三轴搅拌桩施工挤土效应的试验研究

In-Situ Test Study of the Squeezing Effect on Adjacent Soil Due to Tri-Axial Cement Mixing Piling

摘要: 三轴水泥土搅拌桩施工时，在喷浆阶段和沉桩阶段，由于高压注浆和巨大扰动，会导致邻近地层相当大的水平位移。如果邻近地层中存在地下构筑物，特别是存在地铁隧道，这种地层水平移动必须控制在规定的限值内，否则会对这些地下构筑物产生不利影响。为了得到三轴搅拌桩施工的合适参数，针对三轴搅拌桩施工的注浆压力、沉桩速度和地面堆载等参数与邻近土体位移之关系，开展了现场1:1足尺试验研究。基于试验成果，获得了一套合理的沉桩施工参数并应用到某一实际工程中，该实际工程的水泥土搅拌桩邻近已有地铁隧道不到2 m。该工程的应用表明，结果满意，符合设计要求。相信本试验成果和应用实践对类似工程具有借鉴意义。

Abstract: Tri-axial Cement Mixing Piling (TCMP) shall exert rather large displacement on surrounding soil because of the high grouting pressure and profound disturbance when in the grouting stage and driving stage, and this displacement must be controlled under allowable level lest it should lead adverse effect on adjacent underground facilities, especially existing subway tunnel, if any. To obtain a set of suitable parameters for mixing pile driving, an in-situ test study has been carried out on the relation between the displacement and piling parameters, such as grouting pressure, driving speed and ground surface overcharge. Based on this test result, rational option of piling parameter combination has been applied in a practical project involving an adjacent existing metro tunnel with less than 2 m from the mixing pile, and shows that this parameter combination produces a satisfactory result to the design requirement. It is believed that such conclusion and practice shall be a helpful reference for other similar projects.