This paper presents a mathematical model for the analysis of a time-dependent swelling-softening process in clay shale around a drilled hole subjected to fresh water invasion. The model is derived from a set of governing equations involving equilibrium and mass balances for fluid and ions components. Row laws, according to hydraulic, repulsive, and osmotic pressure heads, are required. The effect of modulus reduction due to swelling must be also taken into consideration, The proposed model was used to simulate the experimental results observed in hollow cylinder tests on a Colorado Group shale, A computer tomography scanning method was used to examine the deformation of the hole for a period of 72 days. In addition, the amount of sodium chlorine ions released from the shale specimen into the water was monitored continually. Analysis of the test results,,show that the swelling and softening mechanism is a coupled mechanical-hydraulic-chemical process.