Quantitative Study On The Adsorption Bound Water Of Loess And Related Clay Minerals

The study of Bound-water of loess and clay minerals has always been one of the issues that are closely watched in the fields of Soil Water Kinematics,Hydrogeology,Gnginee r ing Geology,Hydromechanics,Geotechnical oil-gas development and other sphere,sometimes it largely controls the strength,permeability and stability of soil with its existence;however,the current research on the Bound-water of loess and clay minerals is less developed,therefor,it is difficult to support evaluation or solution to problems encountered in engineering constructio n and scientific research;in order to further clarify the relevant physical and mechanic a l characteristics of Bound water that should study the bound-water more.Maran loess that from Jinyang(Shaanxi province)and different particle sizes of il ite,montmorillonite,and sodium-montmorillonite are selected as the research object,obtained the adsorption rate of Bound water,and the temperature range corresponding to the removal of different types of Bound water was determined;the density and volume that after hydration were measured,and analysis its density and related parameters,at the same time,the specific surface area of several research objects was analyzed,and then obtain thethinkness of Bound water.This paper mainly obtains the following results:(1)Take the isothermal adsorption measure the adsorption rate of bound water in loess and clay minerals of different types and sizes.The results show that there is no obvious regular it y between the adsorption rate and particle size of Bound water on illite,and the rate is small;the adsorption rate of montmorillonite,sodium-montmorillonite and Bound water of loess are relatively large,a great difference about adsorption rate exist between the same species and different particle sizes.(2)The isothermal adsorption experiments is used to study the adsorption ratio of strong Bound water to weak Bound water for different research objects.The results showed that the corresponding ratio of illite 200 meshes is the largest,which is 5.273,the minimum is 325 meshes that corresponding to 1.863;for montmorillonites,the ratios are all less than 1,indicating that the adsorption of weakly Bound water dominates the corresponding isotherm adsorption process;sodium-montmorillonite has a significant difference between 300 mesh and 400 mesh that the ratio of 300 mesh is less than 1 and the latter is the opposite;for loess,the ratio close to 3,indicating that adsorption of strong Bound water and second only to illite 200.(3)From the analysis of isothermal adsorption curve types and adsorption characterist ic points,found that all the research objects met the IV type isothermal adsorption curve,that is,with the increase of relative humidity,the adsorption rate showed a gradually increasing trend,tends to be stable while the relative humidity is close to 1;there are two characteristic points on the isotherm adsorption curve,RH=0.58 and RH=0.98;they corresponds to the boundary of strong Bound water and weakly Bound water,weakly Bound water and and free water;for individual subjects,the characteristics of single-layer adsorption to saturation were exhibited at RH=0.11.(4)Thermogravimetric analysis is used to study the temperature range of different types of Bound water.The results show that: different substances have coorespond dehydrate temperature respectively,the temperature range of strong Bound-water is greatly different while free water is not obvious;combined with TG and DTG curve,the adsorption rate of Bound water determined among the isothermal adsorption experiment is verified,the relative error is small and experimental result is reliable.(5)Volumetric flask method has been used to analyze the density of adsorbed Bound water.It was found that as the relative humidity increases,the density gradually decreases,and the density change curve has a strong correlation with the isothermal adsorption curve,the maximum density is 1.41 g/cm3;the density and volume of a single mineral after hydration shows a positive correlation with the adsorption rate,loess shows a certain degree of differe nce due to its complex composition.(6)Using BET theory,combined with isothermal adsorption process,quantitative analys is the thickness of the adsorption Bound water;different studied objects with different water thickness;and a small part of the research object meet the characteristics of monolayer adsorption.