厚层近海回填抛石填土层钻孔灌注桩施工技术

Construction technology of bored pile for thick offshore backfilland stone layers

烟台港万华工业园码头工程改造项目,设计采用600、1000 mm的钻孔灌注桩。上部为厚层近海回填抛石填土层,钻进困难,极易塌孔,成孔难度大,采用大型旋挖钻机带护筒跟管钻进成孔,内外二层套管护壁,穿过回填层及混砂层后,采用泥浆护壁旋挖钻机继续钻进,护筒不再跟进,既可保证成孔质量又能降低施工成本。外护筒可在灌注完成后拔出,重复利用,减少工程造价。

Bored piles of 600 and 1000mm diameter are designed for the Yantai Port Wanhua Industrial Park wharf upgrading project.The upper part is a thick layer of offshore backfilled stones,which is difficult to drill,prone to collapse,and difficult to form a hole.A large rotary drilling rig was used to drill the hole with the sim-casing process,where two layers of casing(inner and outer)were used to protective the wall.After drilling through the backfill layer and the mixed sand layer,the rotary drilling rig continued drilling with mud for wall protection,but the protection casing was no longer followed.In such a way,not only can the quality of the hole formation be ensured,but also the construction cost reduced.The outer casing can be pulled out after the completion of concreting and be re-used to reduce the project cost.