Mineral change and micropore development are important deterioration features of soft rock during water–rock interaction, but ignoring the differences and contributions of potential physical and chemical processes in existing laboratory studies. This paper carried out multiple micro-measurements on mudstone and sandstone after powder immersion and wetting–drying cycles of coarse grains, and proposed a liquid bridge model to distinguish the potential microscale process. The results indicate a complementary relation of mineral composition in the sieved fine particles, increasing clay minerals, and decreasing detrital minerals and cement with wetting–drying cycles. The variation in mineral and ion is slight after 320 days immersion. Micropores develop along mudstone boundaries after the wetting–drying cycle, and fewer clay minerals are found in sandstone whose skeleton of detrital minerals remain undamaged. The repeating liquid bridge force, varied in direction and magnitude, softens the cement strength inter minerals and induces them detaching from rock skeleton and remaining micropores. Combining with the weak chemical action, the rock damage evolution driven by the liquid bridge force helps us clarify the specific microscale processes involved in a short period of water–rock interaction, on the mechanism responsible for desiccation cracks, water-soil erosion and rock slaking.

Mine slope stability and mining sustainability are related to the local geological structures, which could change the rock mass structure in deep mining. After 20 years mining in a mudstone mine, western China, the slope structure transforms from anti-dipping structure into a bedding structure by a recently discovered fault (F1), further inducing the two landslides (Landslide #I and Landslide #II). Landslide investigation suggested the residual deposits in Landslide #I first slid over 100 m and overburdened the rear of Landslide #II. The bedding rock with weak interlayers at footwall is separated from the anti-dipping rock at the hanging wall by F1. After excavation, a weak interlayer was exposed and softened by rainfall, resulting in the slip of footwall rock mass and further inducing large scale toppling deformation. The fragmented rock mass sliding along a weak interlayer triggers consequent deformation of adjacent slope, reducing safety reserve of the open mine. The discrete element analysis reveals that the bedding rock mass of footwall slid once the weak interlayer was exposed by mining. And retrogressive deformation transmitted to the hanging wall and induced bending and toppling deformation of anti-dipping rock mass. Mine feasibility assessment should recognize the potential deep geological structures as important in the future.

In the field of geotechnical engineering, many researchers have studied the disintegration of wet geotechnical bodies, but few have investigated the disintegration of sandy soils cured with water glass. In this study, the effects of modulus and Baume degree on the consolidation rate, particle size structure, pore size structure and gel state of sandy soils cured with water glass were investigated. The disintegration of cured specimens with different compositions was analyzed and discussed from the microscopic point of view. The results of the study show that the time required for consolidation of cured sandy soil decreased with increasing modulus and Baume degree. The Baume degree and modulus of sodium silicate affected the particle size and pore size structure of solidified soil. Due to differences in pore size and particle size structure, the disintegration of the specimens differed. For the samples with high Baume degree, their strength is high, but their water stability is poor, and the maximum disintegration degree is 95.72%. The sample with low Baume degree has low strength, but the water stability is good under the immersion condition, and the disintegration rate is less than 10%. The disintegration mechanism of solidified specimens was analyzed from the aspects of particle size, pore size structure and gel state. It is suitable to use water glass with high Baume degree in projects with dry environment and requiring high strength, while water glass with low Baume degree can be used for curing in wet environment.

