Experimental Study On Creep Mechanics Characteristics Of Fault Gouge In Pingjiang Pumped Storage Power Station

As the product of fault activities,fault gouge is closely related to fault activities,and specific information on related fault activities can be obtained through fault gouge.From the view of engineering geology,fault gouge is a weak zone and it is the controlling factor of many geological disasters;from the perspective of the rock mass mechanics,fault gouge is poor in mechanical properties,low in strength and widely distributed,which is the focus of the work of rock mass engineering.Therefore,the researches of fault gouge in recent years are paid more and more attention.In this paper,the fault gouge in the adit of the Hunan Pingjiang pumped storage power station is taken as the object of study.The conventional three-axis shear test and conventional triaxial creep test are carried out to analyze the creep mechanical properties under different dry densities and moisture contents.Combined with creep empirical constitutive model and the element constitutive model,the creep constitutive models of fault gouge in Pingjiang pumped storage power station are established.The main achievements in this paper are as follows:(1)The triaxial shear test shows when the moisture content is in the range of 12% to 18%,the internal friction angle of the fault gouge decreases with the increase of the moisture content,and the cohesion increases with the increase of the moisture content.The linear equation is used to fit it,and the fitting degree is good.(2)The creep curves and stress-strain isochronous curves under different conditions are obtained by creep tests,and the effects of dry density and moisture content on the creep mechanical properties of fault gouge are analyzed The results show that the creep strain decrease with the increase of the samples' dry density,and the dry density and the total strain are approximately in a power function approximation;the creep strain increase with the increase of moisture content,and moisture content and total strain are approximately in exponential function relations.(3)The intrinsic relationship between stress,strain,and time of fault gouge is analyzed.A new four-parameter creep empirical model of fault gouge is established and the model parameters are determined.This model can describe the creep characteristics of the fault gouge at a certain deviatoric stress level.(4)The typical empirical model Singh-Mitchell model and Mesri model are used to fit the test data so that the Singh-Mitchell model and the Mesri model formulas which are suitable for describing the creep characteristics of the fault gouge are determined,and the model values and test data are compared.(5)In the study of the component model of the fault gouge,a five-parameter Kelvin element model is used to fit the test data and the correlation coefficient is determined.Finally,the creep element constitutive model formula is established,which can describe the creep characteristics of the fault gouge better.