Experimental Study And Simulation On The Relationship Between Volumetric Water Content And Dielectric Constant Of Red Clay

The regularity of variation on soil dielectric constant with volume moisture content is the premise of establishing reasonable dielectric constant model.In this paper,a series of dielectric constants of four kinds of typical red clay in Guangxi area with different moisture content were tested,aiming at the special mineral composition and "two grade" micropore structure of red clay,the regularity of the change on the permittivity with the volume water content was systematically discussed and analyzed.On this basis,the boundary method,empirical formula method and theoretical model method are chosen to simulate the law of change on the relationship between volumetric water content and dielectric constant.The main outcomes are as follows:1.The regularity of the change on dielectric constant with volume water content was obtained through dielectric constant test of four red clays under different volumetric water contents:The dielectric constant of red clay rises with the increase of the volume water content when the dry density is the same.However,the ?e??v curve which reflects the relation between the volume water content and the equivalent dielectric constant has a sudden change at a critical moisture content,and the growth rate of the ?e??v curve increases after the critical moisture content;At lower volumetric water content,the ?e??v relation of four kinds of red clay substantially coincident,but the ?e??v curve between Liuzhou and Laibin red clay began to deviate from the ?e??v curve of Guilin and Wuming red clay after the critical moisture content,no longer coincide;The mineral composition has a certain influence on the variation of dielectric constant with the volumetric water content,the influence of different mineral components on soil ?e??v relationship is:The quartz>The kaolinite?The aluminum ore>The illite.2.Simulation results of the three model methods show that:The measured ?e??vresults fall within the Wiener boundary and Hashin-Shtrikman boundary,the difference between the upper and lower limits is increasing with the increase of volumetric water content.The predicted value of Topp formula is quite different from the measured value,and its prediction result is too large;The Dobson formula has a good simulation at low water content,after reaching the critical moisture content,the predicted value of Dobson formula is quite different from the measured value,and its prediction result is too small;The simulation result of Looyenga formula is related to the value of the parameter ?,the greater the value of?,the greater the calculation results of Looyenga formula.The EMT model and the Friedman model have some limitations on the simulation of media with "two-stage"microporous structure.They can not describe the fact that the "two-stage" microporous structure medium has inflection point,that is,the simulation results are poor after a critical moisture content;Miyamoto model and Blonquist model consider the "two-stage"microporous structure respectively on the relationship between dielectric constant and volume moisture content from different angles,their simulation on red clay is better.3.Based on the three models,new empirical formulas and theoretical models are established,which are simple in form and easy to obtain.The simulation results show that the new model method has good simulation effect,and the error between the predicted value and the measured value is within the allowable error range in engineering practice.