Mechanism-based modeling for interface mechanical behavior during shearing

Abstract

Offshore structures exposed to prolonged cyclic loading necessitate a precise assessment of the soil–structure interface mechanical behavior. This study, building on cyclic shear tests at silty sand–steel and gravelly soil–structure interfaces, offers a comparative analysis of strength characteristic, deformation response, and physical-state evolution. Drawing from those, a well-verified mechanism-based interface modeling is formulated. The findings indicate that the shear strength at both interfaces can be uniformly characterized by the Mohr–Coulomb failure criterion. The interface elastic behavior, plastic shear strain, and compression-induced plastic volumetric strain can be effectively modeled within a unified framework. The shear-induced volumetric strain involves the cumulative and cyclic components, while the cumulative volumetric strain at both interfaces accumulates rapidly at the onset, with its rate diminishing as the cycles progress. Regarding cyclic volumetric strain, double-phase transformation points per cycle were observed at the silty sand–steel interface, whereas only single at the gravelly soil–structure interface, highlighting the influence of interface contact properties. Employing parameters calibrated from the interface shear test under constant normal load condition and confining compression test, the proposed model effectively simulates the interface strength and deformation responses under both constant normal stiffness and constant volume conditions, demonstrating the independence of interface mechanical modeling parameters from boundary conditions.