Experimental Study On Mechanical Properties And Creep Constitutive Model Of Tuffaceous Siltstone

As one of the most important mechanical properties of rock and soil,the creep characteristics are directly related to the stability and safety of civil engineering buildings.Creep is a macroscopic phenomenon in which a particle diffuses along the boundary of the crystal under the action of an external force or a particle passes through the hole in the crystal.With the development of underground engineering in the foundation engineering,the influence of creep on the engineering construction is more and more serious,such as the surrounding rock of the tunnel,the instability of the slope and the floor heave of the roadway.On the other hand,the underground buildings are often buried deep in the ground,and the effect of water environment is more obvious.Although there are many aspects of the research results of rock creep,but for the study of rock creep under different water contents are rare,so this paper combined with previous research results,the preparation of tuffaceous siltstone specimens,and the conventional mechanical properties in different water condition and uniaxial creep test on it according to the results of the experiments,theoretical analysis.The main research work and achievements are as follows:(1)On the road from the Bay Tunnel "collected tuffaceous siltstone in accordance with the provisions of the" new standard "test method of engineering rock mass GB/T50266-2013,the tuffaceous siltstone specimen growth width of 100*50mm cylinder,and the use of"boiling method "specimen preparation for four different water content,respectively ?(28)%0 、?(28)%41.0 、?(28)%75.0 、?(28)%04.1.(2)By using MTS-815 rock mechanics testing machine,the processed samples were subjected to uniaxial compression tests,four kinds of moisture under the condition of elastic modulus,Poisson’s ratio,compressive strength and stress-strain curves were obtained,providing test data base for grading loading of uniaxial creep test.(3)The resistance to slaking test and X ray diffraction test of tuffaceous siltstone,results show that the tuffaceous siltstone is composed of quartz,plagioclase(50%)(19%)(9%),illite,chlorite,calcite(15%)(5%)and pyrite(2%)with a moderate durability of mudstone the composition of the.(4)The test results of uniaxial compression of tuffaceous siltstone under saturated condition is deduced based on hierarchical load grade uniaxial creep test values,the three rock triaxial creep test machine,based on the "Chen loading method" to obtain four different moisture conditions of the rock uniaxial creep test curve,analyzed the creep law tuffaceous siltstone under different water content rate of different load level in the same water and under the same load level.(5)Based on the creep curve of rock specimen,the Burgers model was used to simulate the creep curves of the decaying creep stage and the constant creep stage.Viscoplastic element at the same time the introduction of a nonlinear Burgers model,the viscoplastic element with the conventional series by an improved Burgers model named SBN-burgers model,the accelerated creep stage simulation rock creep curves with the improved model,and deduced the model of one-dimensional and three-dimensional creep force under the condition of constitutive equation.(6)The Originpro data processing software based on the fitting curve of custom function software,Levenberg-Marquardt algorithm based on the SNB-burgers model,one-dimensional creep constitutive model parameters of the regression,the theory of creep curves and experimental creep curve comparison,the correlation coefficients are above 0.9,that "uniaxial creep the characteristics of SBN-burgers model can better simulate the tuffaceous siltstone.