Rock Slope Analysis Research Articles

Three-dimensional upper-bound analysis of rock slopes subjected to seepage forces based on Hoek-Brown failure criterion

Three-dimensional upper-bound analysis of rock slopes subjected to seepage flows is a classical problem in geotechnical engineering. However, it is difficult to obtain a rigorous upper-bound solution of the safety factor of slopes when seepage flows are involved. In order to address this problem, the three-dimensional (3D) hydraulic head distributions inside a slope under steady state hydraulic conditions are solved numerically. The obtained numerical hydraulic head distributions are further employed to compute the seepage forces applying to the 3D discretized rotational failure mechanism to assess the stability of a rock slope. The Hoek-Brown yield criterion is employed to characterize the failure of rock masses. The generalized tangential technique is employed to formulate the problem as a classical optimization problem. The particle swarm optimization algorithm combined with the Nelder-Mead simplex algorithm is used to search for the best solutions of slope safety factor. The proposed approach is validated by comparing with 2D plane strain analysis results in the literature. Parametric analysis shows that the safety factor increases as mi or GSI increases, but decreases with the increase of the slope angle β and B/H. It is also found that the 3D influence is significant for B/H smaller than 10, beyond which it becomes negligible. The computational results in the form of design tables are presented for practical use in rock engineering.

Dynamic analysis of anti-dip bedding rock slopes reinforced by pre-stressed cables using discrete element method

Pre-stressed cables were found to be a viable approach of reinforcing anti-dip bedding rock slopes (ABRSs) in the Wenchuan earthquake. However, the dynamic response law and failure mechanism of reinforced ABRSs are still unclear, which was studied using the Universal Distinct Element Code (UDEC) method in this work. A numerical model of a typical ABRS was first built up using UDEC. Then, a comparison of the dynamic response of reinforced and unreinforced ABRSs was carried out. Moreover, a systematic parameter study was performed to investigate the effect of cable inclination, cable spacing, and pre-stressed force on the reinforcement effect. The results show that pre-stressed cables can be very effective in controlling the deformation and improving the dynamic stability of ABRSs subjected to dynamic loading. For both unreinforced and reinforced ABRSs, a remarkable acceleration amplification occurs on the surface of the slope from half of the slope height upwards. A small cable inclination and a high pre-stressed force are recommended in the seismic reinforcement design of ABRSs. The results of this work could guide the design of reinforcement of ABRS in earthquake-prone areas.

Key techniques for the analysis and evaluation of high rock slopes

Key techniques for the analysis and evaluation of high rock slopes

Rockfall Analyses at Km 13+550 in the New Road of Vlora, Albania

Rockfall dynamics is a complex function of the location of the detachment point and the geometry and mechanical properties of both the block and the slope. Theoretically, knowing the initial conditions, the slope geometry, and the relationships describing the energy loss at impact or by rolling, it should be possible to compute the position and velocity of a block at any time. Nevertheless, relevant parameters are difficult to ascertain both in space and time, even for an observed event. Usually, the geometrical and geomechanically properties of the blocks (size, shape, strength, fracturing) and the slope (gradient, length and roughness, longitudinal and transversal concavities and convexities, grain size distribution, elastic moduli, water content, etc.), and the exact location of the source areas are unknown. In this paper, the sources of potential rock fallings involve a rocky area including between km 13+550 and km 13+600 in the new road of Vlora city in Albania. The area is characterized by a rock ridge, shaped like a dome, located few tens of meters above the design road. The purpose of this paper is the rock slope analysis. This analysis consists mainly of defining the sources of falling rocks, estimating the causes (by toppling, rock slides, single blocks) the size, the geometry, and type of blocks, the structural arrangement of joints, etc.

Flexural Toppling Mechanism and Stability Analysis of an Anti-dip Rock Slope

The occurrence and failure mechanisms of flexural toppling must be considered by researchers and engineers who perform stability analysis of anti-dip rock slope. Taking the Linda landslide near the Le'an Hydropower station in Southwest China as the prototype, this paper carried out physical model tests to study the characteristics and process of flexural toppling failure. The results are used to obtain the characteristics and mechanical mechanism of flexural toppling and the zoning of the slope. On the basis of the physical model testing, an equation to calculate the stability coefficient under flexural toppling is established using the limit equilibrium method and cantilever beam theory, and the most dangerous potential sliding surface is identified. Finally, sensitivity analysis of the geometric parameters is conducted to discuss their influence on the slope stability and the sliding surface location.

