Effects of NaCl concentration on electrical resistivity of clay with cooling

Abstract

The influence of salt concentration and gravimetric water content on the freezing process of clay soil is studied by using electrical resistivity as a measurement. Along with the ultrasonic pulse method, the P-wave velocity of samples is obtained to estimate the unfrozen water content of frozen soil, and the development of cracks due to frost heave at different temperatures is also analyzed. The results indicate that the freezing temperatures of samples with a sodium chloride (NaCl) concentration of 0, 2% and 5% are −4 °C, −6 °C and −5 °C respectively. Cracks due to frost heave propagate rapidly at temperatures below the crack coalescence temperature, which results in a steep increase in electrical resistivity. There is a sigmoid function for the relationship between electrical resistivity and temperature. A good power function is found for the relationship between electrical resistivity and the NaCl concentration of clay soil. There is a power function for the relationship between the electrical resistivity of pore water and salinity. The electrical resistivity decreases linearly with water content at temperatures above freezing but increases logarithmically at temperatures below freezing. The generalized relationships between electrical resistivity and water content, NaCl concentration and temperature are effective for predicting the electrical resistivity of frozen saline soil in practice.