Crack Closure Effect and Energy Dissipation Model for Rocks under Uniaxial Compression

Through the uniaxial compression tests of sandstone, the crack closure effect and the relationship between the crack parameters and the height to diameter ratio (H/D) were analyzed. Then, a nonlinear model for characterizing energy dissipation based on the crack closure effect was established. The results show that the peak strength and peak axial strain of sandstone decrease gradually with the increase of H/D, but the elastic modulus has a small change. The maximum crack axial closure strain and crack axial closure stress of sandstone increase with the H/D. While the peak crack axial strain and axial crack initiation stress decrease. The dissipative energy firstly increases with the axial stress, and the increase rate decreases gradually. Then, the dissipative energy nearly remains as a constant. The axial crack closure model was established to describe the crack closure effect of sandstone, and the equivalent elastic modulus of crack closure of sandstone calculated by axial crack closure model decreases nonlinearly with the H/D. A rock energy dissipation model based on crack closure under uniaxial compression was established. The experimental results agree well with the theoretical values, which indicates that the proposed model can describe the energy dissipation of rocks under uniaxial compression. The research conclusion provides a theoretical reference for the stability evaluation of underground rock masses with different sizes.