In the expansion and reconstruction project of Ningluo Expressway,the cofferdam for Pier No.22 of the Huaihe Riv-er Super Bridge was submerged to a cumulative depth of 34 meters embedded 19 meters into the riverbed,with its cutting edge located in a mudstone stratum.During construction,geological complexities and flood-season constraints posed significant chal-lenges in both precise foundation pit excavation and accurate cofferdam positioning,under a tight schedule.A novel concrete rollerbar limit-and-guide system was designed to control horizontal displacement through the sinking process.By installing a hydraulic reamer at the bottom of the suction pipe and utilizing a rotary drilling rig on a specially erected platform to drill and remove soil,the difficulties of underwater excavation in gravel layers and completely weathered mudstone were effectively over-come.In addition,the installation sequence of the internal supports was optimized to significantly improve construction efficien-cy.As a result,the Pier No.22 cofferdam successfully reached its designated depth and was sealed at the bottom within the scheduled time.The lessons learned from this project offer valuable references for excavating foundation pits and conducting sinking-and-positioning operations of double-wall steel cofferdams with large excavation depths.
关键词
双壁钢围堰/深水泥岩/精准就位/砼滚杠式限位导向/内支撑安装
Key words
double-wall steel cofferdam/deep water mudstone/precise positioning/concrete roller bar limit-and-guide system/internal support installation
维普
万方数据