Rock Slope Stability Research Articles

An interpretable evolutionary extreme gradient boosting algorithm for rock slope stability assessment

An interpretable evolutionary extreme gradient boosting algorithm for rock slope stability assessment

Potential of carboxymethyl cellulose solution to increase the shale stability

Slope failures in Bangladesh's Chittagong division are a growing concern, with fatalities increasing from 19 in 2000 to 162 in 2017 and projected to rise further. This study aims to identify the most vulnerable rock formation and assess Carboxymethyl Cellulose (CMC) as a solution for enhancing shale strength and mitigating slope failures. The research began by evaluating weathering susceptibility and stability of different rock layers, revealing the high instability of shale in the Bhuban Formation. Slake durability tests measured cation concentration to understand shale instability mechanisms. Laboratory experiments, including immersion tests and grained-and-molded shale specimens, examined CMC's potential to improve shale stability. Results indicated that the shale of the Bhuban Formation had the highest hammer value variations, indicating increased weathering susceptibility. Shale instability was attributed to illite layer dissolution, releasing K+. Intact shale specimens treated with CMC showed enhanced penetration resistance, shear strength, and deformation behavior, suggesting CMC's potential in increasing shale stability. Grained-and-molded shale specimens treated with CMC demonstrated increased shear strength, critical shear displacement, and contraction deformational behavior. Optical microscopy and scanning electron microscopy revealed the formation of cross-links between shale grains, contributing to improved shale stability. Further research is needed to explore the application of CMC for enhancing in situ rock slope stability. This study emphasizes the importance of addressing slope failures in the Chittagong division and provides insights into mitigating the risks through CMC-based interventions.

Characterizing large-scale weak interlayer shear zones using conditional random field theory

The shear behavior of large-scale weak intercalation shear zones (WISZs) often governs the stability of foundations, rock slopes, and underground structures. However, due to their wide distribution, undulating morphology, complex fabrics, and varying degrees of contact states, characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging. This study proposes an analytical method to address this issue, based on geological fieldwork and relevant experimental results. The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters. The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC, enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station. The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5–1 times the main powerhouse span, showing local activation. Furthermore, the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697.

Three-Dimensional Discrete Element Analysis of Jointed Rock Slope Stability Based on the Universal Elliptical Disc Model

Three-Dimensional Discrete Element Analysis of Jointed Rock Slope Stability Based on the Universal Elliptical Disc Model

Geological challenges and stabilization strategies for phyllite rock slopes: a case study of Guang-Gansu expressway in Western China.

The increased occurrence and severity of natural disasters, such as landslides, have impacted the stability of phyllite rock slopes in the complex geological regions of Western China. This situation presents significant challenges for infrastructure development in the area. This study investigates the upper span bridgehead slope of Guang-Gansu expressway K550 + 031 as a case study to analyze the sliding failure mechanism of thousand rock slopes in the seismic fault zone and the supporting structure failure through field investigation and exploration. The analysis shows that the slope's rock mass is extensively fractured, primarily influenced by the Qingchuan fault zone. This geological activity leads to slope instability, worsened by seasonal rainfall. The phyllite undergoes alternating dry and wet cycles, weakening its mechanical strength, forming cracks, and accelerating slope displacement, subsidence, and cracking. This results in front slope instability, followed by gradual backward and step-by-step traction sliding deformation on both sides. The geological structure and seasonal rainfall damage the original bolt-grid beam-supporting structure. To address this issue, an anti-slide pile combined with a grid beam treatment method is proposed, and its effectiveness is verified through deep displacement monitoring. This study emphasizes the significance of integrating geological structure and seasonal rainfall impacts into infrastructure design within complex geological areas, ensuring slope and supporting structure stability.

