Abstract: The free slaking studies on the undisturbed soils were performed in order to investigate the rate of the soil slaking and its influence factors. Testing data indicate that the rate soil slaking is influenced by many factors, such as, moisture content, void ratio, unit weight, and coefficient of permeability as well as the frequency of the groundwater fluctuation. The first four items are the physical properties of the soil and they are related to the soil composition, formation conditions and its surrounding environment. These factors are rarely related to the human activities. The groundwater fluctuation frequency, however, are affected by the natural environments as well as by the human activities, especially, the groundwater extraction and the irrigation. Groundwater fluctuation will accelerate the soil slaking and increase the formation of soil cavities at the soilkarst rock interface, finally, increase the development of the sinkhole collapse.

Key words: Slaking, Ground Subsidence in Karst Terrains, Influence Factors, Groundwater Fluctuations