Deformation and failure response characteristics and stability analysis of bedding rock slope after underground adverse slope mining

When mining under bedding rock slopes, bedding landslides are prone to occur. This paper takes the mining-induced bedding rock landslide as the research area. Using a similar simulation experiment method, the effects of underground adverse slope mining disturbance on deformation, failure, and landslide of bedding rock slope were analyzed. The results show that under the influence of underground mining, the physical models exhibited a cantilever-fracture failure mode. Moreover, the deformation, failure, and landslide of the model were basically the same as the prototype landslide, which was a bedding rock landslide of initial traction type and later pushing type. On this basis, the phenomenon and the coefficient of weakening were defined. The stability of mining-influenced bedding rock slopes was studied by the limit equilibrium method. The outcomes indicate that the fractured block was stable after mining. The fractured block B first slid and came into contact with the fractured block A. The interacting pressure caused the fractured block B to push the fractured block A, and the fractured block A locked the fractured block B. Under the sliding extrusion of the fractured block B, the weakening coefficient of the fractured block A quickly weakened until the fractured block A slid. The fractured block B subsequently slipped after losing the resistance slide of the fractured block A. This successive slip process between the fractured blocks A and B obtained through the stability analysis is consistent with similar simulation experiments.

Finite Element Analysis Method of Slope Stability based on Fuzzy Statistics

In order to reduce the risk of slope stability evaluation due to the fuzziness of calculation parameters, a finite element analysis method of slope stability based on fuzzy statistics is proposed. Based on the principle of quasi-static method and with the help of the finite element software COMSOL multiphysics, this paper studies the stability of the gravel soil accumulation rock slope under the action of different seismic acceleration. By analyzing the displacement, plastic zone and safety factor of the rock soil slope, the stability of the rock soil slope is analyzed. The research results show that the fuzziness of mechanical parameters of rock and soil slope will lead to the fuzziness of position displacement and stress analysis results of rock and soil slope, and the analysis of rock and soil slope with the method of fuzzy finite element analysis can strengthen the comprehensive understanding of position displacement, stress and safety of rock and soil slope by engineers and technicians, and reduce the stability of rock and soil slope due to the fuzziness of calculation parameters to a certain extent Evaluate the risk qualitatively.

Development of Improved Semi-Automated Processing Algorithms for the Creation of Rockfall Databases

While terrestrial laser scanning and photogrammetry provide high quality point cloud data that can be used for rock slope monitoring, their increased use has overwhelmed current data analysis methodologies. Accordingly, point cloud processing workflows have previously been developed to automate many processes, including point cloud alignment, generation of change maps and clustering. However, for more specialized rock slope analyses (e.g., generating a rockfall database), the creation of more specialized processing routines and algorithms is necessary. More specialized algorithms include the reconstruction of rockfall volumes from clusters and points and automatic classification of those volumes are both processing steps required to automate the generation of a rockfall database. We propose a workflow that can automate all steps of the point cloud processing workflow. In this study, we detail adaptions to commonly used algorithms for rockfall monitoring use cases, such as Multiscale Model to Model Cloud Comparison (M3C2). This workflow details the entire processing pipeline for rockfall database generation using terrestrial laser scanning.

