高压注浆施工对周围基坑安全影响分析

Study on the Affection of the Surrounding Deep Excavation due to the High-pressure Jet Grouting

众所周知,高压旋喷桩广泛用于地下工程的土体加固,其加固体的强度较大,效果较好。然而,对于基坑工程而言,很少人会关注基坑已经开挖,坑外再进行高压注浆处理方式对基坑的影响。目前的研究成果仅表明旋喷桩附近1~2 m范围内存在切削、压密土体的作用,因此本文认为该范围以外土体以总应力线性分散的简化方式考虑。据此,本文就某基坑工程在施工过程中出现的问题,验证了高压旋喷施工对周边在建基坑的影响是不容忽视的。另外,本文从高压旋喷桩机理入手,发现高压旋喷桩的存在大大增加了围护桩的水平荷载;对上述工程进行了重新计算,所得围护结构位移变化与监测结果完全吻合。

As known to us all,the high-pressure jet grouting is frequently used in soil treatment and gives a good effect,while the treated soil mass has high strength as well. However,for deep excavations,little attention is paid on the effect of the injection on the excavation pit. The present research only shows that the grouting has an effect of cutting and densifying to soil mass in region 1 ~ 2 m around the axis. So,in this paper,it is assumed that the pressure is decreasing with the distance. Finally,on the basis of one pit in Nanjing,the authors declared that the grouting has a great effect on the excavating pit. Besides,from the mechanism of the high-pressure jet grouting,the computation is done,which also shows that the grouting increases the lateral pressure on the retaining walls,and makes the displacement of the retaining wall larger. What's more important,the displacements obtained agreed well with site monitoring results.