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1概述金竹岗隧道系渝黔线二期工程雷崇高速公路项目的重点控制工程,位于重庆市綦县境内。隧道设计为双向四车道,设置为平行的双洞,左、右线隧道中线相距45m。左洞全长2056m,(LK110+164~LK112+220),右洞全长2109m(K110+131~K112+240)。单洞净宽9.75m,净高5m,路面横坡2%,断面轮廓为单心圆拱接圆曲墙,隧道纵断面设计为“人字坡”。金竹岗隧道设计的重点及难点在于其左洞进口端位于偏压、浅埋段。其上覆土层厚0~5m,下覆基岩为砂岩、泥岩互层,岩质软硬不一,裂隙较发育,岩体呈块碎状镶嵌结构,稳定性较差。局部含基岩裂隙水。其围岩类别均为Ⅱ类。隧道跨度大,埋深浅,山体偏压较大,开挖中极易因失稳而跨塌。因此,隧道施工中安全顺利通过进口偏压浅埋段为工程重点之一。
1 Overview The main control project of the Jinzhonggang Tunnel-Yuzhong Line Phase II Project of Chong-Chong Expressway is located in Daxian, Chongqing. The tunnel is designed to be a bi-directional four-lane with two holes arranged in parallel. The center line of the left and right tunnels is 45 m apart. The total length of the left hole is 2056m (LK110 + 164 ~ LK112 + 220) and the right hole is 2109m (K110 + 131 ~ K112 + 240). The width of a single hole is 9.75m, the height is 5m, the slope of the road is 2%, and the contour of the cross section is a single-circle circular arc curved wall. The vertical section of the tunnel is designed as a “humanoid slope”. The key and difficult point of the design of Jinzhugang Tunnel is that its left hole entrance is located in the biased and shallow buried section. The overburden is 0-5 m thick. The underlying bedrock is interbedded sandstone and mudstone. The rock is hard and soft, and the fissures are well developed. The rock mass is fragmented mosaic structure with poor stability. Local bedrock fissure water. The surrounding rock types are class Ⅱ. Large tunnel span, shallow depth, large mountain bias, excavation easily collapsed due to instability and collapse. Therefore, the safe construction of the tunnel through the import of shallow buried shallow section of the project as one of the priorities.