Rock Slope Stability Research Articles

Dynamic stability of rock slopes with hexagonal discontinuity pattern

Various regular discontinuity patterns are observed in rock masses and one of the common discontinuity patterns is hexagonal pattern, which is mostly observed in all extrusive volcanic rocks such as basalt, andesite, ryholite and welded tuffs as well as in some sedimentary rocks subjected to desiccation or freezing-thawing processes. In this study, the authors investigate the dynamic stability of rock slope consisting of hexagonal blocks through model tests on shaking table. Experiments indicated that toppling or sliding failures, which may be of active or passive modes occur. Critical acceleration levels can be estimated from the limit equilibrium method with the consideration of results of frictional properties and geometry of model slopes.

Rock Slope Stability Analysis Based on Comprehensive Failure Mechanism and Engineering Application

The sliding modes of rock slopes are closely related to the strength yield criterion of the rock mass adopted in numerical analysis. In order to make theoretical calculation results meet engineering practice, particularly for complex rock slopes with multiple empty surfaces, multiple control sliding surfaces and potential sliding modes, numerical analysis method used for stability evaluation should take comprehensive failure of the rock mass into consideration. This paper proposes a stability evaluation method based on a comprehensive failure mechanism of the rock mass based on discrete element theory and a modified M-C strength yield criterion to overcome the shortcomings of traditional strength yield criteria, which are mainly derived from shear strength failure. However, the method is used to analyze deformation and failure modes of a typical rock slope in Shuang Jiang Kou Hydropower Station. The results of the findings demonstrated that the method mentioned above can describe different failure modes of rock blocks and joints, deformation trend and stable state of the slope. The experimental results are approved by geological exploring. To adapt to the yield modes of the rock block and joint, a space support system with variable angles, lengths, and design forces is chosen for this typical rock slope. This support system has been proven to be practical and can improve the stability coefficient of the slope. The results presented in this study are useful in engineering practice.

Dynamic mechanical properties and constitutive model for jointed mudstone samples subjected to cyclic loading

The dynamic properties of rocks are of great significance to the stability and safety of rock slopes and geological engineering under dynamic loads (e.g. seismic load). In this paper, triaxial cyclic tests were carried out on jointed mudstone samples with the prefabricated half-through joint, and their corresponding dynamic properties and deformation features are explored and analyzed in accordance with the hysteresis characteristics and the residual deformation forms. Moreover, based on the obtained fatigue properties under test conditions of diverse dip angles, confining pressures and dynamic stress, a dynamic stress ratio is proposed, which gives a logarithmic correlation with the fatigue life of mudstone samples. Finally, on the basis of the breakage mechanics and homogenization theory, a dynamic binary-medium constitutive model is proposed, and the validations accompanied with the comparisons to test results are also given. It shows that this model can not only preferably duplicate the typical features of hysteresis loops and the gradually accumulation of the residual strain, but also gives a good consistence with the deformation features and fatigue life obtained from cyclic tests.

Failure of Rock Slope with Heterogeneous Locked Patches: Insights from Numerical Modelling

Rock slope stability is commonly dominated by locked patches along a potential slip surface. How naturally heterogeneous locked patches of different properties affect the rock slope stability remains enigmatic. Here, we simulate a rock slope with two locked patches subjected to shear loading through a self-developed software, rock failure process analysis (RFPA). In the finite element method (FEM)-based code, the inherent heterogeneity of rock is quantified by the classic Weibull distribution, and the constitutive relationship of the meso-scale element is formulated by the statistical damage theory. The effects of mechanical and geometrical properties of the locked patches on the stability of the simulated rock slope are systematically studied. We find that the rock homogeneity modulates the failure mode of the rock slope. As the homogeneity degree is elevated, the failure of the locked patch transits from the locked patch itself to both the interfaces between the locked patched and the slide body and the bedrock, and then to the bedrock. The analysis of variance shows that length and strength of locked patch affect most shear strength and the peak shear displacement of the rock slope. Most of the rock slopes exhibit similar failure modes where the macroscopic cracks mainly concentrate on the interfaces between the locked patch and the bedrock and the slide body, respectively, and the acoustic events become intensive after one of the locked patches is damaged. The locked patches are failed sequentially, and the sequence is apparently affected by their relative positions. The numerically reproduced failure mode of the rock slope with locked patches of different geometrical and mechanical properties are consistent with the laboratory observations. We also propose a simple spring-slider model to elucidate the failure process of the rock slope with locked patches.

