Rainfall is the main factor inducing landslides. Clarifying rainfall-induced landslides’ mechanisms and establishing adequate warning and prevention measures are crucial for regional disaster prevention and sustainable development. The weathering degree of fully weathered granite slopes is high, and the engineering mechanics property is poor, so it is easy to lose stability under extreme rainfall conditions. In this paper, the Fanling fully weathered granite landslide in Laoshan Scenic Spot in eastern China is taken as the research object, and the fluid–solid coupling landslide numerical model is established using ABAQUS 2022. The numerical simulation is carried out under five different rainfall intensity and time conditions, and the seepage field response, deformation response, and stability of the slope are analyzed. The research results indicate that (1) the fully weathered granite landslide in Fanling is a thrust-type landslide, and the response of horizontal deformation is greater than that of vertical deformation. (2) Compared with a long-term small rainstorm, a short-term heavy rainstorm is more harmful, and the slope is more prone to instability and damage. (3) The established unstable and under-stable rainfall warning curves for fully weathered granite landslides can provide a reference for the warning and prevention of similar regional landslides.

Geological disasters refer to adverse geological phenomena that occur under the influence of natural or human factors and cause damage to human life and property. Establishing prevention and control zones based on geological disaster risk assessment results in land planning and management is crucial for ensuring safe regional development. In recent years, there has been an increase in extreme rainfall events, so it is necessary to conduct effective geological hazard and risk assessments for different extreme rainfall conditions. Based on the first national geological disaster risk survey results, this paper uses the analytic hierarchy process (AHP) combined with the information method (IM) to construct four extreme rainfall conditions, namely, 10-year, 20-year, 50-year, and 100-year return periods. The susceptibility, hazard, vulnerability, and risk of geological disasters in the Laoshan District in eastern China are evaluated, and prevention and control zones are established based on the evaluation results. The results show that: (1) There are 121 collapse geological disasters in Laoshan District, generally at a low susceptibility level. (2) A positive correlation exists between extreme rainfall and hazards/risks. With the rainfall condition changing from a 10-year return period to a 100-year return period, the proportion of high-hazard zones increased from 20% to 41%, and high-risk zones increased from 31% to 51%, respectively. The Receiver operating characteristic (ROC) proved that the assessment accuracy was acceptable. (3) Key, sub-key, and general prevention zones have been established, and corresponding prevention and control suggestions have been proposed, providing a reference for geological disaster prevention and early warning in other regions.

Pile foundations of offshore structures are often subjected to cyclic loads under storm loads, thus reducing their vertical bearing capacity. Therefore, studying the cyclic shear behavior of the soil–structure interface is important for maintaining the stability of offshore structures. A series of cyclic shear tests of the silt–steel interface were carried out using a large interface shear apparatus. The effects of various factors (i.e., normal stress, shear displacement amplitude, roughness, and water content) on the shear stress characteristics of the silt–steel interface were investigated. The stress–displacement model of the cyclic shear silt–steel interface was deduced. The results showed that the shear stress at the silt–steel interface was softened, and the type of bulk deformation was shear shrinkage under cyclic shear. With the increase in shear amplitude, the hysteresis curve gradually developed from “parallelogram” to “shuttle” and “hysteresis cake”. With the increase in normal stress and roughness and the decrease in water content, the interfacial shear strength, volume displacements growth rate, and growth rate increased. The stress–displacement mathematical model of the silt–steel interface based on the modified hyperbolic model was in good agreement with the test data.

The shear behavior and dynamic response of a steel–silt interface are significant for the safety and stability of offshore structures in the Yellow River Delta. A series of steel–silt interface cyclic shear tests under constant normal load conditions (CNL) were carried out to explore the effects of normal stress, shear amplitude, roughness, and water content on the interface shear strength, shear stiffness, and damping ratio using a large interface shear apparatus. The preliminary results showed that the amplitude of normal stress and shear amplitude affected the interface’s shear strength, stiffness, and damping ratio in a dominant manner. The roughness and water content were also crucial factors impacting the rule of shear strength, shear stiffness, and damping ratio, changing with the number of cycles. Under various scenarios, the steel–silt interface weakened distinctively, and the energy dissipation tended to be asymptotic with the cyclic shear.

Pipe bend is a critical integral component, widely used in slurry pipeline systems involving various engineering applications, including natural gas hydrate production. The aim of this study is to assess the capability of RANS-based CFD models to capture the main features of the turbulent single-phase flow in pipe bends, in view of the future investigation of the hydrate slurry flow in the same geometry. This is different from the available literature in which only a few accounted for the effects of a combination of computational mesh, turbulence model, and near-wall treatment approach. In this study, three types of mesh configuration were adopted to carry out the computations, namely unstructured mesh and two structured meshes with a uniform and nonuniform inflation layer, respectively. To explore the influence of the turbulence model, standard k-ε, low-Reynolds k-ε, and nonlinear eddy viscosity turbulence model were selected to close RANS equations. Pressure coefficient, mean axial velocity, turbulence intensity, secondary flow velocity, and magnitude of secondary flow were regarded as the critical variables to make a comprehensive sensitivity analysis. Predicted results suggest that turbulent kinetic energy is the most sensitive variable to the computational mesh while others tend to stabilize. The largest difference of turbulence kinetic energy was around 26% between unstructured mesh and structured mesh with a nonuniform inflation layer. Additionally, a fully resolved boundary layer can reduce the sensitivity of mesh on turbulent kinetic energy, especially for a nonlinear turbulence model. However, the large gradient and peak value of turbulence intensity near the inner wall of the bend was not captured by the case with a fully resolved boundary layer, compared with that of the wall function used. Furthermore, it has been confirmed that the same rule was detected also for different curvature ratios, Reynolds numbers, and dimensionless wall distance y+.

Capillary barriers are widely used as a cover system to enhance the upper-soil-layer water storage capacity and reduce water infiltrate into the lower soil layer. In this paper, the effects of the median soil–particle size ratio on the water storage capacity of capillary barriers were studied using a series of indoor one-dimensional soil column infiltration tests. The results show that the water storage capacity rises with an increase in the median soil–particle size ratio until it exceeds 10. The variation in the total water storage capacity is related to not only the median soil–particle size ratio but also the particle size of coarse-grained soil or fine-grained soil. When the fine-grained soil-layer particle size is constant, the total water storage first increases, then decreases, and finally remains constant after increasing the median soil–particle size ratio. In contrast, when the coarse-grained soil layer particle size is constant, the relationship between the capillary barrier’s total water storage and median soil–particle size ratio can be defined as a power function. Using the capillary barrier can increase coarse-grained sand by 90% in water storage capacity and can only increase fine-grained sand by 7% in water storage capacity. The breakthrough time increases with the increase in the median soil–particle size ratio. The presence of the coarse and fine-grained soil layer interface in the capillary barrier can affect the fine-grained soil layer infiltration rate.