A Constitutive Damage Constitutive Model For A Rock Mass With Non-persistent Joints

The internal crack propagation law of homogeneous material under loading is the research object of fracture mechanics. Using fracture mechanics to study the failure of rock is suitable for some specific conditions, but it can not describe the distribution of geometric discontinuity defects which is very uneven. The macroscopic defects caused by macroscopic cracks can be described by macro damage tensor, but the random distribution of the micro fractures in the rock is not considered. This statistical description provides a bridge to connect the microscopic movement and the macroscopic phenomenon. It is appropriate to describe the intact brittle rock, but can not describe the defects in different scales such as macroscopic defects and microscopic defects in the fractured rock at the same time.To study characteristics of rock mass with non-persistent joints, a damage constitutive model for rock mass with non-persistent joints is established based on coupling macroscopic and microscopic defects. The deformation and strength of fractured rock are analyzed and predicted. The proposed calculation method of coupling macroscopic and microscopic damage is applied to the jointed rock in cold regions. The weathering degree of jointed rock in cold regions is predicted based on this method.(1) The proposed damage model under uniaxial compression based on coupling macroscopic and microscopic defects can describe the deformation and strength of intact rock, the main geometrical and mechanical characteristics of the non-persistent joints and the size effect of specimen. This model can fully consider macroscopic damage with joints and microscopic behavior of loading, overcome the shortcoming that the macroscopic damage variable need to be introduced the pressure transfer coefficient and shear transfer coefficient and the error of infinite theory.(2) The proposed 3-D damage model of jointed rock for conventional triaxial compression is based on the model under uniaxial compression. The 3-D model can well describe the stress-strain behavior when the strain is less than the peak strain. The law of influence of macro and micro defects on the mechanical properties of jointed rock under different confining pressures is discussed by this model and obviously influenced by confining pressure.(3) The proposed freezing-thawing and loading compound damage variable for jointed rock in cold regions can well describe the frost resistance of jointed rock. With the low effects of freezing-thawing cycles on peak strain for jointed rock, the uniaxial compressive strength of intact rock after freezing-thawing and the mechanical parameters of jointed rock before freezing-thawing can reasonably predict the weathering degree of jointed rock.