Rock Slope Stability Analysis Research Articles

Some considerations on the role of joint spacing in rock slope stability analyses using a 3D discrete element approach

Stability assessment of potential wedge failures in rock slopes is usually carried out based on stereographic projection techniques and limit equilibrium analyses. Nevertheless, this methodology presents several limitations (i.e., lack of information on joint mechanical properties, oversimplification of the structure, etc.) that could lead to poorly accurate conclusions. In line with this idea, the main objective of this work is to evaluate the effect of joint spacing in the estimation of the factor of safety of rock slopes affected by potential wedge failures. For this purpose, a 3D numerical distinct element code (3DEC) was selected to carry out a substantial number of simulations in which the factor of safety of two types of slopes, affected by different discontinuity sets, was studied by using the shear strength reduction (SSR) method. Different values of joint spacing, cohesion, and friction angles were considered, combined with two angles of the slope face under study. A discrete fracture network (DFN) model was also implemented, with the aim of benchmarking results with those obtained from the original models. The joint spacing has been found to relevantly affect the values of the factor of safety of the slope, which showed variations of up to 40% in comparison with those obtained from limit equilibrium methods. This work provides an insight to a more realistic interpretation of rock slope analyses against wedge failures, particularly to better estimations of the factor of safety.

A New Discrete Form of Hoek–Brown Criterion and Its Application to Limit Equilibrium Analysis of Rock Slope Stability

The generalized Hoek–Brown criterion (GHB) is recognized as one of the standard failure criteria in rock engineering and its validity extends to a wide range of rock mass quality. A drawback of this criterion is the difficulty of transforming it into an explicit form defining the Mohr failure envelope when its strength parameter a is not equal to 0.5. The information on the functional form of the Mohr envelope for the full range of rock mass conditions enables the implementation of classical engineering approaches, such as the limit equilibrium method and limit analysis, in the framework of the GHB criterion. Knowing that for a≠0.5 the exact closed-form representation of the Mohr envelope is not feasible, an alternative is to express it in an approximate analytical form. The main purpose of this study is to propose a new improved method to define an approximate Mohr envelope of the GHB criterion that is much more accurate compared with the recently published approximations. The idea behind the formulation is to expand the Balmer’s equation, which defines the relationship between the normal stress and minor principal stress at failure, by invoking the finite Taylor series centered at the known solution for a=0.5. The formulation is then completed by substituting this solution into another Balmer’s equation, defining the relationship between the shear strength and the minor principal stress. The Taylor polynomial approximations of up to third degree are considered in the formulation. The accuracy of the shear strength prediction is shown to be much better than that of the approximate formula of Lee and Pietruszczak proposed in 2021. An illustrative example of limit equilibrium analysis of rock slope stability, incorporating the new approximate expression for the Mohr envelope, is provided. The analysis incorporates a modified version of the Bishop approach, which is simpler and more rigorous than the original nonlinear expression. The study confirms that the new approximate representation of the Mohr failure envelope can facilitate the application of the GHB criterion to a range of practical rock engineering calculations.

Analysis of rock slope stability for Mohmand Dam – A comparative study

Analysis of rock slope stability for Mohmand Dam – A comparative study

A novel empirical classification method for weak rock slope stability analysis

This study presents a novel empirical classification system for stability analysis of rock slopes in weak rock based on their geotechnical and geological properties. For this purpose, consideration is given to the marly rock slopes, which include three main groups of weak rock (lime marlstone, marlstone, and marly limestone). The 40 different slopes located in the South Pars special zone (Assalouyeh), southwest of Iran, are targeted in classification. To prepare comprehensive graphical stability charts for weak rocks, extensive field surveys, sampling, geotechnical laboratory tests, and ground measurements are conducted in slope sites. Using the findings of the study, empirical stability charts for slopes composed of weak materials were developed. The charts are associated with geotechnical indexes, geo-units’ weathering impact, and in-situ stress conditions. Using these graphical charts assists in investigating the stability condition of rock slopes and estimating the geotechnical characteristics of clay-based weak rocks such as marlstones.

