Experimental study on creep properties of deep siltstone under cyclic wetting and drying

In order to investigate the influence of moisture content on the long-term stability of deep rock,the siltstone from -906 m of Zhujidong coalmine was studied. A series of uniaxial compressive creep tests of cyclic wetting and drying on the siltstone were carried out in stepped loading on the rock creep testing machine ZYSS2000 under high temperature and high pressure. The test results show that with increasing of wetting and drying cycles,the axial creep strain and axial steady creep rate of siltstone increase nonlinearly,while the instantaneous deformation modulus decreases logarithmically. The axial creep strain and axial steady creep rate increase significantly after the first wetting and drying cycle. The degree of deterioration of the instantaneous deformation modulus from 0 to 1 stage is the biggest which is 10.06%. The creep failure curve of siltstone under various wetting and drying cycles present similar regularities under the last level of stress. With the increasing of the number of wetting and drying cycles,the whole time for creep failure of siltstone decrease gradually under the certain failure stress,while the proportion of transient creep stage and accelerated creep stage in the whole time increase gradually. The long-term strength of siltstone decreases gradually with the increasing of the number of wetting and drying cycles. The largest reduction occurs after the first wetting and drying cycle. The creep failure characteristics of siltstone present a transformation from tension failure to shear failure. © 2018, Science Press. All right reserved.