Analysis Conversion Method of Self-balanced Test Pile and Engineering Application

An analytical conversion method for self-balanced test of foundation pile was proposed. The finite difference method was used to establish the control equations for each micro-section of the upper and lower piles, and the internal forces and displacements at each micro-section of the upper and lower piles can be obtained by programmed solution, which can be substituted into the exact conversion formula to convert the self-balanced test pile results into the form of the load (Q) - displacement (s) curves similar to those of the traditional static test and to solve the ultimate bearing capacity. This analytical conversion method was applied to convert the test results in conjunction with the test project of self-balanced method for three drilled piles in Yuda Wutong Court, Laibin, Guangxi. The internal forces of the three test piles all show that the soil layer closer to the loading end bears a larger load, the axial force gradually decreases from the loading end to both ends, and the change characteristics of the lateral resistances show a hyperbolic distribution. In terms of single pile bearing capacity, the simplified conversion method is conservative, while the analytical conversion method takes into account the differences in the characteristics of the soil layers on the pile side, and the accuracy can be improved by about 12% compared to the simplified conversion method. The analytical conversion method can accurately reflect the distribution law of internal force of upper and lower pile body and the bearing characteristics of soil layer on the pile side, and can efficiently and accurately realize the conversion of bearing capacity, which is widely used in the field of self-balanced test engineering of pile foundation bearing capacity.