CFG桩复合地基现场试验及有限元模拟分析

Test study and finite element analysis of CFG composite foundation

在厚褥垫状态或路堤荷载作用下复合地基的破坏主要取决于桩-褥垫体系的作用,复合地基中单桩的承载力远未发挥出来。由有限元计算结果得出以下规律:(1)随着褥垫厚度增加,桩土应力比减小;褥垫厚度超过300 mm后,褥垫厚度的影响急剧减小;褥垫厚度超过500 mm后,褥垫厚度的影响继续减小。(2)褥垫厚度较薄时(h=100 mm),褥垫模量对桩土应力比影响很大;褥垫厚度超过300 mm时,褥垫模量对桩土应力比的影响减小;褥垫厚度达到500 mm后,褥垫模量对桩土应力比影响很小。(3)承载板刚度小于6.25 MN.m2时,桩土应力比随刚度增大;承载板刚度大于6.25 MN.m2时,刚度对桩土应力比的影响很小。

According to the results of in-situ tests, the failure mechanism of composite foundation is mainly decided by the interaction between soil and cushion in the state of thick cushion or under embankments; and the practical bearing capacity of a pile in composite foundation is not brought into full play. The following rules are got from the calculation results of FEM： （1） the stress ratio of pile to soil （n） decreases with the thickness increasing; as the thickness exceeds 300 mm, the influence of cushion thickness on n reduces sharply; as the thickness exceeds 500 mm, the influence of cushion thickness is small. （2） When the cushion thickness is relatively thin （ h = 100 mm）, the influence of cushion modulus on n is great; as the thickness exceeds 300mm, the influence decreases; as the thickness exceeds 500 mm, the influence is very small. （3） as the rigidity of bearing plate is smaller than 6.25 MN·m^2, the stress ratio of pile to soil increases with the rigidity increasing; as the rigidity exceeds 6.25 MN·m^2, the influence of rigidity on n is very small.