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A novel and robust slope stability evaluation method based on energy method and radial slices method (RSM) is proposed and validated in terms of strength parameter sensitivity and determination of the critical sliding surface. The sensitivity analysis shows that the deviation from the limit equilibrium method (LEM) does not exceed 1.5%, demonstrating the feasibility of the proposed method. Different from LEM, the proposed framework gets functional enhancements: (1) This method considers the failure mode of the slope as a combination of translation and rotation, which is more in line with the actual monitoring results; (2) if the virtual displacement is regarded as a variable, the effect of accumulated displacement on slope stability can be studied; (3) if the factor of safety (FOS) for the slope is less than 1, this method can be extended to analyze movement of landslide mass after instability using the energy balance. Then, the proposed framework is applied to the 1963 Vajont event and Xinhua event to analyze the slope stability at the changes of reservoir water level and the dynamics after instability. Comparing slopes with different deformation patterns in calculating stability, the paper finds that permeability is the key to understanding the deformation response and summarizes the failure mechanism. For 1963 Vajont landslide, the proposed framework calculates the maximum velocity of the intermediate section to be 21.51 m/s, which is in general agreement with the inference by Hendron and Patton (Eng Geol 24:475–491, 1987), and superior to Zaniboni and Tinti (Nat Hazards 70:567–592, 2014)'s calculation of less than 20 m/s. Through research and application, the superiority of the proposed framework in analyzing slope hazards is shown. [ABSTRACT FROM AUTHOR]

A calculation of the safety factor is the basis of slope stability analysis. The three‐dimensional (3D) limit equilibrium method is one of the most effective safety calculation methods, and ignoring the partial shear force between columns is the most common calculation assumption, which will lead to an unreasonable safety factor. By constraining the range of the intercolumn shear function and the position of the action point of the force between columns and integrating machine learning to optimize the net moment of the column, the simulated annealing algorithm is used to obtain the intercolumn shear function under the minimum net moment, and the safety factor is calculated by using boundary conditions. Finally, proving the accuracy of this method by calculating two examples of commonly used slopes. Example A verifies that the result of the proposed method is more conservative than that of other 3D calculation methods and that the coordinates of the action point of the intercolumn forces in the x and y directions have little influence on safety factor. Example B verifies the applicability of this method to various slope forms. This method fully considers the stress of soil under actual conditions, making the calculation results more reasonable. [ABSTRACT FROM AUTHOR]

On 10th October and 3rd November 2018, two landslides and the consecutive twice blockage of the Jinsha River led to sharp fluctuations of the upstream water level. These two events have caused numerous bank failures along the Ouqu River in the upper reaches. In this paper, a numerical model coupling the seepage and stability analyses was established, which was able to capture the fundamental behavior of geomaterials in both saturated/unsaturated conditions. Numerical results show that fluctuations of water level, permeability and shearing strength of the deposit were the key factors that had great influences on the seepage field and slope stability. The slope remained stable when the water level was rising since the water force acted as a back pressure. There was a critical rising level for the positive effect of rising water level, after which the variation of safety factor tended to be minimal. Differences in permeability determined the temporal saturated zone, whose properties consisted of not only the strength reduction due to the loss of suction in the zone affected by fluctuations, but also the instinct strength characteristics between different layers. Furthermore, permeability of the upper two layers had apparent adverse influences on the safety factor of slope. [ABSTRACT FROM AUTHOR]

Landslides are serious natural disasters frequently occurring in the mountainous areas along the Sichuan–Tibet railway. Landslides are often induced by rainfall and greatly threaten people's lives and property. Via the use of GIS technology, a probabilistic analysis model was proposed for rainfall-induced shallow landslides along the above route. The process of the proposed probabilistic analysis model could be divided into three parts: (i) an infiltration hydrogeological model, (ii) a slope stability model, and (iii) probabilistic analysis. In this model, soil cohesion and internal friction angle were regarded as random parameters. The Green–Ampt model was used to dynamically describe the soil infiltration process during rainfall. Combined with the infinite slope stability model, the failure probability in the study area was analyzed. The model was applied to simulate the Bayi catchment landslide event of August 18, 2010, to evaluate its reliability. Through comparison of the simulation results to landslide occurrence locations, it was determined that the model achieves a satisfactory prediction performance. In addition, compared to deterministic analysis methods and the r.slope model, the proposed probabilistic analysis model achieved a satisfactory evaluation performance. The presented physics-based probabilistic analysis model could provide important theoretical support for hazard prevention in regard to rainfall-induced shallow landslides in mountainous areas. [ABSTRACT FROM AUTHOR]

