Experimental study of the interface evolution behavior and softening mechanism of structure-marine soil

The undrained interface characteristics of marine clay-structures are key to the design of offshore platforms. However, it is difficult to acquire interfacial shear-induced pore pressure measurements employing conventional interface equipment. This paper introduces an interface instrument that is suitable for evaluating marine soil-structure interface characteristics. The developed device is utilized to investigate the undrained interfacial evolution behavior and softening mechanism of specimens with different moisture contents. The results indicate that the interface undrained strength curve exhibits high stiffness initially, and then declines as the strain level increases. The interfacial soil particles experience two stages: obvious contraction and slight dilatancy tendency. The moisture content response to interface shear resistance is mainly through changing interface adhesion. Additionally, the reduction in contact area caused by interfacial particle dilatancy is the internal inducement of interfacial strain softening. The increase in interfacial soil moisture content caused by water migration is another external inducement. Accordingly, the stress development state in the whole shear process and the variation in free water migration toward the interface are revealed, providing an excellent analytical basis for further investigation of undrained interface behavior.