Mechanical behavior of sandstone under uniaxial constant cyclical compressive and tensile loading

In order to investigate mechanical behavior of red sandstone under cyclical compressive and tensile loads, a series of short-term uniaxial constant cyclical compressive and tensile loading tests and uniaxial constant cyclical compressive and tensile loading creep tests were conducted. First, based on the results of short-term uniaxial constant cyclical compressive and tensile loading experimental, the permanent residual strain, strains at peak stress were analyzed. Results show that the specimen shows permanent residual strain after suffering short-term cyclic loads; the residual strains and strains at peak stress show the “decay increase” and “steady-state increase” stages with the cyclic number N; the relationship between the strain at peak stress (tensile or compressive stress) and cyclic number can be well described by a modified Burger model. And then, in accordance with the creep experimental results, the creep behavior of the red sandstone was analyzed. Results show that there is obvious instantaneous strain, decay creep, and steady creep under each stress level of tensile or compressive stress stages; the specimen appears accelerated creep stage under the 5th tensile stress of 1.19 MPa. It was also found that power function can better express the relationship between steady strains and cycle number under tensile or compressive stress levels. In the end, a viscoelastic-plastic creep model was proposed; comparison of the test results with the proposed viscoelastic-plastic creep model predictions indicates that the proposed model is capable of describing the creep behavior of red sandstone subjected to cyclic tensile and compressive stress loading.