襄樊汉江四桥大口径灌注桩成孔施工实践

介绍了使用泥浆护壁气举反循环回转钻进工艺进行襄樊汉江四桥大口径嵌岩桩的施工实践。施工中采用下置双护简隔离卵石层，合理选用钻头类型(卵砾石层采用五翼合金刮刀钻头，基岩采用球齿滚刀钻头)和钻进参数(混合器沉没深度，尾管长度，孔内空气流量与压力)，摸索与总结出一套复杂地层成孔施工经验。

Major Diameter Filling Pile Completion Practice at Hanjiang No.4 Bridge Site, Xiangfan City

The paper introduced the use of airlifting reverse circulation rotary drilling techniques in practice of major diameter socket pile operation at Xiangfan city's Hanjiang No.4 bridge site. Operation used lower installed double pile casing to close off pebble beds, rationally select and use applicable bits (in pebble and gravel beds use five-wing tungsten alloy blade bit, while in bedrock use button hobbing bit) and drilling recommendations (mixer sinking depth, tail pipe length, in hole air flow rate and pressure). Finally, a set of successful operational experience of completion in bad ground was fished and summarized out.