RESEARCH ON ELECTRICAL CONDUCTIVITY OF EXPANSIVE SOIL AT YANGTZE-TO-HUAI WATER DIVERSION EXPERIMENTAL PROJECT

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 and increases 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.