西安地铁隧道盾构开挖面支护力安全范围分析

Analysis of Safety Range of Supporting Force on Excavation Face of Tunneling Shield for Xi'an Metro

研究目的:本文以西安地铁2号线某区间隧道工程为依托,根据具体的地质情况,运用FLAC3D数值仿真模拟软件以隧道开挖面上方地表点和洞顶点沉降为衡量标准,确定施工中开挖面支护力的安全范围,从而防止隧道穿过埋深变化较大的地点时地表出现过多的沉降和隆起。研究结论:(1)盾构隧道的开挖面存在最小支护力和最大支护力,即支护力具有合理的安全范围。当支护力超出范围时,隧道周围土体易发生破坏,或埋深较浅时地表出现较多沉降和隆起现象。(2)隧道埋深大于1.5倍洞径后,地表点已不能有效反映隧道周围土体变形,应该用隧道洞内测点来监测控制土体变形。(3)开挖面支护力的安全范围随埋深的增加而增加。当埋深较浅时,支护力的安全范围很小,可采用地面堆载的方式来等效达到增大隧道埋深的目的,扩大支护力安全范围,降低施工难度。

Research purposes： In combination with the tunnel engineering of Line 2 of Xi ＇an, and according to the specific geological conditions, the FLAC3 D numerical simulation software was used to determine the safety range of the supporting force on the excavation face during the tunnelling, taking the settlements of the ground above the excavation face and the tunnel top as the measuring standard, for the purpose of avoiding the over settlement and rising of the ground when the tunnel passed through the place with big variation of the buried depth. Research conclusions： （ 1 ） The excavation face of shield tunnel has its minimum supporting force and maximum supporting force. It means that the supporting force has a reasonable safely range. When the supporting force is out of range, the soil around the tunnel is easy to be damaged, or the over settlement or over rising appears to the ground surface when the tunnel is shallow. （2） When the tunnel buried depth is bigger than 1.5 times of the tunnel diameter, the surface point can not effectively reflect the deformation of soil around the tunnel, and at this time, the soil deformation should be monitored and controlled by the monitoring spots in the tunnel. （3） The safely range of supporting force increases with the increase of the tunnel depth. When the tunnel is shallow, the safely range of supporting force is very small, and at this time, the heap loading on the ground should be used to increase the tunnel buried depth equivalently for increasing the supporting safely range and reducing the construction difficulty.