This paper addresses the issue of crack expansion in adjacent buildings caused by foundation pit construction and develops a predictive model using the response surface method. Nine factors, including the distance between the foundation pit and the building, soil elastic modulus, and density, were selected as independent variables, with the crack propagation area as the dependent variable. An orthogonal test of 32 conditions was conducted, and crack propagation was analyzed using the FEM-XFEM model. Results indicate that soil elastic modulus, Poisson's ratio, and distance between the pit and building significantly impact crack propagation. A predictive model was developed through ridge regression and validated with additional test conditions. Single-factor analysis showed that elastic modulus and Poisson's ratio of the silty clay layer, elastic modulus of sandy soil, and pit distance have near-linear effects on crack propagation. In contrast, cohesion, density, and Poisson's ratio of sandy soil exhibited extremum points, with certain factors showing high sensitivity in specific ranges. This study provides theoretical guidance for mitigating crack propagation in adjacent buildings during excavation.

It has been found that in the event of a strong earthquake, and due to insufficient distance between two adjacent structures, the lateral movement at the top of structures may cause collisions between them. This phenomenon, commonly known as seismic collision, can generate impact forces that were not considered during the initial design of the structure. These forces can cause significant structural damage or lead to complete collapse of the structure. The main purpose of this paper is to study the coupled effects of soil flexibility and impact between adjacent buildings undergoing seismic excitation. To capture the impact forces between the structures during the collision, a modified linear viscoelastic model was used effectively. Particular attention has been paid to studying the effects of shear wave velocity, first on the soil structure interaction and then on the collision response of adjacent structures. Three configurations of adjacent structures were analyzed: light-light, light-heavy, and heavy-heavy structures. The results obtained through this analysis showed that the dynamic response and the impact force of the structures depend essentially on the interaction between the structure, the foundation, and the soil.