Water glass, which can be cured by rapid dehydration, is an ideal environmentally friendly material for engineering grouting solidification and ecological environment restoration. The curing efficiency of water glass at room temperature was low, the curing mechanism and strength characteristics at high temperature were not clear, and the engineering applicability and optimal curing methods were to be explored. In this paper, 10 curing paths were designed within 100°C. The mechanical and acoustic characteristics of water glass-cured sandy soils were tested by uniaxial compressive tests and acoustic emission (AE). The relationship between strength, wave velocity and curing age was established based on the "logistics" model. The characteristic parameter "Q" value was proposed based on the AE characteristic value. Combined with the results of scanning electron microscopy (SEM), the solidification evolution process was revealed in terms of gel structure, crystal morphology and pore space. The process of water glass curing sandy soil was divided into a "strength rising period" and a "strength deterioration period". The enhancement and weakening effects of high temperature on the gel layer were stronger than those at room temperature. The longer the room temperature curing time is, the weaker the effect of high temperature on the specimen. After high-temperature curing, the maximum strength of the specimens increased by 107.85%, and the strength growth rate and strength deterioration rate increased by 586.34% and 3738.79%, respectively. The conversion rate of the gel under high temperature conditions determined the strength of the specimen. The rate of strength deterioration of the specimen was determined by the hardening effect of the undehydrated gel and the excessive dehydration effect of the rigid gel.

Under the action of continuous rainfall or excavation unloading, the strength index of soil deteriorates, but most of the current slope stability calculations directly regard it as a constant. To approach the real failure mode of slope instability, based on the Swedish slice method and the first-order linear strain-softening theory, this paper proposes a new method for slope progressive failure analysis, deduces the limit equilibrium expression of the strain-softening slope, and obtains the safety factor under the corresponding damage progress. Through the analysis of simulation examples, the feasibility of the slice-softening method is illustrated, and the calculation results show that the safety factor in the progressive failure process not only depends on the failure mode and strength parameters of the slope but is also closely related to the softening modulus of the rock and soil mass. At the same time, by comparing and checking the actual cases of the Danba landslide, it is confirmed that there are different attenuation coefficients for its strength index, that is, the attenuation coefficient of cohesion is greater than the friction angle. From theory to application, the finally obtained slice-softening method not only considers the strength degradation effect of rock and soil mass under the action of rainfall and the gradual development of sliding surface but can also effectively serve the stability analysis of slope under the background of practical engineering and provide guidance and suggestions for the prevention and treatment of landslides.

The deformation and failure mode of the sliding–cracking is common in rock slopes, which is mainly affected by the gentle and outward-sloping structural planes. These structural surfaces usually extend to the slope surface. This similar deformation mode has also occurred in the rock slope of the Maji hydropower station. But the slope does not have the structural conditions for sliding-cracking deformation, which is different from the traditional sliding-cracking mode. Therefore, based on the field survey and combined with the deformation characteristics of the slope, the deformation mechanism of the slope was analyzed qualitatively by the process mechanism analysis method. And the numerical analysis was conducted with the finite difference method (FDM) to study the evolution process of the slope in this paper. The results show that the “softening effect of the slope toe and valley floor (SESTVF)” is the key factor for the sliding–cracking deformation of the slope at the Maji hydropower station, which is caused by the weathering of rocks at the slope toe and valley floor; the squeeze deformation of the weathered plagioclase–hornblende gneiss and leptynite at the valley floor and the slope toe leads to the sliding-cracking deformation of the slope; the effect of SEVFST on the slope deformation in the slow river cutting stage is greater than that in the fast river cutting stage.

Artificial waste dumps with ore debris are widely distributed in mines and lead to complex groundwater compositions, which affect slope stability. Soil salinization with calcium sulfate is prominent in a gypsum waste dump in southwestern Sichuan, China. To identify the interaction between the soil and calcium sulfate at this site, this paper aims to study the shear strength of saturated soil, investigate the soil micropore structure, and discuss their contributions to slope stability. The shear test results of the six groups showed that cohesion increased and then decreased with increasing calcium sulfate concentration, while the internal friction angle showed the opposite pattern. Correspondingly, micropore content in the 500–1000 μm range decreased sharply when the concentration was greater than 500 mg/L, accompanied by a uniform size and complex morphology. Because the water film absorbed on the clay minerals was compressed slightly at low calcium sulfate concentrations, soil cohesion was enhanced due to the combination of intergranular attraction and viscosity. In contrast, particles were compacted tightly at high calcium concentrations, which decreased the soil swelling capacity and amplified the effect of the internal friction angle in the shear process. Long-term rainfall infiltration and water discharge repeatedly deteriorated the soil shear strength due to the variation in groundwater ion concentration, which ultimately induced cracks and failure of the waste dump slope. Therefore, the mechanism of water-soil interaction and its contribution to slope stability were revealed.

