Slope Body Research Articles

Progressive failure analysis of soil slopes considering the influences of humidity and loading

To analyze the progressive failure of structural loess slopes due to changes in humidity and loading, this study analyzes the degrees of influence of these changes on slope failure and their relationships with various structural parameters. According to the analysis, the shear failure of the soil gradually develops with the change of the water content. When the water content reaches a 17%, with the development of shear deformation, the shear zone is formed and finally penetrates the soil body. With the increase of the water content, the total displacement of the slope body gradually develops. When the water content reaches 17%, the total displacement of the slope body changes suddenly. This mutation is consistent with the formation of the shear zone. The sudden change of displacement indicates the penetration of the shear zone and the damage and slippage of the slope. With the increase of the soil moisture of the slope, the strain localization phenomenon occurs, the development of strain localization and shear bands increases, the structural damage increases, and the quantitative structural parameters decrease. The quantitative parameters can therefore be used to evaluate the feasibility and rationality of the progressive failure process of homogeneous structural loess slopes.

Alteration of soil structure following seepage-induced internal erosion in model infrastructure embankments

The flooding of infrastructure embankments has the potential to cause lasting destabilisation through seepage-driven internal erosion development. To understand the effects of such erosion on slope behaviour it is imperative to identify where in slopes material alteration most commonly occurs. Laboratory testing on scale models of transportation embankments was undertaken to identify the locations within slopes where material movement, and likely property alteration occurs, caused by seepage through slopes. Changes in material properties were most commonly found to occur along the base of slopes and in regions of slopes adjacent to water inflow. Slope toes were found to have a greater proportion of fine material than elsewhere, with the mean grain size of the slope toe region 4.5% smaller and the coefficient of curvature 9% higher than in the main slope body, suggesting the development of a low permeability region towards the slope toe. The source zone for material deposited at the toe of slopes was the section of slopes adjacent to water inflow and the base of slopes away from the toe, shown by a coarsening of sediment in these zones. Material alteration following flooding was best identified using a combination of coefficient of curvature and mean grain size data. These results have implications for the stability of earthworks during and after flood events, and for the design of earthwork inspection and maintenance regimes.

Dynamic reliability analysis of three-dimensional slopes considering the spatial variability in soil parameters

Slopes are commonly a significant aspect of geotechnical engineering projects. The incorrect evaluation and prediction of slope stability can cause serious disasters when it experiences seismic activity, and reliability is the key index a slope’s dynamic state. Spatial variability is an inherent soil property and has an essential influence on the dynamic response of a slope body. However, in previous studies, soil was often described deterministically, and the interaction between the uncertainty and spatial dimensions was ignored. To fill this gap, in this paper, practical expressions for the cohesion and friction angle in each working condition are given to simulate spatial variability by a lognormal random field. Then, the finite element method and effective dynamic reliability calculation method are used to obtain the safety factor of a 3D slope. Finally, the generalized probability density evolution method is performed to obtained the probability density information of the dynamic slope response and judge the influence of the soil spatial variability probabilistically. Due to the spatial variability in soil, the probability density distribution under each condition is distributed in a large range and thus may not provide results that are much more dangerous than those of the deterministic simulation. Meanwhile, the friction angle is more sensitive than cohesion and shows stronger discreteness in the spatial variability. The change in the cross-correlation coefficient has a greater influence on reliability than the autocorrelation length. Consequently, the simplification of model slopes in dimension and variability could deviate the reliability results from actual dynamic responses, either overestimating or underestimating, resulting in incorrect designs and evaluations.

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.

