The traditional Coulomb friction model is commonly used to illustrate interactions at the soil-structure interface, but it assumes zero tangential resistance when the normal stress on the interface is in tension. This is not realistic for modelling the undrained behaviour of geo-structures deeply embedded in the seabed because the soil adheres to the structure due to the suction generated. This note proposes a new interface model that captures the undrained behaviour of soil at the structural interface, including the ability to maintain frictional shear stresses under tensile normal stress. Based on simple elastic-perfectly plasticity theory the constitutive behaviour of the interface and the algorithm required to numerically implement it into a finite element program are fully described. Computational cases are presented to verify the model’s implementation and demonstrate how the new interface model performs for cases of undrained behaviour encountered in offshore geotechnics.

传统的库仑摩擦模型通常用于说明土-结构界面处的相互作用，但当界面上的法向应力处于拉伸状态时，它假定切向阻力为零。这对于模拟深埋在海床中的地质结构的不排水行为是不现实的，因为土壤由于产生的吸力而粘附在结构上。本说明提出了一种新的界面模型，该模型可以捕捉结构界面处土壤的不排水行为，包括在拉伸法向应力下保持摩擦剪应力的能力。基于简单的完美弹塑性理论，充分描述了界面的本构行为以及将其数值实现为有限元程序所需的算法。