大断面矿山法隧道下穿铁路施工方法比选

CONSTRUCTION OPTIMIZATION FOR LARGE SECTION TUNNEL CROSSING RAILWAY WITH MINING METHOD

城市道路隧道矿山法施工下穿既有铁路,往往具有开挖断面大、地层变形影响范围大和需要严格控制路基沉降等特点。以某城市道路以隧道形式下穿既有二级铁路工程为依托,采用FLAC3D三维数值模拟手段,对比三台阶法和CRD法施工对路基沉降、边坡位移和支护结构内力的影响。数值计算表明,CRD法设置临时仰拱,分块成环、随挖随撑,相比于三台阶法,能更好地控制围岩位移,减小路基沉降和边坡位移,支护结构安全性较高。对本隧道下穿铁路施工而言,CRD法优于三台阶法。

The construction of urban road tunnels under existing railways by the mining method often has the characteristics of large excavation section, large influence range of stratum deformation and strict control of roadbed settlement. Based on the existing second-class railway project which a city road is constructed in the tunnel form, the subgrade settlement , slope displacement and the internal force of support structure are compared under the threestep method and CRD method by FLAC3D software. The numerical calculation shows that, the CRD method can control the displacement of surrounding rock better, reduce the settlement of roadbed and slope displacement and improve the safety of supporting structures by setting temporary inverted arch, dividing into blocks and forming rings and supporting with excavation. The CRD method is superior to the three-step method in such case.