Stability analysis of anti-dip bedding rock slopes using a limit equilibrium model combined with bi-directional evolutionary structural optimization (BESO) method

Anti-dip bedding rock slope (ABRS) is a very common type of rock slopes in nature and engineering construction. However, the stability assessment of ABRSs is still a hard problem for geotechnical engineers due to the difficulty in finding the critical failure surface. In this work, a new method called LEM-BESO was proposed to tackle this problem based on limit equilibrium theory and bi-directional evolutionary structural optimization method. Two model tests reported in previous studies were employed to verify the correctness of the LEM-BESO method. Moreover, a comparative study of the LEM-BESO method and the genetic algorithm was also conducted. The highly consistent results demonstrate that using the LEM-BESO method can accurately predict the failure surface of the slope. Then, the LEM-BESO method was extended to study the influence of two key parameters (i.e. friction angle of the joints and tensile strength of the rock layers) on the failure mechanism of anti-dip bedding rock slopes. The results show that these two parameters have a significant influence on the stability of the slope. However, the failure surface is insensitive to the tensile strength of the rock layers. The LEM-BESO method provides an effective means for the stability evaluation and engineering design of ABRSs.

Psuedo static stability analysis of rock slope using patton\u2019s shear criterion

A deterministic model for the factor of safety of an idealized rock mass for planar mode of failure is developed adopting Limit Equilibrium Method (LEM) using Patton’s shear strength criterion and considering practically occurring conditions such as the effect of tension crack, water filled up in tension crack, horizontal and vertical seismic acceleration, rock bolt stabilizing force and surcharge. In the Pseudo-static analysis horizontal seismic acceleration is taken outward from the slope and vertical seismic acceleration is considered in both the direction i.e. towards the direction of gravity (downward) and opposite to the direction of gravity (upward). An expression of normal stresses as limiting criterion has been derived in order to compare the field normal stresses along the failure surface. A detailed parametric study has been presented to investigate the influence of vertical seismic coefficient for both the direction on the stability of rock slope using developed expression. For high normal stress along the failure plane, it is observed that the factor of safety decreases with increase in the value of vertical seismic coefficient towards the direction of gravity and increases linearly with increase in the value of vertical seismic coefficient against the direction of gravity and the opposite trend has been found for lower normal stress. The vertical seismic coefficient against the direction of gravity has predominant effect on factor of safety of rock slope as the rate of increase/decrease of factor of safety with vertical seismic coefficient is more against the direction of gravity. Hence in determining the critical factor of safety, effect of vertical seismic coefficient against the direction of gravity should be considered.

Application of Extension Theory Based on Improved Entropy Weight Method to Rock Slope Analysis in Cold Regions

In view of the problems existing in the evaluation process of slope stability in cold regions, the improved entropy weight method and extension theory are used to evaluate the slope stability. Nine indexes which affect the slope stability in cold regions are selected, the matter element system of slope stability evaluation is established by extension theory, and the extension correlation degree between evaluation index and evaluation grade is calculated. The improved entropy weight method is used to calculate the entropy weight of the matter element index system, and then the stability grade of the slope matter element is determined. Based on the extension theory and improved entropy weight method, the slope stability of Beizhan open pit mine is predicted. The results show that the prediction results are consistent with the actual situation of the project, and the evaluation method can be applied to the slope stability evaluation in cold regions. By using extension theory and improved entropy weight method, the evaluation index can be changed from a single determined value to an interval value, and the influence degree of the evaluation index can be analyzed more comprehensively. This method improves the evaluation accuracy and provides a new method for the slope stability evaluation in cold regions.

Rock Slope Stability Assessment Along Rawanduz Main Road, Kurdistan Region

The rock slope instability along the Khalifan-Bekhal-Rawanduz main road has been studied in the southwestern limb of the Bradost anticline (Mountain) and both northeastern and southwestern limb of the Korek anticline (Mountain) in the northeast of the Erbil city, Kurdistan Region, Iraq. The major factors of the instability of the rock slopes in the study area are types of discontinuous and the degree of erosion. Ten stations have been chosen for fieldwork. The expected failure types that may occur along the road are plane sliding and wedge sliding. This research is mainly focused on the type of failure along the rock slope and the factor that affect the instability of the studied slopes and have found that they are slope orientation and geometry of the discontinuity. Different remediation methods are proposed for the studied rock slopes base on rock slope analysis. The rock slopes along the road require continuous monitoring because of their hazard conditions.