Occurrence of a reservoir landslide and its potential secondary hazards near a dam can result in significant losses and casualties, such as those that resulted from the Vajont landslide. In this study, a cataclinal rock slope in the Maoergai reservoir was taken as a case to study the characteristics of the gravitational deformation process and to analyse the potential threat. The stability of the rock slope was analysed using the limit equilibrium method, and the potential landslide movement and subsequent waves were simulated. Results indicated that lithology, geological structure, reservoir water-level changes and artificial activities all play an important role in large deformations of rock slopes that are characterized by a combination of bending–toppling and, principally, shear slip. Pre-calculations of potential threats indicated that the impact of a landslide wave would be greater at dead water levels than at the normal water level and could result in the blockage of the inlet to the water-diversion structure on the opposite right bank. These findings provide implications for the control of reservoir rock slopes: (i) serious attention should be paid to the influence of water on rock strength in the early investigation of geological disasters; and (ii) infiltration must be prevented during water-level rise. Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes [ABSTRACT FROM AUTHOR]

The Xinhua slope of Dagangshan Reservoir is taken as an example to study the potential for reservoir landslides under the combined effects of rainfall and water level fluctuations. Through field investigation, monitoring analysis by global navigation satellite system and numerical simulation, the hydraulic response and stability of the accumulated deposits on the Xinhua slope were evaluated. Three occurrences of large deformations were recorded by real-time monitoring. By comparing the deformation records with the hydrological records, it was found that the first one was caused by water storage, and the last two were due to the coupling effect of rainfall and water level drawdown. Deformation of the reservoir overburden cannot simply be thought of as the sliding of a single block (geology survey showed deep sliding surfaces with depths of 50–70 m), but shallow sliding (less than 5 m) is also much likely to occur revealed by a supporting evidence from deformation records. In cases where hydrostatic pressure and transient osmotic forces are favorable for shear resistance, softening may play a major role in the process of impoundment leading to deformation. The deformation pattern of the slope deposits changes as it enters operation. A drawdown of water level during flood season accelerates the deformation, while a following rise of water level inhibits this acceleration. More extensive monitoring (i.e. pore water pressure sensor and inclinometer) and more in-depth analysis are needed in the future, and this article is a synthesis of limit equilibrium and infinite slope analysis to better understand the deformation patterns and response mechanisms of reservoir accumulation. [ABSTRACT FROM AUTHOR]

Local topography and structural features of discontinuities have a great effect on the movement characteristics and failure mechanisms of the unstable rock blocks of the rock slope. By taking full advantage of the geometric information contained in the multi-temporal terrestrial laser scanning (TLS) point clouds, a technique based on a roto-translation method has been developed to track and monitor the movement behavior of blocks in unstable rock slopes. The technique can be completed in three stages: (a) a preliminary change detection is used to distinguish the unstable area by means of a shortest distance (SD) algorithm; (b) an automatic discontinuity identification algorithm is implemented to visually identify the discontinuity sets and to exactly delineate rock blocks in unstable areas; and (c) finally a roto-translation movement monitoring method is applied to track and monitor the unstable rock blocks. This technique permits the user to visually identify the discontinuity sets and to determine their orientation, and therefore provides detailed information of geometric compounding relationships between the slope and joint systems as well as the forming rock blocks which are the key impacts to stability of the rock slope. It permits the user to exactly and visually delineate the rock blocks in the unstable area, and thus the completely tracking and monitoring of lock block movement in unstable rock slopes can be effectively conducted. It overcomes the limited precision of the single TLS points and provides an actual 3D movement measuring method for the blocks rather than a shortest distance. The technique was first used in the movement behavior monitoring of the unstable rock blocks in a post-earthquake high rock slope. The results show that the rock block movement monitoring technique is well suited for providing high-quality data in the assessment of rock failure hazards. [ABSTRACT FROM AUTHOR]

A slope stability analysis method using the finite element method and the limit equilibrium principle is presented in this paper to determine the critical slip surface and to calculate the minimum safety factor based on the stress field produced by a numerical simulation. This method assumes a cutting export and makes good use of geometric combination to reduce the search range during the calculation process. The proposed method was validated using two classical benchmark slopes and an engineering slope; it was also compared with other conventional limit equilibrium methods. The error between the proposed method and the limit equilibrium method was relatively small. The proposed method resolved several limitations of the traditional methods, and a comparison of the benchmark slopes showed that the proposed method exhibited good accuracy and efficiency. The proposed method can thus analyse both the stability of a natural slope and the stability of a soil slope under seismic loading conditions. [ABSTRACT FROM AUTHOR]

