Triaxial Test And Parameter Random Field Study Of New Deposits Of Hongshiyan

The earthquake in Ludian,Yunnan Province,caused a massive landslide in the Niulanjiang Mountains,forming a barrier lake in Hongshiyan Village.The site geological conditions of the quake lake are very complex,and the Hongshiyan barrier body is too large to be removed directly.In order to prevent secondary disasters,it will be permanently strengthened and a hydropower station of Hongshiyan barrier dam will be built on it.In order to analyze the safety of the dam,it is necessary to determine the mechanical properties of the new accumulation body of the dam.Therefore,field borehole sampling and field density test were carried out.The field sampling results of the new deposit body of the weir dam show that its particles are mainly limestone and dolomite,and the density distribution of the new deposit body has a large discretization.The spatial distribution of soil grain gradation has certain discreteness and randomness.Conventional methods cannot accurately describe the variation of mechanical parameters caused by the discreteness of density and spatial distribution of soil grain gradation.In order to describe the inhomogeneity of the spatial distribution of the mechanical parameters of the dam body,the covariance matrix decomposition method is adopted to describe the spatial correlation of the mechanical parameters of the soil body through the correlation distance.According to the experiments,the statistical characteristics of the parameters of the Duncan-Chang E-B model are obtained,and the random field of the parameters of the Duncan-Chang E-B model of the new accumulation body is constructed.In order to analyze the influence of soil gradation and soil density on model parameters,according to the field test results,indoor triaxial tests of new reactor volumes under different densities and gradations were carried out.The statistical characteristics of mechanical parameters K,n,K_band m of random field are determined according to the results of conventional laboratory triaxial tests.The correlation distance of random field is determined by the method of correlation function based on the shear wave velocity,surface wave velocity and apparent resistivity of the new deposit body in the red rock barrier dam.The laboratory test results show that:(1)macroscopically,under the same grading and the same confining pressure,the peak shear stress increases with the increase of dry density,and the volume strain decreases with the increase of dry density;(2)Under the same dry density and confining pressure,the peak shear stress and volumetric strain increased with the increase of coarse particle content.(3)The effect of confining pressure on volumetric strain decreases with the increase of fine grain content,but the volumetric strain modulus still increases with the increase of confining pressure.(4)Under the conditions of different densities and gradations,the mechanical parameters K,n,K_band m of the new Hongshiyan accumulation body obey lognormal distribution.In this paper,the correlation function method is adopted to calculate the vertical correlation distance of Hongshiyan weir plug body is 2.68m according to the field shear wave velocity of new accumulation,and the horizontal correlation distance is 30.46m according to the calculation results of surface wave velocity and apparent resistivity.The covariance matrix decomposition method is used to discretization the random field,and the random field of the parameters of the Duncan-Zhang E-B model is constructed.It can be seen that the distribution of mechanical parameters of the new deposit body of Hongshiyan has obvious discretization.It is proved that the method of constructing the random field of Duncan-Zhang E-B model parameters by covariance matrix decomposition is applicable to the safety analysis of earth-rock dam,and the simulation of the random field of Hongshiyan barrier dam can also provide some reference experience for the construction of similar random field of dam.