临近既有建筑物深水植桩复合围堰施工技术

浪河特大桥15#主墩基础采用锁口钢管桩+钻孔锚固桩复合式无封底混凝土围堰方案,该方案避免了双壁钢套箱围堰先期大尺寸、深范围铣槽清基可能导致的既有建筑物周围土层滑坡坍塌的严重后果,增大了安全净距,解决了钢管桩难以插打进岩层的难题,采取了初步铣孔植入钢管桩、二次钢管桩内施作钢筋混凝土钻孔桩、再次铣孔孔隙混凝土封闭处理、最后排水安装内支撑且不浇筑封底混凝土的明挖施作施工方式,既保证围堰锚固生根的整体稳定性,又能减小地层扰动对既有建筑物周围地层影响,提高了既有建筑物运营安全,显著缩短了工期,降低了投入。

Construction Technology of Inserting Pile for Composite Cofferdam in Deep-water Adjacent to Existing Buildings

The scheme of lock-type steel pipe pile+bored anchor pile composite type unsealed concrete cofferdam is adopted in the No.15 main pier foundation of Langhe Super Bridge,which avoids the serious consequences of landslide and collapse of soil around existing buildings caused by large-scale and deep-range milling groove clearing of double-wall steel box cofferdam,increases the safety net clearance,and solves the problem that the steel pipe pile is difficult to be inserted into the rock layer.In this paper,an open-cut construction method was used,including inserting initial milling hole into steel pipe pile,constructing reinforced concrete bored pile in steel bored pile secondly,then sealing concrete into pore of milling hole,and finally installing internal support after drainage and without pouring bottom-sealing concrete,it could not only ensure the overall stability of cofferdam anchorage and rooting,but also reduce the influence of stratum disturbance on the surrounding strata of existing buildings,improve the operating safety of existing buildings,significantly shorten the construction period and reduce the investment.