Bedrock fault dislocation is a crucial structural factor influencing landslide movement. Accurately predicting the location and scale of rupture zones within a slope body is essential for effective slope construction design and risk mitigation. Based on an analysis of seismic damage in slope cross-bedrock faults, this article creatively realizes the physical model test of the slope and its covering layer site with soil rupture zones at the top and toe of the slope caused by the dislocation of the bedrock normal fault. Through the model test, macroscopic phenomena were observed, and microscopic analysis was obtained by deploying sensors. The main results were as follows: (i) The evolutionary process of the instability mechanism could be divided into three stages: crack damage stage (Stage I), crack expansion and penetration stage (Stage II), and slope instability stage (Stage III). (ii) Two rupture modes of the soil body in the slope under bedrock dislocation were identified, with the rupture mode at the slope crest having a greater impact on the soil slope. (iii) Inferring the position of bedrock faults through the location of the main rupture zones on the slope surface represents a feasible supplementary method for identifying seismogenic structures during field surveys. These research results provide a scientific basis for the stability assessment of cross-fault slopes and the reinforcement design of landslide disasters.

Performance-based seismic design methods for bridges are advancing, yet limited research has explored the damage mechanisms of bridges subjected to extreme seismic effects, such as those near or across faults. To investigate the damage mechanisms under bedrock dislocation and bridge rupture resistance, providing essential insights for the standardized design and construction of bridges in close proximity to seismic rupture sites, we developed a large-scale device to model bridges in the immediate vicinity of tilted-slip strong seismic rupture sites. This included a synchronous bedrock dislocation loading system. Four sets of typical sandy soil modeling tests were concurrently conducted. The results indicate: (1) The overall shear deformation zone of the foundation and surface uneven deformation primarily concentrate the overburdened soil body along the fault dip. The damaged area under the low-dip reverse fault is lighter on the surface and inside the soil body compared to the high-dip-positive fault. (2) The presence of bridges reduces the width of the main rupture zone and avoidance distance to some extent. However, this reduction is not as significant as anticipated. The damage to the bridge pile foundation along the fault dislocation tendency notably leads to the bending damage of the bridge deck. (3) Input parameters for fracture-resistant bridge design (surface rupture zone location, extent, maximum deformation, etc.) can be deduced from the free site. Within the rupture zone, a “fuse” design can be implemented using simply supported girders. Additionally, combining the “fuse” design with simple supported girders on both sides and utilizing simple support beams for “fuse” design within the rupture zone, along with structural “disconnection”, allows for reinforcing measures on the bridge structure’s foundation platform and pile in the soil body.

To investigate the performance of horizontally reinforced composite foundations in resisting surface rupture of normal faults, this study designed and conducted a series of physical model tests. A systematic comparative analysis was performed on the fracture resistance of sites with three-layer sand, five-layer sand, and three-layer clay geogrid horizontally reinforced composite foundations under 70° normal fault dislocation. The results indicate that significant changes in earth pressure serve as a precursor indicator of fault rupture, and their evolution process reveals the internal energy accumulation and release mechanism. Increasing the number of geogrid layers significantly enhances the lateral confinement of the foundation, resulting in a narrower macro-rupture zone located farther from the structure in sand sites, and promotes the formation of a step-fault scarp deformation mode at the surface, which is more conducive to structural safety. Under identical reinforcement conditions, the clay site exhibited comprehensively superior fracture resistance compared to the sand site due to the soil cohesion and stronger interfacial interaction with the geogrids, manifested as more significant deviation of the rupture path, and lower microseismic accelerations and structural strains transmitted to the building. Comprehensive analysis confirms that employing geogrid-reinforced composite foundations can effectively guide the surface rupture path and improve the deformation pattern, representing an effective engineering measure for mitigating disaster risk for buildings spanning active faults.

Buildings crossing active faults often suffer severe damage due to fault dislocation during direct-type urban earthquakes. This study employs physical model tests to systematically investigate the dynamic response mechanisms of the integrated “surface rupture zone–overburden–foundation–superstructure” system subjected to bedrock dislocation. A testing apparatus capable of simulating reverse faults with adjustable dip angles (45° and 70°) was developed. Using both sand and clay as representative overburden materials, the experiments simulated the processes of surface rupture evolution, foundation deformation, and structural response under varying fault dislocation magnitudes. Results indicate that the fault rupture pattern is governed by the bedrock dislocation magnitude, soil type, and fault dip angle. The failure process can be categorized into three distinct stages: initial rupture, rupture propagation, and rupture penetration. The severity and progression of structural damage are primarily determined by the building’s location relative to the fault trace. Structures located entirely on the hanging wall exhibited tilting angles that remained below the specified code limit throughout the dislocation process, demonstrating behavior dominated by rigid-body translation. In contrast, buildings crossing the fault exceeded this limit even at low dislocation levels, developing significant tilt and strain concentration due to differential foundation settlement. The most severe damage occurred in high-angle dip sand sites, where the maximum structural tilt reached 5.5°. This research elucidates the phased evolution of seismic damage in straddle-fault structures, providing experimental evidence and theoretical support for the seismic design of buildings in near-fault regions. The principal theoretical and methodological contributions are (1) developing a systematic “fault–soil–structure” testing methodology that reveals the propagation of fault dislocation through the system; (2) clarifying the distinct failure mechanisms between straddle-fault and hanging-wall structures, providing a quantitative basis for targeted seismic design; and (3) quantifying the controlling influence of fault dip angle and soil type combinations on structural damage severity, identifying high-angle dip sand sites as the most critical scenario.

Ground deformation resulting from strong earthquake fault ruptures can cause significant damage, including the collapse of building structures, garnering considerable research attention. (1) In this study, a large-scale physical model test device was implemented to simulate the loading mode of bedrock dislocation under constant gravity. Based on seismic damage analysis, tests were designed to explore key influencing parameters—bedrock fault dip angle, soil properties, and overburden thickness—on a system comprising strong earthquake normal fault rupture, overburden soil, and independent foundation.(2) The progressive failure of the overburden soil was found to be a dynamic evolution process of the internal rupture zone (IRZ) formed by the tension rupture zone (TRZ) and shear rupture zone (SRZ); this failure process could be divided qualitatively into three stages: the rupture incubation stage (Stage I), development stage (Stage II), and completion stage (Stage III). The failure severity of the independent foundation was reasonably assessed. (3) The setback distance was further refined. This research provides a scientific basis for understanding the failure mechanism and determining the setback distance for buildings in bedrock dislocation sites.