摘要
This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross- passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approx- imately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast （D＆B） excavation. The support con- sisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine （TBM） was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel （with an enlarged cross-section） passed underneath the A2 Swiss highway （the major road axis connect- ing the north and south of Switzerland） at a small overburden and through soft ground. Vertical and sub- horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D＆B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel （at a vertical distance of only 4 m） required special excavation methods through reduced sectors and special blasting techniques in orde
本文总结了在修建15.4 km长切内里基线隧道(CBT)期间获得的经验,这条隧道为从北向南跨越瑞士阿尔卑斯山脉的平轨铁路线的南段。该项目由直径为9 m的双管组成,双管之间每隔325 m设置一个联络通道。在线路中部及其南端,应后勤和运营要求,开挖了大型洞室。总开挖长度大约为40 km。隧道穿越阿尔卑斯山处的岩层由各种岩石类型和若干断层带组成。最大埋深达850 m。主隧道和联络通道的开挖通过钻爆法(D&B)进行。支护由锚杆、钢筋网、纤维增强喷射混凝土和(必要时的)钢拱架构成。为开挖进口隧洞,使用了敞开式隧道掘进机(TBM)。大埋深导致岩石受到挤压,这种状况的特征为在穿越较弱岩层时产生较大的各向异性收敛。较弱岩层要求安装可变形支护。在北洞口,隧道(断面增大)穿过A2高速公路(连接瑞士北部和南部的主要道路轴线)下方,此处埋深较小,且隧道通过的是软地层。为限制地表沉降,成功采用了垂直和近水平喷射灌浆与分部开挖相结合的方法。南洞门位于人口密集的市区。开挖自南洞门开始,包括一条约220 m长的明挖隧道,接着是不良岩层内大约300 m长的钻爆法开挖隧道。由于埋深非常小、岩石质量较差且穿越既有公路隧道(垂直距离仅为4 m)的要求很高,所以需要采用特殊开挖法,以及采用特种爆破技术以限制爆破引起的振动。在开挖过程中应用了全面风险管理程序,实施了密集的隧道外测量并根据遇到的地质条件调整了隧道设计,从而使开挖工程得以顺利完工。
