In this paper two rate dependent constitutive models for porous chalks are presented. The common background of both models formulation is the isotach approach, which is first introduced. The theoretical basis and the mathematical formulation of the models are then proposed. Finally, numerical predictions of both models are compared with experimental results and discussed. The two formulations include strain rate and creep effects. Suction dependency on creep is also discussed. Some perspectives about the constitutive modelling of time-dependent behaviour of partially saturated chalks are given with respect to the description of the coupled effect of suction and time.