基于室内模型试验的砂井复合地基作用机理

Behavior of the sand well composite foundation by indoor model test

为探讨砂井复合地基的作用机理,设计并完成了一组室内砂井复合地基模型对比性试验,获得荷载分配、位移变化与应力分布等有益数据。在此基础上,基于散体材料桩复合地基计算理论,分析了砂井复合地基的承载机理与变形特性,得到砂井复合地基的荷载-沉降曲线、井顶应力分担比随荷载的变化曲线。研究结果表明:砂井可显著改善软土地基的承载能力与沉降特性,但存在"群桩效应",即井数越多时,载荷试验得到的复合地基承载力降低,沉降加大,故工程中应慎选井距,且当以单桩复合地基载荷试验评价复合地基承载力时需考虑适当折减。

To study the behavior of sand well composite foundation, the test device was first designed and a group of indoor sand well composite foundation model testing was then completed with some useful data obtained which including load, displacement and stress. Based on these obtained test data and the relevant research meth- ods used in granular material pile composite foundations, the load - settlement curve and the stress ratio curve changing along with the exerted load at the well top of sand well composite foundations were discussed. The changing rules of these curves show that, sand well can significantly improve the bearing capacity and decrease the settlement of soft subsoil. However, the ＂pile group effect＂ is also found, which means decreasing of the bearing capacity and increasing of the settlement of composite foundation if more sand wells are included under the bearing plate during the loading test. Therefore, appropriate well spacing should be selected in engineering practice. Moreover, proper discount is also advised when the bearing capacity of the sand well composite foundation is estimated by loading test result of single -pile composite foundation.