Study On Mechanical Properties Of Unloading Rheological Mechanics In Soft Rock Chamber Excavation

The soft rock often appears during the excavation of the tunnel,such as the railway,the hydropower station and the mine.Therefore,it is very necessary to study the rheological mechanics characteristics of the soft rock.In this paper,the single three axis test and unloading rheological test were carried out by using the soft rock from the right bank of the Dadu River of the Dadu River,Sichuan Province,Sichuan Province,Ganzi,Sichuan Province,and the main research contents are as follows:1)The single axial compression test and triaxial compression test of soft rock were carried out by RMT-150 C.The stress and strain curves of single triaxial of soft rock,strength,deformation and failure characteristics of different confining pressure and triaxial were obtained,and the cohesive force and internal friction angle of soft rock specimen under peak strength were obtained.2)The triaxial unloading test was carried out by RMT-150 C.The triaxial unloading test of soft rock under the same confining pressure and different axial compression was carried out,and the triaxial unloading test curve was obtained.The comparison of the triaxial unloading test,completely reveals the strength characteristics,three axial unloading test of soft rock deformation characteristics,established different deformation modulus relationship between elastic modulus and stress level.3)RLW-2000 microcomputer controlled rock three axis creep test machine is used to carry out the unloading rheological test.The first order and the graded unloading rheology test under the constant axial pressure unloading confining pressure path are carried out on the soft rock.The axial and lateral deformation of the two tests are compared with the time,and the axial and the axial velocity of the accelerated rheological phase of the soft rock are studied by using the flow rate.The variation of lateral rheological characteristics and rheological rate is analyzed;the long-term strength under different axial compression is analyzed;and the deformation and failure characteristics of the specimens in the two tests are analyzed.4)A new constitutive model is added to the soft rock rheological classical constitutive model by adding a nonlinear rheological model to the soft rock rheological phase and the stable rheological phase by using the western original model,and the nonlinear accelerated rheology of soft rock is fitted.The two models are found by comparing the comparison curve and the experimental data.The high degree of fit indicates that the established nonlinear viscoelastic plastic rheological model is suitable.