A Study On Seepage Characteristics Of Clayey Soil Of High Earth-rockfill Dam With Large Shear Deformation

The seepage property of clayey soil under complex stress and large shear deformation is one of the key issues of earth-rockfill dams. By combining laboratory tests, theoretical analysis and numerical simulations, the seepage characteristics of the clayey soil with large shear deformations were studied. The main results are as follows.1. A new triaxial seepage device was developed and a series of seepage tests on clayey soil with large shear deformation were conducted. The tests results indicate that: (1) The triaxial seepage device can be used effectively to conduct seepage tests on soil in three directions with large shear deformations. (2) The permeability of soil changes with the stress and strain states. (3) The permeabilities in different directions are different slightly and the confining pressure affects the permeability of soil evidently. The seepage follows Darcy's law in a large range of hydraulic gradients used in the tests.2. The mechanism of the change of permeability in the tests was analyzed and a mathematical model for the permeability was proposed to simulate the test results. The results show that: (1) Variations of the void ratio and structure are the main factors to affect the permeability of the soil. (2) The mathematical model for the permeability can reflect the effects of the void ratio and structure of the soil. A boundary of the equation is the isotropic consolidation permeability line. (3) Comparisons with the tests results indicate that the proposed equation is practicable and effective.3. Another test device was developed for seepage tests on clayey soil-structure interface. A series of tests were performed and the results were analyzed. Effects of some factors were investigated and the mechanism was discussed. The tests results indicate that: (1) The test device can be effectively used in contact seepage tests on soil interface. (2) The permeability of the soil-structure interface is affected by stress, strain, hydraulic gradient, style of the interface and the roughness of the interface. (3) When there are surface defects or coarse soil in the clayey soil, the permeability of the interface increases. (4) The large shear deformation zone of the soil near the interface is the main factor to affect the permeability of the soil-structure interface, and the geometry of the interface, the physical and mechanical characteristics of the soil can also affect the interface permeability.4. The mathematical model for the permeability was combined with Biot's consolidation theory and a method was proposed to calculate the stress, strain and seepage fields of earth-rockfill dams. The simulating results of Lianghekou core wall rockfill dam indicate that the model can be used effectively and reasonably in calculating the stress, strain and seepage fields of earth-rockfill dams.