A temperature-dependent mechanical model to assess the stability of degrading permafrost rock slopes

Abstract. Over the last 2 decades, permafrost degradation has been observed to be a major driver of enhanced rock slope instability and associated hazards in high mountains. While the thermal regime of permafrost degradation in high mountains has been addressed in several modelling approaches, no mechanical models that thoroughly explain rock slope destabilisation controls in degrading permafrost have been developed. Meanwhile, recent laboratory studies have shown that degrading permafrost affects both, rock and ice mechanical strength parameters as well as the strength of rock–ice interfaces. This study presents a first general approach for a temperature-dependent numerical stability model that simulates the mechanical response of a warming and thawing permafrost rock slope. The proposed procedure is exemplified using a rockslide at the permafrost-affected Zugspitze summit crest. Laboratory tests on frozen and unfrozen rock joint and intact rock properties provide material parameters for discontinuum models developed with the Universal Distinct Element Code (UDEC). Geophysical and geotechnical field surveys reveal information on permafrost distribution and the fracture network. This model can demonstrate how warming decreases rock slope stability to a critical level and why thawing initiates failure. A generalised sensitivity analysis of the model with a simplified geometry and warming trajectory below 0 ∘C shows that progressive warming close to the melting point initiates instability above a critical slope angle of 50–62∘, depending on the orientation of the fracture network. The increase in displacements intensifies for warming steps closer to 0 ∘C. The simplified and generalised model can be applied to permafrost rock slopes (i) which warm above −4 ∘C, (ii) with ice-filled joints, (iii) with fractured limestone or probably most of the rock types relevant for permafrost rock slope failure, and (iv) with a wide range of slope angles (30–70∘) and orientations of the fracture network (consisting of three joint sets). Here, we present a benchmark model capable of assessing the future destabilisation of degrading permafrost rock slopes.

Artificial Neural Network (ANN) Model for Shear Strength of Soil Prediction

Geotechnical structures, design of embankment, earth and rock fill dam, tunnels, and slope stability require further attention in determining the shear strength of soil and other parameters that govern the result. The shear strength of soil commonly obtained by conducting laboratory testing such as Unconfined Compression Strength (UCS) Test and Unconsolidated Undrained (UU) Test. However, random errors and systematic errors can occur during experimental works and caused the findings imprecise. Besides, the laboratory test also consuming a lot of time and some of them are quite costly. Therefore, soft computational tools are developed to improve the accuracy of the results and time effectively when compared to conventional method. In this study, Artificial Neural Network (ANN) was employed to develop a predictive model to correlate the moisture content (MC), liquid limit (LL), plastic limit (PL), and liquidity index (LI) of cohesive soil with the undrained shear strength of soil. A total of 10 databases was developed by using MATLAB 7.0 - matrix laboratory with 318 of UCS tests and 451 of UU tests which are collected from the verified site investigation (SI) report, respectively. All the SI reports collected were conducted in Sarawak, Malaysia. The datasets were split into ratio of 3:1:1 which is 60:20:20 (training: validation: testing) with one hidden layer and eight hidden neurons. The input parameter of Liquidity index (LI) has shown the highest R-value (regression coefficient) which are 0.926 and 0.904 for UCS and UU model, respectively. In addition, the predictive models were tested and compare with the predicted and observed cohesion obtained from the collected experimental results. In summary, the ANN has the feasibility to be used as a predictive tool in estimating the shear strength of the soil.

