基于环形等效的异形截面复合桩复合地基固结理论研究

Theoretical investigation of the consolidation for composite ground with profiled sectional composite piles based on the equivalent ring model

复合桩是指由两种不同材料经过复合施工形成一种新桩型,同一桩体由两种不同属性材料组成,从而起到互补增强的作用。以素混凝土芯砂石壳复合桩复合地基为研究对象,基于横截面积和周长恒定的原则,将其转化为等效环形单元。引入芯-桩面积比(混凝土芯与复合桩横截面积之比),基于等应变假设和达西定律,并考虑施工扰动及荷载随时间变化、附加应力随深度变化的情况,提出了复合桩复合地基固结解析模型,并给出了4种不同荷载模下的显式解答。最后,通过参数敏感性分析对复合地基的固结特性进行研究。结果表明:周长一定的方桩中,正方形截面桩的空心比最小,超静孔隙水压力消散最快;地基固结与芯-壳压缩模量比、渗透系数比成正相关;随着顶部荷载值的增加,固结逐渐加快。

Composite pile refers to a new pile type generated by two different materials through a dual construction way.The composite pile is composed of two materials with different properties,which play a complementary and reinforcing role.Taking the composite ground improved by the concrete-cored sand-shell composite piles as the research object,the composite pile is transformed into an equivalent ring element based on the principle of constant cross-sectional area and perimeter.The core-pile ratio,i.e.,the ratio of the concrete core and composite pile cross-sectional area was introduced,and the construction disturbance and the depth-dependent stress increment caused by time-varying surcharge loading was considered.A consolidation analytical model of the composite ground with composite piles was proposed based on the equal strain assumption and the Darcy’s law.Furthermore,explicit solutions under four different load conditions were obtained.Finally,the consolidation behaviors of the composite foundation were investigated by a series of parameter sensitivity analysis.The results show that the hollow ratio of the square section pile is the smallest and the excess pore water pressure dissipates fastest among the square piles with a certain circumference.The foundation consolidation rate is positively correlated to the core-shell compression modulus ratio and permeability coefficient ratio.With the increase in the top load,the consolidation rate gradually increases.