管桩水泥土复合桩承载性能影响因素分析

Factors Affecting the Axial Capacity of Soil Cement Mixed Column Inserted with the PHC Pile

管桩水泥土复合桩是适用于软土地基的一种新型复合桩，可由PHC管桩在水泥土初凝前压入水泥搅拌桩中，通过两者特定匹配关系复合而成。结合静载荷试验的相关资料，以ABAQUS为工具建立有限元模型，研究了管桩桩长、截面含芯率、水泥土外径及弹性模量对管桩水泥土复合桩竖向承载性能的影响。得到管桩和水泥土桩的最佳匹配关系，最终实现其优化设计。研究表明：管桩桩长、截面含芯率是影响管桩水泥土复合桩承载特性的主要因素，水泥土弹性模量对其影响较小。管桩与水泥土长度比宜取3／5～4／5；截面含芯率宜取0．19～0．25；水泥土桩外径应比管桩外径大300mm以上，以满足构造要求。

A new composite pile consists of a Pre-stressed High-strength Concrete （HPC） pipe pile inserts into a fresh soil-cement mixed column before it is hardened. This new composite pile can be applied for the soil soft improvement projects. The paper presents the numerical analysis results by using ABAQUS software as well as the static loading test results. The numeri cal analysis studies the influence of various factors on the axial resistance of the composite pile. These factors include： the length of PHC pile ratio of pile diameter to the tributary diameter of the composite pile; diameter of the soil cement mixed column and its stiffness; etc. The optimized PHC pile and the soil cement mixed column relationship are obtained. The analysis results indicate that the key factors that are impacting the axial resistance of the composite pile are the length of PHC pile and the ratio of pile diameter to the tributary diameter of the composite pile. The impact of the stiffness of the soil cement mixed column on the axial resistance of the composite pile is relatively small. The ratio of the PHC pile and to the soil cement mixed column should be between 3 ： 5 and 4 ： 5. The ratio of the PHC pile to the tributary diameter of the composite pile should be ranging from 0.19 to 0.25. The minimum diameter of the soil cement mixed column should be 300 mm greater than that of the PHC pile.