Thread Pile And Soil Interaction Research

Screwed pile is a new pile type. Compared with straight-lined pile, it will improve largely the lateral friction of pile.The model test result of cap, pile, pile-cap and two-pile-cap in clay show that the cap can increase the capacity of foundation. The Cap undertakes the load at first. Because the soil bear the load transfer from pile and cap, it's p-s curve is gently, which indict that destroy of piles-cap is not so violent as cap.Because the cap restricts the displacement between pile and soil, the pile side friction resistance starts at the middle and the bottom area of pile. The property of pile side friction resistance on up area is complex. When the load and the settlement are increase, the pile side friction and the pile end friction are increase. When the load is not large, there are pull stress around the pile end.The settlement of the pile and the cap can cause the settlement of soil around the pile and the cap. When the shearing stress caused by pile spread in the soil, the shearing stress can cause the settlement of soil around the pile, there are soil settlement funnel in the area about the scope of 3.5d, and then there are soil arch between piles, which change the original structure of soil.According to the difference of stress and strain properties, we can study the pile-soil interaction in different area. Single pile has two areas: the shearing stress area around pile and the pull stress area around the pile end. The single-pile-cap has three areas:the multi-stress area, the shearing stress area and the pull stress area. The two-pile-cap has four areas:the press area, the soil arch affection, the shearing stress area and the pull stress area. The soil arch affection cause the main stress is middle-internal force in the central area of the soil arch, the toque and the shearing stress are large nearby the piles, the soil-soil interaction is strong in other area.Project practice shows that pile-soil interaction design can solve the problems of the foundation capacity can't satisfy building load requirement and the settlement of soil is too much when we build few layer and multi- layer building in clay area.