高压旋喷桩施工对既有铁路路基变形影响研究

Influence of high pressure jet grouting pile construction on deformation of existing railway subgrade

高压旋喷桩在湿软黄土地基加固时效果良好,施工方便,适用于黄土地区既有路基帮宽工程地基处理,但其施工过程中会产生挤土效应,影响既有线路的运营安全。以某在建高速铁路引入既有城际铁路工程为依托,结合挤土试验和实测数据,探究高压旋喷桩施工对既有铁路路基变形影响规律。结果表明,对于单桩挤土试验,高压旋喷桩挤土效应与桩周土体距桩心距离呈负相关变化,距离桩心越近,挤土效应越明显。高压旋喷桩沿竖向挤土效应与土层位置、土层压缩系数和湿密度等相关,沿桩深度方向周围土体侧向位移变化在埋深0~5 m范围最为显著。高压旋喷桩施工后,周围土体会出现回缩现象,现场测试各测斜孔回缩值在0~2 mm之间。多桩施工时,高压旋喷桩周围土体会产生位移累积效应,挤土试验中所选4根桩全部施工完成后,距桩心2 m位置处的测斜孔,其侧向位移在埋深0~2 m范围达8 mm以上。既有路基变形实测发现,应力释放孔和高压旋喷桩施工时可导致既有路基上拱或沉降,既有路基监测点最大累计上拱量5.95 mm,最大累计沉降量7.13 mm。通过采取在既有路基坡脚设置应力释放孔、高压旋喷桩由内向外施工并严格控制高压旋喷桩施工参数的措施,可保证既有线路基稳定。

The high pressure jet grouting pile has good effect and convenient construction in the reinforcement of wet and soft loess foundation,which is suitable for the foundation treatment of existing subgrade widening engineering in loess area.However,the compaction effect will occur during the construction process,which affects the operation safety of existing lines.Based on the existing intercity railway project introduced by a highspeed railway under construction,combined with soil compaction test and measured data,the influence of high pressure jet grouting pile construction on the deformation of existing railway subgrade was explored.The results show that the soil squeezing effect of high-pressure rotary jet grouting pile is negatively correlated with the distance between the soil around the pile and the pile center for the single pile compaction tests The closer the distance to the pile center,the more obvious the soil squeezing effect.The lateral displacement variation of soil around the pile depth is the most obvious in the depth range of 0~5 m from the ground,which is related to soil position,soil compressibility coefficient,wet density and etc.After the construction of high pressure jet grouting pile,the surrounding soil experienced retraction,and the retraction value of each inclined hole was between 0~2 mm.During multi-pile construction,the soil around the high-pressure jet grouting pile experiences displacement accumulation effect.After the completion of the four selected piles in the soil compaction tests,the lateral displacement of the inclinometer hole at 2 m away from the pile center can reach more than 8 mm in the depth range of 0~2 m from the ground.The deformation measurement of the existing subgrade widening shows that the construction of stress release hole and high pressure jet grouting pile can lead to existing subgrade arch or settlement,existing subgrade monitoring points maximum cumulative arch 5.95 mm,maximum cumulative settlement 7.13 mm.The stability of existing roadbed can be ensured by setting stress releasing hole at the foot of existing roadbed,constructing high pressure jet grouting pile from inside to outside and strictly controlling construction parameters of high pressure jet grouting pile.