A sophisticated node-pair model for interface problems

Based on the virtual work principle of interface problems, this paper presents an innovative finite element solution for interface problems by mixing nodal contact forces with nodal displacements. The proposed mixed finite element solution can overcome some numerical difficulties encountered in the analysis of contact problems in geomechanics. These difficulties include contact of large area, non-smooth contact, alleviation of ill-condition and treatment of rigid displacements. The well-posed issue of the formulation and a criterion for judging collapse of the system are also discussed in detail. The paper then presents two simple examples and a very challenging example from the shiplock of the Three Gorges Project in construction. These examples illustrate that the proposed mixed finite element solution is robust and suitable for solving interface problems encountered in geomechanics.