Physical model tests on bearing performance drilling with pre-stressed concrete pipe cased pile considering hole collapse

The drilling with pre-stressed concrete pipe cased pile (Referred to as DPC pile) is a typical non-squeezing soil PHC pipe pile foundation. During the process of its hole drilling, soil dumping and pile sinking, the hole collapse around its pile shaft will affect the flow path and effects of the grouting in the clearance between the DPC pile wall and hole wall, and ultimately affect its skin friction. The physical model and static load tests on the DPC piles are carried out. The load-carrying properties, load transfer characteristics and skin friction distribution characteristics of the DPC piles are analyzed. Three-dimensional geometric size and spatial point information of grouting body for the DPC piles are quantitatively characterized. The essential reason for the skin friction of the DPC piles due to hole collapse is revealed. The following conclusions are drawn: (1) The load-displacement curves of DPC piles are all steep drop types under the conditions of no rock-socketed pile end. The DPC piles are a kind of friction end-bearing ones. (2) After grouting, the collapsed hole is filled with grouting to increase the friction resistance, and the bypass of the slurry in the falling sand area causes the friction resistance to drop. (3) The existence of hole collapse affects the flow law of the groutting in the pile-soil gap, and changes the area and thickness of the pile body covered by the grouting body, which is an important reason for affecting the skin friction. The area and thickness of the grouting body covering the DPC piles are the important factors that affect the skin friction. The skin friction of the DPC piles has a good cubic function relationship with the grouting volume.