Sudden Slide Mechanism of a Rock Block in Road Cutting Slope with Soft and Hard Interlayered Bedding Structure Based on Energy Balance Theory

After the road excavation of the hard and soft interlayered bedding slope in the mountainous region's valley area, the bedding slope often results in a catastrophic phenomenon, especially in the project's construction and operation where existed severe safety hazards. A geomechanical two-component model consisting of the slider and the underlying layer is proposed to analyze the rock block instability under the fissure water pressure, the shear deformation, and the compression deformation. The slider's complex stress field is derived by using elastic mechanics. The incremental energy equilibrium Equation is established based on the energy balance theory, and the generalized sliding force relative function of the slider and the generalized shear force relative function of the underlying soft rock are obtained. The deformation energy accumulation, transfer, and energy dissipation characteristics are analyzed. Put a rock slide in the bedding rock cutting slope happened at Jiaojiatan, Pengshui County, Chongqing municipality, China as a case. Results indicate that considering both the compression deformation and the shear deformation of the slider, the kinetic energy, the rapid launch speed of the projectile, the average projectile acceleration, and the failure stroke increase about 15.7 times, 4.0 times, 1.8 times, and 8.9 times respectively than that of only considering the shear deformation, and the dynamic disaster intensity is more severe and worthy of attention. The results that ignored the fissure water pressure and the compressive deformation energy coincide with the existing literature, which verifies the reasonable applied method in this paper. Considering the slider's different displacements and the height-length ratios, when the energy ratio function that represents the ratio of the incremental compression energy to the incremental shear energy concludes that when the range of the height-length ratio is between 0 to 0.95(flat and narrow sliders), the compression energy's contribution to the system's elastic energy should be taken into consideration. The advantage of the energy balance method applied in the stability analysis of the bedding rock slope is that the potential unstable rock block's status can be predicted dynamically according to the variation of the underlying soft rock's deformation and that the elastic impact dynamic parameters can also be obtained compared with other instability analysis approach.

Stability analysis of rock slopes using kinematic analysis and numerical modeling: Foça–Bağarası State Highway, Turkey

Stability analysis of rock slopes using kinematic analysis and numerical modeling: Foça–Bağarası State Highway, Turkey

Stability analysis of Xiluodu Hydropower Station right bank slope based on discontinuous deformation analysis method

PurposeThe purpose of this study is to investigate the deformation characteristics and failure modes of the right bank slope of Xiluodu Hydropower Station after excavation.Design/methodology/approachMicro-seismic monitoring technology is applied to obtain the microfracture information and study the internal damage evolution law of the slope rock mass. A numerical model for discontinuous deformation analysis (DDA) is established to analyse the deformation characteristics and failure mode of the slope. Micro-seismic monitoring and DDA can verify and supplement each other's results in the investigation of slope failure.FindingsThe results show that the slope has a downhill displacement along the weathered zone under natural conditions; the maximum resultant displacement at the monitoring point is 380 mm. The micro-seismic events are concentrated in an area located 30–100 m horizontally away from the slope surface and at an elevation of 390–470 m. The distribution of these micro-seismic events is consistent with the location of the unloading and weathered zones; it is the same as the DDA simulation result.Originality/valueThe study is anticipated to be used as reference for the stability analysis of rock slopes. By combining the continuous (micro-seismic monitoring technology) and discontinuous (DDA) methods, the entire process starting from the gradual accumulation of internal rock micro-damage to the macroscopic discontinuous deformation and failure of the slope can be investigated.

