MJS工法桩在滨海地区软基加固工程中的应用

Application of MJS pile in soft foundation reinforcement at coastal area

为探究MJS(Metro Jet System)工法桩大面积施工对周边环境的影响及其安全性,基于福建省滨海地区首例MJS工法桩加固涉铁软基工程实例,通过试桩试验探讨施工工艺并全面分析桩施工对周边环境影响规律。结果表明:单桩施工对土体扰动微小,而多桩施工产生的累积效应不可忽略;土体深层水平位移沿土体深度总体呈“上大下小”趋势,根据桩侧不同距离土体的深度影响范围,结合工程实际将桩周边土体划分为主影响区、中影响区和微影响区;土体孔压变化率沿深度方向总体呈先增大后减小现象,深处结构性扰动较小的软土对喷浆压力较敏感;MJS试桩施工中,临近高铁桥墩台的变形基本呈无规律振荡状态,试桩施工结束后随软土结构重组,墩台变形趋于稳定,且绝对值及差异沉降均远小于规定值,不会危及墩台结构稳定性及高铁运营安全。

In order to explore the influence of large area construction of piles by MJS(Metro Jet System)construction method(MJS pile for short)on the surrounding environment and to evaluate its safety,based on the first example of strengthening railway-related soft foundation by MJS piles in the coastal area of Fujian Province,the construction process was discussed through pile test and the influence law of construction method piles on the surrounding environment was comprehensively analyzed.The results showed that the soil disturbance caused by single pile construction was small,while the cumulative effect caused by multi-pile construction can not be ignored.The horizontal deformation of the soil along the depth generally presented a trend of"up big and down small",and the influenced depth range of the soil at different distances from the pile side was obtained.Based on this range,the soil around the pile was divided into the main influenced area,the medium influenced area and the mild influenced area.The change rate of soil pore pressure increased first and then decreased along the depth,indicating that the deeper soft soil with less structural disturbance was more sensitive to the shotcrete pressure.During the construction of MJS piles,the deformation of piers and abutments adjacent to the high-speed railway bridge was basically in an irregular oscillation state.After the completion of the test pile construction,with the reshaping of the soft soil structure,the deformation of piers and abutments tended to be stable,and the absolute value and differential settlement were far less than the specified value,which would not endanger the stability of pier and abutment structure and the safety of high-speed railway operation.