Electrical resistivity of freezing clay : Experimental study and theoretical model

Electrical resistivity of soil has become one of the most important indicators of compactness and compressive resistance. In previous studies, the temperature of soil tested was always above 0°C. When the soil temperature is below the freezing point, a part of the pore water undergoes a phase change. The electrical resistivity of freezing soils are different from that of unfrozen soils; therefore, it is necessary to clarify the influence of temperature on electrical resistivity of freezing soil. To achieve this goal, according to the bundle of the cylindrical capillary model, the pores in the soil were treated as conducting tubes, and two simple log-normal functions were introduced to describe the distribution of the conducting tubes. Based on the conductivity theory, a new model considering the temperature and the pore size distribution was presented. The results show that only a part of the conducting tubes can be treated as the effective conducting tubes, which are determined by the soil temperature. Furthermore, a small portion of the pores with the smaller size controlled the electrical resistivity of the freezing clay. In other words, the change in the electrical resistivity of freezing clay was caused mainly by the change of unfrozen water content through the decrease in temperature. Based on the experimental results conducted on clay from Northeast China, the validity of the presented model was verified. The comparison results indicate that there was a good agreement between the calculated results and the experimental results.