大间隔格栅墙加固地基的抗液化效果研究

Effects of Large-Space Latticed Walls for Liquefaction Mitigation

2011年东日本大地震引起了大范围的砂土地基液化,液化严重损坏了大量的住宅、厂房及公共建筑。为提高既有建筑地基的抗液化能力,文章提出了一种大间隔格栅状水泥土搅拌墙与垂直塑料排水管联合加固地基的方法。通过动离心模型试验与动有效应力有限元分析研究其抗液化效果,发现格栅墙阻止了可液化层的侧向变形,排水管保证了格栅内可液化层在振动时不会产生过高的超静孔压,维持了可液化层的地基强度,也防止了格栅墙外侧向建筑物以下可液化层的渗透排水;探讨了格栅状水泥土搅拌墙间隔对抗液化效果的影响,发现格栅墙所围面积越大建筑物沉降量也越大,说明格栅间隔越大格栅墙的抗液化效果越小,但是即使格栅间隔扩大后,格栅墙仍可在_定程度上限制可液化层的侧向变形。以实际可液化场地上的低层办公楼为研究对象,通过数值计算验证了大间隔格栅状水泥土搅拌墙与垂直塑料排水管联合加固地基的抗液化效果。

The 2011 East Japan earthquake induced widespread liquefaction not only in the Tokyo bay area but also in the inland area of the Kanto region,which damaged numerous residential houses and public buildings.A research project was conducted to develop large-space latticed soil-cement mixed walls and vertical drains and their combination,which can be installed as measures to mitigate liquefaction of grounds of existed residential houses and buildings.This paper reports the results of dynamic three-dimensional effective stress analyses for reproducing the dynamic centrifugal tests.The results show that the latticed walls can prevent lateral deformation of liquefiable layer.At the same time,the vertical drains not only ensure that a high level of excess pore water pressure won't be generated in liquefiable layer within the latticed walls during earthquake,accordingly maintain the foundation strength of liquefiable layer,but also prevent seepage drainage from the outsides of the latticed walls into the liquefiable layer.Parametric studies were carried out to investigate the effects of the spacing of latticed soil-cement mixed walls and vertical drains on the liquefaction mitigation.The results show that the larger the spacing of the latticed walls and the smaller the effects of liquefaction mitigation,however,even the spacing of the latticed walls expanded,they still can limit in a certain extent the lateral deformation of liquefiable layer.Numerical analysis was also carried out to evaluate the effects of liquefaction mitigation for the liquefiable ground of a three-story office buildings.