Slope Stability Considering Joint Networks and Creep Parameters of Rock Mass

Rock slopes with soft interlayer are common in nature and engineering projects. They are usually the characteristic of poor stability and low safety level. Landslides that induced by the instability and destruction of rock slopes with soft interlayer have caused a large number of casualties and heavy economic losses around the world. Therefore,the stability of rock slopes containing soft interlayer is one of important research topic in engineering geology and geotechnical engineering. This paper is based on the collection and review of the domestic and foreign literatures related to the stability of rock slopes with soft interlayer. It summarizes the advances of some important aspects on the research current situations and progress of rock slope stability in the aspect of gravity load conditions,excavation conditions,heavy rain and reservoir storage conditions,and earthquake conditions. The findings are as follows. (1)The presence of a soft interlayer usually plays an adverse role in slope stability. The stability is poorer for rock slopes with soft interlayer than for homogeneous rock slopes and layered rock slopes without soft interlayer. (2)The stability and deformation failure mechanism of rock slopes containing soft interlayer are linked to the water content,shear strength,dip angles,thickness,the number of layers,intervals of soft interlayer and the slope angles. (3)Slope failure can easily occur along soft interlayer after the completion of slope excavation without support. When excavation with supporting in time,the stability of slopes can be effectively controlled. (4)Lamination effect caused by blasting changes the contact state between soft interlayer and surrounding rock and decreases the cohesion and friction of contact interfaces,thus decreases the stability of rock slopes. (5)Heavy rainfall and reservoir impoundment are both against the stability of rock slopes with soft interlayer. (6)The dynamic responses,deformation and failure process of rock slopes with soft interlayer under earthquakes are related to the property of soft interlayer(thickness,dip angle and water content),the characteristics of seismic wave(wave types,vibration intensity and frequency of earthquake waves,loading direction) and slope structure(bedding and counter-tilt rock slopes with soft interlayer). (7)The amplification or weakening effect of soft interlayer on the horizontal dynamic responses of rock slopes under earthquake and the role of thick soft interlayer in energy dissipation and shock absorption during shakings are not unified. Subsequently,on this basis,the advantages and disadvantages of research methods are analyzed in detail. Furthermore,the main problems existing in current research are also discussed. Finally,on account of research status in this field,some important research emphases and directions in the future are proposed. The contents are listed as follows: the progressive failure process and stability of rock slopes with multi-soft interlayer; the effect mechanism of individual factors(including excavation unloading,blasting,earthquake,heavy rain,the change of reservoir water levels,underground water) on the stability of rock slopes with soft interlayer; the stability of rock slopes with multi-soft interlayer under multi-factor coupling participation; and the reinforcement mechanism of retaining structural system for rock slopes with multi-soft interlayer.

The tensile strength of crystalline rocks in Brazilian tests (BT) shows a more significant size dependency than the uniaxial compression strength in uniaxial compression tests (UCT), while the micro-mechanism is still unclear. This study seeks to elucidate the micro-mechanism by comparing different microcracking processes under UCT and BT. We adopt a grain-based model in the discrete element method (DEM) to reproduce the interlocked microstructure of crystalline rocks and perform UCT and BT with different sizes ranging from 0.5 to 3 times the standard sample size. It was found that peak stresses in UCT are nearly insensitive to sizes, which is consistent with experimental results measured at very low loading rates. Due to the homogenous stress distribution, no clear cracking paths are observed; instead, randomly distributed microcracks appear at failure. In contrast, numerical results indicate that the tensile strength measured in BT decreases as size increases and continuous cracking paths are observed at failure. Larger specimens have a higher possibility to include weaker cracking paths, hence tensile strength shows stronger size dependency. The findings of this work offer microscopic explanations for different size effects observed in UCT and BT, which can bridge the gap between laboratory-scale strength data and field-scale applications. INTRODUCTION Rock engineering applications often require assessing the strength and failure characteristics of rock masses. These rock masses are composed of intact blocks across various scales. However, the strength and cracking mechanism of these field-scale intact blocks are usually indirectly measured and studied through laboratory-scale tests on intact specimens (Duan et al., 2017; Duan and Kwok, 2015; Fei et al., 2021; Mahabadi et al., 2014; Martin and Chandler, 1994; Wong et al., 1996). Uniaxial compression test (UCT) and Brazilian tests (BT) are standard tests that measure the uniaxial compression strength (σf) and tensile strength (σt) of rocks (Eberhardt et al., 1999; Li and Wong, 2013; Martin, 1994). The sizes of UCT and BT specimens in the laboratory usually vary from 5-10 cm in diameter, much smaller than in fields. However, a dependence of strength on size is widely known in rocks (Bažant, 1984; Choo et al., 2023; Paterson & Wong, 2005). The strength determined by these laboratory-scale tests may overestimate the loading capacity in fields, and the cracking process observed in the laboratory-scale specimens may also not accurately manifest the failure mechanism in the field scale. Therefore, to apply laboratory-scale experimental data to practical applications, it is vital to investigate the influence of specimen size on strength and cracking patterns.

