Bearing capacity and critical plate spacing of piles with expanded branches and plates based on the minimum resistance

By analyzing the shape of failure surface between two neighboring plates, the integral failure surface judgment method of the cast-in-situ piles with expanded branches and plates is summarized. The formulae for the bearing capacity and the critical plate spacing based on th minimum resistance of the pile are deduced and verified. There are two types of failure surface between two neighboring plates — large cylindrical surface and small cylindrical one, and the most possible one is the smaller resistance. The overall failure surface is the combination of each failure surface with the minimum resistance, and the sum of the minimum resistance of each section is the total bearing capacity of the whole pile. The bearing capacity of the pile is the minimum resistance of all kinds of overall failure surfaces that may appears along the whole pile. For the bearing pressure on the pile, we should obey the order from bottom to top to judge the type of overall failure surface of the pile, and the failure surface of the most upside and the most lower segment of the pile body is the small cylindrical one. For the bearing tensile force on the pile, we should obey the top-down order, and the failure surface of the most lower segment of the pile body is the small cylindrical one.