Rock Slope Stability Analysis Research Articles

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.

Evaluating the Use of Unmanned Aerial Systems (UAS) for Collecting Discontinuity Orientation Data for Rock Slope Stability Analysis

Evaluating the Use of Unmanned Aerial Systems (UAS) for Collecting Discontinuity Orientation Data for Rock Slope Stability Analysis

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.

Analysis of rock slope stability under rainfall conditions considering the water-induced weakening of rock

This study provided a feasible approach for more accurate analysis of rock slope stability under rainfall infiltration. To quantitatively analyse the influence of rainfall on slope stability, we attributed the influence of rainfall on slope stability to the change in pore pressure and the decrease in rock strength due to the effects of water-induced weakening. The variation law of the mechanical behaviour of rock under the effects of water was studied by performing mechanical tests of rock specimens with different water contents. Based on this variation law, functions were established for the water-induced weakening of rock. Based on the theory of unsaturated seepage, functions for simulating the rock slope under the influence of rainfall were established. Two engineering cases were presented to demonstrate the application of the simulation method. The results proved that the proposed simulation method can accurately reflect the changes in the mechanical behaviour and stress-strain distributions of the rock mass in a rock slope under rainfall conditions.

Retracted: Stability analysis of blocky structure system using discontinuity layout optimization

AbstractThe collapse mechanism identification and limit load calculation of block composite structures are essential tasks in practical engineering. In this work, the discontinuity layout optimization (DLO) is utilized to simulate a stable blocky system structure under static and pseudostatic loading by considering soil–structure interaction effects. The program refers to the discretization of the system under consideration by utilizing the potential slip lines to connect nodes. Then, linear programming is applied to identify the critical layout. The DLO procedure is extended to mimic rotations in the approximate simulation of rotational and translational failures along boundaries, thus simulating the mechanism on the rotating block. The simulated failure mechanism and collapse load are consistent with the experimental observations and numerical modeling results. Furthermore, the procedure is applied to two potential practical applications: the stability analysis of a jointed rock slope and concrete masonry retaining wall. The results show that the DLO is a simple but scientific method for identifying the mechanism of the critical failure of blocky structures.

Application of Photogrammetric Technique in Determination of Rock Slope Stability of Quarry

Identify the characterization and orientation of the discontinuities such as joint, bedding and fault is a requirement in rock slope stability analysis because discontinuities control the type of failure. Until today, geologist still practices the classical method to determine the dip and strike of discontinuities which is by using Brunton compass at the field. It is difficult to measure at the inaccessible area, dangerous when having physical contact with the steep, fractured slope and time consuming to cover a large area are limitations of this method. A recent development in remote sensing has introduced Terrestrial Laser Scanner (TLS) as an indirect method in mapping the rock slopes by using the point cloud data. TLS allows for extremely rapid acquisition of large amounts of 3D coordinates of objects’ surfaces, with high precision measurement. The aim of this paper is to apply Terrestrial Laser Scanner (TLS) in determine the dip and strikes of the joints and compare the value with the hand measurement at a granite quarry in Ulu Choh, Johor. Analysis of the data shows the TLS method able to obtain the data for the joints and show almost the same trend. Thus, TLS is an efficient technology in geological practice.

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.

Stability Charts for Pseudostatic Stability Analysis of Rock Slopes Using the Nonlinear Hoek–Brown Strength Reduction Technique

This paper presents a set of stability charts for the stability assessment of rock slopes that satisfy the Hoek–Brown (HB) criterion under various seismic loading conditions. The nonlinear Hoek–Brown strength reduction technique is used to conduct pseudostatic stability analysis of rock slopes subjected to horizontal seismic excitation. Based on an extensive parametric study, first, a set of stability charts with a slope angle of β = 45° under static and pseudostatic conditions are proposed by using ABAQUS 6.10 software. Second, the slope angle weighting factor (fβ) and the seismic weighting factor (fkh) are adopted to characterize the influence of slope angle (β) and horizontal seismic acceleration coefficient (kh) on the rock slope stability. Finally, the reliability of the proposed charts was validated by three typical examples and two case studies, and the results show that the values of the factor of safety (FOS) obtained from the proposed charts are consistent with the values from other methods. The proposed charts provide an efficient and convenient way to determine the FOS of rock slopes directly from the rock mass properties (γ and σci), the HB parameters (mi and GSI), the slope geometry (H and β), and the horizontal seismic coefficients (kh).