Stability of rock slopes is a critical issue in many mining and civil engineering projects. The current state of practice for slope stability analysis is based on obtaining the factor of safety (FOS). Stability charts are widely used by engineers to obtain a FOS for a quick assessment of the initial stability of slopes. The stability of rock slopes with vertical walls in urban areas adjacent to existing structures is another important issue in this regard. However, the stability of earth or rock slopes are usually analyzed ignoring surcharge loads. The effect of adjacent structures (as surcharge load) on slope stability (considering these loads) can be very useful in slope stability analyses in urban or even non-urban areas. In the present study, it is tried to investigate the effect of surcharge load on the stability of rock slopes based on the generalized Hoek–Brown failure criterion using a finite element numerical software and the related charts are presented. Since there is a stability chart for each slope angle, a comprehensive mathematical model utilizing artificial neural networks is proposed to predict the stability factor of rock slopes. The independent variables in this study were slope angles, slope height, the intensity of surcharge load, Geological Strength Index (GSI), and unconfined compressive strength of the intact rock. Sensitivity analysis showed that the changes in GSI, effect of surcharge and unconfined compressive strength of rock have the highest effect on the slope stability assurance coefficient.

The asymmetric excavation unloading activity of a rock slope with a fault has an important influence on the stability of the slope and the division of the surrounding surface influence area. Based on the engineering background of the West Open-Pit Mine in Fushun City, orthogonal testing, K-means clustering, range analysis, and variance analysis were used to study the linkage mechanism of the asymmetric excavation unloading action and the weak structure in the rock slope, as well as their effects on slope stability and the influence area. This analysis showed that the significant factors affecting the stability zones of the north and south slopes were the excavation inclination angles of the opposite slopes. When the excavation inclination of the north slope increased by 10 degrees, the safety factors decreased by 25.9% and 16.6%. When the excavation inclination of the south slope increased by 10 degrees, the safety factors decreased by 13.7% and 1.9%. A second significant factor was the excavation depth. The occurrence of faults in the slope was the main factor affecting the range of slope instability. In order to ensure production safety, the excavation inclination angle of a slope with a fault should be limited to no more than 40°, and the excavation depth of an unstable area with two slopes should be designed to be no more than 450 m. The influence of asymmetric excavation unloading on the stability of a rock slope with a fault structure is expounded. This also provides a theoretical basis for controlling slope stability and influence areas in large-scale open-pit mining projects.

The stability of the slope is essentially controlled by the ratio between available shear strength and acting shear stress, expressed as the factor of safety, along the sliding surface. The slope is deemed stable if the computed factor of safety is larger than unitary and unstable if the computed factor of safety is less than unitary. Although the current analytical method for computing the factor of safety of the jointed rock slope subjected to wedge failure mechanisms allows predictions of the stability of the slope, it tends to oversimplify the key geological features that may influence the resulting factor of safety of the slope. The simplified analytical model was applied to determine the factor of safety of the physical jointed rock slope subjected to the wedge failure mechanisms. Furthermore, numerical model that incorporates key geological feature such as joints and foliations on the same physical case was built to simulate the stability of the jointed rock slope subjected to wedge failure mechanisms. The analytical model results indicate that the computed safety factor is above unitary, suggesting a stable slope while the numerical simulations result of the same physical slope predicted unstable slope. The obtained conservative factor of safety entails unrealistic predictions of the stability of the jointed rock slope subjected to wedge failure mechanisms. A numerical simulation model that incorporates key geological features could provide realistic predictions of the stability of the jointed rock slope subjected to wedge failure mechanisms.

The slope stability of large open-pit mines has always been a concern and the analysis of large-scale slope landslides is a focus. However, shallow failure in soft rock slopes also has a serious impact on safe production. The northern slope of Baiyunebo West Mine has many shallow landslides in the final slope, resulting in damage of the maintenance channel of the belt transportation system, which has a serious impact on the safety of production. In order to reduce the shallow failure in weak rock slope, it is necessary to analyze the behavior and characteristics of shallow failure in weak rock. Firstly, the mechanical parameters of the intact rock were obtained by using the exploration data; secondly, through the analysis of blasting-damage range, the distribution characteristics of fractures after the failure of weak rock were obtained. Finally, through theoretical analysis, numerical simulation, surface displacement monitoring and on-site shallow-failure case analysis, the deformation and characteristics of shallow failure of weak rock slope in West Mine were obtained. It was found that the mechanical parameters of rock mass strength on the surface of weak rock slope and the original rock were quite different after mining disturbance. The mode of failure of shallow weak rock slope in the West Mine was creep-cracking; the numerical modelling analysis was carried out by using the assignment method of shallow lithology weakening and gradual change, which is more in line with the deformation characteristics of weak rock slope in West Mine. The lower deformation of the soft rock slope in West Mine is 3–5 times that of the upper deformation. The research results are helpful to understand the influence of blasting on the stability of soft rock slope. At present, West Mine has started to adjust blasting parameters according to the research results, so as to reduce the excessive damage of blasting to rock mass, so the stability of the slope is improved.