The influence of defect shape on the cracking behavior of brittle materials

To understand the influence of defect shape on the cracking behaviors of brittle materials, three types of gypsum specimens containing different shape defects are designed, and three-point bending tests have been conducted. The results show that the shape of defects can affect the initiation and occurrence of tensile cracks, as the load continuous to increase, the tensile crack usually propagates along the direction of applied compression. The defect shape can also influence the strength of the specimen, and both tensile and shear cracks occur when the load is close to or greater than 50% of the peak strength. Defects with sharp corners are easy to induce the initiation and occurrence of tensile crack, whereas, for the defects with smooth edges, if the defect area is not large enough, it is difficult to breed tensile cracks. Additionally, defect shape has no effect on the fracture toughness, whereas the defect shape can influence the unstable toughness, and when the defect shape is triangular, the distribution of the unstable toughness value varies randomly, and when the defect shape is trapezoidal, the unstable toughness decreases with the increase of defect area. These results are expected to improve the understanding of brittle fracture and can be used to analyze the durability of concrete structures and the stability of rock slopes.

THE VAN DER MEER FORMULA FOR ROCK SLOPE STABILITY AT SHALLOW WATER

In Van der Meer (2021) the stability formula for rock slopes under wave attack has been rewritten to remove the mean period Tm and to include the spectral period Tm-1,0. This formula is now identical to the Modified Van der Meer formula in the Rock Manual (2007 – Eqs 5.139 and 5.140), except for its coefficients and the use of H2 percent in the Rock Manual and H1/3 in Van der Meer (2021). A method has been given in Van der Meer (2021) by coefficients cpl and csu in the rewritten formula, to include (new) data on rock slope stability where results differ from the original formula and data. The re-fit of the shallow water data by Van Gent (2004) leading to the Modified Van der Meer formula for shallow water comes now to cpl=0.92 and csu=0.96, showing that rock slopes are less stable in shallow water than in deep water (coefficients smaller than 1 show less stability). The main objective is then: when and where do shallow water stability results deviate from the known stability formulae and how can we describe the deviating results. The original dataset by Van Gent (2004) and additional tests by Eldrup (2019) as well as other data have been analysed in depth to come to an improved understanding of rock slope stability in shallow water.

Polyphase rock slope failure controlled by pre-existing geological structures and rock bridges

Even after decades of intensive research, assessing rock slope stability remains a challenge. One reason for this is the spatial variability of rock bridges (RBs) related to non-persistent, pre-existing geological structures, especially as the detection of RBs is generally limited to the post-failure period. Thus, the identification and classification of RBs and their inclusion in numerical studies are demanding, yet essential, since even small quantities of RBs can be decisive for rock slope stability. In our study, we demonstrate how brittle RB failure and pre-existing geological structures control the mechanisms of a polyphase rock slope failure. Therefore, we present a case study in the Austrian Alps, where three rock falls with a failure volume of 30,000 m3 occurred in 2019. Based on detailed process reconstructions, high-resolution terrain models, and comprehensive geological and rock mechanical investigations, we derived high-quality input for our distinct element model (DEM). By applying asymmetric Voronoi tessellation in the DEM, we modelled the coalescence of pre-existing geological structures by brittle RB failure. As a result, we identified toppling as the predominant failure mechanism at the study site. Distinctive geological structures decisively affected the failure mechanism. However, the toppling failure was only reproducible by incorporating RBs in the DEM in their pre-failure position. Finally, we found that joint persistence, and consequently the presence of potential RBs, controls which initial rock fall failure mechanism was developed. In conclusion, we state that the initial toppling failure of the Hüttschlag rock falls is controlled by non-persistent geological structures in interplay with RBs.