Methodology for Resloping of Rock Slope Using 3D Models from UAV-CRP Technology

Assessing the stability of rock slopes is essential to ensuring the typical performance of adjacent transportation infrastructures but simulating the existing field topography and boundary conditions for stability analysis is challenging. This paper describes a case study in which highly weathered rock slopes adjacent to a railroad track in Texas were analyzed using close-range photogrammetry data obtained from an unmanned aerial vehicle with close-range photogrammetry (UAV-CRP). A highly weathered rock mass with low intact strength was considered as a single continuum that undergoes circular failure and was analyzed using Spencer’s two-dimensional (2D) and three-dimensional (3D) limit equilibrium method (LEM) analyses. A 3D critical slip surface was obtained to identify the critical sections on which to conduct the individual 2D stability analysis and obtain a safe resloping angle. These angles were further used to reslope the whole rock slopes and conduct a 3D analysis to arrive at a safe and economic slope angle for each side of the rock-cut. The realistic geometrical slopes developed from the aerial imagery were used to develop a framework for comprehensively analyzing the stability of a rock slope undergoing circular failure.

Study on Anisotropic Mechanical Properties and Failure Modes of Layered Rock Using Uniaxial Compression Test

Abstract To reveal the failure mechanisms and strength anisotropy of layered rock, uniaxial compression tests were conducted on dolomite samples with seven different bedding dip angles, and the compressive strength and the Young’s modulus with dip angle β were analyzed. Meanwhile, five failure modes (rock tensile cracking, rock shearing failure, bedding cracking, bedding sliding failure, and rock bending) were observed from laboratory phenomena, and the corresponding anisotropy constitutive model was further developed based on the transversely isotropic model and the plastic mechanics flow rules. Finally, the self-defined anisotropic constitutive model was coded in FLAC3D to carry out a numerical simulation of uniaxial compression. Results showed that the numerical simulation agreed well with experimental tests results, which proved that the assumption of a transversely isotropic model was reasonable. Furthermore, the proposed model could be applied to evaluate the stability of rock slopes with different bedding dip angles, and the bedding dip angle played an important role on failure modes and the stability of slope.

Stability Analysis of Rock Slope Based on Improved Principal Component Analysis Model: Taking Fuwushan Slope as an Example

Aiming at the problems of low accuracy, low efficiency, and many parameters required in the current calculation of rock slope stability, a prediction model of rock slope stability is proposed, which combines principal component analysis (PCA) and relevance vector machine (RVM). In this model, PCA is used to reduce the dimension of several influencing factors, and four independent principal component variables are selected. With the help of RVM mapping the nonlinear relationship between the safety factor of slope stability and the principal component variables, the prediction model of rock slope stability based on PCA-RVM is established. The results show that under the same sample, the maximum relative error of the PCA-RVM model is only 1.26%, the average relative error is 0.95%, and the mean square error is 0.011, which is far lower than that of the RVM model and the GEP model. By comparing the results of traditional calculation method and PCA-RVM model, it can be concluded that the PCA-RVM model has the characteristics of high prediction accuracy, small discreteness, and high reliability, which provides reference value for accurately predicting the stability of rock slope.

Effects of bedding planes on mechanical characteristics and crack evolution of rocks containing a single pre-existing flaw

The existence of bedding planes in rock materials has an obvious impact on the material mechanical properties and the failure process of engineering projects. In this study, a series of pre-cracked models with different bedding plane properties (i.e., strength reduction factor, bedding plane angle and spacing) were established and simulated to fail under the uniaxial compression. The results indicate that the increases of the strength reduction factor and the bedding plane spacing lead to the increasing peak strength, the change of peak strength regarding the bedding plane angle presents a concave upward trend. In terms of crack evolution, the proportion of cracks formed in rock matrix increases concerning the increasing strength reduction factor and bedding plane spacing, the abovementioned crack proportion in models with increasing bedding plane angles firstly decreases and then increases. The rock matrix has higher mechanical characteristics than bedding planes, the change of crack proportion can account for the changing peak strength from the microscopic viewpoint. By summarizing the failure patterns, the failure of models with the 45° ~ 75° bedding plane angle is induced by cracks formed in bedding planes, which can be depicted and discussed by the plane of weakness model. The above results imply that the rock slope stability can be evaluated by analyzing bedding plane properties in the field.

