Study On Creep Mechanical Properties Of Post-peak Fractured Sandstone

The key problem of this paper is to study the mechanical properties of surrounding rock large deformation failure.Uniaxial and triaxial creep test of broken rocks after peak were carried out,and creep mechanical properties of uniaxial and triaxial were obtained.In this paper,the effect of confining pressure on triaxial creep characteristics is analyzed,and rheological models of uniaxial and triaxial were established.Particle flow analysis software was used to simulate uniaxial creep test to obtain difference of axial,hoop and volume strain for post-peak broken rocks,and we select the unloading point of rupture of the appropriate parameters as the quantitative characterization of the peak damage factor after rupture injury,and the damage factor and the creep parameters are established,and the influence of the damage degree of the surrounding rock on the creep behavior is analyzed quantitatively.The effect of confining pressure and damage degree on creep characteristic was studied.The main works of this paper are as follows:(1)Pre-peak yielding and post-peak fracture completely unloading test were done for sanstone by RMT-150 B rock mechanics test system,so pre-and post peak fracture samples with different fracture damage degree were prepared.Based on that,uniaxial creep test were done for damaged sanstone rocks by RLW-2000 rock rheological testing machine.In this paper,the uniaxial creep mechanical properties of the post-peak sandstone were obtained,and the uniaxial creep constitutive model of the rock is established.(2)Based on the previous research results(uniaxial,triaxial and creep test),uniaxial creep test were simulated by particle flow code for post-peak fracture rocks.So uniaxial creep characteristics of sandstone specimens with different fracture damage after peak were analyzed,and different of creep law of axial,hoop and volume were studied for post-peak fracture rocks.Choosing appropriate parameters as rock damage factor,we can explore the quantitative relationship between the damage factor and rock creep parameters,and reveal the development rule of crack in the whole process of creep.(3)Post-peak fracture completely unloading test were done for sanstone by RMT-150 B rock mechanics test system,and preparation of post peak fracture damage samples with the same degree of fracture damage(the ratio of unloading strength to peak strength is same).Based on that,triaxial creep test with different confining pressure were done for damaged sanstone rocks by RLW-2000 rock rheological testing machine.The characteristics of triaxial creep under different confining pressures are obtained.The effect of confining pressure on the triaxial creep characteristics was analyzed,and the corresponding parameters of triaxial creep wereidentified by one-dimensional creep model.(4)Based on the instantaneous mechanical properties and triaxial creep test,the model same to lab test was established by using the numerical simulation software of particle flow.The post peak fracture samples with different degrees of damage were prepared by post peak unloading simulation test.The further study on the triaxial creep behavior of samples under different confining pressures was carried out.The different of creep law of axial,hoop and volume were studied for post-peak fracture rocks.Creep behavior under the influence of confining pressure and damage factor were analyzed.The effect of post peak fracture damage on the triaxial creep mechanical properties of sandstone samples is analyzed quantitatively.The law of crack propagation in the whole creep process of triaxial compress is revealed.