超大粒径砂卵石地层条件水中基础围堰施工技术方案与经济效益探讨

Discussion on Construction Methodology and Economic Performance of Cofferdam under Water Based in Super-size Sandy Gravel Stratum

成昆铁路黄水安宁河双线特大桥28^#~32^#墩位于超大粒径砂卵石地层环境条件,其中30#墩位于水中,原设计采用钢板桩围堰的施工方案施工时,因地质原因,钢板桩无法直接插打。通过对围堰技术方案比选,研究采用了引孔插打CT锁口钢管桩围堰的技术方案,既解决了大粒径砂卵石地质条件下锁扣钢管桩直接插打难、在深水条件下不易止水、深基坑围堰内狭小空间土层难开挖的技术难题,又降低了安全风险,并提高了经济效益,可供类似桥梁基础施工参考借鉴。

The piers P28-P32 of Anning River Double-track Large Bridge on Chengdu-Kunming Railway are located in the geological condition of large-size sandy pebble stratum,of which the pier P30 is located in water.The construction methodology of steel sheet pile cofferdam was applied by the original design.However,the steel sheet piles could not be directly inserted and driven into the stratum due to geological reason.Through the comparison and selection of the technical scheme of cofferdam construction,the methodology of CT locking steel pipe pile cofferdam was scrutinized and adopted at the end.Such methodology solves the technical problems including difficulty on directly inserting and driving the lock steel pipe pile under the geological conditions of large-size sandy gravel,stopping water under the deep-water condition,and excavation work within a narrow space of the deep foundation pit cofferdam.It also reduces the safety risk and improves the economic benefits of the project,which can be used for reference for other bridges construction with similar condition.