A four-way enhanced numerical manifold method for crack propagation and failure analysis of rock slopes

A four-way enhanced numerical manifold method (NMM) is proposed in order to simulate crack propagation in rock media and progressive failure of jointed rock slopes. Specifically, the original NMM is improved in the following four aspects: (1) An “enriched local approximation” is employed to characterize singularity and discontinuity of the displacement/stress fields near the crack tip. (2) A “modified generalized Duffy transformation” is proposed to improve the accuracy of numerical integration associated with the 1/r and 1/r singularities. (3) A “critical length cracking criterion” is introduced to determine propagation length and direction for both tensile-shear and compressive-shear cracks in rock mass. (4) A “cone-complementary-based contact formulation” is incorporated to resolve the cohesive/frictional contact phenomena between discontinuous interfaces more accurately. Some examples demonstrate the performance and application prospect of the presented NMM in stability and failure analysis of the jointed rock slopes.

Stability analysis of rock slope along selected road sections from Gutane Migiru town to Fincha sugar factory, Oromiya, Ethiopia

The slope instability was one of the common problems along the road that connects Gutane Migiru town to Fincha sugar factory, Western Ethiopia. The effect of the problem was intense mostly; during the rainy season, that triggers different modes of rock slope failure. As a result, the road was frequently damaged and blocked by the failed rock that in turn hinders the traffic activities. Thus, this study aimed at stability analyses of the critical slope sections using kinematic and limit equilibrium methods (LEM). The estimation of the most important input parameter in LEM analyses like cohesion and friction angle along the failure plane is often intricate and cumbersome. Hence, this paper used Rocscience software to effortlessly and instantly compute cohesion and friction angle along specific failure planes and then to carry out kinematic and LEM analyses. Besides, the strength of the intact rock was determined by the Schmidt hammer in the field and point load laboratory test. According to the kinematic analysis result, the wedge mode of rock slope failure occurred at slope sections D1S2 and D1S3 though the planar mode of failure occurred at slope sections D1S4 and D4S1. The factor of safety determined under all anticipated conditions became less than and greater than one at slope sections D1S2, D1S3, D1S4, and D4S1, and this depicts an unstable and stable slope, respectively. From the analysis result, the combined effect of rainfall, steepness of the slope dip, and joint set was the main factors that caused the slope insatiability.

Modeling of Shear Crack Propagation in Rock Masses Using Mesh‐Free LRPIM

The modeling of shear cracks in materials is critical in various engineering applications, such as the safety analysis of concrete structures and stability analysis of rock slopes. Based on the idea of Goodman element, the elastic‐plastic constitutive model of the shear cracks is derived, and the elastic‐plastic analysis of shear crack propagation is realized in the local radial basis point interpolation method (LRPIM). This method avoids the loss of accuracy caused by the mesh in the analysis of fracture propagation, and the crack propagation of rock brittle material is simulated. The investigation indicates that (1) the LRPIM results are close to the FDM results, which demonstrates that it is feasible to analyze shear cracks in rock masses. (2) Compared with the results of the built‐in oblique crack model, when the LRPIM is used to analyze crack propagation, the results are close to the experimental results, showing that the LRPIM can model shear crack propagation in a rock mass. (3) The propagation path using the LRPIM is not sufficiently smooth, which can be explained as the crack tip stress and strain not being sufficiently accurate and still requiring further improvement.

Stability analysis of rock slopes using strength reduction adaptive finite element limit analysis

The main aim of this study is to propose an effective approach to conduct the stability analysis of rock slopes. Based on the strength reduction technology, the recent developed adaptive finite element limit analysis is adopted to investigate the stability of rock slopes for the first time. The rock mass strength is described by the latest generalized Hoek-Brown failure criterion. To better estimate the rock slope stability, the rock mass disturbance D and slope angle B are also incorporated into the determination of factor of safety by implementing the disturbance weighting factor s and the slope angle weighting factor fB, respectively. The factors of safety obtained from this study are validated by those from existing works based on two real slope cases. For practical use, the factors of safety for the cases of B=45o in undisturbed rock masses are provided in the form of design charts. Finally, a set of design charts for s and a fitting formula for fB are presented and discussed.