Laboratory Investigations on the Mode of Failure in Frictional and Low-Cohesive Materials Under the Load of a Ground Anchor

Ground anchors are widely used in many types of construction works, such as stabilization of rock slopes, wind turbines, concrete dams and bridge towers. Some of the modes of failure for these anchors still have an insufficient scientific basis, and that applies especially to what happens in the ground when overloaded. This paper presents investigations on the failure development in frictional and low-cohesive materials which are subjected to loading by an embedded anchor with a free length towards the surface. The failure development is demonstrated through a series of small-scale physical model tests performed in the laboratory. The physical model setup consists of a transparent PVC test chamber, a rigid «anchor block», and a hydraulic jack. The model is instrumented with a camera, an extensometer and a load cell to continuously record the failure development and resistance from the material as the anchor block is pushed through the sample material. The main question investigated is how the failure appears, as a failure along the whole pull-out body at once or as an advancing fracture along the plane, where in the first case the shear capacity of the material will be the main input in calculations, and for the second case, one also needs to take failure propagation into account.

Stabilization of rock slopes by anchor based on upper bound analysis incorporating Hoek–Brown failure criterion

Stabilization of rock slopes by anchor based on upper bound analysis incorporating Hoek–Brown failure criterion

Fuzzy-Based Intelligent Model for Rapid Rock Slope Stability Analysis Using Qslope

Artificial intelligence (AI) applications have introduced transformative possibilities within geohazard analysis, particularly concerning the assessment of rock slope instabilities. This study delves into the amalgamation of AI and empirical techniques to attain highly precise outcomes in the evaluation of slope stability. Specifically, our primary objective is to propose innovative and efficient methods by investigating the integration of AI within the well-regarded Qslope system, renowned for its efficacy in analyzing rock slope stability. Given the complexities inherent in rock characteristics, particularly in coastal regions, the Qslope system necessitates adjustments and harmonization with other geomechanical methodologies. Uncertainties prevalent in rock engineering, compounded by water-related factors, warrant meticulous consideration during all calculations. To address these complexities, we present a novel approach through the infusion of fuzzy set theory into the Qslope classification, leveraging fuzziness to effectively quantify and accommodate uncertainties. Our approach employs a sophisticated fuzzy algorithm encompassing six inputs, three outputs, and 756 fuzzy rules, thereby enabling a robust assessment of rock slope stability in coastal regions. The implementation of this method capitalizes on the high-level programming language Python, enhancing computational efficiency. To validate the potency of our AI-based approach, we conducted preliminary tests on slope instabilities within coastal zones, indicating a promising initial direction. The results underwent thorough evaluation, affirming the precision and dependability of the proposed method. However, it is crucial to emphasize that this work represents a first attempt to apply AI to the evaluation of rock slope stability. Our findings underscore a high degree of concurrence and expeditious stability assessment, vital for timely and effective hazard mitigation. Nonetheless, we acknowledge that the reliability of this innovative method must be established through broader applications across diverse scenarios. The proposed AI-based approach’s effectiveness is validated through a preliminary survey on a slope instability case within a coastal region, and its potential merits must be substantiated through broader validation efforts.

Dominant Partitioning of Discontinuities of Rock Masses Based on DBSCAN Algorithm

In the analysis of rock slope stability and rock mass hydraulics, the dominant partitioning of discontinuities of rock masses is a very important concept, and it is still a key for establishing the three-dimensional (3-D) network model of random discontinuities. The traditional graphical analysis method is inadequate and greatly influenced by subjective experience. A new method using density-based spatial clustering of applications with noise (DBSCAN) algorithm is proposed for the dominant partitioning of discontinuities of rock mass. In the proposed method, we do not need to determine the centers of every cluster before clustering, and the acnodes or outliers can be eliminated effectively after clustering. Firstly, the spatial coordinate transformation of the discontinuity occurrence is carried out and the objective function is established by using the sine value of the angle of the unit normal vector as the similarity measure standard. The DBSCAN algorithm is used to establish the optimal clustering centers by searching the global optimal solution of the objective function, and the fuzzy C-means clustering algorithm is optimized and the mathematical model of the advantage grouping of rock discontinuities is established. The new method and the fuzzy C-means method are compared and verified by using the artificially randomly generated discontinuity occurrence data. The proposed method is a better method than the fuzzy C-means method in general cases, and it can provide more accurate results by eliminating the acnodes or outliers. Finally, the proposed method is applied to discontinuity orientation partition data at Maji dam site, Nujiang River, and there is good agreement with the in situ measurement.

