Study On Unloading Rheological Behavior Of Different Unloading Rate And Stress Level Of Limestone

Large-scale water conservancy and hydropower projects have a design life span of several decades or even a hundred years.The site selection is usually in a location where the regional structure is stable and the strength of the rock mass is high.During the construction period of the project,the excavation of the slope rock mass is often accompanied by the change of the instantaneous mechanical properties of the rock mass and the characteristics of slow deformation and failure over time.A lot of achievements have been made in the study of the rheological failure mechanism of unloading rock mass,but the research literature on the unloading-rheological failure mechanism of hard rock is rare.In this paper,the limestone on the right bank of the right bank of Wudongde Hydropower Station is taken as the research object,and the unloading-rheological test of indoor rock mass is carried out,and the limestone unloading-rheological mechanical model is established.The main contents of the full text are as follows:1)The conventional uniaxial,triaxial compression test and triaxial unloading-rheological test of limestone were carried out by RMT-150 C rock mechanics tester and RLW-2000 triaxial creep tester.The basic physical parameters and instantaneous mechanical properties of limestone are studied.The influences of different confining pressures on the elastic modulus,deformation modulus and peak strength of limestone are discussed.The deformation and failure characteristics of limestone specimens under different confining pressures are analyzed.2)Carry out three-axis unloading-rheological tests with different unloading rates and different initial stress levels to study the mechanical properties of limestone unloading-rheological under different conditions,from stress-strain curve,rheological rate,flow The axial and lateral deformation laws of limestone are analyzed in three aspects.The deformation and failure modes of limestone in different rheological phases are analyzed.The strain laws and macroscopic failure modes of limestone under different unloading rates and stress levels are analyzed.3)Analysis of the residual strength law and difference of limestone combined with different deviatoric stress difference,and introduce the influence of ? parameter correction test unloading process on axial and lateral average rheological rate,using improved "steady-state rate intersection method" "Analyze the long-term strength of limestone and determine long-term strength values."4)The damage characteristics of the rock in the unloading-rheological process are simulated by the(1-K)factor on the original viscoelastic-plastic model.The modified mechanical model is identified by parameters,and the results show that it can be to some extent.Reflect the strain change law of limestone in the rheological stage.