Bearing Capacity Analysis of the Weak Basement, Progressive Destruction Analysis, and Evaluation of the Dump on an Inclined Strip Section Using the Upper-Limit Method: A Case Study in an Anonymous Open-Cast Coal Mine

Due to terrain and transportation constraints, some open cast mines have to choose a weak basement as their tailings dumping grounds. Therefore, ensuring the bearing capacity and slope stability of dumping grounds on the weak basement is of great significance for the production capacity and economic benefits of open cast mining. To ensure the safety of surrounding facilities and the normal production of open cast mines, the bearing capacity of the dumping ground of a certain open cast mine was calculated using the oblique strip method and verified by numerical simulation. On this basis, the potential failure mode of the dumping ground base was analyzed, and the ultimate bearing capacity of the dumping ground under current conditions was calculated. The results are as follows: (1) The ultimate bearing capacity of the current dumping ground base is 3781 kPa, and the failure mode of the base is overall shear sliding along the base of the dumping ground. (2) When the slope foot increases from 12° to 18°, the stability coefficient and critical bearing capacity coefficient of the slope base decrease by about 21% and 46%, respectively. The slope angle has a greater impact on the bearing capacity of the base, and the height of the slope body has a relatively small impact, with almost no width effect. (3) Compared with the classic Terzaghi method and Prandtl method, the ultimate bearing capacity of the dumping ground base determined using the oblique strip method proposed in this paper is closer to the numerical simulation results, with an error of no more than 5%, a consistent critical sliding surface, and results that are relatively consistent with the engineering practice monitoring of the surface uplift part. The calculation results of the bearing capacity of the weak basement of open cast mine dumping grounds using the oblique strip method are reliable.

Study on the Prevention and Control of Downhole Debris Flows Based on Disaster Chain Theory

The occurrence of downhole debris flows in caving mines has burst, concealment, and destruction characteristics. This study aimed to investigate accurate prevention and control measures for downhole debris flows. The research background was a downhole debris flow in the Plan copper mine. The disaster chain theory was applied to study prevention and control methods for downhole debris flows. Using a model of source generation, chain breaking, and disaster reduction, we proposed accurate prevention and control measures for downhole debris flow disasters, which prevent and control the downhole debris flows at the source. The results showed that the disaster chain type of downhole debris flow disasters is the compound periodic cycle chain, which has the characteristics of the branch basin chain and the periodic cycle chain. Based on the chain-effect nature of disasters caused by downhole debris flows, active and passive prevention and control methods for downhole debris flow disasters were proposed. The active prevention and control measures for chain breaking and disaster reduction involve isolating the generation conditions from the source, inducing a downhole debris flow disaster. This prevention and control method is difficult to implement during the actual production process. The idea of disaster reduction through passive defensive chain breaking is based on the fact that if the three essential types of conditions for the downhole debris flow formation are not present at the same time, then a disaster accident of a downhole debris flow can be effectively prevented and controlled. Accordingly, the following measures are proposed for preventing and controlling downhole debris flows: (1) reinforcement measures applied to the slope body of the landslide material source in the collapse pit; (2) adopting comprehensive flood control measures such as locking, intercepting, dispersing, draining, and blocking under hydraulic conditions; (3) blocking the formation of the channel by adjusting the ore drawing conditions; (4) addressing the inducing factors by blasting with a small amount of explosive. According to the disaster chain theory, prevention, and control methods for downhole debris flow in caving mines were investigated in this study, which not only broadens the research of the debris flows but also fills the gap in the systematic research on downhole debris flows.

Study on the mechanism of water-induced degradation of slip zone soils and FDEM coupled simulation of slopes based on multi-scale characteristic

