Research on the Analytical Conversion Method of Q-s Curves for Self-Balanced Test Piles in Layered Soils

Abstract

An analytical conversion method was developed for the self-balanced test results of monopile bearing capacity in layered soils to realize the better applicability of the self-balanced test theory for the bearing capacity test of foundation piles. To the additional settlement of the lower pile bottom brought on by the negative friction of the upper pile soil during the loading process in layered soils, the interaction effect between the upper piles and lower piles is first taken into account. To accurately convert the results of the self-balanced test pile into the traditional static load test curve form and solve the ultimate bearing capacity, the displacements and internal forces at micro-segment piles in each layer of soil were obtained using the finite difference method. Then, for verification, conventional static test piles and indoor model tests were conducted in a multi-layered ground foundation. The outcome demonstrates that the simplified conversion method’s bearing capacity of the test pile is greater than that of the traditional static pressure test, the analytical conversion method’s Q-s curve is relatively similar to the results of the conventional static load test, and the accuracy of the analytical conversion results is increased by about 9.3 percent. At the same time, the analytical conversion method was applied to the self-balanced test project of bored cast-in-place piles in Wutong Garden, Laibin, Guangxi, China, and the accurate bearing capacity and internal force deformation characteristics were obtained. The accuracy of the calculation result is improved by 12% compared with that of the simple conversion calculation result. Therefore, it can be widely promoted and applied in self-balanced pile bearing capacity test projects.