砂卵石地层洞桩法车站成桩技术与创新

Technology and Innovation of Piling in Underground Stations with PBA Method in Sandy Cobble Strata

在砂卵石地层中,地铁车站洞桩法施工成桩问题备受关注。以北京地铁16号线二里沟车站为工程依托,针对其大粒径砂卵石地层特性,对单层导洞法施工中存在的洞内大直径机械成桩问题进行了研究。在施工过程中注重技术创新,首先采用履带式行进系统对钻机进行改进,提高钻机稳定性,解决了钻机在大粒径卵石地层成孔过程中晃动大,桩身垂直精度低的问题;其次对钻头进行改进,采用液压钻高频振动冲击破碎漂石以减小卵石粒径;最后通过分级钻进和调整泥浆配比的方法,解决了钻进过程中卵石堵管、卡钻、扩孔过大等问题。经施工优化后成桩过程钻进工序时间减少了90.20%,整体成桩时间减少了89.16%,提高了施工效率。

In the sandy cobble strata,the piling problem in subway stations with PBA method has attracted much attention.Based on the project of Erligou Station of Beijing Subway Line 16,the problem of large diameter mechanical piling in the hole in the construction of single-layer guide hole method was studied in view of the characteristics of its large grain size sandy cobble strata.During the construction,technical innovation is concerned.Firstly,the drilling rig was improved by using crawler type travel system to improve the stability of the drilling rig,which solved the problems of large shaking and low vertical accuracy of the pile in the process of pile formation in large grain size pebble strata.Secondly,the drill bit was improved by using hydraulic drill with high frequency vibration and impact to reduce the pebble size.Finally,the problems of pebble blockage,jamming and over-expansion during drilling were solved by grading drilling and adjusting the mud ratio.After construction optimization,the drilling process time was reduced by 90.20%and the overall piling time was reduced by 89.16%,which improved the construction efficiency.