Stability analysis of rock slope and calculation of rock lateral pressure in foundation pit with structural plane and cave development

In this study, numerical simulations were carried out to analyze the influence of caves in different positions and shapes, in combination with structural planes, on the stability of the slope and the failure characteristics of a rock slope in a deep foundation pit with high inclination structural planes and cave development. The schemes for substituting a single karst cave for karst caves were constructed. Based on the penetration failure characteristics of karst caves between parallel structural planes, calculation methods for the safety factor of the rock foundation pits and the upper bound of the lateral pressure of supporting structures under the combined influence of the caves and structural planes have been developed, which can be used to assess the safety factor of a rock mass and to calculate the lateral pressure under complex geological conditions. The example of Xuzhou Metro Line 3 Sanhuan South Road Station is taken as an example to verify. The displacement calculation results show that the proposed rock and soil pressure calculation method is close to the actual measured value.

A Machine Learning Approach to Extract Rock Mass Discontinuity Orientation and Spacing, from Laser Scanner Point Clouds

This study wants to give a contribution to the semi-automatic evaluation of rock mass discontinuities, orientation and spacing, as important parameters used in Engineering. In complex and inaccessible study areas, a traditional geological survey is hard to conduct, therefore, remote sensing techniques have proven to be a very useful tool for discontinuity analysis. However, critical expert judgment is necessary to make reliable analyses. For this reason, the open-source Python tool named DCS (Discontinuities Classification and Spacing) was developed to manage point cloud data. The tool is written in Python and is based on semi-supervised clustering. By this approach the users can: (a) estimate the number of discontinuity sets (here referred to as “clusters”) using the Error Sum of Squares (SSE) method and the K-means algorithm; (b) evaluate step by step the quality of the classification visualizing the stereonet and the scatterplot of dip vs. dip direction from the clustering; (c) supervise the clustering procedure through a manual initialization of centroids; (d) calculate the normal spacing. In contrast to other algorithms available in the literature, the DCS method does not require complex parameters as inputs for the classification and permits the users to supervise the procedure at each step. The DCS approach was tested on the steep coastal cliff of Ancona town (Italy), called the Cardeto–Passetto cliff, which is characterized by a complex fracturing and is largely affected by rockfall phenomena. The results of discontinuity orientation were validated with the field survey and compared with the ones of the FACETS plug-in of CloudCompare. In addition, the algorithm was tested and validated on regular surfaces of an anthropic wall located at the bottom of the cliff. Eventually, a kinematic analysis of rock slope stability was performed, discussing the advantages and limitations of the methods considered and making fundamental considerations on their use.

Upper-Bound Limit Analysis of Rock Slope Stability with Tensile Strength Cutoff Based on the Optimization Strategy of Dividing the Tension Zone and Shear Zone

Upper-Bound Limit Analysis of Rock Slope Stability with Tensile Strength Cutoff Based on the Optimization Strategy of Dividing the Tension Zone and Shear Zone

Mechanical behavior of non-persistent joints with different geometric configurations and roughness in solid rock and concrete material

The shear behavior and failure mechanism of non-persistent joints or cracks in rock mass and concrete material are determined by both the rock bridges and the joint geometric configurations. In the present study, the synthetic rock mass (SRM) numerical models are established based on the particle flow code 2D (PFC2D), and numerical direct shear tests are then conducted to investigate the mechanical behavior of non-persistent rock joints. Effects of joint geometric configuration, normal stress, joint roughness, and joint aperture on the shear behavior of non-persistent joints are discussed. Results show that shape of the shear stress curves is greatly influenced by the joint geometric configuration. Besides, specimens with a non-persistent joint in the central have the largest shear modulus, the lowest peak shear strength and the smallest number of microcracks as compared with the other two joint types. The average residual shear stress is not significantly influenced by the joint geometric configuration, but fluctuates more dramatically with the increase in JRC value. For the same joint configuration, the microcrack propagation is restrained under higher normal stress, leading to the decrease of the maximum length of cracks with increasing normal stress. The peak shear strength decreases linearly with the increment of joint aperture under a low normal stress, while it tends to be stable when the joint aperture is larger than 2.0 mm under a high normal stress. The shear modulus of joint specimens is rarely influenced by the JRC values and the joint apertures. The obtained conclusions can provide valuable guidance for the stability analysis and micro-seismic (acoustic emission) monitoring of rock slopes, concrete dams and foundations with embedded non-persistent joints or cracks.