As a common fracture model in the rock slope, the gentle dip fracture system is significant in geological engineering for slope evolution and stability evaluation. In this paper, based on the characteristics of stress field, the rock shear tests were carried out by applying the particle flow program, revealing the formation and evolution mechanism and impact factors of the gentle dip rupture system in the slope. The results show that: (1) the gentle dip angle system in the rock slope is a set of Riddle low angle shear rupture system, which consists of high-order sub-sexual geese fractures and low-order sub-conjugate shear fractures; (2) the evolution of the fracture with a gentle dip angle can be divided into several stages, showing that the propagation of the fracture system firstly occurs at a set of echelon rupture and then the conjugate shear cracks of the low order begins to expand and connects with original echelon ruptures; (3) the crack coalescence mode is different under different confining stress. The crack develops along the tips of the echelon rupture and finally links under a low confining stress, and it develops through the middle part of the original rupture under a moderate confining stress, and the coalescence will occur through a new set of echelon ruptures in the high confining stress; (4) the morphology of the rupture surface in the rock after the shear tests is closely related to the confining pressure, showing that the rupture surface is flat but the roughness is large under the medium and low confining pressure; under high confining pressure, however, the fracture presents curved surface, and it is smooth but the roughness is small.

Gently dipping fractures subjected to river incision are widely distributed on rock slopes. In this paper, a rock slope on the Nujiang River (China) is investigated to study the role of gently dipping fractures in the rock slopes evolution. Detailed field surveys indicate that gentle fractures are concentrated in four main zones. Moreover, the kinematics of the fracture system suggest that the genesis of these fractures can be synthesized into a progressive evolution model. This model indicates that the joints begin with the formation of an array of en echelon cracks that are subjected to continued crack elongation and shearing before ultimately approaching one another and interacting to form a complex joint system. Geomechanical analysis is performed to reveal the mechanisms of this genesis, and three main fracture patterns are identified based on the slope stress and are classified with respect to the slope evolution. Based on the detail field investigations and the evolutionary history of the river valley, we propose that intermittent incision by the river was the main factor contributing to the concentrated distribution of gently dipping joints.

Rock mass unloading is an important rock engineering problem because unloading may impact the stability of a rock mass slope. Based on hydroelectric engineering principles, this study focuses on the classification of unloading zones to reflect the rock mass structure characteristics. Geological background and slope structure of the study region were considered to investigate the distribution and deformation of the unloading process. Quantitative indices were classified according to the formation mechanisms and the geological exhibition of unloading zones. The P -wave velocity ( V P ), the ratio of the wave velocity ( K V , the ratio of the test P -wave velocity along the adit depth to the P -wave velocity of intact rock), the sum of joint openings every 2 meters ( S t ), and the density of open joints ( D t ) were calculated as quantitative indices for the rock mass unloading zone. The characteristics of the unloading zone of rock mass slopes at the dam site were successfully determined. The method of combining qualitative data with quantitative indices was found to be effective for the classification of slope unloading zones.

This paper presents a study on the gravity-induced rock slope deformation observed along the Nujiang River in China. We performed a comprehensive field investigation and analysis to identify the deformation pattern of the slope and its triggering factors. Moreover, a geological-evolutionary model was developed, and it considers the effects of river incision and rock mass degradation caused by weathering and simulates the mechanisms underlying the initiation and progression of the slope deformation. The results support the proposed failure mechanism in which fractures within the slope are induced by rock mass degradation caused by weathering. Importantly, the modeling reveals that compressional deformation at the toe of the slope results in a tensile failure in the upper portion of the slope, demonstrating that the rock mass in the slope toe is the key factor inducing slope deformation. This analysis of slope deformation and its spatial and temporal correlations with rock weathering and river incision reveal the main triggering factors that control the evolution of the studied slope and provide insights into the deformation process.