The evolution of the mechanical properties of slip zone soils had a greater impact on the structure of soil slopes with large upper porosity and excellent infiltration conditions. Especially under the rainfall effect, it was easy to be affected by the infiltration effect of internal injury, which will lay a ‘hidden danger’ for the slope body to trigger sliding in the secondary transformation process. In this paper, based on Haijiao ping landslide in Guizhou, SEM image recognition techniques were used to reveal the water-induced degradation mechanism of the sliding zone soil from multiple scales and the damage parameters were obtained. Meanwhile, the FDEM numerical model was established to simulate the stability of the slope coupled with indoor TCT test results. The results proved that the angle of internal friction decreased linearly with the increase of water content on the macroscopic scale, but the cohesive force showed an increase and then a significant decrease. The effect of matrix suction in the microscopic scale was significant at lower water content, the internal cohesion formed a large number of agglomerate structures to resist external deformation, but the microstructure was loose and porous after sufficient water immersion. The pore space spreads directionally and the area increases by 2.66 times. The cross-scale discrete-finite element coupled simulation method based on image recognition can visually respond to the macroscopic mechanical properties and stability change response of the slope body caused by microscopic damage. The water-induced degradation effect of rainfall on slip zone soils was the inherent factors for the initiation deformation of landslide. The artificial excavation was the external factor that triggered the slope to slide. This type of landslide was more concealed in its natural state and prone to deformation when excavated after long-term rainfall.

Analysis of Seismic Damage Modes of Landslides Containing Tunnels under Horizontal Earthquake Action

With the vigorous development of railway and highway construction, tunnel construction often follows the mountains and rivers, crossing high-intensity landslide areas, and potential earthquakes triggering damage in areas including tunnel landslides have become a hot issue today. Based on this, this paper performs a shaker test on the tunnel-containing landslide body, inputs horizontal seismic waves, and tests the acceleration response data of different bits in the landslide body. By analyzing the temporal and frequency domain transformations of the acceleration response at different positions in the slope body combined with the deformation characteristics of the slope, and then analyzing the seismic response of the slope under the action of the front and back seismic sequences, the results show that (1) the existence of the tunnel has the effect of energy dissipation and vibration reduction, making the energy input at T8, and the measuring point on the upper part of the tunnel at the lowest. (2) When the seismic wave is transmitted, it will cause reflection around the tunnel, forming complex seismic wave field, resulting in the irregular distribution of acceleration amplification coefficient. (3) There is a high correlation between seismic responses of different levels. When the acceleration response of the preseismic response to the landslide-containing tunnel is not considered, the acceleration response of the postseismic response to the slope and the structure will be lower than the real value. (4) The sequence of failure at different locations of landslide mass containing tunnel is found through marginal spectrum analysis. It is concluded that the failure mode of landslide mass with tunnel is extrusion and sliding out of the middle slope. The research results can provide some reference for the reinforcement design of landslide with tunnel in high-intensity area.

Calculation for Permanent Displacement of Single Slip Surface of Multi-Stage Loess Slope Based on Energy Method

At present, there are still some gaps in the theoretical calculation of the permanent displacement of the multi-stage loess slope under the action of earthquake. Therefore, this paper firstly uses the GEO-Studio finite element software to explore the influence of the comprehensive slope rate on the permanent displacement when the slope rate of each grade of multi-stage loess slope changes and the stage of multi-stage slope changes. The results show that it is feasible to use the comprehensive slope rate to calculate the permanent displacement of the sliding body of the multi-stage loess slope under the action of earthquake. On the basis of this conclusion, in order to simplify the calculation of permanent displacement of potential sliding soil, the other geometric parameters of the multi-stage loess slope are replaced by the comprehensive slope rate, combined with the Newmark slider displacement analysis method and energy conservation principle, and then the calculation method of permanent displacement of potential sliding soil of multi-stage loess slope under the action of earthquake is deduced. Through an example, the permanent displacement calculated by the proposed algorithm are compared with those calculated by the PLAXIS 3D software and GEO-Studio software. The results show that the permanent displacement calculated by this method is close to that calculated by the GEO-Studio software, and the difference is only 2%, and thus, the rationality of the proposed method for calculating the permanent displacement of the multi-stage loess slope under the action of earthquake is verified. The algorithm proposed in this paper provides a theoretical reference for the calculation of the permanent displacement of multi-stage loess slope under the action of earthquake.

