路堤下复合地基“三等沉区模型”

路堤下复合地基桩顶沉降小于桩间土沉降，桩体上部为负摩擦力，因此不能采用常规复合地基理论分析受力和变形。试验和数值分析表明，路堤下复合地基的路堤、桩身、下卧层范围内均存在一个等沉区，等沉区内同一水平面上不同点的沉降相同的区域。据此提出了“三等沉区模型”，该模型不但地基与桩体参数对复合地基的影响，而且可以考虑路堤高度、下卧层厚度、强度等参数对复合地基的影响。实测和数值模拟表明该模型是合理可行的。

Three-equal-settlement-zone model for composite ground under embankment

Since the settlement of piles of composite ground under embankment is smaller than that of soil between piles, the friction stress on upper part of piles is negative. Therefore the deformation and stress theory for normal composite ground cannot be applied for composite ground under embankment. It is shown by experiments and numerical analyses that there is an equal-settlement zone respectively in the embankment, piles and substratum of composite ground under embankment where the settlement of different position of the same horizontal plane is equal. Therefore, three-equal-settlement-zone model is put forward for composite ground under embankment. Not only are the effects of parameters of ground improvement on composite ground under embankment taken into account by this model, but also the effects of height or thickness, bearing capacity of embankment and substratum are taken into account. The model is proven reasonable and practical by experimental results and numerical analyses.