Rock mass is an important engineering material. In hydropower engineering, rock mass of bank slope controlled the stability of an arch dam. However, mechanical characteristics of the rock mass are not only affected by lithology, but also joints. On the basis of field geological survey, this paper built rock mass material containing parallel concentrated joints with different dip angle, different number under different stress conditions by PFC (Particle Flow Code) numerical simulation. Next, we analyzed mechanical property and fracture features of this rock mass. The following achievements have been obtained through this research. (1) When dip angle of joints is 15 degrees and 30 degrees, with the increase of joints number, peak strength of rock mass has not changed much. But when dip angle increase to 45 degrees, especially increase to 60 degrees and 75 degrees, peak strength of rock mass decreased obviously with the increase of joints number. (2) With the increase of confining stress, peak strengths of all rock mass have different degree of improvement, especially the rock mass with dip angle of 75 degrees. (3) Under the condition of no confining stress, dip angle of joints is low and joint number is small, existence of joints has little influence on fracture mode of rock mass, but when joints number increase to 5, tensile deformation firstly happened at joints zone and further resulted in tension fracture of the whole rock mass. When dip angle of joints increases to 45 degrees, fracture presented as shear along joints, and with increase of joints number, strength of rock mass is weakened caused by shear-tension fracture zone along joints. When dip angle of joints increases to 60 degrees and 75 degrees, deformation and fracture model presented as tension fracture zone along concentrated joints. (4) Influence of increase of confining stress on fracture modes is to weaken joints' control function and to reduce the width of fracture zone. Furthermore, increase of confining stress translated deformation mode from tension to shear.

Engineering mechanical properties of rock mass are largely influenced by the characteristics of weak joints. Concentrated parallel joints are well developed in a large hydropower station in southwest China, and the deformation behavior of these joint belts is a key factor affecting slope stability. Therefore, this paper performed a simulation by particle flow code (PFC) and smooth joint model (SJM) to study the deformation and failure modes of rock mass containing concentrated parallel joints with different spacing and number. The following findings were obtained. (1) Four deformation phenomena of rock mass with concentrated joints were identified by field investigation: shearing along a single joint, shearing along multiple parallel joints, shearing across joints, and shearing through multiple joints and shaping as step-path deformation. (2) With the increase of joint number, peak strength and elastic modulus of rock mass decreased and the stair-shaped phenomenon of fracture became obvious. (3) The distance between tensile cracks, which are developed between joints during deformation process, has something to do with the joint spacing. Large spacing formed large distance, and small spacing formed small distance. (4) Although the elastic modulus decreased with the increase of smooth joint (SJ) number, no matter how big or small spacing is, for the rock mass with the same number of smooth joint, the elastic moduli are very close to each other. This may be the result of behavior of hard rock material and SJM assumption. The results of this paper illustrated that fracture developed along concentrated parallel joints should consider the interaction between joints. But how to consider and deal with the concentrated parallel joints for the slope stability calculation still needs more discussion.

This paper is about the geological investigation results at a proposed large hydropower station site.The sheet joints with gentle and medium dips are developed in the superficial slope and manifested as disjunctive distribution of joint concentration areas and joint sparse areas.They control the rock mass structure and stability of high slope.This finding is based on massive field investigation.The paper summarizes and analyzes the basic geological characteristics and distribution characteristics of the sheet joints at the dam site,and explains the joints'formation mechanism and development model.The results of the study show that:(1 )Sheet joints paralleled to bank slope belong to tension joints-system due to down-cutting of valley and displacement of stress.(2)The formation of bank slope is a result of repeated down-cutting of valley.After down-cutting,the angle of slope becomes steeper. That's mean dip angle of sheet joints formed in the late is steeper than that in the early stage.When the valley generates down-cutting and lateral erosion,the convex bank slope is beneficial to save earlier gentle joints.This is the reason that both gentle dip joints and moderate dip joints are available in the upper-middle part of the convex bank.(3)The canyon is formed by intermittent rapid down-cutting.During relative stable stage,sheet joints are developed in bank slope.During rapid down-cutting stage,vertical unloading mainly develops in the valley bottom. Thus in the bank slope,the disjunctive distribution of joint concentration areas and joint sparse areas are observed, which corresponds to relative stable stage and rapid down-cutting stage,respectively.

