Analysis of chemo-mechanical behavior of silty soil under long-term immersion in saline reservoir water

During Yangtze River reservoir impoundment, the widely distributed natural soil on the bank landslide experiences long-term water immersion. The later has a significant effect on soil deterioration, which may also aggravate landslide deformation and even cause landslide triggering. However, scarce attention has been paid to investigate the performance of bank soil immersed in reservoir water for a long period and its possible contribution to landslide deformation. This paper investigates the chemo-mechanical behavior of silty soil in the Three Gorges Reservoir area subjected to long-term Yangtze River water immersion. Chemical and mineralogical analyses, in addition to oedometer and triaxial shear tests, were carried out before and after immersion to investigate the effect of water immersion on the tested soil properties. The results showed considerable change in the soil chemo-mechanical properties induced by water immersion. The changes comprised a slow dissolution of carbonates over time, which became notable at 7 days of immersion, an increase in the silt percentage on the expense of clay, which was observed during the first stage of immersion. The effect of immersion time on the progressive change in the soil properties was dominated at 7 days, but it eventually reached equilibrium at approximately 20 days. The results indicate that soil volume change and deterioration of strength are strongly correlated to the dissolution of carbonates and changes in the soil particle size distribution.