敞开式顶管洞内改造扩挖硐室围岩稳定性分析

Stability analysis on the surrounding rock of the chamber after reconstruction and expansion inside the tunnel of the open-ended pipe jacking

顶管机的累计掘进距离一般小于新机的设计值,在满足地质适应性的前提下,可以考虑充分利用现有的顶管,通过实施改造以满足新工程的施工。以深圳北环电力隧道工程为例,鉴于该工程在砂砾地质条件下刀具刀盘磨损严重,故对该地层条件下DN 3000顶管的刀盘刀具的布置方式、刀具形状进行洞内改造。考虑到扩挖硐室过程中围岩受到扰动产生变形,存在一定的施工风险,为验证该技术方案的可行性,对扩挖段硐室进行有限元建模,研究硐室开挖产生的地表沉降和硐室变形及受力情况。研究结果表明:顶管机改造及洞内组装施工对周边环境的影响在安全范围内,该施工方案具备可行性。

The total driving distance of the pipe jacking machine is generally less than the design service life of new machine. On the premise meeting the geological adaptability,the existing pipe jacking can be fully considered to meet the construction of the new project through implementation of transformation. Based on the north ring power tunnel project in Shenzhen,in view of the serious abrasion of the cutter head under geological conditions of sand gravel,the layout and the shape of the cutter head for DN3000 pipe jackingunder the condition of this stratum are reconstructed in the tunnel. Considering that the surrounding rock is disturbed and deformed during the process of expanding the tunnel with a certain construction risk,in order to verify the feasibility of the technical scheme,finite element modeling for the chamber in the expanded excavation section of the project is taken place to study the surface settlement,chamber deformation and stress caused by the excavation of the chamber. The results show that the impact to the surrounding environment of the pipe jacking machine renovation and assembling inside the tunnel is within a safe range,which verifies the feasibility of the construction scheme.