浅埋铁路隧道下穿高速公路施工方法比选

采用三维数值模拟方法,着重从开挖全过程结构体系转换和施工过程的空间效应的角度,分析比较了覆跨比小于1的浅埋铁路隧道下穿高速公路施工采用不同施工方法时的拱顶和地表沉降、衬砌变形和结构体系内力等关键参数的变化.计算结果表明,尽管双侧壁导坑法在开挖过程中断面较小,但由于分块多,前后掌子面滞后距离长,施工过程复杂,结构体系转换频繁,因而在地表沉降控制方面较中隔壁法并不具有明显的优势.而中隔壁法由于分块相对较少,各工序衔接紧密,拱顶沉降和地表沉降控制较好.其中CRD法由于采用了临时仰拱,对洞周收敛和中隔壁的变形较CD法具有更好的控制作用.基于施工全过程的不同开挖方法的三维数值分析比选研究对于选择恰当的施工方法并确保工程顺利实施具有重要意义.

Optimal Analysis of Excavation Method of a Shallow Tunnel Beneath Expressway

By using the three-dimensional numerical modeling,the different excavation processes of a shallow tunnel with cover to depth ratio of less than 1 were modeled. The key parameters such as settlements of crown and ground surface,displacements of lining and the stress changing during the threedimensional excavation processes were compared and analyzed. Results show that although the excavation area of each excavation step is relatively small when using the double-side-drift method,the controlling effect of which on the ground and crown settlements is far from satisfied due to its complex excavation process and late closing time of the primary lining. Compared with the double-side-drift method,the central-diaphragm-wall method is better in effectively controlling the settlements of crown and ground surface,which is especially true for the central-cross-diaphragm-wall method due to the strengthen effect of the temporary inverts. The optimal analysis before excavation is very important in choosing appropriate excavation method to insure finishing the tunnel construction in time.