基于电阻率CPTU探头快速评价膨胀土电阻率特性研究

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

为了验证采用电阻率CPTU探头评价膨胀土电阻率变化的可行性,以商用膨润土和高岭土相互拌合而成的人工膨胀土为研究对象,通过自行研制的电阻率探头贯入模型试验,探究不同含水率和不同自由膨胀率下膨胀土的电阻率变化规律,并对比分析室内电极法与电阻率探头所测电阻率之间的关系.研究结果表明,不管是使用电阻率探头还是室内四电极法测量,最终测得的膨胀土电阻率规律相似,在定含水率情况下膨胀土电阻率随膨胀特性的增强而减小,在定膨润土占比情况下膨胀土电阻率随含水率的增大而减小,并证明了含水率对电阻率的影响大于膨润土占比对电阻率的影响;室内两电极法或四电极法与电阻率探头所测电阻率之间均呈现良好的线性相关关系,其中室内四电极法与电阻率探头所测电阻率基本呈现1∶1的直线关系,说明采用电阻率探头评价膨胀土电阻率的变化是可行的,证明了自行研制的电阻率测试设备在膨胀土场地中的适用性.

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.