Research on Deformation Failure Mechanism and Stability of Bedding Cataclastic Rock Slope Containing Multi-Muddy Interlayers

Based on the excavated slope of a waste incineration power plant in Yuxi, Yunnan Province, China, the finite element strength reduction method was used to investigate the variation rules of the safety factor, displacement, and deformation of the bedding cataclastic rock slope containing multi-muddy interlayers under the different conditions of number of muddy interlayers n, inclination angle θ, cohesion c, and angle of internal friction φ. Moreover, the deformation failure mechanism and stability of bedding cataclastic rock slope containing multi-muddy interlayers were revealed. The results showed that, as n increased, the maximum horizontal displacement of the slope increased, the factor of safety decreased, and the key influence on the stability of the slope was the muddy interlayers through the toe of the slope. As θ increased, the horizontal displacement of the slope first increased, then decreased, and then increased again, the safety factor first decreased, then increased, and then decreased again, and the stability of the upright laminar slope was slightly larger than that of the horizontal laminar slope. When the slope angle β was 45°, with the increase in θ, the failure mechanism of the slope manifested as a compression-shear failure, traction-sliding failure, traction-sliding-bending-shear failure, flexural deformation, and bending-buckling-collapse failure in sequence. As c increased, the slope evolved from traction-sliding failure to traction-sliding-bending-shear failure; the stability of the slope increased as c and φ increased.

Strength reduction strategy for rock slope stability using the variation principle based on the Hoek–Brown failure criterion

Strength reduction strategy for rock slope stability using the variation principle based on the Hoek–Brown failure criterion

Seismic dynamic stability of double-slider rock slopes containing tension cracks

Seismic dynamic stability of double-slider rock slopes containing tension cracks

Application of the deterministic block theory to the slope stability design of an open-pit mine in Morocco

Purpose. Discontinuities in rock masses are natural fractures that delimit various block shapes and sizes, which can fall, slide or topple from the excavation and collapse under their own weight inducing probably severe damage. Thus, it is essential to carry out a block analysis before beginning any surface or underground excavation project. This paper proposes a methodology based on key block theory analysis to select the suitable slope of different discontinuous rock masses of an open-pit mine in Morocco. Methods. At first, the main discontinuities of each bench are determined and projected onto a stereonet with a maximum dip angle of the excavation plane. Then, it is possible to identify the removable blocks by using the theorem of removability according to block theory. After that, a limit equilibrium analysis is performed to determine the failure mode and the friction angle required to stabilize the blocks. When the selected dip angle of the slope plane is found to be unsuitable, it is changed and reduced by one degree, and the same approach is repeated until the maximum safe slope dip angle is obtained. Findings. The results of the proposed methodology based on key block theory analysis have shown that the maximum safe slope angles of the studied benches are in the range of 63-73°. When compared to the slope angles used in the mine, which are between 58-78°, the results of this study are close to in-situ conditions. Originality. In this research, the maximum safe slope angle of fractured rock masses was optimized by eliminating slope angles inducing unstable blocks (key blocks) and by using the stereographic projection method of key block theory. Practical implications. Using this methodology, stability of rock slopes in civil or mining-engineering projects can be designed or assessed when geotechnical data are very limited.

Stability Analysis of Rock Slope under Rainfall Infiltration Based on A Zero-Thickness Cohesive Element

There are often a large number of joints, fissures and other water channels in rock slopes. Under the condition of short-term heavy rainfall or continuous rainfall, a large amount of rainwater enters the slope body, which can easily induce landslide disaster on rock slopes. Therefore, it is of great significance to study the stability of rock slope under the infiltration of rainfall. Based on the ABAQUS numerical simulation platform, this paper implements continuous-discontinuous simulation of the deformation and damage of rock slopes under rainfall conditions by embedding zero-thickness cohesive elements and focuses on the effects of rainfall intensity, rainfall duration and rainfall infiltration location on the slope stability using vector method safety factors as indicators. The results show that as the rainfall intensity and rainfall duration increase, the depth of fissures in the slope gradually becomes larger, and the stability of the slope gradually decreases. The farther the initial location of rainfall infiltration is from the shoulder of the slope, the shorter the rain-induced fissure extension length is and the better the stability of the slope is. The research results provide reference for the engineering treatment of rock slope under rainfall conditions.

