AN EXPERIMENTAL STUDY FOR INFLUENCE OF FREEZE-THAW CYCLES ON STRENGTH AND PORE CHARACTERISTICS OF SOLIDIFIED LEAD-CONTAMINATED SOIL

Cement-based curing agent blocking is one of the main technology for the remediation of heavy metal contaminated soils in recent years. Freeze and thaw cycles(FTcs) is an important external agent affecting the mechanical properties of cement solidified heavy metal contaminated soil. In present study, the artificial lead-contaminated soil is prepared using a systematic design. FTcs tests and laboratory soil tests are employed to reveal the influence of freeze and thaw cycle on the unconfined compression strength of lead-contaminated soil. The results show that:with the increasing of the proportion of cement, the unconfined compression strength(q_u) of cement solidified lead-contaminated soil increases, while failure strain decreases. With the increasing of the proportion of lead ion(higher pollution level), the unconfined compression strength(q_u) of cement solidified lead-contaminated soil decreases. However, the trend of stress-strain curves is similar. The unconfined compressive strength of cement solidified lead-contaminated soil decreases with the increasing of freeze-thaw times. When the freeze-thaw times is the same, the loss rate of unconfined compressive strength of cement solidified lead-contaminated soil decreases with the increasing of the proportion of cement. The microstructure of solidified lead contaminated soil is quantitatively analyzed using SEM image. It is found that the proportion of fine particles(< 1 μm) and fine pores(< 2 μm) in the samples increases with the increasing of freeze-thaw times. It may be the main reasons leading to the decreasing of unconfined compressive strength of the soil that failure of freeze and thaw cycles on soil structure.