also help engineers to gain a better understanding of the mechanisms of bi-planar failure in such rock slopes. • Geological model of footwall slope is summarized based on the study of eleven diabase mines. • Detailed process of bi-planar failure is captured using UDEC trigon approach. • A new columnar mechanical model is proposed for bi-planar failure. • Critical height of footwall slope can be determined using the columnar model. [ABSTRACT FROM AUTHOR]

Seismic slope stability assessments in active fault zones are very important prior to designing and constructing large engineering structures. However, in most previous regional-scale analyses, ground motion records are either used directly or replaced by empirical regression equations. In this paper, we present an improved regional seismic slope stability assessment method considering the vertical slope aspect and ground motion. Based on limit equilibrium models and finite element models, best fit equations are obtained to calculate the sliding angle and factor of safety (FOS). Then, a two-stage integration process is applied to obtain the permanent displacement. The new model has been tested in the Chenghai active fault zone, China, under a seismic precautionary intensity of 9, and the results of the new model are compared with those of traditional infinite slope models. The results show that ignoring the vertical ground motion and slope aspect leads to underestimation of co-seismic landslide hazards on regional scales, and the new model provides a more accurate index to evaluate co-seismic slope behaviours in large areas. • A more accurate model considers the vertical ground motion and slope aspect. • New regression equations to calculate sliding angle and FOS are generated. • The ignorance of these two factors underrates the co-seismic landslide hazard. • The dominant sliding direction is determined by two horizontal ground motions. [ABSTRACT FROM AUTHOR]

Effective and efficient liquefaction hazard assessment is critical in making disaster mitigation plans for urban regions. In this paper, we present a numerical-simulation (NS)-based method for assessing urban-wide liquefaction hazard. The method includes an automatic modelling for individual sites and an application of high-performance computing (HPC) for efficient assessment. The feasibility of the method is demonstrated by conducting simulations for more than 10,000 individual sites in an urban region. The urban-wide assessment results depend on a pressure threshold of liquefaction occurrence and the dependence increases as the ground motion increases. A comparison with a conventional method using engineering indices (EI) shows a tendency of the EI-based method to predict a considerably greater number of liquefied sites than the proposed method. With the continuing improvement on numerical simulations and on computer efficiency, NS-based assessments can be regarded as promising alternatives to conventional EI-based methods for urban-wide liquefaction assessment. • For assessing urban-wide liquefaction hazard, a method based on a numerical simulation enhanced with HPC is proposed. • More than 10,000 sites in an urban region were assessed for liquefaction hazard, by applying the proposed method. • The urban-wide assessment depends on a pressure threshold, and the dependence increases as the ground motion increases. • A conventional method using Factor of Safety determined a much greater number of liquefied sites than the proposed method. • The prediction from the conventional method may indicate its tendency of overestimation of the liquefaction occurrence. [ABSTRACT FROM AUTHOR]