A method for seismic stability analysis of jointed rock slopes using Barton-Bandis failure criterion

Earthquakes are the main cause of slope failure in seismic active regions. In this study, we present a method for analyzing the seismic stability of a plane jointed rock slope with two blocks. In this analysis, the Barton-Bandis failure criterion is applied, considering the nonlinear characteristics of rock joints. Based on the limit equilibrium principle, we derived the safety factor of a jointed rock slope subjected to the modified pseudo-dynamic seismic forces. In addition, the analytical method developed in this study explains the interaction force between two blocks. Hence, it can effectively analyze the stability of a jointed rock slope and distinguish the failure modes. Further, a parametric study was conducted to investigate the effects of geometric and material properties on the safety factor of a hypothetical slope. The results show that the slope stability is significantly influenced by the geometry of the slope and the parameters including the joint roughness coefficient JRC, the horizontal seismic acceleration coefficient kh, the joint compressive strength JCS, and the basic friction angle of the structural plane ϕb. Moreover, the accuracy of the derivation is verified by the universal distinct element code UDEC 6.0. A parametric sensitivity analysis is used to determine the key parameters affecting slope stability. Finally, a set of seismic stability design charts is produced for preliminary design.

A stability analysis of rock slopes using a nonlinear strength reduction numerical manifold method

To investigate rock slope stability, a nonlinear strength-reduction numerical manifold method (NSRNMM) using a generalized Hoek-Brown (GHB) criterion is proposed. As it is difficult to implement the nonlinear strength reduction method (NSRM) with the use of the GHB criterion by directly reducing the GHB parameters, two equivalent Mohr-Coulomb (MC) criteria, namely, the instantaneous and average equivalent MC criteria that are derived from the GHB criterion, are adopted in the NSRNMM. The implementation details of the NSRNMM are discussed. The stability of two rock slopes, namely, a rock slope with a GHB material and a rock slope with a GHB material and two MC materials, is investigated using the NSRNMM. The numerical results indicate that 1) the proposed NSRNMM using the instantaneous equivalent MC criterion can accurately calculate the safety factor (Fs) of rock slopes and that 2) the Fs predicted with the NSRNMM using the average equivalent MC criterion is more conservative than that using the instantaneous equivalent MC criterion.

Study on the unloading damage constitutive model of sandstone based on hydro-pressure cycle

The periodic rise and fall of reservoir water level under hydro-pressure cycle leads to the deterioration of physical and mechanical properties of rock and seriously triggers the instability of the reservoir slope. From the laboratory data and characteristics of the stress–strain curve under different hydraulic cycles, combined with the generalized Hooke’s law, the Weibull distribution theory, and the Hoek–Brown strength criterion, the energy dissipation in the unloading process is assumed as the damage variable, and the unloading damage constitutive model of saturated sandstone under hydro-pressure cycle is established. Under hydro-pressure cycle, the parameters m and F of the constitutive model are gradually decreasing, and the sandstone brittleness and macroscopic strength are gradually weakened. In addition, the scattered energy increases, while plastic deformation slowly plays a dominant role. The comparative analysis shows that the constitutive model fits well with the experimental curves. The damage constitutive equation can be expressed under hydro-pressure cycle. This research can help in the stability analysis of rock slope under the reservoir water in the field.

Rock slope reliability analysis using Barton-Bandis failure criterion with modified pseudo-dynamic approach

A modified pseudo-dynamic approach was used for a reliability-based stability analysis of plane failure rock slopes. The Barton-Bandis nonlinear failure criterion and the limit equilibrium principle were adopted to account for the nonlinear characteristics of rock joint shear strength and safety factor of slope, respectively. The Monte Carlo simulation method was used to analyze the rock slopes. Comparisons of the present method to a numerical simulation and to a pseudo-static case, were implemented. The influence of different parameters and tension cracks on slope stability was analyzed. Results showed that the stability of the rock slope decreases with increasing rock unit weight, horizontal seismic coefficients and vertical seismic coefficients, and increases with increasing residual friction angle, joint roughness coefficient and joint compressive strength. The location of the tension crack has significant influence on the stability of rock slopes, while the influence of inclination of the tension crack is negligible.