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Landslide dams formed by successive rock slides in the same location may cause severe and long-term destruction to affected areas. However, studies on the formation of landslide dams that result from successive rock slides are still at early stages. In this paper, a flume test that could model rock fragmentation and the flow of fragmentary material is used to study the formation of landslide dams triggered by successive long-runout rock slides. The tests assess the effects of number of blocks, the number of times the blocks are released, and the initial arrangement of blocks before release on the dam geometry. The maximum and minimum landslide dam heights rise with the increasing number of blocks in each series of tests, while there is minimal or even no growth in the dam length for some series. Additionally, more block releases produce larger minimum dam height but smaller maximum dam height. Together, these results indicate that more releases are prone to fully block the flow channel by forming a steep dam. Furthermore, the initial block arrangement is also found to influence the landslide dam formation. In this study, landslide dams caused by successive rock slides are divided into two types: the stable type, namely, the landslide dam(s) already formed by the previous slide event(s) maintains general stability before the next slide lands on the dam surface; the unstable type, namely, the landslide dam(s) by the previous slide episode(s) has failed before the next damming slide occurs. Field investigations showed that slide episodes in both types of successive landslide dams are influential for the dam formation and river morphology.

Cemented tailings backfill (CTB), an evolutive man-made soil or porous medium, is extensively utilized in underground mines as a sustainable solution for the disposal of tailings (mine waste) and/or ground control. At the early stages of curing, CTB is commonly saturated and weakly cemented, and thus subjected to the risk of seismically-induced liquefaction caused by mine blasts, rock bursts and earthquakes. The resulting intrusion of liquefied backfill mass into the mine tunnels may give rise to significant casualties and loss of production. In the present study, an evolutive bounding surface plasticity model is developed to capture the hydro-mechanical response of hydrating CTB under cyclic loading. Specifically, the changes of model components (yield and plastic potential functions, etc.) due to evolution of material properties are incorporated into the prototype bounding surface model. Then, the material property changes induced by binder hydration are determined and coupled to a binder hydration model that quantifies the curing process of CTB. Therefore, the developed model can be employed to assess the cyclic response of hydrating CTB at any given time of interest during its early age of curing when seismically induced liquefaction is of primary concern. The simulated results show good agreement with the experimental data for both monotonic and cyclic loadings. The proposed model can therefore provide more insight into the behavior of early-age CTB under seismic loading, and contribute to designing cost-effective CTB structures and assessing the risk of liquefaction.

In the process of underground cavern excavation, the existence of the interlayer shear zones or large faults often makes the surrounding rock tend to be unstable or even deformed. Under the influence of interlayer shear zone C2, different degrees of deformation and failure occurred in many parts during the excavation of the Baihetan left bank underground powerhouse. Based on field monitoring and numerical calculation, this paper studies the deformation and failure characteristics of the rock mass with C2 in the whole excavation process and the failure mechanisms are analyzed. The results show that C2 has poor mechanical properties. In the process of excavation, it mainly induces two failure modes: rock collapse and shear deformation, which specifically leads to rock collapses, large deformation and shotcrete cracking in the main powerhouse, and shear deformation in the omnibus bar caves. In addition, the similarities and differences between this study and other studies on the deformation and failure of surrounding rock of underground powerhouse in recent years are discussed, and the relevant treatment measures for C2 are given. The above research results can be a reference for other related studies.

The 2019 Shuicheng landslide was a typical landslide in that failure occurred in the slope deposits and there was a close correlation with the antecedent rainfall. The initiation mechanism was analysed using field investigations, laboratory tests and numerical simulations and the characteristics of mass movement were quantitatively assessed. The numerical results indicated that the infiltration of rainfall decreased the shear resistance of the slope and increased the pore water pressure and soil weight, resulting in a large deformation of the slope and a gradual deterioration in its stability. After saturation, as the pore water pressure coefficient (ru) approached 0.3, the overall safety factor decreased to 1 and failure eventually occurred. Quantitative mass assessment showed that the unique terrain aggravated the erosion and entrainment effects and that the inclusion of loose material and water promoted the movement of the debris avalanche by changing it into a fluidized state, resulting in a much larger landslide volume with a long runout distance. As a result, the volume of the failed mass, which was calculated by an unmanned aerial vehicle and terrestrial laser scanning modelling techniques to be c. 4.7 × 105 m3 in the source area, almost quadrupled to >2.0 × 106 m3.

