【摘要】 隧道斜井进入主洞三岔口段断面大、受力复杂、施工难度大,是长大隧道施工的关键。三岔口将隧道分为多个施工作业段同时施工,缩短了工程的工期,加快了隧道的整体施工进度。某山岭隧道斜井进入主洞处三岔口采用台阶扩挖法。斜井末端采用上下台阶,从上台阶向上挑挖4.2 m确定导洞高度,继续向前扩挖至对侧主洞边墙轮廓线完成导洞施工。主洞采用三台阶法,按照上台阶5.3 m、中台阶3.59 m、下台阶3.31 m依次向进口和出口方向开挖。三岔口段主洞断面面积92.1 m~2,为大断面隧道。大断面隧道的跨高比大,导致围岩和支护的稳定性变差,所以主洞在施工过程中应加强支护来保持隧道的稳定。利用ABAQUS有限元软件对隧道进行了数值分析,并直观地模拟了隧道开挖后围岩的应力分布,为隧道的施工提供合理依据。锚杆、钢筋网、衬砌、格栅和钢架根据不同的围岩等级按相应的要求进行了施工。通过对围岩及支护微小变形的监测,掌控了在开挖过程中围岩的稳定程度和支护结构的力学动态信息。对监控量测数据进行了回归分析,以较好地反映围岩变化规律,并分析各阶段的位移速率,预测最终位移值。监控量测数据表明:拱顶下沉和周边收敛的累计变形范围为8～14 mm。更多还原

【Abstract】 The fork road where the intersection of inclined shaft and main hole is the key to large section tunnel construction because of its large cross-section, complex force and great difficulty in construction. Fork road divides the tunnel into several simultaneous construction work sections, which can shorten the construction period of the project and speed up the overall construction progress of the tunnel. The step expansion method is used for the fork road where the intersection of inclined shaft and main hole of a mountain tunnel. The end of the inclined shaft is designed as up and down steps, upward construction 4.2 m from the up step is conducted to determine the height of the pilot tunnel, and the excavation is continued to the side wall boundary line of the main hole to complete the pilot tunnel construction. The three-step method is adopted for the construction of main hole. The excavation of 5.3 m height of upper steps, 3.59 m height of middle steps and 3.31 m height of lower steps is conducted in turn to the directions of entrance and exit. The sectional area of the main hole of the fork road is 92.1 m~2, which is a large cross-section tunnel. The large span-depth ratio of large cross-section tunnel leads to poor stability of surrounding rock and support, so the main hole should be strengthened in the construction to keep the tunnel stable. By using ABAQUS finite element software,the numerical analysis of the tunnel is carry out, and the stress distribution of surrounding rock after tunnel excavation is simulated intuitively to provide reasonable basis for tunnel construction. The anchor, steel mesh, lining, grille and steel frame are constructed according to the requirements of different surrounding rock grades. Through monitoring measurement of small changes in surrounding rock and support, the stability of surrounding rock during excavation and the dynamic information of supporting structure are controlled. The regression analysis of monitoring data is conducted to better reflect the change rule of surrounding rock, analyze the displacement rate of each stage, and predict the final displacement value. The monitoring data shows that the accumulative deformation range of the subsidence of the vault and the surrounding convergence is 8-14 mm.更多还原