The State of the Art and New Insight into Combined Finite–Discrete Element Modelling of the Entire Rock Slope Failure Process

The stability of rock slopes is of significance, as even the slightest slope failure can result in damage to infrastructure and catastrophes for human beings. Thus, this article focuses on the review of the current techniques available for rock slope stability analysis. The rock slope stability techniques can be classified as conventional methods and numerical methods. The advantages and limitations of the conventional method are briefly reviewed. The numerical methods mainly included three types, i.e., continuum methods, discontinuum methods, and the combined/hybrid continuum–discontinuum methods. This article pays more attention to the last type. The combined/hybrid finite–discrete element method (FDEM), which might be the most widely used continuum–discontinuum method, is introduced and we illustrated its abilities in modelling the entire rock slope failure process. The fundamental principles of FDEM, i.e., the contact interaction of the discrete bodies and the transition from continuum to discontinuum, are introduced in detail. The abilities of the FDEM in modelling the rock slope failure process are calibrated by modelling the entire typical rock slope failure process. Then, the application of the FDEM in the analysis of slope stability is introduced and discussed. Finally, the authors give insight into the GPGUP-parallelized FDEM modelling of the high rock slope failure process by the implementation of the strength reduction method (SRM). It is concluded that the FDEM can effectively model the entire rock slope failure process, even without the implantation of any slope modes, and the GPGUP-parallelized FDEM is a promising tool in the study and application of rock slope stabilities.

Application of combined terrestrial laser scanning and unmanned aerial vehicle digital photogrammetry method in high rock slope stability analysis: A case study

Recent advancements in remote sensing techniques have made it possible to overcome the risky issues using conventional methods and have opened up new opportunities for collecting data on discontinuity characteristics. This research compares the application of a Terrestrial Laser Scanner (TLS) and Unmanned Aerial Vehicle (UAV) in rock slope stability analysis. Two case studies, Ulu Choh Quarry and Jelapang Rock Slope are analysed using Kinematic Analysis and Slope Mass Rating (SMR) to depict rock through the 3D point cloud. The techniques are compared with the hand mapping method concerning the accuracy of the data acquisition in assessing the rock slope. The standard deviation for the dip and dip direction between digital capture and hand mapping is 2.97° and 2.86°, which falls under the acceptable tolerance limit. The integration of UAV and TLS also generates excellent clear point cloud data from the top to the toe of the slope.

A Pseudo-dynamic Approach for Seismic Stability Analysis of Rock Slopes in Hoek–Brown Media

A Pseudo-dynamic Approach for Seismic Stability Analysis of Rock Slopes in Hoek–Brown Media

Novel Three-Dimensional Sarma Method with Vertical Slices for Stability Analysis of Rock Slopes

Novel Three-Dimensional Sarma Method with Vertical Slices for Stability Analysis of Rock Slopes

Application of a Comprehensive Rock Slope Stability Assessment Approach for Selected Malaysian Granitic Rock Slopes

In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope stability including identifying potential failure modes, an information gap still exists between geologists and engineers in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was assigned to each potential failure based on rock mass ratingbasic and the slope mass rating based on readjustments for discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope stability to complement kinematic analysis and stability ratings often used in Malaysia.

The Use of Innovative Techniques for Management of High-Risk Coastal Areas, Mitigation of Earthquake-Triggered Landslide Risk and Responsible Coastal Development

Coastal areas constitute a very dynamic environment, balancing between numerous natural and anthropogenic processes liable to sometimes hazardous geomorphic phenomena. Especially in tectonically active coastal regions and areas of high economic value, slope failures can have significant impacts and therefore need careful and detailed examination. This work uses Unmanned Aerial System (UAS)-aided photogrammetry and Terrestrial Laser Scanning (TLS) in tectonically active segments of the coastal zone of the Ionian Islands in Greece, to explore how their capabilities can help to improve our understanding of the structural integrity of the slopes. Results show that the two approaches are able to extract large numbers of discontinuity facets, in a more practical, rapid and safe way than conventional methods of rock slope stability analysis extending to unreachable yet important parts of the slope. Through this holistic record of the structural condition of the slope the two applications allow the identification of segments that are more prone to instability and failure. In this way, they improve our understanding of the prioritization of interventions aiming to enhance the prevention of slope failures, mitigating the associated risk and improving local development in these high-value locations.

