Experimental evidence shows that the chemical composition of the liquid inside the pores and its variation over time can have significant implications on the mechanical and hydraulic behavior of clayey geomaterials. The magnitude of these implications depends on the characteristics of the geomaterial and on the conditions to which it is subjected. This paper develops an effective stress model which includes a chemical-dependent variable. Some experimental results reinterpreted using the proposed effective stress and the generalized Bishop’s effective stress are presented in order to show some potentialities of the proposed approach.