Soft Rock Slope Research Articles

Study on Seepage and Stability of Soft Rock Slope with Fissures Under Extreme Rainfall

Study on Seepage and Stability of Soft Rock Slope with Fissures Under Extreme Rainfall

Simulation of cyclic slow-to-fast landslides based on the coupled creep and frictional slip model

Soft rock slopes may undergo long-term cyclic slow-to-fast landslides due to the softening of clay minerals and frictional sliding under hydromechanical disturbance. We proposed a meso/macroscale cyclic slow-to-fast landslide model by coupling creep and frictional sliding model to address the abovementioned problem. The model can reveal the macroscopic catastrophic phenomena caused by the accumulation of mesoscale damage in soft rocks, thus providing a scientific basis for the simulation of cyclic slow-to-fast landslides. For modeling validation, we applied the model to the Spriana soft rock slope, which undergoes long-term instability under periodic groundwater level variation. By adopting the coupled finite element method and distinct element method (FEM-DEM), the model can mimic the stable creep and fast sliding in different phases of matured slow-moving landslides. The difficulties in simulating cyclic accelerated sliding are solved, where the simulation error of displacement is less than 5.7 % compared with field monitoring data. It may serve as a prediction tool for cyclic slow-to-fast landslides.

Evaluation of the Stability, Preventions and Control Effect of a Bedding Low-Angled Red-Bed Soft Rock Slope

Evaluation of the Stability, Preventions and Control Effect of a Bedding Low-Angled Red-Bed Soft Rock Slope

Failure Mechanism of Anti-Dip Layered Soft Rock Slope under Rainfall and Excavation Conditions

The phenomenon of toppling deformation and failure is common in slopes with anti-dip structures, especially in soft metamorphic rock slopes. This paper aims to explore the instability mechanism of anti-dip layered soft metamorphic rock landslides. Taking the slope of a mining area in the southern Qinling Mountains of China as a geological prototype, a large-scale centrifuge model test and a numerical simulation based on the combined finite and discrete element method (FDEM) were performed. The deformation and failure process, failure mode, and failure path of the slope under rainfall and excavation conditions were simulated. The results show that both the physical centrifuge model test and the new numerical model test can simulate the instability process of anti-dip layered soft metamorphic rock slopes, and the phenomena simulated by the two methods are also very close. Rainfall mainly weakens the mechanical properties of rock, while the excavation at the slope toe mainly changes the stress field distribution and provides space for slope deformation, both of which accelerate the instability of the anti-dip soft metamorphic rock slope. The failure process of an anti-dip layered soft rock slope can be described as follows: bending of the rock layer–tensile fracture along the layer–flexural toppling and cracking perpendicular to the rock layer–extension and penetration of the tensile fracture surface–sliding and instability of the slope.

An analytical solution of critical sliding displacement for the flexural buckling failure of layered rock slopes

In mountain areas, flexural buckling failure of layered rock slopes due to self-weight is common, and it frequently results in serious disasters. Previous research has focused on qualitatively evaluating slope buckling stability and rarely studied the whole process from deformation to failure. In this work, we intend to quantitatively analyze the progressive movement of buckling landslide by solving the critical buckling sliding displacement. Layered rocks are simplified as an inclined multiple beam model with axial concentrated force. The sliding process of buckling is divided into three stages, which correspond to the upper rock stress reaches tensile strength, the lower rock stress reaches compressive strength, and the rock layers below the maximum uplift height of buckling segment begin to overturn under the action of self-weight. By considering tensile and compressive strength, the calculation method of critical sliding displacement is put forward, and corresponding criterion for assessing slope buckling stability is developed. The feasibility and accuracy of the proposed method were confirmed based on the good agreement among numerical manifold simulation, theoretical calculation and field data. In addition, the parameter sensitivity analysis of layered slopes stability shows that longer, thinner, and steeper soft rock slopes are more prone to buckling failure. The formation of buckling failure will be aggravated for layered rocks with smaller compressive strength, lower geological strength index and higher degree of disturbance, but the value of critical sliding displacement remains unchanged.

