The Study For Properties Of Bound Water On Clayey Soils And Their Quantitative Methods

Clay mineral is small in particle size and large in specific surface area,andhydration-activation centers on particle surface.Under the interaction of particle-water-electrolyte system,the adsorbed bound water film formed on particle surface is an importantmicroscopic physical factor that remarkably influences the engineering characteristics of softsoil.The thickness and types of bound water changes with mineral composition, property andconcentration of porewate,and temperature and so on.The test results show that combinecohesive soil is control physical condition (solid,semi-solid,plastic state,flow state) and thestrength and deformation of the engineering characteristics microeconomic factors. The mainresearch content is divided into three parts. The first part is the strong bount water’squantitative tests, and through qualitative judgments of the test data to determine the boundwater’s form and demarcation. The second part is a test by changing the mineral compositionor pore fluid solubility to determine the bound water content and morphological changes, andfrom the theoretical level, analysis the nature of the bound water. The third, through a seriesof the plastic liquid limit tests, direct shear and unconfined compression tests under differentconditions, discusses the impact of the bount water on the engineering properties of soil, suchas physical condition, strength, deformation and so on. The outline of the research achievem-ents of this dissertation are listed as follows:(1) Using unit-weight method to determine the strong bound water of various specimens inthe same external conditions. The results showed that, the specific surface area can characteri-ze the bound water of soil particle, the different mineral composition of the particles due to thedifference of the specific surface area, therefore, the particle surface energy and activity isdefferent, so the different adsorption of the bound water; the different of pore fluid solubilityand cation valence will change the clay surface’s micro-electric field effect, thus affecting thebound water’s film thickness and form of existence in particle surface.(2) The thermoanalysis is applied to quantitive determination of water absorbed on clays,water types and dividing line. The bound water in the soil is divided into weak bound water,strong bound water and free water. Because of various effects is strong combine firmly in thesoil surface, the strong bound water’s nature is close to solid. The formation of weakly bound water is the balance between the clay surface negative charge and the electrolyte free solutionion solubility. Compared with free water, the bound water’s nature is weak activity, lowliquidity, high viscosity and shear deformation stiffness.(3) The determination of liquid and plastic limits for single and mixed-viscosity mineralcomposition in different media solution to explain the impact of various factors on thecohesive soil physical state, from the micro-level analysis is closely related with the bountwater’s film thickness and variations. The weakly bound water’s nutare is a viscous state, cannot pass the hydrostatic pressure, and don’t flow freely, but can be deformed by the force, thewater from the thicker film move to the neighboring thinner film.So the reasons for the soilwith plastic state is the existence of weakly bound water. The studies show that the clayplastic limit usually corresponds to the water content of the strong bount water, and clayliquid limit usually corresponds to the water content of the weakly bound water.(4) Research of the strength and deformation features of soft soil with different watercontent were carried out. According to the test results, the determinant of soft soil strength isfrictional and cohesive effect among mineral particles, which can be changed by the variety ofbound water film and results in the change of strength and deformation properties. The boundwater is coated particles, its water content of the particles directly affect the soil’s state andnature of the engagement and sliding friction, thus affect the particles of soil deformation,rotation, such as dislocation movement and deformation. The bound water content in the soilfrom small to large, the nature of the deformation of the soil gradually shift from a brittlesolid plastic body and viscous flow of media.