Using a combination of close-range photogrammetry and three-dimensional (3-D) limit equilibrium theory, a determination method for the shear strength parameters of rock-soil mixture is presented. A close-range photogrammetry method is used for measurement of the 3-D terrain of the experimental target. AutoCAD Lisp and EXCEL VBA are used to perform 3-D limit equilibrium analysis of the stability of sliding mass and perform backanalysis of shear strength parameters. The presented method was used to determine the shear strength parameters of rock-soil mixtures at the Liyuan Hydropower Station. The 3-D terrain of sliding surface could be measured notably well using of closerange photogrammetry. The computed results reveal that the cohesion and friction angle of rock-soil mixtures were 3.15 kPa and 29.88° for test A, respectively, and 4.43 kPa and 28.30° for test B, respectively, within the range of shear strength parameters, as determined by field and laboratory tests. The computation of shear strength parameters is influenced by the mesh grid number, especially the cohesion of the rock-soil mixture. The application of close-range photogrammetry can reduce the site works and improve the computational efficiency and accuracy. [ABSTRACT FROM AUTHOR]

Abstract: On 28 October 1996, a landslide occurred on the Huashiban slope near the Liangjiaren Hydropower Station. The landslide was caused by a failure mechanism induced by an earthquake (Mw 7.0) at Lijiang on 3 February 1996, after which a tensile fracture zone formed on the Huashiban slope. The subsequent impact of several small earthquakes on the slope increased the tension crack connectivity and the tensile strength gradually decreased. Severe rainfall in the rainy season between May and October, especially in July and August, decreased the shear strength of the bottom sliding surface, resulting in a landslide on the Huashiban slope on 28 October 1996. The stability of the Huashiban slope is important for plant site selection. If a further landslide occurs on the slope, the Liangjiaren Hydropower Station project will be critically affected, so analysis of the current slope stability is extremely important. At present, the Huashiban slope can be divided into five subzones: (1) a landslide deposit zone; (2) a landslide zone; (3) a tensile fracture zone; (4) a crescent-shaped zone; and (5) an upper slide zone. Using historic landslide data for 28 October 1996, retrospective analysis of the landslide process revealed shear strength parameters for the Huashiban slope. The cohesion strength is 0.024MPa, the friction angle at the bottom sliding surface is 14°, and the tension crack connectivity is 50%. These parameters were used to compute the stability of the Huashiban slope. Under the same conditions, the stability of the whole slope is better than that of part of the slope, and the overall stability is dominated by the tensile fracture zone. Under earthquake and rainfall conditions, it is possible that failure will occur in the tensile fracture zone. Thus, the Huashiban slope should be reinforced for construction and operation of the Liangjiaren Hydropower Station. [Copyright &y& Elsevier]

With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional slopes under fluctuating water conditions. Based on soil parameter variations in engineering practice, the calculation models were established using heterogeneous layers, including a cover layer with inferior properties. An analysis of seepage, deformation and slope stability was carried out with 27 different models, including three different slope gradients and nine different corner angles under five different hydraulic conditions. The failure mechanism has been shown to be closely related to the change in matric suction of unsaturated soils and the geometric slope configuration. Finally, the effect of geometry (surface shape, turning corner and slope gradient) and water (fluctuations) on slope stability are discussed in detail. Emphasis is given to comparing safety factors obtained considering or ignoring matric suction. [ABSTRACT FROM AUTHOR]

A new derivation of the three-dimensional (3D) limit equilibrium method for slope stability analyses is presented, which applies linear algebra operations to matrices to achieve a highly efficient algorithm while maintaining the rigorousness of the formulation. It satisfies six equilibrium conditions and includes all of the components of the intercolumnar forces. The generalized 3D Morgenstern-Price's (MP) assumption for the intercolumn forces is recast into incremental forms. The advantage is that the unknowns of the different physical meanings (i.e., factor of safety (FS) and the coefficients in the MP assumption) are determined by balancing the forces and moments independently. Along with the recasting correction coefficients, they are solved with the triple nested algorithm. The numerical instability that is related to the different orders of magnitude for the residuals is avoided. The varication examples show: (i) the insensitivity of the FS to the prescribed functions in the MP assumption, (ii) the reliability of the method to cope with a complicated slope geometry (simplified methods may provide a larger FS for certain cases), and (iii) the superior efficiency of the algorithm (requires several seconds to converge). This study proposes a practical way to track the irregular 3D tension cracking by repeating the analysis and excluding the columns with the negative normal forces at the bottom. This formulation is applied to a valley landfill slope in China. In comparison to the two-dimensional analysis, there are more reasonable/cost-effective measures to increase the system stability through 3D analyses for several conditions (e.g., seismic loading). • A new three-dimensional method is devised by concise linear algebra operations. • It considers 6 equilibrium conditions and all intercolumnar force components. • Triple nested algorithm achieves a high-efficiency and a good convergence. • Factor of safety is insensitive to the intercolumn force distribution function. • A practical way is proposed to track highly irregular tension cracking surface. [ABSTRACT FROM AUTHOR]