Structural effect of soft rock rheology

Abstract

In order to study the structural effect of soft rock rheology, the normal uniaxial compression test, and the triaxial compression test and the uniaxial compression creep test were performed using the similar material samples of soft rock with the single surfaces of different obliquities. On the basis of the test results a new multiple rheological model was put forward to describe the strong nonlinear creep and failure course of soft rock containing the structure face by combining two non-linear components of CYJ body and L body with the classic KELVIN body and HOKE body. Then the quantitative influence of the structure face and its varying obliquity on every strain component of soft rock creep was probed into so that the nonlinear experiential regressive equations between the obliquities of the structural surface and the mechanical parameters of the multiple model or the long-term strength can be gained. The results show that the creep deformation of soft rock contains components of the instantaneous elastic, instantaneous plastic, visco-elastic and the visco-plastic deformation and the existence of the structure face would enhance the capabilities of the instantaneous plastic, visco-elastic and the visco-plastic deformation when the soft rock creeps so that it shortens the time of the stable creep phase and hastens the appearance of the third phase of soft rock creep. In the meantime, the variation of the obliquity of the structure surface will make the creep failure of soft rock in one of three modes of “X” shear failure, the sliding failure along the structure surface and the mixture failure of shear and sliding.

Keywords

soft rock / creep / structural effect / rheological model / failure mode