引江济淮试验工程膨胀土电导率特征实验研究

摘要

南水北调中线工程实践研究表明,膨胀土的电导率与自由膨胀率呈现线性关系.引江济淮试验工程为开发膨胀土判别快速方法以及提出针对江淮地区土质的电导率法判别适用标准,开展膨胀土电导率特征实验研究.工程现场取多组土样进行基本性质、膨胀性和不同含水率下的电导率实验,寻求该地区膨胀土电导率与含水率和自由膨胀率的关系.研究表明,电导率随土体含水率增加呈现先增加后减小的变化趋势,土体处于液限含水率附近状态下,具有最强的导电性,电导率具有峰值特征.相同含水率条件下,土体的膨胀性越强电导率越大;电导率和自由膨胀率总体上线性相关,试样在液限含水率附近时相关性最大;线性经验模型的精度由相关性水平控制,本试验提出的江淮地区弱膨胀土电导率经验模型的精度控制标准为R2=0.78,可以达到自由膨胀率实测值的精度水平,具有实用价值.%The practical research show that the conductivity of expansive soil has a linear relationship with the free expansion rate at the middle route of the south-to-north water diversion project. This paper aims to develop a rapid method for the discrimination of expansive soils at the Yangtze-to-Huai Water Diversion project and to present the standard for the electrical conductivity of soil of Yangtze-to-Huai area. It examines the electrical conductivity characteristics of expansive soils. It investigates the relationship between the conductivity of expansive soil and water content and free expansion rate in this area. Basic properties, swelling index and electrical conductivity tests are conducted on multi-group soil samples with varying water content obtained from the project field. The study shows that the lead rate increases with the increase of soil moisture content and then decreases. The soil has the highest electrical conductivity in the vicinity of its liquid limit. The electrical conductivity shows peak characteristics andincreases with the swelling index of the soil under the same moisture content. The conductivity and the free swell index are linearly correlated in general. The correlation reaches a maximum in the vicinity of the liquid limit of the soil. The precision of the linear empirical model is controlled by the correlation coefficient. For weakly expansive soils, the model can achieve a high accuracy level of the free swell index when the R2 value is equal or greater than 0.78. and the findings have practical value in predicting the free swell index of soils.