Stability evaluation of cut slopes in highly weathered schists using limit equilibrium, kinematical and empirical methods

1. Extended abstractThe traditional limit equilibrium method and the kinematic analyses are the first choices in the geotechnical practice for the assessment of the slope stability of a particular rock slope. The reason is that very few empirical methods exist for this purpose.This paper presents results of the slope stability assessment with limit equilibrium, kinematical and empirical methods for over 50 deep cut slopes in highly weathered schists along the A2 motorway section Kicevo-Ohrid in RN Macedonia. The research area is mainly composed of phyllite, sericite schists, quartz-sericite schists and graphitic schists. These rocks are highly weathered, tectonically disturbed and often folded, which means they are prone to local deformations, especially in aspects of the long-term impact of atmospheric influences and the existence of unfavourable joint sets. Although most of the failures that occurred had local character, on several cut slopes global failure occurred. The slope stability assessment of the subject rock formations is a difficult challenge because the highly weathered phyllite and schists are difficult to be characterised, considering the uncertainties associated with the material anisotropy and the network of discontinuities.This study employs different failure mechanisms of cut slope stability in complex geological media. The rock masses were modelled according to the generalized Hoek-Brown criterion while the joints behaviour was modelled using the Barton-Bandis shear strength criterion. Rocscience software package was used for executing the limit equilibrium analyses and the stability analyses along discontinuities. The relatively new and intuitive empirical method Q-slope was applied for the stability assessment of the excavated rock slopes.According to the results and the findings, it can be emphasized that although the limit equilibrium analyses showed relatively stable slopes, significant failures on several cut slopes occurred on site. The stability conditions on site were confirmed with the kinematical analyses and the Q-slope method.The final decision of the slope geometry should be made after the inspection of the excavated surfaces because it is very difficult to register the discontinuity conditions before the construction phase starts. The best way to assess the stability condition is with a combination of different tools and methodologies, especially when we face highly weathered rock formations.The next step of this research will be to propose a methodology, where the long-term rock slope stability and the associated level of risk will be evaluated using graphical diagrams.

Computational tools for the analysis of circular failure of rock slopes

Among other types of failure in slopes created by excavation or filling, circular (also referred to as rotational) type of failure plays an important role in the design and stability analysis of high rock slopes, such as those encountered in deep open pit mines. When a rock slope of significant height involves predominantly one type of jointed rock mass, the scale of the problem is frequently such that the rock mass (intact rock and rock discontinuities) can be regarded as a homogeneous isotropic material. In such case, if the rock slope is unstable and collapse occurs, circular (or rotational) failure as in failed slopes in soils is also observed for the rock slope. One main goal in practical design of deep open pit mines is to determine safe inclination angles for the pit faces to be excavated to avoid failure. Computational tools for quick assessment of the stability conditions, in particular determination of factor of safety and location of the critical circular failure surface, are useful during the preliminary stages of open pit design. Among others, such tools allow the engineer to gain insight in the role that the different variables controlling the problem have in defining the stability conditions for the rock slope. This paper provides first an overview of typical numerical techniques used to assess the stability of high rock slopes. For the case of slopes in rock masses that are assumed to obey the Mohr-Coulomb or the Hoek-Brown failure criteria, the paper discusses how application of transformation rules leads the criteria to be re-casted in dimensionless form, so when these are applied to the solution of slope problems, the results (factor of safety and coordinates that define the location of the critical circular failure surface) can be summarized in dimensionless compact forms. The paper presents then computational tools in the form of dimensionless charts and computer spreadsheets for stability analysis. These are developed from numerical limit equilibrium models that use the mentioned transformation rules. Among others, the computational tools allow the concept of mechanical similarity of rock slopes to be naturally introduced. Finally, the paper presents various rock slope examples that illustrate the use of the computational tools. In these examples, results from limit equilibrium models are also compared with results obtained with full numerical analysis, in particular with finite difference models implementing the shear strength reduction technique.

