Research On Rock Damage Characterization Method And Constitutive Model Based On Linear Energy Dissipation Law

As a kind of natural geological body,rock has many complicated original defects,which makes the rock exhibit obvious nonlinear mechanical properties.Especially,the nonlinear mechanical properties of rock under cyclic loading are more complex than those under monotonic loading.Therefore,an in-depth study of the non-linear characteristics of rocks will be helpful to deepen the understanding of the rock deformation,failure laws and strength properties.Based on the linear energy dissipation law existing in rock materials,a new damage characterization method is proposed by improving the existing damage expression.Meanwhile,the deficiency of damage constitutive model based on the strain equivalent hypothesis is analyzed,and a new damage constitutive model containing the correction coefficient in the form of a power function of strain is proposed.In addition,after considering the damage evolution characteristics and constitutive relation of rock under cyclic loading,the damage constitutive model which can represent the cyclic loading and unloading process of rock is derived using the cyclic iterative algorithm.The results and conclusions are as follows:(1)Based on the linear energy dissipation law,a rock damage characterization method containing compression energy dissipation coefficient is proposed.This method can directly calculate the damage of brittle rock by measuring the stress-strain data in uniaxial compression test,and has better advantages than the traditional method which uses the triangular area approximate energy calculation.(2)Aiming at the deficiency that the traditional damage constitutive model based on strain equivalence hypothesis simplified the constitutive relation of rock and could not describe the compaction section,a correction coefficient in the form of a power function of strain is proposed.The damage constitutive model of brittle rock considering linear energy dissipation law and correction coefficient is comprehensively established,which can well describe the strength and deformation characteristics of brittle rock under uniaxial compression.(3)The damage evolution characteristics and constitutive relationship of brittle rock under cyclic loading are analyzed.Based on the linear energy dissipation law,rock damage variable under cyclic loading is established,and the damage constitutive model describing the cyclic process of brittle rock is derived using the cyclic iterative algorithm.Moreover,the rationality of the model is verified by loading and unloading test data of rocks with different cycles,which lays a foundation for studying the damage evolution and constitutive model of rock under complex stress paths.