A Preliminary Assessment of Rock Slope Stability in Tropical Climates: A Case Study at Lafarge Quarry, Perak, Malaysia

The stability analysis of rock slopes is a complex task for the geotechnical engineers due to the complex nature of the rock mass in a tropical climate that often has discontinuities in several forms, and consequently, in several types of slope failures. In this work, a rock mass classification scheme is followed in a tropical environment using the Rock Mass Rating (RMR) and Geological Strength Index (GSI) combined with the kinematic investigation using the Rocscience Software Dips 6.0. The Lafarge quarry is divided into ten windows. In the RMR system, the five parameters uniaxial compressive strength (UCS), rock quality designation (RQD), discontinuity spacing, discontinuity condition, and groundwater conditions are investigated. The RMR values range from 51 to 70 (fair to good rock mass), and the GSI values range from 62 to 65 (good to fair rock mass). There is a good and positive correlation between RMR and GSI. The kinematic analysis reveals that window A is prone to critical toppling, window H to critical wedge-planar failure, and window G to critical wedge failure. From the results obtained, it can be concluded that the kinematic analysis combined with the rock mass classification system provides a better understanding to analyze the rock slope stability in a tropical climate compared with considering the rock mass classification system individually.

Stability analysis and design charts for over-dip rock slope against bi-planar sliding

Bi-planar sliding is one of the main instabilities in over dip rock slope. The geometry and strength of the bi-planar sliding surface comprised of two sets of cross-discontinuities play an important role in slope stability assessment. However, few studies had been conducted to systematically investigate the influences of them. In this study, three categories of failure modes related to the failure region, namely, the shallow, intermediate and deep, are proposed. Corrected Implicit Transfer Coefficient Method (CITCM) with the modified sliding surface is proposed as an alternative to the Limited Equilibrium Method (LEM) for calculating the slope factor of safety (Fos). The change patterns of slope stability are derived from the Fos values calculated via CITCM considering different scenarios of geometrical and mechanical parameters of the critical bi-planar sliding surface. The equivalent slope model for the overlap rock slope under bi-planar sliding is proposed to explain slope stability change patterns reasonably. The design charts for preliminary slope stability assessment are presented in the over-dip rock against bi-planar sliding. Finally, compared with other traditional Limited Equilibrium (LE) approaches, case history engineering applications validate the proposed design charts in calculating Fos, determining the critical sliding surface, and recognizing the failure mode is more effectively.

Application of Dynamic Sarma Method to Stability Analysis of Rock Slope

In this paper, the shortcoming of Sarma method, a slop safety factor calculation method based on pseudo-static method, are improved by adding real seismic force, calculating acceleration amplification coefficient of each block by using numerical simulation and drawing the time-history of safety factor by using matlab software. The dynamic Sarma method is proposed. Through the calculation of an example, the rationality of the calculation result of slope safety factor by using dynamic Sarma method is verified.

Slope Stability Analysis Based on the Numerical Manifold Method and the Graph Theory-Case Study Evaluation

Contemporary major methods among the most common and traditional methods for soil and rock slope stability analysis are the limit equilibrium method and the strength reduction methods. Both methods are based on the limit equilibrium conditions. However, the limit equilibrium methods are limited to the stiff body assumption, while the strength reduction method has expansive calculations and simulation progresses. In this study, a search algorithm is proposed to access the critical slip surface and safety factor. The numerical manifold method, which based on existing stress, is used to analysis and obtain the stress distribution of soil and rock slopes cut by joints. Based on the stress results obtained, a graph theory is used to convert the solution of the critical slip surface to a shortest path problem, which can be directly solved by the Bellman–Ford algorithm. This method can completely remove the rigid body assumptions in the limit equilibrium method and reduce computations which existing in the strength reduction methods.

Analytical method of stability analyses of toppling rock slopes subjected to flexural toppling failure damage

The mechanism of toppling deformation and failure is important in the stability analysis of anti-dip layered rock slopes, especially in a complex hydrogeological environment. In this paper, the flexural failure model is proposed for describing the mechanical behavior of toppling rock slope using the cantilever beam theory. A method for safety evaluation, considering the action of hydrodynamic force from groundwater, is developed. This model is then applied to conduct a case study of a toppling rock slope at a hydropower station on the Lancang River. The results show that the variation of reservoir water level increases both the tensile stresses and the deflections of rock slabs, which is manifested macroscopically by flexural displacements and failure. Based on the failure surfaces, the slope can be divided into three parts: toppling zone, creep zone, and shear zone. The failure mode of toppling rock slope is a combination of shear and toppling. Under the combined action of earthquake and rapid water drawdown, the toppling rock slope is at risk of shear instability at the leading edge; hence monitoring should be strengthened and prevention measures should be taken.

