To investigate the deterioration rule and failure criterion of rock in the acid-based environment

experiments were conducted on sandstone specimens after 1

5

10

15

and 20 times of wetting and drying cycles in the environment of pH=7

5 and 3

respectively. By analysing uniaxial compressive strength (UCS) and triaxial compressive strength (TCS) after different cycles

the parameters of Mohr-Coulomb failure criterion and Hoek-Brown failure criterion were calculated

and the effect of wetting and drying cycles on these parameters is also analysed. Finally

according to the relationship formula between the deviatoric stress and the strength criterion parameters in the stress space

the failure envelopes changed with cycles in the π-plane were drawn under the action of solutions with pH values of 7

5

and 3. The results show that the parameters of strength criterion decrease with the increase of cycle time

at the early stage of cycles

the deterioration is more significant

and then the deterioration is relatively low. The lower the pH value is

the more serious the deterioration is

and the degrees of deterioration effect from large to small are as follow UCS

cohesion

material constant and internal friction angle. In the same environment of pH value

when the cycle number is low

the failure envelopes in the π-plane are relatively sparse. However

the greater the number of cycles are

the denser the failure envelope is; in the different immersion environment of pH value is

the lower the pH value is

the smaller the failure plane is. The deviatoric stress is positively correlated with UCS and cohesion

but negatively correlated with the material constant and internal friction angle.