麻拉寨隧道安全贯通施工技术

On the Safe Run-Through Construction Techniques for the Malazhai Tunnel

云贵高原岩溶发育强烈,工程地质复杂,隧道双向掘进,在最后贯通阶段,容易出现突泥、突水、塌方等灾害,必须注意施工方法以保证隧道安全贯通。中铁十七局沪昆项目麻拉寨隧道DK611+055^+085最后30m贯通段,进口工作面停止掘进,进、出口及时跟进仰拱和二衬;贯通段前24m由出口工作面采用微台阶加临时仰拱的方法开挖掘进,后6m先采用超前小导管进行超前支护、后采用留核心土环向开挖法,以每循环1榀钢拱架的施工速度逐步贯通。顺利完成施工,工期效益、经济效益显著。

Owing to the fact that karst landform is usually much developed on the Yunnan and Guizhou highlands where engineeringgeology is very complex, earth gushing, water gushing, collapsing or other geological disasters often happen when atunnel is drilled in opposite directions, especially at the final stage of the run-through of the tunnel. Therefore, the constructionmethods at this stage have to be carefully chosen to ensure the safe run-through of the tunnel. When the last 30-m section（DK611 ＋ 055-＋ 085） of the Malazhai Tunnel Project of the Shanghai-Kunming Railway built by the 17th Bureau Group ofChina Railway is to be run-through, the drilling at the entrance end stops,the inverted arches at both the entrance end and theexit end^and the secondary lining are provided immediately; the 24-m running-through section from the exit work face is drilledby means of the micro-step plus the temporary inverted arch method,with the last 6-m section excavated by the advanced guidingtube being used as the advanced support firsthand the core earth-retaining radially excavating method; with the speed of eachsegment of steel arch support for each cycle of drilling operation, the tunnel is run-through step by step until the whole tunnelis smoothly completed. The tunnel is successfully completed, with a good effect in construction duration and obvious economicbenefits achieved.