Abstract: Most of researches related to the immobilization mechanisms of stabilized/solidified heavy metal contaminated soils were depended on the mechanical tests and chemical analysis. Thus, proposing a physical method that is un-destructive, time-saving, convenient and cost-effective is the urgent issue to be solved currently. In this paper, a series of laboratory tests including electrical resistivity test was performed to investigate the microstructural mechanism of cement-fly ash stabilized heavy metal contaminated soils. Furthermore, the prediction model of unconfined compressive strength was established based on the electrical resistivity. The tests results presented that with increasing of curing time, electrical resistivity, pore water electrical resistivity, structure factor, as well as shape factor of the specimens increased, and the anisotropy coefficient decreased. While increasing the heavy metal ions concentration leaded to an obvious reduction in electrical resistivity, pore water electrical resistivity and shape factor, and the anisotropy coefficient increased gradually. The SEM results was consistent with that of the electrical resistivity, which confirmed the feasibility that revealing the microstructural mechanism of the stabilization/solidification of heavy metal contaminated soils by electrical resistivity method. Finally, a good linear relationship between the electrical resistivity and unconfined compressive strength can be obtained. It is suggested that the electrical resistivity can be used as the index to evaluate the mechanical properties of the stabilized soil.

Key words: heavy metal contaminated soils, solidification/stabilization, electrical resistivity, unconfined compressive strength, microstructural mechanism