砂卵石地层超长管棚技术应用与研究

摘要

成都地铁盾构始发及接收采用管棚加固措施,既有经验及工程实践表明,管棚支护对控制沉降及盾构始发/接收安全起到有效控制作用,为将管棚支护技术应用于下穿既有运营地铁线等高风险工程,有必要对成都砂卵石地层超长管棚应用进行系统研究,以成都在建地铁车站基坑内管棚试验为基础,对管棚直径、打设工艺、打设长度、打设精度及引起地层沉降进行研究分析.结果表明:在卵石粒径大(最大粒径60cm)、卵石含量高(60％～80％)的成都砂卵石地层,采用带冲击锤头的潜孔钻机,可实现管棚长距离施工,当施作长度小于35 m时能有效控制管棚偏移量,试验过程中最大偏移量为0.6m,且管棚采用跟管顶进法可有效控制管棚施工过程中引起的地层沉降.%The application of shed-pipe support for receiving and starting of shield in Chengdu metro shows that shed-pipe support technology is effective in controlling the stratum settlement and ensuring the receiving and starting of shield safe.In order to apply the over-length shed-pipe support technology to the high risk projects such as tunneling under existing metro,this paper studies the diameter,drill depth,construction technology,operating precision of pipe shed and the stratum settlement caused by pipe shed construction based on the pipe shed experiment in the foundation fit of an under-construction metro station in Chengdu.The results show that long-distance pipe jacking can be achieved in Chengdu grit gravel stratum with large-diameter cobble (maximum aggregate size can reach 60 centimeters) and high cobble content (from 60 percent to 80percent) by using in-the-hole drill with impact hammer.When the construction length of pipe roof is shorter than 35 meters,the maximum offset can be 60 centimeters and the stratum settlement is controlled by using pipe-following drilling technology.