新建大跨公路隧道小角度斜交既有线时,如何在施工时控制既有线的沉降技术是工程成功的关键.对既有线采用便梁形式加固既有线由于小角度斜交,跨度大导致加固范围过大,必然造成施工费用高,施工难度大等.通过有限差分数值软件FLAC3d对隧道施工进行三维数值模拟,对隧道施工时既有线两轨道水平高差和前后高差进行分析,得出大跨隧道小角度斜交下穿既有线施工时采用一次施作超长管棚+小导管注浆方式,采用CRD工法施工,并结合既有线预扣轨加固措施,能有效地控制施工沉降,保证既有线的运营安全.%In the case of a newly-built large-span tunnel obliquely crossing existing railway at a small angle, settlement control during the construction process is critical to the success of project. However, using temporary beam to reinforce the existing railway results in an excessive reinforced area, which increases construction cost and difficulty, owing to the project characteristics of small-angle crossing and large-span tunnel. By conducting numerical simulation of tunnel construction by FLAC3d (finite difference numerical software), it is concluded that, in the construction of large-span tunnel obliquely crossing under existing railway at a small angle, adopting one-off construction of overlong pipe roof along with grouting mode of small duct, integrated with CRD excavation method and reinforcement measure of pre - fastened track, can effectively control the settlement and guarantee the operating safety of existing railway.
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