Abstract: The working pattern of single pile embedded in expansive soil will be influenced by the soil’s water content directly. In order to study how the soil influencing pile when it is soaking with water, the prototype test of expansive force of bored pile is carried out. The test result shows that the vertical displacement of soil increases slowly and to be stable finally. Influenced by soil water content and compactness, the vertical displacement of shallow area is always greater than that in depth. During the soil expansive process, the uplift force of pile top increases rapidly and then increases slowly; and at last to be stable. According to mechanical analysis of pile and test results, the expansive force is a comprehensive representation parameter of expansive shear force, pile weight and pile-soil interface friction. For more safety, pile length should be long enough to make sure the anchoring force of pile is larger than ultimate expansive force.

Key words: expansive soil, pile, expansive force, prototype experiment