The research on the stability of rock slopes under the multi-field coupling has important theoretical and practical significance for the analysis and prevention of freeze–thaw disasters of engineering in cold regions. In this paper, COMSOL Multiphysics numerical simulation software and numerical simulation methods are adopted. Based on the coupling theory of rock stress field, seepage field, temperature field, and chemical field, and field test data, the stability of rock slope under the multi-field coupling is studied under the research background of the highway slope of Jinghe to Yining County of G577 line. Based on the study of multi-field coupling theory, a numerical calculation model is established, the rationality of the numerical calculation model is verified, and the maximum frozen thickness of the slope is determined. On this basis, the change rules of the relevant parameters such as stress, temperature, deformation and damage of the highway slope in the engineering area are studied. The slope stability analysis is performed based on the YAI slope stability evaluation method. The stability of the slope is analyzed from the freezing, thawing and freeze–thaw process states of the shallow layer of the slope. It provides a theoretical basis for engineering construction in cold region.

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.

Study on the effect of depth on physical and mechanical parameters of rock plays an important role in understanding the deformation and failure of rock at depth and analyzing the mechanism of engineering disasters at depth. In this work, basalt specimen are taken from at 7 different depths ranging from 410 m to 1010 m at Datai Coal Mine, Beijing, which are processed into 77 standard rock samples (21 for uniaxial compression tests, 35 for conventional triaxial compression tests, 21 for Brazilian tests). With the rock mechanics test system of MTS815 and RMTS150, some physical and mechanical parameters are obtained, including rock density, uniaxial compressive strength, uniaxial tensile strength, elastic modulus, Poisson’s ratio, cohesion, friction angle, by uniaxial compression tests, conventional triaxial tests and Brazilian tests. The results show that, rock density, uniaxial compressive strength, uniaxial tensile strength, elastic modulus, cohesion and friction angle increase linearly with increasing depth, and there is a linear decreasing in Poisson’s ratio with increasing depth. Furthermore, the cause of the difference of physical and mechanical parameters of the same rock at different depth is analyzed.

Rock rupture phenomenon and pillar failure in tuffs in the Cappadocia region (Turkey)

Thermoelastic deformation of rock significantly affects the stability of rock slope because thermoelastic strains may cause fracture propagation under favorable condition of failure. Rock slope stability depends on the balance between shear stress and shear resistance along the plane of weakness. Due to warming of rock slopes by heat transfer phenomena, viz. conduction and convection, considerable change in induced stresses (normal and shear) and resistance takes place which further causes instability in rock slope. In this paper, a two-dimensional finite element model has been used to simulate the stability of jointed rock slope containing crack in its upper surface. Four different cases have been simulated on the basis of infilling material (air, water, ice, water and ice) in the crack. Stability of rock slope is examined in terms of shear displacement and factor of safety for different thermal conditions of slope surface. A comparative study has been done for the four cases of infilling material in the crack. The various affecting parameters, viz. shear displacement, factor of safety, shear strength along the joint, and different surface temperature conditions, are illustrated by means of graphs. It has been found that the values of horizontal and vertical displacements are in the range of millimeters. The maximum values of horizontal and vertical displacements are 2.17 mm. Moreover, the maximum values of vertical compressive and tensile stresses are 15.4 MPa and 4.45 MPa respectively for the said four cases. According to the infilling material in the crack, the stability of the rock slope for the given geometry of slope is found in the following order: crack filled with ice < crack filled with ice and water < crack filled with water < empty crack. Validations of numerical results have been done from previous studies, and it has been found that the trends of normal stress, shear strength, and shear displacement along the joint are well matched.