Failure Mechanism and Stability Control Technology of Slope during Open-Pit Combing Underground Extraction: A Case Study from Shanxi Province of China

With the development of society, the demand for mineral resources is gradually increasing, and the current situation of decreasing total resources dictates the inevitable interaction between open-pit combing underground extraction (OPUG) in time and space. In this research, we took the Anjialing coal mine in Shanxi Province of China as a case study, and tested the physical and mechanical properties of coal rocks in the laboratory. The similarity criterion was used to build a similar experimental model for the deformation evolution of the slope of the open-pit mine section; the digital scattering method was used to test the influence of the underground mining process parameters on the deformation evolution of the open-pit slope. The results showed that there was an obvious distribution of “three zones” above the mining goaf, namely, a collapse zone, fracture zone, and slow subsidence zone. When the mining face was continuously advanced towards the bottom of the open pit, the supporting stress of the mining face transferred to the side of the open-pit slope. Additionally, large displacement and stress concentration were observed on the slope near the stoping line, which caused the slope body to move along the uppermost part of the slope first, and thereafter along the lower part. Various techniques for slope stability control are discussed, including the optimization of spatial and temporal relationships between open-pit and underground mining, the optimization of mining plans, and the use of monitoring and early warning systems. The results can provide a guide for slope stability control of similar open-pit mines in the process of mining coal resources.

Study on the Ground Fissure Development Law of Coal Mining Based on UAV Photogrammetry and the Particle Flow Theory

Ground fissures caused by underground coal seam mining easily result in secondary geological disasters and destroy the ecological environment, which seriously impacts the production and life of mining areas and residents. The traditional monitoring methods, such as manual measurement and satellite monitoring, have their disadvantages. Therefore, it is urgent to develop a large-scale monitoring technology for ground fissures and study its development law. In this article, we analyzed the distribution characteristics of ground fissures based on the low-altitude UAV remote sensing images and combined them with field investigation as validation. Moreover, we introduced the particle flow theory to study the development law and formation mechanism of ground fissures. This article takes the 8092 working face of a mine in Ordos City as the study area. The results showed that the accuracy rate of ground fissures based on the visual interpretation of UAV images was 95%. The ground fissures were mainly distributed near the stopping line and the groove of the working face. The plane forms of ground fissures were mainly two types: the linear type and arc type, and the location relationship can be divided into the parallel type and bifurcation type. The types of ground fissures were the tensile type and step type. Whether the upper and lower parts of the key strata were broken simultaneously is the root cause of tensile ground fissures and step ground fissures. The stability of the overlying strata had a significant influence on the change of abutment pressure above the goaf. The process of surface movement and deformation can be divided into three stages: tensile failure of the slope bottom, traction failure of the slope body, and sliding failure of the slope top. In addition, the zero point of the surface horizontal movement value and the maximum surface subsidence were not in the center of the goaf. Due to the horizontal slip of the downhill direction in the horizontal movement on the surface, the value of the downhill direction subsidence was zero. However, the value of the horizontal movement was not zero, and there was even a large horizontal movement. In conclusion, the research results can provide a useful reference for the rapid monitoring of large-scale geological disasters caused by underground coal seam mining and the application of the particle flow theory.

Combined ERT and GPR Data for Subsurface Characterization of Weathered Hilly Slope: A Case Study in Zhejiang Province, Southeast China

Rain-triggered landslides frequently threaten public safety, infrastructure, and the economy during typhoon seasons in Zhejiang Province. Landslides are complex structural systems, and the subsurface features play a significant role in their stability. Their early identification and the evaluation of potential danger in terms of the rupture surface and unstable body are essential for geohazard prevention and protection. However, the information about the subsurface acquired by conventional exploration approaches is generally limited to sparse data. This paper describes a joint application of ground-penetrating radar (GPR) with a 100 MHz antenna and the electrical resistivity tomography (ERT) method with the Wenner configuration to identify the stratum structure and delineate the potentially unstable body of a clay-rich slope, the results of which were further verified using borehole data and field observation. The acquired results from the GPR and ERT surveys, consistent with each other, indicate two stratigraphic layers comprising silty clay and silty mudstone. Moreover, the potential rupture zone very likely exists in the highly weathered mudstone in the depth range of 3–7 m, and the average depth is 5 m. In addition, the thickness of the unstable mass is greater on the east and crest parts of the slope. Conclusively, the optimum combination of ERT and GPR is reliable for conducting rapid and effective delineation of subsurface characteristics of clayey slopes for risk assessment and mitigation during the typhoon season.

