Strength-Deformation Behavior and Engineering Applications of Residual Soil Under Drying-Wetting Cycles and Construction Vibration

Under the coupled effects of drying-wetting cycles and construction vibration, both strength and deformation parameters of residual soil undergo significant degradation, thereby compromising the safety of excavation support systems. Through direct shear tests and consolidation tests, this study characterizes the strength-deformation behavior of residual soil under drying-wetting cycles and construction vibration, develops predictive models for deteriorated parameters, and implements them in high-fidelity numerical simulations of a metro excavation project. The experimental results indicate that: cohesion c undergoes nonlinear decay with increasing drying-wetting cycles n and vibration duration t; internal friction angle φ exhibits oscillatory increase with n, while vibration effects on φ diminish progressively at higher n; without vibration, compression coefficient a_v1-2 increases linearly with n, whereas reference tangent modulus E_oed^ref decreases gradually; under vibration, a_v1-2 shows triphasic evolution: rapid initial decrease → slow secondary decrease → eventual increase. By considering the effects of drying-wetting cycle and construction vibration, the excavation is divided into 6 impact zones: fully drying-wetting-affected, over drying-wetting-affected, strongly coupled drying-wetting and vibration, weakly coupled drying-wetting-affected, vibration-only, and unaffected. Degraded soil parameters corresponding to each impact zone were implemented in high-fidelity numerical simulations of the excavation sequence. Results reveal that surface settlement first decreases then increases with horizontal distance from the excavation edge. As the excavation depth increases, diaphragm wall horizontal displacement exhibits a “small-large-small” profile along the wall height. Both ground settlement and wall horizontal displacement are consistently smaller on the side adjacent to an existing building than on the unobstructed side. Incorporating the coupled effects of drying and wetting cycling and construction vibration, the simulated surface settlements and wall horizontal displacements match the field measurements more closely, thus providing a practical guidance for the design and construction of the residual soil excavations.