Flexural toppling characteristics of anti-dip soft rock slope with base friction test

Flexural toppling characteristics of anti-dip soft rock slope with base friction test

Seismic behavior analysis of soft and hard interbedded rock slope considering vibration deterioration of discontinuities at the interface between different rock types in meizoseismal area—a case study

Seismic behavior analysis of soft and hard interbedded rock slope considering vibration deterioration of discontinuities at the interface between different rock types in meizoseismal area—a case study

Analysis of the effect of rock layer structure on the toppling failure evolution of soft-hard interbedded anti-dip slopes

The soft-hard interbedded anti-dip rock slopes (SHIADRS) are unique among all layered rock slopes, as the mechanical properties of hard and soft rock layers are completely dissimilar. These slopes are abundant in south-western China. Therefore, this study examined the evolution of SHIADRS toppling failure using a centrifuge model test. The test results indicate that the entire SHIADRS failure process can be roughly divided into three stages: 1) the slight deformation stage involving tension and bending of rock layers, 2) the development stage involving tensile cracks at the slope top and the formative stage of toppling zones as well as 3) the total failure stage. Furthermore, the toppling deformation process of the SHIADRS can be divided into three stages concurrently, based on the magnitude of the displacement rate: 1) stable deformation stage, 2) unstable deformation stage, and 3) accelerated deformation stage. The universal distinct element code (UDEC) is utilised further to investigate the impact of rock layer structures on SHIADRS failure patterns. The simulation results indicate that variations in the thickness of soft and hard rock layers have no significant effect on the failure process and macroscopic failure patterns of SHIADRS. Additionally, the failure patterns of anti-dip hard rock slopes, anti-dip soft rock slopes and SHIADRSs were discussed, with SHIADRSs having the most complex failure pattern. Based on the fracture mechanics theory and the independent cantilever beam model, an improved method for calculating the stability of SHIADRS is proposed, which can determine the stability of rock layers by calculating the residual sliding force.

Dynamic response and failure evolution of low-angled interbedding soft and hard stratum rock slope under earthquake

Dynamic response and failure evolution of low-angled interbedding soft and hard stratum rock slope under earthquake

Shallow Failure of Weak Slopes in Bayan Obo West Mine.

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.

Multiscale modelling of the seepage-induced failure of a soft rock slope

Multiscale modelling of the seepage-induced failure of a soft rock slope

Early Risk Warning of Highway Soft Rock Slope Group Using Fuzzy-Based Machine Learning

Maintaining the stability of highway soft rock slopes is of critical importance for ensuring the safety of road networks. Although much research has been carried out to assess the stability of individual soft rock slope, the goal of efficient and effective risk management focusing on multiple highway soft rock slopes has not been fully achieved due to the many complex factors involved and the interactions among these factors. In the present study, a machine learning algorithm based on a fuzzy neural network (FNN) and a comprehensive evaluation method based on the FNN is developed, in order to identify and issue early warnings regarding the risks induced by soft rock slopes along highways, in an efficient and effective way. Using a large amount of collected soft rock slope information as training and validation data, an FNN-based risk identification model is first developed to identify the risk level of individual soft rock slope based on the meteorological conditions, topographical and geomorphological factors, geotechnical properties, and the measured horizontal displacement. An FNN-based comprehensive evaluation method is then developed, in order to quantify the risk level of a soft rock slope group according to the slope, road and external factors. The results show that the risk level identification accuracy obtained based on validation of the FNN model was higher than 90%, and the model showed a good training effect. On this basis, we further made early warnings of the risks of soft rock slope groups. The proposed early-warning model can quickly and accurately evaluate the risk posed by multiple soft rock slopes to a highway, thereby ensuring the safety of the highway.

Influence of Elevation on Slake Durability Index of Quartz Mica Schist: A Case Study of East Slope of Manjiazhai Open Pit

In order to study the influence of elevation on the slake durability index of the quartz mica schist, the quartz mica schist with different elevations on the east slope of the Manjiazhai open-pit mine is taken as the research object, and based on laboratory tests and statistical analysis, the variation of negative correlation between the slake durability index and elevation is obtained. The disintegration mechanism of quartz mica schist at different elevations is also discussed. The test results show that the disintegration characteristics of quartz mica schist at different elevations are related to its mineral composition, fissure channel size, and rock damage effect. As the slope height increases, the ratio of mica to quartz in the rock increases, and the greater the porosity of the rock, the more fissures in the rock, the greater the permeability coefficient, and the more obvious the change of effective stress of rock under osmotic pressure. At the same time, the higher the slope elevation of open-pit mine, the longer the weathering time of rock, the higher the cumulative damage of rock, and the lower the rock slake durability index. This study provides a new idea for guiding the research on the disintegration characteristics of similar soft rock slopes in the elevation direction.