A comprehensive literature review has been carried out on existing models that characterize soil response under the impact of blast shock waves. Various models in the literature are reviewed and discussed in terms of their equations of state that account for the effect of high pressure, failure models that control the yield behaviour, and strength models that represent the effect of high strain-rates, along with a comparison of their advantages and limitations. Then, the application of different soil models to blast-induced liquefaction is elucidated and compared. Consequently, this review provides a comprehensive understanding of the fundamental and unique aspects of modelling soil response subjected to such transient impulsive loading on the grounds of increasing global interest in blast response of soils.

Tailings backfill, which is a subsurface fill mass, has been extensively utilized worldwide in underground mines to fill mined-out cavities for the purposes of ground control and tailings disposal. Just after placement, very early-age backfill which commonly contains a large volume of water exhibits little or no interparticle bonding, and is subjected to the risk of liquefaction induced by routine mine blasting. In this study, a modified total-stress viscoplastic cap model is developed to investigate the blast-induced liquefaction susceptibility of very early-age fill mass under various practical backfilling and field conditions. The developed model well represents the strain-rate and fluid-compressibility dependence of nonlinear material behavior under such dynamic conditions, and also captures the development of excess pore pressure due to irrecoverable volume changes. The model is validated against a series of blast and impact tests on saturated natural soils (sand and silt) and tailings fill masses, and a good agreement is found between the experimental and simulated results. Subsequently, the model is applied to investigate the effects of drainage conditions, distance from detonation, stope size, location of retaining structure, and blast sequence on the liquefaction susceptibility of early-age fill mass after mine blasting. The results obtained from the study will provide practical insight into the blast liquefaction potential of backfill mass in field conditions.

Although a large number of previous researches have significantly contributed to the understanding of the quasi-static mechanical behavior of cemented tailings backfill, an evolutive porous medium used in underground mine cavities, very few efforts have been made to improve the knowledge on its response under sudden dynamic loading during the curing process. In fact, there is a great need for such information given that cemented backfill structures are often subjected to blast loadings due to mine exploitations. In this study, a coupled thermo-hydro-mechanical-chemical (THMC)-viscoplastic cap model is developed to describe the behavior of cementing mine backfill material under blast loading. A THMC model for cemented backfill is adopted to evaluate its behavior and evolution of its properties in curing processes with coupled thermal, hydraulic, mechanical and chemical factors. Then, the model is coupled to a Perzyna type of viscoplastic model with a modified smooth surface cap envelope and a variable bulk modulus, in order to reasonably capture the nonlinear and rate-dependent behaviors of the cemented tailings backfill under blast loading. All of the parameters required for the variable-modulus viscoplastic cap model were obtained by applying the THMC model to reproducing evolution of cemented paste backfill (CPB) properties in the curing process. Thus, the behavior of hydrating cemented backfill under high-rate impacts can be evaluated under any curing time of concern. The validation results of the proposed model indicate a good agreement between the experimental and the simulated results. The authors believe that the proposed model will contribute to a better understanding of the performance of hydrating cemented backfill under blasting, and also to practical risk management of backfill structures associated with such a dynamic condition.

In this study, a coupled thermo-hydro-mechanical-chemical (THMC)-viscoplastic cap model is developed to investigate the characteristics of blast wave propagation in a fill mass made of granular material (cemented backfill, CB) that is undergoing cementation under different curing conditions. The THMC model allows to evaluate its behavior and the changes in the material properties of the cementing granular material during the curing process, with rigorous evaluation of the coupled THMC factors. The THMC model is then coupled with a modified viscoplastic cap model to capture the nonlinear and rate-dependent behaviors of CB under blast loading. All of the material properties of CB required for the modified viscoplastic cap model are obtained from the THMC model. To validate the model, experiments carried out in high columns and impact testing on hydrating cemented backfill, as well as blast wave propagation experiments on soil and cemented backfill are adopted and simulated. A good agreement is found between the experimental and simulated results. Finally, by applying the coupled THMC-viscoplastic cap model, the effects of curing time, cement content, stope (mine cavity) size, initial backfill temperature, and filling rate on blast wave propagation in backfill mass are investigated. The obtained results provide new insight into blast wave propagation in fill mass under field curing conditions.

