基于电阻率法的膨胀土膨胀性评价研究

Evaluation of expansibility of expansive soil using resistivity method

目前膨胀土的膨胀率一般只能通过室内试验获取,无法通过简单快速的测试得到。结合课题组前期的相关膨胀土电学特性试验研究发现,膨胀土吸水膨胀会改变土体内部结构,而土体内部结构的变化会引起电阻率的改变。通过对取自合肥的膨胀土进行电阻率、膨胀率等相关性能的试验,分析电阻率指标,并对膨胀土的吸水膨胀特性进行预测评价。研究发现,膨胀率随着初始电阻率的增大而增大,且随着上覆荷载的增大而减小;竖向电阻率与实时膨胀率基本呈直线增加关系,直至土体电阻率达到孔隙液电阻率为止。根据膨胀土基本电学试验和膨胀土吸水膨胀及相应横纵向电阻率实时测试试验研究发现,膨胀土的膨胀性能与电阻率结构参数吻合很好,因此,可以通过电阻率相关指标对膨胀土的膨胀特性进行预测。由于相应膨胀率为无量纲指标,故通过黏性土电阻率结构参数去除孔隙率影响,建立了无量纲综合电阻率指标Er与膨胀率之间的关系,以供后期膨胀土的膨胀率预测。

Currently, it is is difficult to obtain the expensive rate of expansive soil simplely and rapidly. Generally, the expensive rate can only be obtained through indoor test. It is shown that the internal structure will be changed with water swelling by previous experiments about the electrical characteristics of expansive soil in laboratory. The change of internal structure can lead to the change of resistivity. Resistivity, expensive rate and other related performance experiments are performed by using Hefei expansive soil. The resistivity index is used to predict the water swelling characteristics of expansive soil. It can be found that the expansive rate increases with the increase of initial resistivity and decreases with the increase of the overlying load. In addition, the vertical resistivity exhibits a linear increase with real-time expansion rate until the soil resistance rate reaches pore fluid resistivity. The previous experimental studies of our research group about resistivity characteristics of expansive soil are used to analyze and contrast. It can be found that expansion characteristics of expansive soil have a good fit with resistivity properties. Hence, the resistivity can be used to predict expansion rate. As the corresponding expensive rate is a dimensionless index, through the normalization of cohesive soil resistivity and regardless of the influence of the porosity, the relationship between dimensionless integrated resistivity index Er and the expensive rate is developed. The conclusions can be used for the expansion rate prediction of expansive soil.