Considerations on failure mechanisms of rock slopes involving toppling

Probably, the most relevant issue in stability analysis of rock slopes is the correct identification of the potentially occurring failure mechanism, which should be mechanically analyzed to assess stability, later on. Traditional rock slope stability approaches consider planar, wedge, rotational and toppling failure as potential instability mechanisms. Whereas the three first types involve sliding associated to different geometries of the unstable element or mass, toppling often involves also sliding and very complex geometries of multiple elements. In this sense, toppling should be contemplated more like a group of mechanisms than like a simple mechanism such as planar or wedge failure. Toppling could involve moreover one or many blocks. Initial studies classified toppling failure mechanisms in three groups: block, flexural and block-flexural toppling. The stability analysis of rock slopes prone to toppling involves the mechanical analysis of individual slab like blocks, which are considered to present perfect rectangular cross-section. However, the actual shape of these rock elements may not be so regular, so the influence of more realistic irregular shapes is usually not accounted for. In this article, the author will address how some geometry variations may be included in this analysis based on analytical considerations and physical models. Additionally, failure mechanisms observed in rock cuts and open pits often combine toppling with other sliding phenomena in different more or less complex manners. These combined mechanisms involving toppling will be reviewed and some case studies worked out by the author will be presented. Moreover, all along this document, considerations will be put forward regarding the nature of toppling related phenomena where small equilibrium variations may produce a release of a large mechanical energy, which can ultimately produce the destabilization of large slopes or groups of blocks. This suggests that it is wise in these cases to analyze not only the factor of safety, but also the evolution of the potential failure mechanism to understand what is happening and eventually provide sensible and reliable designs or appropriate remedial measures.

Rock slope stability analysis adopting Eurocode 7, a limit state design approach for an open pit

In this paper we compare the partial factors approach of Eurocode 7 with a traditional deterministic limit equilibrium analysis approach and probabilistic approach. The example case is a simplistic model profile of an open pit mine cut slope configuration. The controlling parameters in a structurally dictated failure mechanism were introduced as random variables in the model, to account for the different types of uncertainties arising in rock engineering data. The limit equilibrium method was used in this study to conduct rock slope stability analysis, while the impact of naturally uncertain and variable parameters, among others water pressure and earthquake activities were considered. Different scenarios from the best to the worst-case were analysed and later compared. The sensitivity analysis revealed the importance of the joint failure plane, joint roughness coefficient and joint friction angle and how the actions (groundwater pressure and earthquake action) affect the slope’s stability. These results emphasize some advantages of the approach, and the potential further embracement from the rock engineering fraternity.

RETRACTED ARTICLE:Seismic stability of rock slope based on dynamic monitoring and efficacy analysis of psychological intervention in the treatment of depression

RETRACTED ARTICLE:Seismic stability of rock slope based on dynamic monitoring and efficacy analysis of psychological intervention in the treatment of depression

Rock Slope Stability Assessment Using Kinematic Analysis of the Limestone Quarries in Al Huson-Shatana Area, Jordan

The current study presents the first results of a kinematic analysis to investigate the type of failures in six abandoned limestone quarries in the Al-Huson-Shatana area, North Jordan. A serious problem appears in abandoned quarries. When the work in the quarry finish and the companies withdraw their equipment and workers, they leave behind unstable rock masses due to the repeated explosives. This may cause hazards in properties and civilians especially when they are close enough to residential areas. Both stereographic projection and kinematic analysis were used as tools in this study, to determine the mode and orientation of the failures. Results show that toppling, planar and wedge failures are likely to occur in all stations mainly along structural discontinuities, faults and joints. This indicates the role of structures in the rock landslides, particularly those related to planar, wedge and toppling failures. In addition, rock falls were observed in most stations that have steep slope cutting.

