A Study On The Influence Of Water's State In Clay On Its Engineering Properties

With the development and construction of soft clay areas,the engineering performance of soft clay has been paid more and more attention.The soft clay has high clay content,large specific surface area and strong hydration activity center on the particle surface.Strong water-soil interaction occurs when the water is adsorbed.The bound water layer on the surface of the particles is the important microscopic factors affecting the physical state(solid state and Semi-solid state,plastic state,flow state)and the strength and deformation characteristics of the soft clay.The thickness of bound water film is influenced by mineral composition,the type and concentration of pore fluid and other environmental factors,so that the macro-physical and mechanical properties of the soil changes.In this paper,we have miscrocosmicly studied and mechanism analyzed the impacts that the mineral composition and pore fluid have on the adsorption characteristics of clay particles surface and that the thickness and type of the bound water film have on the physical state,strength and deformation characteristics of the soil.This article mainly contains the following three aspects of research.The first aspect is the experimental study on the microscopic parameters of soft soil and the test of content of strong bound water.The second aspect is the experimental study on the plastic properties of soil samples with different mineral composition and pore type and concentration.The third aspect is the experimental study on the strength and deformation characteristics of soil samples with different water content and different mineral composition.The main research results of this paper:(1)The crystal structure of the mineral component has a great influence on its specific surface area.Particles of mineral composition varis with particle surface hydration changes resulted by large differences between surface areas,which results in different content of bound water.So the specific surface area can be used to characterize the adsorption of mineral components combined with water.The types and concentrations of the pore fluid will change the clay surface's micro-electric field effect,thus affecting the bound water's film thickness and form of existence in particle surface.(2)The empirical calculation of strong bound water is carried out by using the empirical formula of strong bound water(Wg=0.885Wp),which is consistent with the experimental results,and the intrinsic relationship between plastic limit and strong bound water is analyzed.The strong bound water is strongly bound to the surface of the soil particles by physical-chemical adsorption,which is close to the solid.the weakly bound water is of non-solid phase and can be deformed under external forces and remain in the original state.the presence of weakly bound water is the essence of the plastic deformation characteristics of the soil.Studies have shown that the plastic limit of clay can characterize the content of the strong bound water,and the liquid limit of clay can characterize the content of the weakly bound water.(3)Bound water is inherent factor to determine the strength and deformation characteristics of the soil.The experimental results show that the the thickness and type of the bound water film directly affect the connection performance between the particles and the sliding friction state,thus changing the soil strength and deformation characteristics.The generation of weakly bound water is the root cause of weakening soil strength.When the bound water content in the soil is changed from small to large,the deformation properties of the soil gradually change from brittle solid to plastic body and viscous medium.