Research On The Thickness Of The Bound Water Film And Its Influencing Factors In The Weihe River Basin Loess-Ppaleosol And Its Effects

The thickness of bound water film on the surface of loess particles is closely related to the properties of loess.This paper takes the loess paleosol in Weibei,Shaanxi Province as the research object,and analyzes the factors affecting the thickness of bound water film of loess paleosol from the aspects of porosity,electrification,mineral composition,chemical composition,etc.through particle size analysis test,mercury intrusion test,Zeta potential test,XRD and FT-IR test,The reasons for the difference in the thickness of combined water film between loess and paleosol are discussed,and the following research results are obtained:（1）Due to the different soil forming environment of loess paleosol,the mineral composition and functional groups of loess paleosol will be different.The content of quartz and hematite in paleosol is higher than that of loess,and the content of illite and calcite is lower than that of loess.The number of CO₃^2-functional groups in paleosol is lower than that in loess,and the silicon oxygen bond in the silicate contained in loess is easier to break and hydrolyze with water to generate silanol group.（2）The thickness of combined water film between Late Pleistocene loess and paleosol is quite different.Through the analysis of porosity and phase composition,it is found that the pore volume and pore diameter of paleosol are smaller than that of loess,and the pore distribution is more uniform than that of loess;Compared with loess,paleosol contains less illite,while paleosol contains more high valence cations with strong exchange capacity,and paleosol surface is distributed with ferromanganese film with strong hydrophobicity,which weakens its hydrophilicity.These reasons will lead to a significant reduction in the thickness of bound water film of paleosol.（3）In addition to the influence of porosity and material composition,the difference in the thickness of the combined water film between the Late Pleistocene loess and paleosol is also an important reason for the great difference in the thickness of the combined water film between loess and paleosol.The electrical property of loess is positive,while that of paleosol is negative.The particles with positive electricity are more hydrophilic,and the thickness of combined water film is larger.（4）The thickness of the combined water film between loess and paleosol is an important reason for the difference of its engineering properties.The thickness of the bound water film of loess paleosol will affect its collapsibility.The collapsibility increases with the increase of the thickness of the bound water film,and decreases with the decrease of the thickness of the bound water film.There is a positive correlation between the thickness of the combined water film and the unloading rebound coefficient and permeability.