Expansive soils always have high plasticity and strong hydrophilicity. Because of high clay mineral contents

high cation exchange capacity

and relatively larger specific surface area

the electrical conductivity of expansive soils increase with swelling capacity. Strong

middle and weak expansive soils are selected to study the relationships between conductivity and swelling capacity. By using non-contacting electrical resistivity device and portable conductivity probe

the electrical conductivity of both the soil slurry and the pore water are tested. And atomic absorption spectrometer is used to detect ion species and contents of pore water. Researches show that the conductivity of slurry and pore water both increased with swelling capacity

and the increasing trend show a good linear relationship. Thus

conductivity can be a good method for rapid identification of expansive soils.