浅埋大断面隧道下穿既有道路的施工工法

Construction method of shallow tunnel with large section down-traversing existing road

针对浅埋大断面隧道下穿既有道路爆破掘进中,极易引起上部路面结构的损伤和破坏,危及道路和行车安全的问题,以宝汉高速新建关林子隧道下穿既有316国道为工程依托,提出“路面架桥,超前加固,分部开挖,监测反馈”的系统施工方法.同时,采用有限元法模拟了正常通行条件下有、无铺设钢架桥时路面沉降,结合现场爆破振动监测结果,对比分析了CRD法施工的安全性和可行性.研究结果表明:不铺设钢架桥时的地表沉降量远大于铺设钢架桥,且数值超过规范允许限值的2/3,模拟数值与实测值平均相对误差为95.7%;铺设钢架桥时,模拟的地表沉降量与实测值相对误差范围为2.7%~12.4%,平均相对误差仅为6.1%,远低于不铺设钢架桥,表明提出铺设钢架桥的施工方法是非常有效的.

To solve the problems of easy damaging and destructing to endanger the road and traffic safety, in the blasting excavation process of large section shallow tunnel down-traversing existing road, the Guanlinzi Tunnel down-traversing the 316 National Road in the Baoji-Hanzhong Expressway was selected as research objective. The construction method of bridging on the pavement, advanced reinforcement, excavation by steps, monitoring and feedback information was proposed based on the project. Under normal traffic on the road, the finite element method was used to simulate the road surface settlement with and without steel frame bridge. Combined with the monitoring results of blasting vibration in the field, the safety and the feasibility of CRD method were compared and analyzed. The results show that the surface subsidence value without steel frame bridge is larger than that with steel frame bridge, and the value exceeds 2/3 permissible limits of the standard. The relative error between simulated value and measure value is 95.7%. Under the condition with steel frame bridge, the error between the simulated ground settlement and the measured value is from 2.7% to 12.4%, and the average relative error is 6.1%, and much lower than that of non-paving steel bridges, which shows that it is very effective to put forward the construction method of laying steel bridges.