Experimental Study On Surface Free Energy Of Loess In Weibei Area

The surface free energy is a measure of the surface energy of the object,which reflects the interaction between molecules on the surface of the object,and has a very important influence on the solid surface,interface properties and interface reactions.Therefore,measuring the contact angle of loess and calculating the surface free energy of loess are of great significance for correctly evaluating the engineering properties of loess.In this paper,the capillary water rising test was carried out on the capillary tubes with different inner diameters,the contact angle was measured and the surface free energy was calculated.The contact angle measurement test of Weibei Q₃^eol loess,Q₂^eol loess and Q₃^elpaleosol in Shaanxi Province was carried out and the surface free energy was calculated.The reasons for the difference of surface free energy of loess at different depths were analyzed by laser particle size analysis test,scanning electron microscope test,XRD test and FT-IR test.The main research results of this paper are as follows:（1）With the increase of the inner diameter of the quartz capillary,the contact angle decreases first and then increases,and the surface free energy increases first and then decreases,reaching the extreme value when the inner diameter is 0.6 mm.Compared with the harmonic mean method,the geometric mean method is less affected by the choice of liquid combination when calculating the surface free energy.（2）The surface free energy of loess calculated by different surface free energy calculation methods and different liquid combinations is different.It is more appropriate to measure the contact angle of loess with distilled water,diiodomethane and formamide,and to calculate the surface free energy of loess with geometric average method.The surface free energy of Q3^eolloess is the largest,the surface free energy of Q2^eol loess is the second,and the surface free energy of Q3^el paleosol is the smallest.（3）The surface free energy of loess has an important influence on its engineering properties,and the smaller the surface free energy,the higher the strength of the soil,the less prone to collapse.（4）Through laser particle size analysis test,scanning electron microscopy test,XRD test and FT-IR test,it is found that the surface free energy of loess is positively correlated with specific surface area（SSA）,pore area ratio and illite content,and negatively correlated with Si-O-Si and Si-O-Al content.The unique hematite in Q3^el paleosol results in a smaller surface free energy than Q₃^eol loess and Q₂^eol loess.