Slope displacement and soil pressure of soilbag-retaining wall influenced by arrangement

Soilbags have a good effect on slope reinforcement. In this paper, five kinds of physical model tests were carried out on slopes strengthened by reinforced soilbag-retaining wall, namely analysis of the failure mode and failure pressure of the slope, the variation trend of horizontal displacement of the slope, the maximum horizontal displacement and the horizontal transmission and vertical distribution of earth pressure. Thus, the influence of the arrangement mode of the soilbags on the slope reinforcement effect were studied. The results show that the alternate arrangement between layers (arrangement mode 1) had the deepest slip surface, the maximum bearing capacity and the minimum horizontal displacement, thus its reinforcement effect was the best. In addition, the reinforcement effect of the slope was related to the amount of tail embedded into the slope body, the interaction of soilbags in the layer and the embedment between the upper and the lower layers of soilbags. It was found that when the embedding degree of the tails into the slope was higher, the horizontal deformation constraint of the slope was stronger, resulting in a deeper sliding surface and a higher ultimate bearing capacity of the slope. This shows that the slope reinforcement effect was better with soilbags.

Experimental Study on the Accumulation Characteristics and Mechanism of Landslide Debris Dam

According to physical model tests, we analyzed the accumulation characteristics of landslide dams formed under three different slope characteristics, namely, uniform slope, parallel slope, and intersecting slope and investigated the accumulation mechanisms of the debris dams. The relationship between slope types and accumulation characteristics was also explored using the tracer particle analysis method. The damming process and accumulation mechanism of the landslide dam were changed with slope conditions, which lead to the difference in the accumulation characteristics of the dam, especially in transverse cross-sectional shape and grain size distribution. The transverse cross-sectional shape of the landslide dams formed by different slope conditions can be divided into three categories: the flat pattern, unidirectional pattern, and undulating pattern. The characteristics of the slope body are closely related to those of the landslide dam with respect to debris distribution. The debris distributions in the longitudinal and transverse directions of the slope body are consistent with those in the longitudinal and sliding regions of the dam. A general inverse grading characteristic of debris gains occurs in the vertical direction of landslide dams. For the uniform and parallel slopes, obvious inverse grading distribution is induced by overall-starting initiation of the slope body and strong vertical infiltration of the fine sands during the movement. However, inverse grading distribution is generated by the effects of pushing–climbing and lateral infiltration that existed among particles caused by a layered-starting mode for the intersecting slope body. This study provides a basis for the prediction of landslide dam formation and backtracks the initial structure of the slope.

Force and deformation response analysis of dual structure slope excavation and support

Aiming at the problem of fuzzy selection basis of dual-structure slope simulation calculation parameters and the complicated force and deformation of the slope body in the supporting process. The study relies on the treatment project of the right side slope of the K5 + 220-K5 + 770 section of the TJ1A section of the Jiangwen Expressway. The slope is a gravel soil-weathered bedrock dual structure slope, which is referred to as Hetangba slope in the study. Use Midas/GTS NX to build a trial calculation model. A new method for checking simulation parameters of deep displacement monitoring data is proposed. The superposition calculation method of pore water pressure is proposed to realize the slope stress-seepage coupling. The analysis method of slope excavation and support process is put forward. The analysis shows that the most dangerous working condition in the slope excavation and support process is the second-level excavation. When there is a local displacement and plastic strain concentration area on the slope, the reference significance of the extreme value and the safety factor is reduced. Compared with the application of pore water pressure and no pore water pressure, there is no obvious change in the position of the extreme value of horizontal displacement and plastic strain in working conditions 2–8, but the extreme value changes are different. The slope safety factor of working conditions 2–8 is reduced. The continuous distribution zone of plastic strain inside the slope disappeared in condition 7. There is a very small unstable area on the top of the third-level slope of working conditions 9–11. The research results have great theoretical guiding significance for the measurement and control simulation and early warning analysis of the dual structure slope construction process.

