In order to study the time-dependence of damage and degradation effect for soft rock under water corrosion, subcritical crack growth of soft rock was studied by double torsion test using Instron1342 type electro hydraulic servo test machine and the mechanics parameters test using RYL-600 rock test machine after marinated soft rock in water for different time. Based on testing results, the rate of water content(ω), the mechanics parameters, the subcritical crack growth velocity(V), the stress intensity factor(KI), and the fracture toughness (KIC) were obtained, respectively. The results showed that the rate of water content(ω) VS the time of water-rock interaction relations accord with good linear rule and could be used to establish the function relationship of damage and degradation velocity(D~) for soft rock by means of the rate of water content(ω)and elasticity modulus(E). The relationship of subcritical crack growth velocity(V)and stress intensity factor(KI) of soft rock in different time were studied by double logarithm coordinate, and the results showed that lgKI-lgV relations accord with good linear rule and the fracture mechanics effect of water corrosion action of swelling soft rock is evident and time dependent, and the water corrosion damage can accelerate subcritical crack growth velocity(V) and can weaken fracture mechanical characteristic of swelling soft rock.
