Theoretical Study on Freezing Separation Pressure of Clay Particles with Surface Charge Action

Abstract

This study aimed to clarify the mechanism of the effect of surface charge of clay particles on the separation pressure between adjacent frozen clay particles. A general mathematical model of separation pressure between adjacent spherical clay particles was given based on the extended colloidal stability (DLVO) theory; it was introduced into the frost heave process, and the functional expression of separation pressure and freezing temperature between clay particles was derived by using the relationship between the pore throat’s radius and freezing temperature, which was verified by the existing experimental results. Finally, the effects of the freezing temperature, mineral species and solution concentration on the freezing separation pressure and ice-lens growth were analyzed. Our results show that the surface distance of adjacent charged bodies is a single-valued function of their separation pressure, but the freezing temperature is the main factor affecting the separation pressure between adjacent frozen clay particles; the separation pressure between adjacent clay particles is proportional to its surface-charge density. For the same particle spacing, the separation pressures of kaolinite and illite are not much different, but they are both about one order of magnitude lower than montmorillonite; the separation pressure between clay particles is negatively correlated with the solution concentration. When the solution concentration is less than 0.1 mol·m−3, the effect of the solution concentration on the separation pressure between particles is negligible. The research results can provide a theoretical reference for improving the existing geotechnical frost heave theory.