Research On Triaxial Creep Characteristics Of Granites And Its Constitutive Models

The long-term stability of rock mass engineering in deep stratum rock engineering are closely related to the aging deformation characteristics. Hard rock under the conditions of high geo-stresses present obviously rheological property. triaxial rheological tests under different stress paths were carried out on TAW-2000 rock machine. On the basis of the experimental results, by theoretical and numerical analysis methods, analyzed the deformation law, the volume rheological characteristics and failure mode during granite creep. The results show that:in the creep process of granites, the instantaneous elastic deformation account for the major on all grades of granite creep, radial creep deformation present more obviously than axial; When the loading to failure stress, the radial accelerated creep occurs slightly earlier than the axial. Meanwhile, the relationship between radial creep and axial creep shows approximately linear variation, and the creep failure dominated brittle shear; The volume deformation and creep of granite have synchronous characteristics; Under higher stress level, internal crack of the rock began to expand, resulting in expansion phenomenon. at the same time damage began to evolve and accumulate, causing the deterioration of internal properties of the rock; Based on Nishihara model and damage theory, establish nonlinear creep damage model, and the parameters in this model are identified by least square method. The good degree of agreement prove the nonlinear creep damage model the rationality and feasibility of the nonlinear creep damage model during the whole process of rock creep characteristics description.