Rock slope stability analysis and charts based on hybrid online sequential extreme learning machine model

The stability of rock slopes is a difficult problem in the field of geotechnical and geological engineering. Less than 20% of all landslides are predictable each year, so a simple, fast, reliable and low-cost method to predict the stability of slopes is urgently needed. This study investigates a new regularized online sequential extreme learning machine, incorporated with the variable forgetting factor (FOS-ELM), based on intelligence computation to predict the factor of safety of a rock slope (F). The Bayesian information criterion (BIC) is applied to establish seven input combinations based on the parameters of the Hoek-Brown criterion and geometrical and mechanical parameters of the slope, such as the geological strength index (GSI), disturbance factor (D), rock material constant (mi), uniaxial compressive strength (σci), unit weight of the rock mass (γ), slope height (H) and slope angle (β). Seven models are established and evaluated to determine the optimal input combination. Various statistical indicators are calculated for the prediction accuracy examination. Compared to the classical extreme learning machine (ELM) model predictions of F, the results of the applied FOS-ELM model demonstrate a better prediction accuracy and are more effective when accounting for an increase in data. The FOS-ELM model with all seven input parameters is used to establish stability charts with the influence coefficient of slope angle change (ηβ), disturbance change (ηD) and slope height change (ηH). Using stability charts with a combination of ηβ, ηD and ηH can be used to quickly and preliminarily analyze rock stability as a guide for engineering practitioners in rock slope design.

Discontinuous rock slope stability analysis under blocky structural sliding by fuzzy key-block analysis method

This study presents a fuzzy logical decision-making algorithm based on block theory to effectively determine discontinuous rock slope reliability under various wedge and planar slip scenarios. The algorithm was developed to provide rapid response operations without the need for extensive quantitative stability evaluations based on the rock slope sustainability ratio. The fuzzy key-block analysis method utilises a weighted rational decision (multi-criteria decision-making) function to prepare the ‘degree of reliability (degree of stability-instability contingency)’ for slopes as implemented through the Mathematica software package. The central and analyst core of the proposed algorithm is provided as based on discontinuity network geometrical uncertainties and hierarchical decision-making. This algorithm uses block theory principles to proceed to rock block classification, movable blocks and key-block identifications under ambiguous terms which investigates the sustainability ratio with accurate, quick and appropriate decisions especially for novice engineers in the context of discontinuous rock slope stability analysis. The method with very high precision and speed has particular matches with the existing procedures and has the potential to be utilised as a continuous decision-making system for discrete parameters and to minimise the need to apply common practises. In order to justify the algorithm, a number of discontinuous rock mass slopes were considered as examples. In addition, the SWedge, RocPlane softwares and expert assignments (25-member specialist team) were utilised for verification of the applied algorithm which led to a conclusion that the algorithm was successful in providing rational decision-making.

Stability analysis of flawed rock slope by using virtual-bond-based general particles dynamics

General particle dynamics code (GPD) with a virtual bond model is adopted to investigate the stability of rock slopes subjected to gravity. The natural discontinuities are represented by straight flaws in the numerical model. The failure process of rock samples containing three pre-existing and four pre-existing flaws subjected to uniaxial compression is simulated. The numerical failure processes of rock samples are in good agreement with the experimental observations as well as the complete stress–strain curves. Moreover, six en-echelon flaw arrays including collinear flaw array, en-echelon flaw array with bridge angle of 90°, en-echelon flaw array with bridge angle more than 90°, en-echelon flaw array with bridge angle less than 90°, multiple rows of en-echelon flaws with doubly periodic rectangular array, multiple rows of en-echelon flaws with diamond-shaped array in rock slope are studied. The crack initiation, propagation and coalescence process in rock slopes with six en-echelon flaw arrays subjected to gravity are analyzed. Two crack initiation modes including primary crack and secondary crack are found as well as nine crack coalescence modes. The stress distributions as well as displacement fields are investigated during the crack evolution. The gravity increase method is implemented into the VB-GPD to obtain the safety factor of rock slopes. The proposed method was then verified by the case study of the Xingluokeng mine in China. The results indicate a good accordance between simulation and field monitoring. This study reveals that the proposed method can tackle flawed rock slope failure problems.