The seepage calculation of water fluctuation is the crucial precondition for landslide stability evaluation. It is controlled by the initial condition, boundary condition, and soil or rock structure as well as geotechnical parameters. Although the geotechnical parameters and boundary condition have greater influence on seepage and the stability of landslides, the role of the initial groundwater position cannot be ignored. To investigate the influence of an initial groundwater table on landslides, especially the influence of cyclical reservoir water fluctuation on their long-term stability, seven different methods to determine the initial groundwater table were proposed in the presented study, among which one is the actual groundwater table, and the other six are obtained with simplified methods. According to the results of the calculations, at the beginning, there is some difference in the factor of safety among different initial groundwater tables. The maximum value of relative tolerance reduces to less than 1.0 % 160 days later. After a filling–drawdown cycle, the relative tolerance of all methods reduces to less than 0.8 %, which could be ignored. It is also observed that, the closer the hydraulic gradient of the proposed initial groundwater table is to the actual condition, the smaller is the relative tolerance. Therefore, to study the influence of cyclical reservoir water fluctuation on landslide long-term stability, the initial groundwater table could be proposed as (1) equal to reservoir water level and (2) on a straight line with the hydraulic gradient equal to the weighted average of actual groundwater table for simplification.

The depletion of shallow-buried reserves has been driving the exploitation activities into the deeper crust, and the rising lithostatic stress thus poses substantial challenges to dynamic rock breakage. In this paper, we present new mechanistic insights into the effects of in-situ stresses on blast responses of intact rocks via integrated analytical and numerical analyses. An elastodynamic framework was first developed to characterize the blast wave propagation in pre-stressed rocks. The analytical solution suggests that the rock pressure can essentially promote dynamic compaction by diverting the explosive loading path and suppress fracturing by imposing circumferential compression. Such effects are more pronounced in the minor principal stress (σ3) direction of anisotropic stress fields. The rock responses under the coupled static-dynamic loadings were then simulated using a constitutive framework that was proven valid in this study for broad spectrums of pressures and strain rates. Image processing of the breakage patterns shows that the crushed zone contracts as the rock pressure rises. The crushed zone becomes elliptic in anisotropic stress fields, and its major axis coincides with the major principal stress (σ1) direction and declines more slowly than the minor axis aligned with σ3. The orientation distribution shows quantitatively that fractures get increasingly more clustered around σ1 as stress anisotropy rises, and the fracture density decreases more rapidly in equibiaxial conditions with greater vertical stresses. The consistent insights of the analytical and numerical studies can improve the mechanistic understanding of the evolution of dynamic rock behavior in different in-situ stress conditions.

In order to analyze the sensitivity of bending and toppling deformation of anti-dip slopes on the selected impact factors, numerical simulation is conducted and combined with grey relation analysis. Physical geometry, physical and mechanical properties of rock, and mechanical characteristics of joints are adopted as the first-grade impact factors on bending and toppling deformation; and they are further subdivided into second-grade factors of slope angle, strata dip, rock flexibility, etc. In the numerical simulation, eleven different levels of values are assumed for each of those impact factors, and eleven sets of numerical schemes are established randomly, then UDEC is used to perform the simulation for each case. Finally, by applying the grey relation analysis, the correlation of each impact factor (both first- and second-grade) on bending and toppling deformation are calculated. The results indicate that: (1) the correlation of the 12 s-grade impact factors on bending and toppling deformation are, in a descending order: strata dip > slope angle > kn/ks > Poisson’s ratio > Friction of joints > friction of rock mass > tensile strength of rock mass > flexibility > cohesion of rock > elastic modulus > cohesion of joints > density. (2) Among first-grade impact factors, the physical geometry has the greatest impact on the bending and toppling deformation of the anti-dip slope, and it is followed by mechanical parameters of joints, while the physical and mechanical parameters of rock are found to have the minimal influence.

Rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels, resulting in a significant impact on the continuity of mountainous rivers. Based on the extent of blocking, the blockage type is divided into three categories in this paper: no blockage (submerged dam), partial blockage, and complete blockage. The accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams. In this study, rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides, and the factors that dictate the formation of landslide dams are critically analyzed. The experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition. In addition, the less fragmented rocks result in larger maximum deposit height (maxi-DH) and smaller minimum deposit height (mini-DH), while the better fragmented rocks result in smaller maxi-DH and larger mini-DH. Furthermore, the water depth has a significant impact on the river blockage type. A new Blockage Index (BI) that combines the landslide volume and the wet cross-sectional area is proposed to assess the damming capacity of rock slides. Then a method for predicting the river blockage type of rock slides is developed based on the relationship between Blockage Index and the ratio of maxi-DH or mini-DH and water depth. The model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future.