RHEOLOGICAL CHARACTERISTIC OF VOLCANIC CLAY AND IMPLICATION TO ITS LONG-TERM STRENGTH AND TIME DEPENDENT BEHAVIOR

As a natural phenomenon, land movement does not occur suddenly, but it is a long-term phenomenon in the form of un-recoverable low rates deformation caused by constant stress on a slope body and known as creep. Therefore, it is very important to understand the rheological characteristics of the soil under constant stress and implication to its long-term strength and time dependent behavior of a soil mass. The laboratory shear creep tests were carried out on 15 undisturbed volcanic clay samples taken from the southern slopes of Lembang Village, Cililin, West Java, Indonesia. The tests were carried out by applying a constant shear stress level of 50% - 95% from the peak shear strength. The results show that the level of constant shear stress will affect to the rheological characteristics of the soil samples. The higher level of shear stress, the shorter failure time. Based on the shear creep tests, the rheological model was established, the failure time of the soil samples were estimated and the long-term strength equation was obtained. The long-term shear strength of the volcanic clay is decrease 52.38% from the peak shear strength and achieved after 925 days (±31 months). The cohesion (c) and internal friction angle (f) decrease from 41.548 kPa and 17.051o become 21.188 kPa and 9.129o, respectively. The shear creep test also shows that the soil shear strength parameters (c and f) are a function of time.

Dynamic Response of Bridge-Landslide Parallel System under Earthquake

In order to further understand the instability mechanism and geohazard causation when the main sliding path of the slope body is parallel to the path of the bridge, the corresponding bridge-landslide parallel system is constructed for shaking table tests. This paper summarizes the combination forms of bridge-landslide model under different position and focused on the slope body located above the bridge deck. Firstly, based on the shaking table test results of El Centro (1940), the failure behavior of bridge-landslide parallel system was evaluated, and the changes of acceleration and deformation of bridge pile were subsequently analyzed. Then, the interaction bridge structure and sliding body were explained by the spectral features. The main conclusions are as follows. First, in the model test, the landslide belongs to the thrust-type landslide. Due to the barrier function of the bridge, the main failure site of landslide occurs in the middle and trailing edge of slope body. At the same time, the acceleration value of earthquake waves is 0.3 g, which is the key to this variation. Second, the acceleration response of the measuring points on the bridge pile and landslide increases with the increase of ground elevation. If the slope structure is damaged severely, the deformation response of weak interlayer is inconsistent with the surrounding soil structure. Third, with the increase of excitation power, the dominant frequency of bridge-landslide parallel system gradually transitions from low to high frequency rate, and the interaction of the parallel system weakens the influence of river direction on frequency. Finally, under the same working condition, the dynamic response of the measuring points has obvious regularity with the change of situation. But the response of the same points is not regular due to the different earthquake excitation intensity.

