| The effect of seepage on the stability of earth and rock dam slopes is the focus of research and an essential part of the design of earth and rock dams.As one of the core wall materials of earth and rock dams,the permeability of the soil and rock mixture has a major impact on the slope stability of earth and rock dams when affected by rainfall infiltration and the sudden rise and fall of the reservoir water level.The changes in permeability can be explained from a microscopic point of view,so it is important to study the changes in the microstructure of earth and rock mixtures under different conditions and the impact of permeability on the analysis of dam slope stability,as well as the operation and maintenance of dams and the removal of risk and reinforcement.In this paper,GDS triaxial seepage and NMR tests are carried out on soil-rock mixtures with stone content,number of freeze-thaw cycles,and initial water content as the research variables to investigate the variation of permeability and differences in permeability properties of soil-rock mixtures under different conditions,and to explain the seepage phenomena from a microscopic perspective.At the same time,the NMR permeability coefficients of the soil-rock mixture are predicted by different models based on the NMR technique and compared with the measured permeability coefficients for analysis.Finally,based on the two-dimensional anisotropic seepage calculation theory,numerical simulations of the sudden rise and fall of the reservoir level and of the rainfall infiltration conditions occurring at different moments during the sudden rise and fall phase of the reservoir level were carried out by numerical simulations,with the main work as follows:(1)The initial water contents of 13.12%,15.16%,17.20%,and 19.24% were selected from the physical index tests of the clay foundation,followed by compaction tests on soil-stone mixtures with different stone contents to obtain the relationship between stone content and maximum dry density and optimum water content respectively.(2)The microscopic pore structure of soil-rock mixtures with different stone contents,different numbers of freeze-thaw cycles,and different initial water contents were obtained by NMR tests,and the influence of different stone contents,different numbers of freeze-thaw cycles and different initial water contents on the permeability of soil-rock mixtures was revealed based on the microscopic scale.(3)The GDS triaxial permeability test was carried out in the presence of perimeter pressure to investigate the permeability of soil-stone mixture specimens under different conditions.The relationship between the permeability coefficient and different stone contents,different numbers of freeze-thaw cycles,and different initial water contents were obtained,and the accuracy of the existing permeability coefficient prediction models was evaluated based on the NMR test data of soil and stone mixtures with different initial water contents in this paper.(4)Combining the NMR technique with Young-Laplace’s theory and fractal theory,a theoretical model for predicting SWCC in unsaturated soil-rock mixtures is developed,and the unsaturated permeability coefficient function is predicted by the Fredlund and Xing model,providing a basis for subsequent finite element simulations.(5)Finite element simulation using GEO to establish a finite element analysis model for the slope of a heart wall earth and rock dam under the coupling conditions of sudden rise and fall of reservoir water level,rainfall infiltration,and the sudden rise and fall of reservoir water level,and to introduce the unsaturated soil and rock mixture SWCC and the measured saturated permeability coefficient.The SEEP/w module and SLOPE/w module are used to analyze the permeability stability of the upstream and downstream slopes of the heart wall earth and rock dams considering permeability anisotropy,providing some theoretical reference for diseased earth and rock dams and future practical projects. |
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