基于围岩变形控制的海底隧道突水安全风险分析

Analysis of Water Inrush Safety Risk of Subsea Tunnel Based on Rock Deformation Control

以厦门海底隧道左线风化槽为例,研究海底隧道突水安全风险控制。选择与风化槽地质条件类似的五通端陆域段进行地层变形监测。监测结果表明:地层沉降具有明显的分层传递性和阶段性;当地表沉降30～40mm、拱顶沉降55～70mm时,地表开始出现裂缝。采用FLAC3D对海域风化槽段进行数值模拟。结果表明:海域风化槽地层变形规律与陆域段现场实测一致性良好;在帷幕注浆、超前支护等辅助工法发挥作用后,风化槽段拱顶沉降能够控制在70mm以内。结合监测结果和数值模拟结果制定的安全风险控制标准:在采用十字中隔壁工法(CRD工法)施工条件下,海域风化槽地表沉降控制标准及施工突水对应的拱顶极限沉降值分别为40和70mm;突水安全风险管理级别分为预警、报警及极限3个等级。应采取的技术控制措施包括:辅助工法的合理应用、地层变形的过程控制、信息的及时监测与反馈、施工质量控制及紧急预案制定。

The left lane weathered slot of Xiamen subsea tunnel is chosen as an example to study the tunnel water inrush safety risk control. Wutong land side segment which is similar to the geological conditions of the weathered slot is chosen to monitor the strata deformation. Monitoring result shows that the deformation of the ground settlement has the obvious layered transitivity and gradualness. And the surface starts presenting cracks as the surface subsidence is 30～40 mm and the arch subsidence is 55～70 mm. FLAC^3D is used in the numerical simulation of the marine weathered slot. The result indicates that the stratum subsidence rule of the marine weathered slot is consistent with the terrestrial segment well. Vaults settlement of the weathered slot can be controlled within 70 mm with the auxiliary methods of curtain grouting and advanced support. Combined with the monitoring and numerical simulation results, safety risk control standards will be formulated. With the method of CRD, the surface subsidence control standard of the sea weathered slot and the limit value of vaults is 40 mm and 70 mm each. Water inrush safety risk management level is divided into three aspects, warning, alarm and limit. The corresponding technical measures of control are given, including the reasonable application of auxiliary methods, process control of strata deformation, timely monitoring, information feedback, construction quality control and emergency plan.