Unified framework for geotechnical cross-contact problems with interfacial fluid flow

In the hydro-mechanical coupling analysis of multi-body contact systems, challenges arise from the fluid flow at the interface and the over-constraint at the cross line, necessitating special treatments. In this paper, a novel algorithm is developed to address these challenges comprehensively. The proposed method introduces an intermediate interface, serving as a bridge for contact stress transfer and fluid exchange between different subdomains. The intermediate interface concurrently carries the degrees of freedom related to the displacement, pore pressure, and Lagrange multiplier. As a result, the contact constraint and interfacial fluid flow can be integrated into a unified formulation, resulting in a simplified algorithm implementation; the elimination of over-constraint behaviour can also be achieved in a simple manner. Additionally, the storage capacity of interfaces is adequately considered in the current framework, enabling the accurate computation of water suction generated by the opening of contact interfaces. Finally, several numerical experiments are conducted to validate the performance of our proposed method. Results show that our method can provide a reliable computational tool for the two-phase contact problems with interfacial fluid flow.