A Modified Model for Soil-Structure Interface Considering Random Damage of Mesoscopic Contact Elements

The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism process. In this study, the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural heterogeneity. The evolution equation of damage variable is developed based on the Weibull function, which is able to cover a rather wide range of distribution shapes by only two parameters, making it applicable for varying scenarios. Accordingly, a statistical damage model is established by incorporating Mohr–Coulomb strength criterion, in which the interfacial residual strength is considered whereby the strain softening behavior can be described. A concept of “semi-softening” characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain softening. Finally, a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are conducted. The predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature, indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.