Effect of Varying Normal Stiffness on Soft Rock Joints under Cyclic Shear Loads.

The evaluation of changes in shear resistance on soft (or weathered) rock joints under cyclic shear loads with constant normal load (CNL) and constant normal stiffness (CNS) significantly contributes to increasing the safety and stability of rock slopes and underground structures. In this study, a series of cyclic shear tests were conducted on simulated soft rock joints with regular (15°-15°, 30°-30°) and irregular (15°-30°) asperities under different normal stiffnesses (kn). The results indicated that the first peak shear stress increases with the increase in kn up to the normal stiffness of the joints (knj). Beyond knj, no significant change was observed in the peak shear stress. The difference in peak shear stress between regular (30°-30°) and irregular joints (15°-30°) increases as kn increases. The minimum difference of peak shear stress between regular and irregular joints was observed (8.2%) under CNL and the maximum difference was found (64.3%) on knj under CNS. The difference in peak shear stress between the first and subsequent cycles significantly increases as both the joint roughness and kn increases. A new shear strength model is developed to predict peak shear stress of the joints for different kn and asperity angles under cyclic shear loads.

Reliability analysis of rock slopes considering the uncertainty of joint spatial distributions

To reasonably and effectively evaluate the stability of jointed rock slopes, this study proposes a reliability analysis method that considers the uncertainty of the joint spatial distribution. First, the discrete fracture network (DFN) model is used to characterize the variability of joint geometric parameters, and a random variable of joint location is assumed to be a random integer that follows a uniform distribution in the random number library. Then, Latin hypercube sampling is used to sample uncertain random variables to generate random numbers, and construct the corresponding DFN model. Finally, the safety factor (Fs) of each numerical model under sampling is calculated by strength reduction method, and the failure probability of jointed rock slope is obtained by statistical analysis of Fs. The comparative analysis results demonstrate that considering the uncertainty of joint spatial distribution is crucial for accurately analyzing the reliability of rock slopes. This method comprehensively considers the main internal factors that affect the reliability of jointed rock slopes, including the uncertainty of rock strength parameters and variability of geometrical parameter and the location randomness of joints, making the results of the evaluation of the reliability of rock slopes more precise and reasonable.

Dynamic stability analysis of jointed rock slopes using the combined finite-discrete element method (FDEM)

The combined finite-discrete element method (FDEM) is an advanced finite element and discrete element coupling method, which is commendably suitable for simulating the slope’s entire evolution process from cracking, expansion, penetration, sliding, collision to deposition under seismic load. The original FDEM has apparent shortcomings in simulating the dynamic instability process of earthquake-induced landslides, and some targeted improvements are made to the original program. Numerical tests are carried out to prove the accuracy and robustness of the improved FDEM, and the influence of the structural plane on the dynamic evolution mechanism and process of the slope is studied. The results show that the improved FDEM can accurately reproduce the entire dynamic evolution processes and failure forms of different jointed rock slopes under seismic load and can quantitatively evaluate the dynamic stability of jointed rock slopes (dynamic safety factor and critical failure surface). In addition, the results also emphasize that the slope failure degree significantly affects the dynamic response of the slope and suggest that the combination of the cut-through of the failure surface and the increase of kinetic energy should be used as the criteria for slope dynamic instability simulation by FDEM. This study provides scientific and technological support for revealing the failure mechanism of jointed rock slopes and disaster reduction and prevention.