The Research On The Static And Dynamic Characteristics Of Gravel Clay

Core-wall rockfill dam is one type of the most widely used earth and rockfill dams in engineering practice. Clay with tiny permeability coefficient is usually selected as the impermeable material for core-wall rockfill dams. But clay is characterized by low strength, large compression deformation and not favorable to mechanical construction, which seriously limits the development of 300-m-high clay core dams. However, clay mixed with gravel takes advantages of very small permeability, high shear strength, small compression deformation and consistent with the deformation of dam shell material et al, which is widely used as core-wall material of high core-wall rockfill dams, such as the Rogun dam in Kazakhstan and the Nuozhadu dam in China.At present, the properties of clay mixed with gravel, such as compactability and permeability, are studied comprehensively. While few studies have considered the static and dynamic properties, and the research of model applicability in numerical analysis is also rare.Under the support of the national science fund project(51279025,51379028), the national natural science fund integration project(91215301) and the new century excellent talents support plan(NCET-12-0083), and combined with the under-construction 300-m-high core-wall rockfill dam in China, the main research works in this thesis are listed as follow:(1) A series of reproducible consolidation draining shear tests, consolidation draining loading-unloading shear tests, consolidation exhaust shear tests of unsaturated samples, dynamic modulus and damping tests and residual deformation tests using the static and dynamic triaxial apparatus are conducted, in order to analysis the static and dynamic properties of clay mixed with gravel.(2) The applicability of the Duncan-Chang E-B model and the generalized plastic model of the stress-strain relationship of clay mixed with gravel is studied. FEM analysis of the deformation properties of a core-wall rockfill dam during impoundment using the Duncan-Chang E-B model and the generalized plastic model is performed, respectively. The rationality of the generalized plastic model is analyzed according to the settlements distribution by the two models.(3)The general assumption of unloading coefficient and index of the Duncan-Chang E-B model is not appropriate by analyzing the law of unloading modulus parameters of clay mixed with gravel, and rational unloading modulus parameters for clay mixed with gravel are proposed. (4) For the difficulty of measuring volume change of the gravel clay during the process of test saturation, pressure consolidation and the shearing, adopting the external hydraulic equipment measuring the change of the sample’s volume, avoiding the influence of saturation of sample and improving the efficiency of test greatly. Compare the result of this method with the conventional method of measure the volume change, and verify the accuracy of this paper’s method. By compare the unsaturated and saturated sample parameters of the generalized plasticity model, and testify the possibility of using unsaturated sample instead of the saturated.(5) the results of the static and dynamic simulation show that generalized plasticity model can be chosen as the constitutive model on numerical calculation.