The weak mechanical properties of weak interlayers are crucial for controlling landslide deformation and failure under water level fluctuation. The instability and failure of landslides in reservoirs can lead to unpredictable consequences. In this study, the reservoir bank landslide with a weak interlayer was selected as the research subject. The material composition, structural characteristics, mechanical properties, and permeability of the landslide were determined through field investigations and tests. Additionally, a physical model test was conducted to explore the groundwater variation rules and deformation failure modes of landslides with weak interlayers under different water level fluctuation rates. The results indicate that due to the low permeability of the interlayer, there was a significant lag in monitoring data such as pore water pressure within the interlayer under the same water level fluctuation rate. At the same point, the faster the water level fluctuation rate, the greater the degree of lag. The deformation and failure mode of landslide with weak interlayer under reservoir water level fluctuation can be summarized as the following five stages: slope toe erosion stage, cracks on slope surface and interlayer stage, micro-collapse of slope toes and crack expansion of slope surface and interlayer stage, local micro-collapse of slope toe and crack penetration of slope body stage, crack development leads to landslide of slope body stage. This study provides theoretical support for prevention and control of landslides with weak interlayers in the gravel soils of reservoirs.

This research combines scaled model experiments with theoretical analysis to investigate the impact of underground utility tunnels (UUTs) on foundation bearing capacity and to examine the interaction between soil-rock composite strata and the stress-strain responses of the tunnel. The findings indicate that UUTs alter the foundation mechanism by reducing soil depth, streamlining the load transfer path, and causing stress to converge at the tunnel's top. Additionally, the results reveal that the influence range of the tunnel on both sides is approximately 1.5 times its width and remains unaffected by the position of load application, the tunnel's burial depth, or the width of the composite stratum. Moreover, when the width of the soil-rock composite stratum equals the width of the tunnel, the tunnel experiences a laterally flexural stress state. Within this specific stratum context, the central axis area of the tunnel roof and the connection with the side panels represent the core sensitive areas for crack initiation and propagation. In the failure scenario, the tunnel roof displays typical characteristics of fracture and depression, with the damage degree decreasing from the load center towards both ends. Meanwhile, the side panels do not exhibit characteristics of plastic deformation. This research provides a theoretical framework for the design, construction, and maintenance of UUTs, emphasizing its practical significance in engineering.

Nodular diaphragm wall (NDW) is a novel foundation type with favorable engineering characteristics. In contrast to traditional diaphragm walls, the vertical bearing capacity of NDW is significantly enhanced by the existence of nodular sections. Currently, the application and research of NDW are limited, and further clarification is needed regarding its deformation properties and failure modes. This study employs particle image velocimetry (PIV) technology to analyze the displacement and failure mechanisms of the foundation under vertical uplift. The findings indicate that positioning end and middle nodular sections extend the influence range to both deep and shallow soil layers, while multiple nodular sections facilitate in mobilizing broader spectrum of soil. The failure pattens of NDW involve interconnected sliding planes, including vertical sliding planes, inverted pyramid-shaped, or tangent curves, and vase-shaped curves (referred to as curve sliding planes). Overall, compared to pile foundations, the failure surfaces of the retaining wall exhibit complexity, influenced by the number and arrangement of sections, with certain sliding plane orientations correlated with the soil's internal friction angle.

Relying on the tunnel engineering crossing large active fault fracture zone in high intensity seismic area in Western China, a large-scale model test of tunnel through multiple slip surfaces under strike slip motion was carried out. The deformation patterns and damage characteristics of tunnel structure and surrounding rock were studied based on displacement, strain and internal force response, as well as crack morphology. The results revealed that microscopically the model soil experienced the process of contacting, compaction and relative movement under fault dislocation, and was macroscopically accompanied with fracture occurring, and further expansion. Compared with fault movement form containing single slip surface, the active wall produced nonlinear linkage displacement to fault fracture zone when there existed multiple slip surfaces. The model soil exhibited a multistage dislocation along longitudinal direction after test. The dislocation of model soil on both sides of major slip surfaces reached to 25.9 mm and 18.8 mm, which was about 2.2-3.4 times of the dislocation on both sides of the minor slip surfaces in fault fracture zone. The overall deflection of lining segments and the torsion of flexible joints corporately undertook the fault dislocation. Lining segments near the major slip surfaces had opposite trends of tensile and compressive deformation, where the failure of tensile bending damage was dominant. Tunnel segments near minor slip surfaces underwent integral linear deflection along with surrounding rock, and were less affected by fault dislocation. The fragile sections of tunnel structure were located near main slip surfaces, the fragile parts were invert, arch springing and arch spandrel, which were mainly damaged by tensile, compressive and shear affection. Based on the deflection corner beta of each lining segment, combined with damage pattern and internal force distribution trend, it is suggested that 2d similar to 3d (d represents the span of tunnel) in range near major slip surfaces is the main affected zone, while the range of 4d in the middle of fault fracture zone is the minor affected zone. The partitioned fortification needs to be adopted when tunnel is to cross fault fracture zone.