This paper deals with a new model for solving coupled hydromechanical problems, based on an existing unified model. Firstly, the unified model for granular media, describing solid and fluid states with the transition between them, is briefly presented and extended to the unsaturated domain using Bishop’s effective stress. Secondly, an adapted stress–strain relationship is derived from modified Van Genuchten–Mualem’s water retention curves. On this basis, a finite element formulation with Lagrangian integration points in a visco-elasto-plastic framework is proposed and implemented in a FEMLIP tool. Finally, the formulation is validated with reference to several benchmarks. The results and analysis show its reliability, and by means of FEMLIP, more complex and realistic problems are expected to be solved in the field of natural risks.