Creep behavior of dry and saturated medium-grain sandstone and its relationship with short-term mechanical properties

Abstract

Abstract With the continuous exploitation of coal and the increase of abandoned goafs under weakly cemented aquifer strata in Western China, the study of the time dependent mechanical properties of the unique weakly cemented medium-grain sandstone, which is susceptible to water, is imminent. In this paper, creep mechanical properties of dry and saturated medium-grain sandstone, which represent two limit states affected by water, were studied and compared. The results showed that water greatly weakens the compressive resistance of medium-grained sandstone, but balances the volumetric compressive deformation by filling in the internal defects of rock samples with different confining pressures. The rock showed a state of volume expansion except for the first or second loading stage. Compared with short-term compressive strength, the turning point of saturated rock from viscoelasticity to viscoplasticity is earlier than that of dry rock. The short-term elastic modulus has a negative exponential relationship with deviating stress, and creep rate has a positive exponential relationship with deviating stress. Based on Burges model with exponential damage variables, the method of obtaining creep model parameters by short-term mechanical parameters of rocks was introduced, and the linear relationship between elastic modulus of medium-grained sandstone and parameters of Burgers model with damage was found. This conclusion will enrich the framework of the above-mentioned methods for obtaining time-dependent properties.