Mechanical properties of sandstone and an improved Duncan-Chang constitutive model
WANG Junbao1，LIU Xinrong1，2，LIU Jun2，SONG Zhanping1
(1. School of Civil Engineering，Xi?an University of Architecture and Technology，Xi?an，Shaanxi 710055，China；2. School of Civil Engineering，Chongqing University，Chongqing 400045，China)
Abstract：In order to study the mechanical properties of sandstone，the conventional triaxial compression tests under different confining pressures were carried out on sandstone specimens. The test results indicate that the peak stress，the strain at peak point and the residual strength of sandstone increase gradually with the increase of the confining pressure. When the confining pressure is less than 15 MPa，the elastic modulus of sandstone increases with the increasing of confining pressure，but the rate of variation is smaller and smaller. When the confining pressure is larger than 15 MPa，the elastic modulus is independent of the confining pressure. The Duncan-Chang constitutive model was revised to describe the stress-strain response in the failure process of sandstone. The method of parameter determination was put forward based on the characteristic of the slop is 0 at the peak point of stress-strain curve. The triaxial compression test results of sandstone were used to evaluate the reasonability of the revised Duncan-Chang model. The comparison of predicted curves from the model and the test results shows that this model can accurately describe the strain softening property of sandstone and the other four stages of the failure process of sandstone under different confining pressures except for the closure stage of cracks. Especially，the model reflects the residual strength after sandstone failure. The further analysis on the model characteristics indicates that in addition to the strain softening property，the revised Duncan-Chang model can also simulate the strain hardening behavior of rock under the action of high confining pressure. So，this model has the good adaptability.
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2016, Vol. 35 
