Review of the seismic design for sandy shell of Dahuofang earth dam

On the design of Dahuofang hydraulic project during 1952, the problem of anti liquefaction for the sandy shell was extensively researched and learned from foreign reference books. With respect to our laboratory result of critical porosity ratio, we adopted the relative density 0 83 for the sand mass,its corresponding dry density and shear strength were cited in the analysis of slope stability by pseudostatic method, and two directions of earthquake inertia force were applied to this analysis. ln order to compact the sand to meet the relative density mentioned above, we developed the heavy machine tamper. During 1992, 5 exploring pits were dug in the sand shell to determine the undisturbed porosities,dry densities,relative densities and the mean value of relative density for 5 samples is 0 81 with 2 samples valued 1 0. The maximum shear modulus,maximum damping ratio,the relationship between shear modulus vers shear strain, damping ratio vers shear strain ,dynamic pore water pressure vers dynamic shear stress were determined by resonance column and dynamic triaxile tests. The static and dynamic stresses and strains of the dam were computed by FEM. The contours of liquefaction degree and the seismic safety factor graph were shown in the paper. The conclusion is: when earthquake with intensity Ⅷ occurs, the maximum liquefaction degree is 0 6,the minimum safety factor is 1 08.