Stability Analysis of Anti-dip Rock Slopes with Flexural Toppling Failure Based on Deformation Compatibility

Flexural toppling often occurs in layered rock slopes, and rock columns behave like inclined superimposed cantilever beams that bend under their own weight. However, anti-dip rock slopes always have nonuniform joint spacing, and rock columns do not have the same ability of deformation due to different stiffness. To have the same deflection, based on the mechanics of materials, the moment and shear force at the failure surface should satisfy a certain proportional relationship. An analytical model based on deformation compatibility against the flexural toppling failure has been established. In the proposed model, the slope is divided into free deflection zones and compatible deflection zones by shear forces on the failure surface. The safety factor of each block can be calculated by the bending moment, and the least factor is used to represent the safety of the slope. In addition, for an equal thickness model, the average stiffness method is suggested to determine the calculated thickness for foliated rock slopes with nonuniform joint spacing. Finally, a case study is used for practical verification of the proposed method.

Probabilistic stability and sensitivity analysis of rock slope subjected to seismic loading

Being located on the Pacific Ring of Fire, Indonesia has to cope with the constant risk of earthquakes which often trigger landslides in mountainous area, causing significant and even catastrophic damage. This paper presents probabilistic stability and sensitivity analysis of rock slope subjected to seismic loading based on Generalized Hoek-Brown failure criterion. Two approaches namely Limit Equilibrium Method (LEM) and Finite Element Method (FEM) were utilized using computer programs of Rocscience Slide and Phase2, respectively. The Generalized Hoek-Brown parameters such as, σci, GSI and mi were distributed normally with their coefficients of variation (COV) of 0.25, 0.125 and 0.1, respectively. The different seismic loadings expressed as Kh of 0.1, 0.3, and 0.5 were then subjected to the rock slopes and the probability of failure (Pf) was evaluated for each slope. Eventually, the results of Pf obtaining from LEM and FEM were compared and the most decisive parameter in slope stability were evaluated in sensitivity analysis. Based on the presented results of the analysis, the probability of failure (Pf) of the rock slopes which are subjected to the seismic loading generated by both FEM and LEM will decrease as the mean of GSI, σci, and mi increase. Moreover, the increment of the D value and seismic loading will induce the probability of failure (Pf) of the rock slopes which are generated by both FEM and LEM increase.

Rock slope stability analysis using Slope Stability Rating (SSR) method

Nupabomba village roads frequently undergo landslides, so that detain transportation access flow pattern as a result of rock slope stability problem, which has become the landslides trigger. Furthermore, to find out landslides prone area slope stability level, an analytical study using a scientific approach is required to reveal this question in the study area. The slope elevation in this area is ± 75 meters, with an average slope angle of 60°, where its lithology consists of Schist, Greenschist, Filite, and Granite. Some of these rocks have different weathering levels (e.g., slightly - high weathering), and there are lots of discontinuity. Moreover, its geological strength index (GSI) value showed around 15-75 with the surface shape of blocky and disturbed. Besides, the uniaxial compressive strength (UCS) value was obtained based on the compressive strength carried out in the field, and slope stability rating (SSR) values have gained the range of 9-81.

Characterization, Modelling and Engineering of Rocks and Rockmasses

Rocks are heterogeneous materials usually associated with geological discontinuities making them weak for sustaining the loads due to civil and mining engineering structures. Characterization details of different isotropic, anisotropic and weathered rocks are presented along with the newly formulated classification system for weathered rockmass. Physical modelling of jointed rockmass under uniaxial, biaxial and polyaxial stress state through newly designed polyaxial system yielded significant results. Critical role of intermediate principal stress on strength and deformation for jointed rockmass is highlighted. New polyaxial failure criteria are proposed and compared. New observations on brittle fracture propagation and interlocking phenomena in crystalline rocks are modelled under polyaxial stress state. Extensive large-scale test results on rock joints under constant normal load and constant normal stiffness in static and cyclic modes were presented along with new predictive models. A new closed-form analytical solution is provided for circular openings in isotropic, homogeneous and elastoplastic rockmass for assessing the wellbore stability and openings. Results of physical modelling tests conducted on shallow tunnels subjected to impact loads and new predictive models developed for squeezing behaviour are also included in this paper. Understanding gained from the extensive characterization and physical modelling of materials in appropriate stress regime used effectively to solve real-time cases. The case studies included are: stability analysis of jointed rock slopes of Chenab bridge abutments, Subansiri power house slope stability, Tindharia landslide in Darjeeling, evaluation of bored tunnelling practices in rocks for Delhi metro and coupled hydromechanical modelling for the slopes in Beas catchment.