ABSTRACT
In order to study the mechanical behavior of pile foundation in collapsible loess area under different immersion states, the lateral friction, bearing capacity, axial force of single pile and settlement of soil around pile in collapsible loess foundation in Lanzhou area under three conditions (non-immersion state, loading after soaking state, loading until the soil approached saturation point) are studied by numerical analysis. The analysis results show that the bearing capacity of single pile foundation is significantly reduced after saturated loess foundation is immersed. The immersion causes obvious collapsible deformation of loess foundation and negative friction resistance occurs on the side of pile. The axial force distribution of pile body also changes with the amount of immersion. In natural state, the side friction resistance of the pile is positive, the friction resistance above the middle of the pile body is small, and the friction resistance below the middle of the pile body gradually increases. The negative friction resistance is not only related to the water-bearing state of the foundation soil, but also to the sequence of immersion and loading and the vertical load on the top of the pile. The bearing capacity of single pile decreases with the increase of water immersion. Axial force of pile body redistributes with the increase of immersion volume of pile and soil; Settlement deformation of the soil layer around the pile is caused by both collapsible deformation of loess and negative friction resistance on the side of the pile, which increases the collapsible deformation. The research results have important theoretical value and guiding significance for the design and construction of pile foundation in the loess area of Lanzhou.