Comparative Test on the Bond Damage of Steel and GFRP Bars Reinforcing Soft Rock Slopes

Soft rock slopes were anchored with traditional steel bars and new Glass Fibre Reinforced Polymer (GFRP) bars. The difference in the anchorage performance of the two kinds of anchorage elements in soft rock and expansive soil was studied by an in-situ test. The results show that cyclic load can aggravate the bond damage of the interface between grouting body and both kinds of bars used in soft rock. Compared with the number of cyclic loads applied, the previous maximum load is the main factor that influences the bond damage of the anchorage bar. Under constant loading, the interface bond behaviour of GFRP bar is better than the steel bar. Because of the small difference in elastic modulus between the GFRP bar and the grouting body, the interface bond around the GFRP bar can invoke more resistance of the grouting body efficiently which demonstrates its more effective anchorage performance than the steel bar under the same conditions. The anchorage structure of steel bar in soft rock can generate larger interfacial relative displacement with increasing load than the GFRP bar in the anchorage section, even though the elastic modulus of steel is much larger than GFRP. In the expansive soil, the anchorage structure deformations of steel and GFRP bars are almost the same because of the weaker bond at the interface of the grouting body and the surrounding soil than that of the bar interface. Under the ultimate loading of the anchorage structure in soft rock, the steel bar with 450 MPa which is less than its ultimate strength shows the failure of the bar body pulling-out, and the GFRP bar with 508 MPa which is larger than its ultimate strength shows the failure of the bar body by fracture. The steel bar anchorage structure in soft rock is destroyed at the interface around the grouting body. The results show that the GFRP bar performs more efficiently than the steel bar.

Stability Reinforcement of Slopes Using Vegetation Considering the Existence of Soft Rock

This study investigates the effectiveness of vegetation reinforcement on the stability of a slope with red-bed soft rock in a slope along the Xining-Chengdu railway, China. Four kinds of vegetation were considered to reinforce the soil and the slope. The rooted soil parameters were determined based on the laboratory tests. A numerical model was developed based on the actual geometry and soil layer distributions. The soils were modeled as elastic perfectly plastic materials and the vegetation reinforcement was represented as addition cohesion of a series of subsoil layers within a given depth. The effectiveness of vegetation on slope reinforcement under both dry and rainfall conditions was investigated regarding this case. The potential failure surface and corresponding factor of safety of the red-bed soft rock slope for those different conditions were analyzed and compared. It has been found that the addition of vegetation increased the safety of slope stability whether the slope is under a dry condition or a rainfall condition, while the increasing proportion of factor of safety due to vegetation reinforcement for this case is very limited. The results and findings in this study are still significant for the practitioner to evaluate the reasonability of vegetation reinforcement.

Analysis of the deformation mechanism and stability of bedding soft rock slope

The lithology of the inlet side slope of the diversion tunnel on the right bank of Wudongde Hydropower Station is dominated by thin marbled dolomite. During construction, numerous cracks form along the elevation direction, and large monitoring deformation values appear in the consequent slope section. In this study, engineering geological analysis, deformation monitoring data analysis, and three-dimensional numerical simulation are combined to investigate the formation mechanism of cracks, the range of local deformed bodies, and the deformation and failure mechanism of deformed bodies. The stability of the slope is rechecked via the rigid-body limit equilibrium method based on the above analysis. Results show that the local convex terrain in the consequent slope section is cut through unfavorable structural surfaces and form a deformable body. Under the influence of unfavorable factors, such as the bedding cut foot caused by the lower excavation unloading and rainfall, the deformation of the shallow slope surface continuously increases; as a result, the shotcrete layer cracks. The deformation force comes from the middle and rear parts of the slope, and the instability mode slides along the bottom boundary level. After prestressed cables are added, the safety factor of the deformed part can satisfy the code requirements, and the existence of the deformed part does not affect the overall slope stability. Therefore, this study can provide technical support for engineering construction and a reference for similar slope engineering research.

