Taking into account the high cost of damage to structures caused by uneven ground movements associated with expansive soils, the mechanical behavior of these materials is critically important to be studied theoretically and experimentally. A simplified constitutive model is proposed based on a 1-D mechanical design containing a parallel connection of the linear spring and the dashpot element, and its mathematical formation is presented in terms of the physical mechanism. The procedure of model parameters is introduced using cyclic suction-controlled tests by an expansive soil in France and a silt-bentonite mixture. The comparison between model simulations and tests is accomplished and this comparison explains that the simplified constitutive framework can describe basic features of expansive soils under wetting and drying cycles.