In order to investigate the environmental dependence on strength of rock, uniaxial compression test and Brazilian test under water vapor environment were conducted on Kumamoto andesite and Kitagishima granite. Tests were carried out under various water vapor pressures, which are controlled in special chambers, at a constant strain rate. The results obtained by the uniaxial compression test and Brazilian test are follows:The Young's moduli are almost constant with the change of water vapor pressure. On the other hand, the water vapor pressure largely affects the uniaxial compressive strength and the tensile strength of rock. Namely, the strengths of rock increase with decreasing water vapor pressure.The relationships between uniaxial compressive strength Sc , tensile strength St and water vapor pressure p can be represents by the following equation: long Sc ∝ -Nc log p and long St ∝ -Nt log p, where Nc and Nt are the inclination of lines.Comparing the above equations based on the test results with equation (5), the stress corrosion indexes are obtained as 24 in Kumamoto andesite and 62 in Kitagishima granite on uniaxial compression test, then 58 in Kumamoto andesite on Brazilian test. It is discussed that the difference between the stress corrosion indexes obtained from uniaxial compression test and Brazilian test is caused by the stress state within rock specimen in each test. The estimation method of long term-strength of rock is shown according to equation (8), then the long-term strength of Kumamoto andesite and Kitagishima granite can be estimated concretely, that is, uniaxial compressive strengths of Kumamoto andesite and Kitagishima granite after 1000 years are estimated 75% and 89% of uniaxial compressive strengths at the present time respectively.

Rock burst and Slope Stability is one of the common failures in hard rock mining and civil construction. This study focuses on the prediction of rock burst and Slope Stability classification with case instances using cloud models and attribution weight. First, cloud models are introduced briefly related to the rock burst and Slope Stability classification problem. Then, the attribution weight method is presented to quantify the contribution of each rock burst and Slope Stability indicator for classification. In addition, analysis and prediction of slope stability is of great importance in geotechnical engineering. With the development of economics, the number of slopes is increasing and landslides caused by slope instability have become one of the three major geological disasters in the world along with earthquakes and volcanoes. To reduce or prevent landslide damage, slope stability analysis and stabilization are required. However, accurately predicting slope stability is challenging because of the complexity of slope structures and the difficulty to determine the precise input data associated with key geotechnical parameters the proposed methodology PSO feature extraction preserves important distance relationships, such as : The Random forest, Naive Bayes of each object of the original dataset. This leads to preservation of any mining operation that depends on the ordering of distances between objects, such as Random forest, Naive Bays -search, SVM, J.48 and MLP classification, as well as many visualization techniques. In particular, it establishes a restricted isometric property, i.e., tight bounds on the contraction/expansion of the original distances.

To solve the main shortcoming of numerical method for analysis of the stability of rock slope, such as the selection the convergence condition for the strength reduction method, one method based on the minimum energy dissipation rate is proposed. In the new method, the basic principle of fractured rock slope failure, that is, the process of the propagation and coalescence for cracks in rock slope, is considered. Through analysis of one mining rock slope in western China, this new method is verified and compared with the generally used strength reduction method. The results show that the new method based on the minimum energy dissipation rate can be used to analyze the stability of the fractured rock slope and its result is very good. Moreover, the new method can obtain less safety factor for the rock slope than those by other methods. Therefore, the new method based on the minimum energy dissipation rate is a good method to analyze the stability of the fractured rock slope and should be superior to other generally used methods.

The knowledge about thermo-mechanical properties of granite is still limited to some extent. Individual measurements are necessary to obtain reliable properties for specific granite types. A reliable numerical model of thermal cracking behaviours of granite exposed to extreme high temperatures (e.g. 800–1000 °C) is missing. In this study, the impact of temperature up to 1000 °C on physical, mechanical, and thermal properties as well as thermo-mechanical coupled behaviour of Eibenstock granite was investigated by laboratory testing and numerical simulations. The physical properties including mineral composition, density, P-wave velocity, and open porosity are measured to be temperature dependent. Uniaxial compression and Brazilian tests were carried out to measure uniaxial compressive strength (UCS), Young’s modulus, stress–strain relationship, and tensile strength of Eibenstock granite before and after thermal treatment, respectively. Thermal properties including specific heat, thermal conductivity, thermal diffusivity, and linear thermal expansion coefficient are also measured and found to be temperature dependent, especially the expansion coefficient which shows a steep increase around 573 °C as well as at 870 °C. The numerical simulation code FLAC3D was used to develop a numerical scheme to simulate the thermal-induced damage of granite at high temperatures. Statistical methods combined with real mineral composition were used to characterize the heterogeneity of granite. The numerical model is featured with reliable temperature-dependent parameters obtained from laboratory tests. It can well reproduce the laboratory results in form of thermal-induced micro- and macrocracks, as well as the stress–strain behaviour and the final failure pattern of Eibenstock granite after elevated temperatures up to 1000 °C. The simulation results also reveal that the thermal-induced microcracks are randomly distributed across the whole sample. Although most thermal-induced damages are tensile failures, shear failure begins to develop quickly after 500 °C. The obvious UCS reduction in granite due to heating is mainly caused by the increase in shear failure. The simulation also shows that the dominant impact of α–β quartz transition is widening pre-existing cracks rather than the formation of new microcracks.