The Influence Law of Multi-point Cumulative Blasting in Slope

In order to study the cumulative blasting stress wave produced by the vibration of soft rock slope, the deformation regularity of the influence of blasting, caused by the horizontal and axial acceleration along with other additional stress waves were analyzed. The vibration displacement formula along with the vibration source stress wave superimposed model were established. The research also deduced the deformation rule for the gangue slope of Lijiahao Coal Mines as a vibration signal recorder was used to collect the blast vibration wave and the simulated analysis of displacement monitoring profile of the X and Y displacement rule under the influence of blast vibration were obtained. The results indicate that with the increase of the shot point distance, the displacement in the Y direction shows a logarithmic decline rule while the change in displacement of the X direction is small. The result also shows that the greater the initiation of multipoint shot firing, the greater the slope deformation and displacement of the rock mass and as a result multipoint nonsimultaneous blasting and control detonation time difference, can effectively reduce the effects of vibration on the slope deformation.

A complex slide-buckling-toppling failure of under-dip soft rock slopes

This study investigates a complex slope failure that occurred in Chongqing Xi railway station. The studied slope belongs to a under-dip shale slope. Onsite surveys and UDEC numerical modelling were conducted to describe the deformation characteristics and potential failure mechanism of this slope. The simulated results suggest that sliding, buckling and toppling can occur in the deformation process, which is verified by the actual deformation characteristic of the slope and monitoring results. Moreover, the effects of bedding dip angle, slope angle, bed thickness on the deformation characteristics of the slope were also investigated with UDEC models. Finally, the possible slope structure for occurrence of slide-buckling-toppling failure and several numerically validated remedial measures were proposed.

Soil-engineering properties and failure mechanisms of shallow landslides in soft-rock materials

Tertiary soft-rock strata exposed on the eastern side of Changbai Mountain are landslide-prone strata. In recent years, shallow landslides have frequently occurred along the highway in this region, leading to great challenges in highway construction and safe operations. National Highway 302, which is under construction, crosses an old landslide group close to the village of Xinyan. A shallow landslide that recently occurred in this section, the Xinyan landslide, which occurred in a road embankment composed of soft-rock materials, is studied herein as a case study. The field survey identifies the geological characteristics and current conditions of the landslide area and confirms an inheritance relationship between the Xinyan landslide and previous landslides. Through a laboratory geotechnical test, mineral composition analysis and microstructure analysis of landslide soils, it is found that the examined soft-rock materials exhibit both dispersion and expansion. The coupling effect of soil expansion and dispersion contribute to the formation of seepage channels and to the degradation of soil properties. Under the combined effects of these factors, local shear failure first occurs at the weakest toe of the embankment. Then, unloading effects and strain softening lead to the progressive propagation and expansion of the sliding surface. Finally, the failure of the Xinyan landslide enters a progressive failure mode from the slope toe to the interior area. Therefore, this study reveals that expansibility, dispersivity, extremely low shear strength levels, softening behavior and preferential flows are the main causes of the repeated failure of the gentle soft-rock slopes in this region. These results may serve as a good reference for the prevention and treatment of similar soft-rock landslides occurring in the Yanbian region or worldwide.

Research on the Disintegration Characteristics of Carbonaceous Mudstone and Properties of Modified Materials

This work presents the results of an experimental investigation aimed to study the disintegration of carbonaceous mudstone and properties of modified materials. The mineralogical composition of carbonaceous mudstone was determined with X‐ray diffraction. The microscopic characteristics of carbonaceous mudstone disintegration were determined with scanning electron microscopy. The surface modification effect of carbonaceous mudstone was researched by comparative tests on coatings’ hydrophobic property, fastness, and waterproof before and after modification, and the modification mechanism of polymer‐cement composite modified carbonaceous mudstone was analyzed. The results show that the mineral composition of carbonaceous mudstone mainly contains illite, quartz, and kaolinite. It is found that the disintegration of carbonaceous mudstone can be divided into external factors and internal factors. External factors are water and temperature difference, and internal factors are the swelling of the kaolinite and illite mineral particles. There are differences in the modification effects under different cement dosage. When the cement dosage is 30%, the modification effect is the best. The results may provide a reference for the prevention and control of soft rock slopes.