Dynamic evolution mechanism of a rock slope with discontinuities under earthquake motions using shaking table tests

Under the impact of earthquake, even if the slopes do not fail, the integrity of rock slope structure would be damaged subjected to the seismic motion. The process of damage, destruction and failure for slopes is characterized by the dynamic evolution of stability. In the areas with active tectonic activities, frequent earthquakes have a significant effect on the attenuation of slope stability. To investigate the dynamic evolution of a rock slope under earthquake motions, a series of shaking table tests were performed. An artificial synthetic earthquake seismic wave was adopted to investigate the horizontal acceleration response. The results show that the wave field propagation results in acceleration amplification for the slope body above the tuff structural surface are larger than those inside the slope, and a maximum value of 3.7 is observed at slope crest. The structural surface results in a mutation of the acceleration response, which is not conducive to the slope stability. The modeled slope entered the plastic stage (input motion of 2.97 m/s2) earlier than landslides occurred (input motion of 4.46 m/s2). In addition, the safety factor of the sliding blocks was calculated based on pseudo static analysis. A good correspondence was found between the safety factors and the failure mode of the slope. The damage evolution process for the rock slope can be divided into three stages: an elastic stage (1.6 < safety factor ≤ 4.7), a plastic stage (0.8 < safety factor ≤ 1.6), and a damage stage (safety factor ≤ 0.8).

STUDY ON RHEOLOGICAL CONSTITUTIVE MODEL OF CILILIN VOLCANIC CLAY, INDONESIA IN RELATION TO LONG-TERM SLOPE STABILITY

: Ground movements do not remain constant over time but it is a time-dependent phenomenon in the form of long-term deformations due to in-situ stresses acting all the time on the slope body. Therefore, the time-dependent behavior of soil mass is an important factor that influences long-term slope stability. To understand the long-term slope stability, research on soil rheological characteristics is required so that the time-dependent soil strength reduction can be known. The result of the research will be very useful for the policymaker in disaster mitigation and regional planning. To determine the rheological characteristics of Cililin Volcanic Clay, a laboratory shear creep test was carried out on soil samples taken from the Cililin area, West Java, Indonesia, which is well known as landslide-prone areas. Fifteen undisturbed soil samples were prepared for laboratory shear creep tests. The level of shear stress applied to the shear creep test is 50% - 95% of the peak strength. Then, the soil rheology constitutive models were established which are used to understand the creep behavior of the soil, determine the soil long-term strength, estimate the reduction of soil parameters as a function of time and calculate long-term slope stability. The result shows that the long-term strength of soil is reduced 48.80% from its peak strength after 16 years. The cohesion and internal friction angle reduced from 44.72 kPa and 30.34o become 21.82 kPa and 15.94o, respectively, and the slope safety factor is reduced from 2.16 to 1.04. Rheological modeling also shows that slope stability is a function of time.

Slope stability analysis and protection of deep accumulation excavation foundation pit in the Sichuan Bank of the Kahalo Jinsha River Bridge

The Kahalo Jinsha River Super Large Bridge of the Sichuan Riverside Expressway spans the deep canyon of the Jinsha River and is situated in a high-intensity, complex, and dangerous mountainous area. Long-term deformation and stability of the gravity anchor slope are the main controlling factors affecting bridge safety. The maximum slope height formed by the excavation of the gravity anchor foundation pit on the Sichuan Bank of the Kahalo Jinsha River Bridge is 110m, and the anchorage area is located on the Q3h thick accumulation with a thickness of more than 170 m. First, the important soil mechanical parameters, such as shear strength, deformation modulus and bearing capacity eigenvalues of rock and soil were obtained by conducting field shear tests, deformation tests, and load tests. On this basis, the pseudo-static method was used to simulate the seismic conditions, and a three-dimensional numerical analysis and calculations of the potential instability range of the high slope of the gravity anchor foundation pit excavation were conducted. The results reveal that the slope of the super-deep foundation pit with a huge thick mixed accumulation layer will deform and become unstable under the influence of an earthquake, with a maximum deformation of about 20 m in the slope body. A two-level earthquake prevention and disaster-reduction target for the bridge foundation pit and slope engineering protection is proposed based on the two-level seismic fortification requirements of super-long-span suspension bridges. An active reinforcement scheme of excavation pre-reinforcement, step-by-step excavation, and zoning protection is designed and proposed based on this target and the deformation and stability analysis results of the field test and three-dimensional numerical calculation.