Rapid Evaluation of Resistivity Characteristics of Expansive Soil Based on Resistivity CPTU Probe

In order to verify the feasibility of using the resistivity CPTU probe to evaluate the resistivity change of expansive soil,the artificial expansive soil made of mixing commercial bentonite and kaolin is taken as the research object.Through the penetration model test using self-developed resistivity probe,the resistivity variation of expansive soil under different water contents and free swell ratios is explored.The relationship between the resistivity measured using the indoor electrode method and resistivity probe is compared and analyzed.The resistivity measured by the resistivity probe is similar to that measured by the indoor four-electrode method.When other parameters are kept constant,the soil resistivity decreases with increasing water content,while the soil resistivity decreases with increasing the free swell ratio at a water content.The effect of water content on the resistivity is greater than that of the bentonite ratio.In addition,there is a good linear correlation between the resistivity measured by the indoor two-electrode method or four-electrode method and the resistivity measured by the resistivity probe.The slope of the linear correlation for the four-electrode method is basically 1∶1,indicating that it is feasible to use the resistivity probe to evaluate the change of the resistivity of expansive soil.At the same time,the applicability of the self-developed resistivity measurement equipment to expansive soil field is also demonstrated.