Probability Methods for Stability Design of Open Pit Rock Slopes: An Overview

The rock slope stability analysis can be performed using deterministic and probabilistic approaches. The deterministic analysis based on the safety concept factor uses fixed representative values for each input parameter involved without considering the variability and uncertainty of the rock mass properties. Probabilistic analysis with the calculation of probability of failure instead of the factor of safety against failure is emerging in practice. Such analyses offer a more rational approach to quantify risk by incorporating uncertainty in the input variables and evaluating the probability of the failure of a system. In rock slope engineering, uncertainty and variability involve a large scatter of geo-structural data and varied geomechanical test results. There has been extensive reliability analysis of rock slope stability in the literature, and different methods of reliability are being employed for assessment of the probability of failure and the reliability of a slope. Probabilistic approaches include Monte Carlo simulation (MCS), the point estimate method (PEM), the response surface method (RSM), first- and second-order reliability methods (FORMs and SORMs), and the first-order second-moment method (FOSM). Although these methods may be complicated, they provide a more complete definition of risk. Probabilistic slope stability analysis is an option in most commercial software; however, the use of this method is not common in practice. This paper provides an overview of the literature on some of the main probabilistic reliability-based methods available for the design of the rock slope in open pit mining. To demonstrate its applicability, the paper investigates the stability of a rock slope in an open pit mine in the Goldfields region, Western Australia. Two different approaches were adopted: deterministic stability analysis using two-dimensional limit equilibrium and finite element shear strength reduction methods using SLIDE and RS2 software, respectively, and probabilistic analysis by applying the MCS and RSM methods in the limit equilibrium method. In this example, the slope stability analysis was performed using the Spencer method with Cuckoo search optimization to locate the critical slip surface. The results obtained were compared and commented on.

A General Block Stability Analysis Algorithm for Arbitrary Block Shapes

In rock engineering, block theory is a fundamental theory that aims to analyze the finiteness, removability, and mechanical stability of convex blocks under different engineering conditions. In practice, the possible combinations of the fractures and joint sets that may generate key blocks can be identified by stereographic projection graphs of block theory. However, classic key block theory does not provide solutions for nonconvex blocks, which are very common in civil projects, such as those with underground edges, corners, and portals. To enhance the availability of block theory, a general algorithm that can analyze the removability and stability of blocks of arbitrary shapes is proposed in this paper. In the proposed algorithm, the joint pyramid for blocks of arbitrary shapes can be computed, and the faces of the blocks are grouped according to their normal vectors such that parallel or nonadjacent sliding faces with the same normal vector can be immediately identified when the sliding mode is determined. With this algorithm, blocks of arbitrary shapes can be analyzed, and users do not need to have experience interpreting graphs of block theory to take advantage of its accuracy and effectiveness. The proposed algorithm was verified by several benchmarking examples, and it was further applied to investigate the stability of the left bank rock slope of a dam. The results showed that the proposed algorithm is correct, effective, and feasible for use in the design and support of excavation in complex rock masses.

Assessment of the rock slope stability of Fushun West Open-pit Mine

Assessment of the rock slope stability of Fushun West Open-pit Mine

Investigation of rock slope stability using a 3D nonlinear strength-reduction numerical manifold method

Due to rock masses' nonlinear failure property, it is inappropriate to investigate the stability of rock slopes using the traditional SRM (strength reduction method) which is based on the linear MC (Mohr-Coulomb) failure criterion. To conduct 3D analysis (three dimensional) of rock slopes, we propose a 3D-NSRNMM (3D nonlinear strength reduction numerical manifold method) that is based on the nonlinear GHB (Generalized Hoek-Brown) failure criterion. To effectively implement the proposed 3D-NSRNMM, two methods are adopted to convert the GHB parameters into the average and instantaneous equivalent MC parameters. With the proposed 3D-NSRNMM, the influences of different types of equivalent MC parameters, and boundary conditions on rock slopes' stability are investigated. The numerical results assessed from the proposed 3D-NSRNMM indicate that: 1) boundary conditions will significantly influence the safety factor and failure mode of a rock slope obtained from 3D analysis; 2) the safety factor from two-dimensional analysis is more conservative compared with 3D analysis; 3) Furthermore, safety factors based on the instantaneous equivalent MC parameters are very close to those based on the average equivalent MC parameters, but 3D rock slopes' failure modes based on the two different types of equivalent MC parameters are a little different from each other.