Study on Cyclic Lateral Bearing Behavior of Pile in Cohesive Soils

This study is a three-year project. Its purpose is to investigate and quantify the effects of cyclic loads on the lateral and axial bearing behavior of a pile using model pile load tests. The non-linear analysis models of single pile and pile group will be established based on the test results. Using the above models, non-linear pushover analysis will be performed on real cases to explore the influences of cyclic loads on the design solution of piled foundation. The proposed analysis model and procedure for cyclic loads will be a useful guide to the practices of earthquake and ocean engineering. The first-year project is to design and assembly a set of equipment for performing model pile load tests under cyclic lateral loads. The equipment includes loading and reaction system, instrumented model pile, control and measuring system, and test specimen preparing device. In this study, the low-plasticity clay form Zengwen Dam will be used to prepare the test specimen to simulate in-situ strata, which is remolded by a pneumatic consolidation system. Two sets of static ultimate lateral pile load tests will be carried out first in the model grounds. Then, six sets of one-way and two-way cyclic lateral pile load tests will be performed by considering different stress level of cyclic load. The p-y curves of the cohesive soils will be deduced from the test results for static and cyclic loads. In the second year, the low-plasticity silt will be used as the test specimens. The test procedure is the same as the first-year project. The test results of low-plasticity clay and silt will be compared, including the differences of p-y curves under static and dynamic loads between. Furthermore, the influences of number of cycles and the stress level of cyclic load on p-y curves and the accumulated displacement at pile head will also be discussed. In the last year of this study, the p-y, t-z, and q-z curves from international standards and this study, as well as the curves of plastic hinges of different piles will be coded into an analysis module using EXCEL software. Non-linear models (both pile and ground are non-linear behavior) of single pile and pile group will be established using LPILP and Group software by integrating the results of EXCEL module into the input interface of LPILP and Group. The pushover analysis of the nonlinear models will be performed on real cases to evaluate the effects of cyclic loads on the design solution of piled foundation. Finally, a nonlinear analysis model and procedure for piled foundation under cyclic loads will be proposed for the use in the engineering practice.