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在德国曼海姆的费尔莱茨(Fabrlach)公路隧道位于通往该市的终点站铁路线10股道之下,为了掘进安全,使用AVN300型微型隧道施工系统,准确地敷设水平冷冻管,以冷冻加固地层。围绕此双孔公路隧道,AVN系统从两端洞口钻进,完成了46孔长90m×内径454mm(外径470mm)的钻孔,覆盖全长186m的公路隧道。 在每个90m的钻孔终点,微型钻机必须向预先垂直冷冻的墙钻入1m,在冷冻墙的中点处退回,以避免钻孔变冷结冰。经过革新的切割轮,使得AVN机器能通过完成的管路退回。AVN机器掘进通过的地层为含水的砂层、粉砂、砾石和夹有老树根的回填土。
The Fabrlach highway tunnel in Mannheim, Germany, is under the 10-lane railroad terminal to the city. For tunneling safety, the AVN300 mini tunnel construction system is used to accurately level the horizontal freezing pipe, To freeze the formation. Around this two-hole highway tunnel, the AVN system was drilled from both ends of the tunnel, completing 46 holes of 90m long × 454mm (OD 470mm) holes to cover a 186m-long highway tunnel. At each 90m borehole end, the micro-rig must drill into the pre-vertical frozen wall at 1m and retract at the mid-point of the freezer wall to avoid chilling and icing of the borehole. The innovative cutting wheel allows the AVN machine to be retracted through the completed tubing. The ground strata through which the AVN machines go through tunnels are aquifers, silt, gravel and backfill with old tree roots.