Study On Mechanical Properties And Constitutive Equations Of Tuffaceous Siltstone

In the nature,water and rock exist simultaneously,and the complex physical and chemical action between the two influences the mechanical properties of rock.The erosion damage of the natural water to rock in the natural world starts from the surface of the rock structure,so the mechanical properties of the same rock vary greatly under different water bearing conditions.It is the guarantee of engineering safety,quality and progress to accurately grasp the mechanical properties of rock in excavation and support of tunnel.So it is very important to study the mechanical properties of rock under different water content,which is the most important task in the research of underground space and tunnel.In this paper,the tuffaceous siltstone in Lishui Bay Tunnel in Zhejiang city was taken as the research object,and the mechanical properties of the tuffaceous sand were studied by the combination of theory and experiment.The main contents are as follows:(1)Take a small amount of rock powder samples of materials and chemistry Chengdu University of Technology Institute of chemical experiment center,tuffaceous siltstone material composition and content of DX-2700 by X ray diffraction analysis.(2)Water absorption test of tuffaceous siltstone in natural state.To understand the relationship between tuffaceous siltstone and natural water absorption time,set the direct shear,uniaxial compression and triaxial compression tests of the three water samples in time.(3)The direct shear test of standard samples with different soaking time was carried out by using the portable rock mechanics multifunctional tester developed by Chengdu University of Technology.Based on the experimental results,the relationship between soaking time and water content was analyzed,and the relationship between the shear force and mechanical parameters and the soaking time was obtained.The Mohr-Coulomb criterion.(4)The uniaxial compression test of tuffaceous siltstone at different temperatures was carried out by using the MTS rock comprehensive test system.Rock curves and different soaking state under uniaxial compressive strength and mechanical parameters,to study the relationship between soaking time and water content,and explore the effect of soaking time on rock strength,deformation and the mechanical parameters,and to establish the immersion time for the constitutive relation of rock variables.(5)Using the MTS815.03 type rock three axis servo rigidity testing machine to carry on the compression test of 5,10,25,60 MPa and in the natural state.The curves of rock mass,rock strength and mechanical parameters are obtained under different confining pressures.Furthermore,the influence of confining pressure on rock strength,failure characteristics and mechanical parameters is studied,and the conventional three axis constitutive equation is established.(6)Using the MTS815.03 type rock three axis servo rigidity testing machine to carry on the 60 MPa compression test under the condition of high confining pressure and different soaking conditions.The three axis curve,the axial compressive strength and the mechanical parameters of the samples under the soaking time of 0,4,12 and 360 h were obtained.Furthermore,the influence of soaking time and water content on the strength,deformation and mechanical parameters of rock under high confining pressure is studied,and the constitutive relation of three axes of rock is established.