Rockslides along a stepped failure surface have characteristics of stepped deformation characteristic and it is difficult to predict the failure time. In this study, the deformation characteristics and disaster prediction model of the Fengning granite rockslide were analyzed based on field surveys and monitoring data. To evaluate the stability, the shear strength parameters of the sliding surface were determined based on the back-propagation neural network and three-dimensional discrete element numerical method. Through the correlation analysis of deformation monitoring results with rainfall and blasting, it is shown that the landslide was triggered by excavation, rainfall, and blasting vibrations. The landslide displacement prediction model was established by using long short-term memory neural network (LSTM) based on the monitoring data, and the prediction results are compared with those using the BP model, SVM model and ARMA model. Results show that the LSTM model has strong advantages and good reliability for the stepped landslide deformation with short-term influence, and the predicted LSTM values were very consistent with the measured values, with a correlation coefficient of 0.977. Combined with the distribution characteristics of joints, the damage influence scope of the landslide was simulated by three-dimensional discrete element, which provides decision-making basis for disaster warning after slope instability. The method proposed in this paper can provide references for early warning and treatment of geological disasters.

The foundation of a large river crossing bridge is often located on high and steep slopes in mountainous area, and the stability of the slope has a significant impact on the safety of the bridge. Not only the bridge load, but also the hydro-dynamical action in the reservoir area has a significant impact on the stability of the bank slope where the bridge foundation is located, especially for the toppling bank slope. This paper takes the stability of the toppling bank slope where the one major bridge foundation is located at on the Lancang River in China as an example. Through on-site exploration, drilling data and core conditions, and television images of the borehole, the geological structure of the on-site bank slope were conducted. Based on the development of the dumping body obtained from on-site exploration, corresponding indicators have been proposed from the perspectives of rock inclination, deformation, and rock quality to clarify the degree of dumping along the depth of the bank slope. The failure mechanism of the overturned bank slope under the action of a bridge was analyzed from a mechanical perspective. Numerical simulations were conducted using GeoStudio 2018:SEEP/W and FLAC3D 6.0 software to analyze the failure modes of bridge loads and hydrodynamic forces under different water levels and rainfall conditions. The seepage field characteristics, failure modes, and stability characteristics were analyzed from a two-dimensional perspective, while the displacement characteristics, plastic zone, and stress–strain characteristics were explored from a three-dimensional perspective, which revealed the evolution mode of overturned deformation under the action of bridge foundation loads. Finally, the stability of the wide slope was numerically calculated using the strength reduction method, and the stability calculation data was combined with the numerical simulation results to determine the optimal location of the bridge foundation.

Toppling is a common deformation and failure phenomenon in the reservoir bank slopes of hydropower projects. This paper studies the genesis and evolution of different toppling bodies during water impoundment at the Miaowei Hydropower Station Reservoir on the Lancang River in southwest China. Toppling properties were determined and second failure characteristics analyzed in different reservoir impoundment stages. Different degrees of toppling deformation were primarily affected by the transverse bending stress, while the regional tectonic stress has been shown to have a significant effect on the transverse bending of the rock layers. Combined with the on-site investigation and monitoring results, the failure mechanisms of the different toppling deformation bodies were analyzed. The second failure of the toppling rock mass caused by the reservoir impoundment process is mainly the hydrodynamic splitting along fractures, wave impaction and softening on the slope foot. The transverse bending effect of gravity is transmitted upward through joint misalignment, rotation and slip, accelerating the speed of secondary toppling failure and forming a compression-shear failure along the toppling tension crack. A model to predict the scope and time of failure in the toppling deformation banks under the action of reservoir hydrodynamics was proposed.

In view of the broken rock mass in the surrounding rock of large underground caverns, the 3D distribution model of the joints is obtained through the on-site investigation of the joints and the digital imaging technology, and the image processing software. Based on the analysis of the mutual cutting degree of the joints and the geometric shape of the block, the concepts and calculation methods of the degree of fragmentation and the degree of bite are proposed, and the degree of rock mass fragmentation is quantitatively described. Furthermore, the multi-factor analysis method is used to establish the quality evaluation method and the standard of broken rock mass based on the degree of rock fragmentation and the degree of bite, and the failure mode and safety criterion of broken rock mass of surrounding rock are proposed. Applying the discrete element numerical analysis method, the mechanical parameters of different broken rock masses are obtained. The reinforcement analysis of the surrounding rock of different broken rock masses shows that the degree of fragmentation, the degree of bite, and the classification of surrounding rock proposed in this paper can implement precise reinforcement measures for the surrounding rock of different broken rock masses, as it provides an important theoretical basis for the surrounding rock safety of large underground caverns in the broken rock mass and has wide applicability.

Geologic material properties of hillslopes are inherently heterogeneous, with complex layering structures due to geological deposition processes. Lacking detailed sampling of the properties’ spatial distribution has led to the stochastic representation of the properties to address uncertainty in the hillslope stability evaluation. This study treats the spatial distributions of the shear strength parameters, the cohesion (c), and the internal friction angle (φ), in a synthetic two-dimensional slope as stochastic random fields characterized by their means, variances, and correlation scales. This study then evaluates the cross-correlation between these parameters and the factor of safety (FS) using unconditional Monte Carlo simulation (MCS). Different from classical sensitivity analyses, the cross-correlation analysis of FS and the stochastic parameter fields stresses the importance of the orientation of the large-scale geological layering, the correlation between the geological media’s cohesion, and the internal friction angle at the local scale on the probability and uncertainty of failure of the heterogeneous hillslope. The analysis further guides the field sampling strategy to reduce uncertainty in the slope stability analysis due to unknown heterogeneity. More importantly, it suggests the location of stability reinforcement measures. The results of this study provide cost-effective tools for geoengineers to deal with field slope stability analysis under uncertainty.

The surrounding rock stability of large underground caverns in a pumped storage power station is one of the most crucial problems in hydropower project design and construction. In the construction of hydropower projects in Southwest China, many underground soft-rock caverns in are excavated. Influenced by the high sidewall, high ground stress, large burial depth, and hydrodynamic pressure action, the deformation of the cavern is special, especially in terms of its soft-rock distribution. At present, most research of underground engineering on soft-rock stability focuses on small-scale tunnel excavations in homogeneous geological conditions, with limited studies on the large-scale excavation of deeply buried underground powerhouses in complex geological structures, featuring extensive soft-rock-layer exposure on the cavern wall. Therefore, it is particularly important to investigate the excavation method of and support measures for soft-rock caverns under complex geological conditions. Based on laboratory rock mechanics testing (petrographic analysis, uniaxial compressive strength tests, shear tests, and triaxial compression creep tests) and the distribution characteristics of the surrounding soft-rock layer of the proposed underground powerhouse, obtained from the survey, we discuss the excavation and support measurements. These include the influence of support measures on the deformation of the underground excavated cavern considering the inclination of rock layers, the impact of the excavation under supported conditions on the deformation of the underground cavern, and the correlation between the lining thickness and stress variation within the lining.