Key group analysis based on DDA method for rock slope stability analysis

Inhomogeneity and discontinuities play a key role in resistance and behavior of rock masses. Today engineers have a wide range of methods to analyze the stability of rock slopes. Due to its simplicity and speed of evaluation, static analysis methods continue to play a special role in the stability assessment of jointed rock slopes. One of the most well-known static methods used in the stability analysis of rock slopes is the Key Block method (KBM), which is based on the key block finding and analyzing. In this method, if none of the key blocks are unstable, it implies that rock mass is stable. Occasionally, the combination of a number of stable blocks has led to formation a group of blocks that sometimes leads to instability. Therefore, the stability analysis of the jointed rock masses leads to study of groups of blocks that are potentially dangerous for the stability of a rock slope. The Key Group method (KGM), with its progressive approach, finds these critical groups and focuses the stability calculations on these groups. In order to increase the efficiency, accuracy and speed of this method and to develop it in three dimensions, it is decided to combine it with one of the numerical methods. The standard Discontinuous Deformation Analysis method (DDA) is an implicit method based on the finite element method. This is a sophisticated numerical method for modeling the quasi-static and dynamic behavior of rock block systems in discontinuous rock masses. The goal of this paper is to use of the potency of the numerical method of DDA to analyze the candidate key group. For this purpose, the DDA computer program was developed with Mathematica programming language and combined with the KGM software. The resulting package, after selecting the key group by the KGM method, proceeds to analyze it with the DDA method. Two examples solved illustrating the reasonable results and the efficiency of this developed method compared to that of the original KGM and SKGM. The results validated the proper accuracy and good performance of the procedure developed in this research.

Stability Analysis of Rock Slope with Multilayer Weak Interlayer

The existence of the weak interlayer of the rock slope changes its mechanical characteristics. To ensure the safety of the slope, it is necessary to analyze the overall stability of the slope. Taking the double-layer weak interlayer rock slope beside 318 National Road in Qiyue Mountain, Hubei Province, as an example, a slope model with a weak interlayer was established through GTS software, and the model was imported into FLAC3D for calculation, and the deformation of the slope by the double-layer soft interlayer was studied. The influence of characteristics and safety factors reveals the controlling effect of the double-layer weak interlayer on the stability of the slope and its failure mode. The potential sliding surface of the slope is determined to be the lower weak interlayer, and the weak interlayer after the anchor cable reinforcement is carried out. Numerical analysis shows that the reasonable application of anchor cables significantly improves slope stability. The research results can provide reference significance for slope stability analysis of similar projects.

Investigations of a Weathered and Closely Jointed Rock Slope Failure Using Back Analyses

This study presents the case of a landslide triggered by a high groundwater level caused by several days of continuous rainfall in the northeastern region of Taiwan. The slope where this landslide occurred consists of closely jointed and weathered bedrock. By means of finite element limit analysis and the Hoek–Brown failure criterion, this study performed a slope failure simulation similar to the actual landslide and deduced the reasonable value range for the combination of key Hoek–Brown failure criterion parameters through back analyses. The results indicate that the key parameters affecting the bedrock’s slope stability were the geological strength index (GSI) and the disturbance factor (D), whereas the effects of the unconfined compressive strength (σci) were less significant. The results of the back analysis reveal that the suitable D-value range and GSI of closely jointed and weathered sandstone in the northeastern region of Taiwan are 0.8 to 0.9 and 20 to 30, respectively. These back-analyzed value ranges can serve as a reference for broader applications in the preliminary stability analysis of similar rock slopes where it is difficult to perform in situ investigation.