Research On Bound Water And Its Influence On Thermal Conductivity Of Red Clay

In soil-water-electrolyte systems,the binding water on the surface of soil particles is an important factor affecting soil properties.Red clay is a special kind of soil,widely distributed in China's Guangxi,Guizhou,Yunnan and other places.Because of its special pore structure,it has high water content,high porosity ratio,strong plasticity,high mechanical strength and low compressibility.Compared with the general clay soil,red clay has special thermo-physical properties.The thermal characteristics of red clay are affected by many factors,and the water content is the most important influencing factor.Therefore,it is necessary to study the effect of water content on the thermal characteristics of red clay.This paper focuses on the characteristics of soil water and its influence on the thermal conductivity of red clay.We emphatically research the test method of bound water in soil,the characteristics of water bound in red clay,and the effect of water on the thermal conductivity of red clay.The main research results are:1.The specific surface area of the mixed soil was measured by the Methylene Blue adsorption method and the Ethylene Glycol Monoethyl Ether adsorption method.Although the two kinds of test methods were different in the way of adsorbing the molecules of the soil particles,the test results of the two methods were similar.And with the increase of montmorillonite content,the change trend is the same.So both methods can be used to test the specific surface area of soil.However,the Methylene Blue adsorption method because of easy operation,with a short time,can be used to test the specific surface area of red clay.2.The adsorption and bound water content of a series of mixed soils was measured by isothermal adsorption method.The effects of mineral composition and specific surface area on the bound water were analyzed.The results showed that there are two inflection points in the adsorption isotherm of the mixed soil,and the type of adsorbed bound water can be divided;Different mineral composition due to the different surface area,the amount of adsorbed water is different.The amount of adsorbed bound water increases with the increase of montmorillonite content,and the larger the specific surface area,the greater the amount of adsorbed water.The GAB model was found to be well fitted by the adsorption model.3.The isothermal adsorption line of Guilin red clay and Liuzhou red clay also exists inflection point,by which the type of bound water can be divided.Based on the analysis of the properties of hydrated red clay and the properties of bound water,it is found that the parameters such as the volume of hydrated red clay and the thickness of adsorbed water are similar to those of isothermal adsorption lines.The GAB model has good applicability to the adsorption data of the two red clays.4.By testing the thermal conductivity of red clay and combining with the results of the combined test of red clay,it is found that the thermal relationship between the thermal conductivity and the water content of the red clay is not a single linear relationship,but it is linear with the bound water With the increase of the amount of bound water the thermal conductivity increases linearly.