Influencing Mechanism Of Pore Water Chemistry On Volume Change Behavior Of Kaolinite

Any human engineering and construction activities is carried out in the rock-soil mass of crustal surface, and any building is based on the rock-soil mass as building foundation,building medium or constituded by multiple components, and there are usually residual charges in the solid skeleton. When the soil is fully contacted with the water, there is an imbalanced charge distribution between the clay particles and water molecules, in addition to the pore water contains different levels of ions. As a result, in chemistry and other environmental loads, the rock-soil mass, as a multiphase and multicomponent porous material,will exihibit an extremely complicated chemical mechanical coupling effect and engineering mechanical behavior, which has a significant impact on building construction and the safety,stability and normal use of building. However, the existing thoeries of rock and soil mechanics have obvious limitations in describing the chemical mechanical behavior of rock-soil mass under complex environmental loads, which has severely restricted the effective solution of many major engineering problems.Based kaolin as research object, through a variety of laboratory tests, such as liquid-plastic limit, free settlement and one-dimentional confining compression, this dissertation systematically studies the influence rule of the changes in the chemical composition of pore fluid on the water holding capacity, the arrangement of clay particles and the interaction between particles and the deformation characteristics of kaolin. At the same time, from the perspectives of the physical and chemical interaction between the clay and pore solution, and the changes of the contact between particles, this paper further explores the mechanism of the changes in the chemical composition of pore fluid on the deformation characteristics of kaolin. The study finds that:First of all, the influence of the composition changes of pore solution on the liquid-plastic limit of cohesive soil is related to the content change of loose bound water and capillary water in soil pore. For more reactive cohesive soil, the content change of loose bound water is the dominant factor in determing the influence of the composition changes of pore fluid on the liquid-plastic limit of cohesive soil, manifesting that the liquid and plastic limit decreases with the increase of pore solution concentration or cation valence.Secondly, the influence of the compositon of pore solution on kaolin deposit's porosity is connected with kaolin crystal surface charge, charge density and induced particle arrangement and difussion layer thickness variations. All factors that suppressing the development of electric double layer will cause clay particles to form large pore E-E or E-F flocculatedstructure; on the contrary, decentralized F-F structure will be formed.Thirdly, soil deformation depends on the effective stress that the soil has suffered. And the effective stress has connection with substitution fluid concentration and cation valence.That is to say, as the rise of substitution solution concentration or cation valence, the increase rate of the effective stress will be bigger and faster. As a result, under various levels of constant pressure, the fianl deformation and the deformation rate induced by chemisty increases as the rising of the substitution fluid concentration or cation valence.Fourthly, when the composition of pore solution changes, the compression index and the coefficient of consolidation of soil will change significantly. Compression index of soil decreases with the increasing of the pore solution concentration. The reason is that the higher the concentration of pore solution and the greater the effective stress that the soil suffered, the larger the initial compactness will be, thus decreases the compressibility of the soil. Under the same concentration of pore solution, coefficient of consolidation increases with the increase of vertical press. Under the same consolidation pressure, the higher the concentration of pore solution, the smaller the consolidation coefficient will be. The change rule is related with the permeability coefficient and the volumn compression coefficient, while the two coefficients are connected with the variation of consolidation stress and concentration.Finally,as to one-dimensional compression test, the change of chemical composition of water has nothing to do with the deformation of more reactive cohesive kaolin and the mechanical force loading route that kaolin has experienced. Additionally, when kaolin suffered the erosion of chemical solution, the deformation of specimen is irreversible, which is mainly due to the deformation mechanism of chemical induction. That is to say deformation is dominated by the sliding of particles or the particles rearrangement which is caused by the rolling action.