Deformation Characteristics Of Saturated-Unsaturated Soil Under Elastic Modulus Varying With Depth

In the nature , the soil's elastic modulus varies with depth continuously because of a long natural geologic deposited history. The model which shows this characteristic of the soil is applied to simulated engineering practice better. Based on the poroelastic governing equations for groundwater flow in saturated-unsaturated media, the numerical model is verified against correlating to the result of the literature with the finite element software COMSOL Multiphyscis. Considering the non-homogeneity of the soil whose elastic modulus varies with depth, the parameter m is switched to control the rate of change for elastic modulus varying with depth. The discipline of influence of the non-homogeneity is obtained by parameter analysis method. This method is applied to simulating consolidation process of 1-D and 2-D saturated-unsaturated soil due to surface loading.The research shows the parameter is bigger, the dissipating process of excess pore water pressure of the non-homogenous model is more different with homogenous model'. At the beginning consolidation, excess pore water pressure increases with the parameters m decreased; at consolidation process, the dissipating velocity of excess pore water pressure increases with the parameters m decreased, the greater the parameters m is, the quicker the dissipating velocity of the excess pore water pressure; After the consolidation, the excess pore water pressure does not dissipate completely, and the final excess pore water pressure increases with parameter m decreased.The non-homogeneity of elastic modulus varying with depth has its significant influence to vertical displacement of the model: At the beginning consolidation, the vertical displacement of the non-homogenous model is quite different with the homogenous model', the amplitude of vertical displacement of the non-homogenous model increases with the parameters m decreased; at consolidation process, the velocity of vertical increases with the parameters m decreased, the greater the parameters m is, the quicker the deformation velocity is; After the consolidation, the final vertical displacement of the non-homogenous model is obviously smaller than the homogenous model, and the final vertical displacement of the non-homogenous model increases with parameter m decreasedThe non-homogeneity of elastic modulus varying with depth has its significant influence to water-table fluctuation: at consolidation process, the water-table rises with the parameters m decreased; after the consolidation, the excess pore water pressure does not dissipate completely, and the final water-table increases with parameter m decreased.The method which is applied to studying 1-D and 2-D saturated-unsaturated soil due to surface loading is applied to analyze 3-D saturated-unsaturated soil due to surface loading and groundwater pumping shutoff. Additional discipline is obtained: the effective stress in the soil increases with the excess pore water pressure dissipating due to groundwater pumping shutoff; at the new stable state, t the excess pore water pressure the effective stress in the soil will remain unchanged, and the final vertical displacement at the top of the non-homogenous model increases with parameter m decreasedIn order to more accurately predicate the pore water pressure change and ground surface settlement and lateral displacement of foundation,The non-homogeneity of elastic modulus varying with depth will be never ignored as one of the most important factors.