There are very complicated engineering geological conditions in the left abutment slope of the Jinping I hydropower station with the stress-release opening of fractures along existing faults and where lamprophyre veins are present. Prior to the excavation for the dam, the slope generally consisted of a thick marble mass between fault f(5) and the free face. As a consequence of the removal of some of the marble to create the abutment, the stability of the slope would be reduced. The paper reports the stability assessments undertaken, based on engineering geological analysis and block theory and the results of the analysis of key rock masses under four conditions: natural, heavy-rain, earthquake and heavy-rain plus earthquake.

At #Ⅳ～#Ⅵ ridges in the left bank slope of Jingping First Hydropower Station,there are numbers of deep cracks and faults,such as F2,F5 and F9,which result in huge latent instable block in this area.So the stability of huge block becomes an important problem under the conditions of excavation and flood discharge.The cracks' distribution character and the influence on slope's stability are summarized;and the deformation model of #Ⅳ～#Ⅵ ridges under the condition of flood discharge is analyzed based on plentiful geologic investigation data.Additionally,the change of stress,especially the zone of tension stress is analyzed at the course of excavation by means of three-dimensional numerical simulation,in which the influence of excavation on slope stability is studied.It is the conclusion that there is no evidence difference to stress and whole stability of the ridges after excavation.On the other hand,the deformation of #Ⅳ～#Ⅵ ridges is analyzed and computed under the changed hydrogeological geology condition by FLAC3D.The calculation based on parameter and water table sensitivity indicates that the whole slope's stability is more sensitive to rock mass parameters than different water table.

In the right bank slope of Jingping No. 1 hydropower station, Pusiluogou dam site slope is steep, over 1000 in high and the man slope is over 400 m high. The shape of man slope is complex and excavation volume is massive. So it is necessary to study the stability problem of the high slope. In the present paper, it is known that the whole stability of every engineering slope is good, but the local stability problem is severity based on plentiful geologic investigation data. Based on plentiful investigation data and the test results, a numerical model of the Pusiluogou slope is built with FLAC3D. According to the result of simulation, it is known that the integral stability is good, but the stability of local block is bad at the course of excavation.

After the accumulation slope above the left bank intake of Xiluodu Hydro-electrical Power Station is excavated, it has been discovered by drill-monitoring that there exist obvious deformations at the deep-seated of the slope. Based on a lot of studies, we think that the deformation should be caused by excavation. Being characterized by stable-creep, the deformation is practically a kind of deformation-adjustment due to stress re-distribution during cutting. Although the safety factor with respect to strength is more than 1.0 (under natural conditions), it is not satisfied with safety standards of building slope engineering.

The geologic exploration shows that except the normal relaxed cracks,there exists a kind of deep-seated deformation-fracture system inside the left bank slope in the front of a dam.The genesis of the fracture system is studied in this paper.It can be concluded that the fracture system observed in the high slope,being reverse and in a high-intensive geo-stress environment,is caused by the stress release during the rapid down-cutting of the river.Therefore,this fracture system is a stable structure.This conclusion will be conducive to the evaluation of the high slope stability.

A brief description is given to the currente status of the study on slope rochmass deformability and FLAC-3D soft mare firstly and then, using FLAC-3D,deformation of Gapa landslide is studied by means of numerical simulation under natural situation and impounding conditions. On the basis of calculation results obtained from simulation, by means of analysis of displacement value of character ristic points in the main section and displacement vector, deformation features under natural situation and different impounding conditions are given . The relation of deformation features and stability of landslide is established . Finally, essential theory is given to evaluate stability of Gapa landslide in the future.