A New Type Of Pile Used In Freezing Soil Foundation

With the West Developing plan, more and more problems of frozen soil engineering were inevitably encountered during constructions in vast cold regions. One of the most important one is the piles on the poor geological conditions such as saturated permafrost soil or underneath ice layers, such as: 1. frozen soil beside piles is thawed caused by construction and cement hydrate heat, it need quite time to recover freezing again; 2. frost heaving sometimes pull up piles; 3. thaw settlement cause negative friction. This paper base on the thought of "initiative cooling", aim at three problems existing in common concrete pile used in frozen soil, a new type of pile is proposed to overcome the disadvantages of the classical pile used in frozen soil. Pile body within active layer is fluted and refilled with porous materials such as gravels and ballasts, convection will be occur and then thermal exchange inside porous material in winter while only heat conduction exists in summer, as a result the soil around flutings will be cooled, so the top line of permafrost will be drive up. In this paper, temperature field and bearing capability of bore perfusion pile in low temperature permafrost and of bore inserting pile in high temperature permafrost will be contrasted respectively before and after fluted. The simulation analysis and discusses about some factors which affect the frozen soil and pile stability are also given, finally some details for pile fluting are studied. The numerical simulation indicate that it promote permafrost growth and accelerate the course of recover frozen greatly after fluting via natural convection dropping temperature effect, the top line of permafrost rises greatly, consequently enhance pile bearing capability and so do the capability for resisting frost heaving and thaw settlement. Comparing to the classical piles, the capability of pile with flutings stand out, and the disadvantages are all not exist.