可液化土中劲芯复合桩的地震响应特征

劲芯复合桩是将预制混凝土管桩插入水泥土桩中复合而成的新型桩基。通过振动台模型试验及有限差分程序FLAC3D数值模拟分析，研究可液化地基中劲芯复合桩的地震响应。利用模型试验结果验证数值模型的准确性和可靠性，进而通过参数分析讨论水泥土桩桩径、桩长、剪切模量等因素对可液化土—复合桩—上部结构地震响应的影响规律，定量评价水泥土桩加固对场地抗液化性能及桩基弯曲破坏的影响特征。结果表明：增大水泥土桩桩径和桩长可有效提高复合桩的抗震性能；增大水泥土剪切模量对复合桩抗震性能的提高有限；桩基在桩头附近或水泥土与可液化砂土交界处易产生较大的弯矩响应，该部位应采取必要的抗震构造措施。根据研究结果，提出了可液化地基中劲芯复合桩的抗震设计要点。

Seismic response of strength composite piles in a liquefiable soil

Strength composite pile is a new type of pile formed by inserting a precast concrete pipe pile into soil-cement column. A series of shaking table model tests and finite difference analysis using FLAC3D were carried out to examine the seismic response of strength composite pile in a liquefiable ground. The accuracy and reliability of the numerical model were verified by the model testing results, and the effect law of diameter, length and modulus of soil-cement columns on the seismic response of sand-composite pile-superstructure were clarified. In addition, the anti-liquefaction performance of liquefiable ground and the bending failure of composite piles were evaluated. Results show that increasing the diameter and length of soil-cement column can effectively improve the seismic performance of composite pile. Increasing the shear modulus of soil-cement column to improve the seismic performance of composite piles is limited. A large moment response may occur in the pile near pile head or at the interface of cement-improved soil and liquefiable sand, so necessary seismic structural measures should be considered at the part. Based on the evaluation results, the key points of seismic design for composite piles in liquefiable soil were proposed.