湘江隧道江心洲竖井上软下硬地层旋挖成孔关键技术

旋挖灌注桩成孔施工在长沙营盘路湘江隧道江中竖井施工中分别遇到严重塌孔、漏浆和无法钻进、效率低的问题，通过研究砂卵石地层和中风化岩层工程地质特性和分析旋挖工艺特点，采用严格控制泥浆指标、采用聚合物泥浆、采用耐磨合金子弹头截齿旋挖钻头和换填优质土等措施，克服了旋挖钻机在长沙地区砂卵石、中风化板岩地层中塌孔漏浆、无法钻进的问题，确保了围护桩按计划实施和桩体施工质量满足要求。

Key Technologies for Borehole Drilling by Rotary Drilling Machines in Heterogeneous Ground:Case Study on Bored Piles of Vertical Shaft of Xiangjiang River Crossing Tunnel

The bored piles of the vertical shaft of Xiangjiang river crossing tunnel on Yingpan road in Changsha are located in heterogeneous ground, i.e., sandy cobble strata in the upper part and medium weathered slate in the lower part. During the construction of the bored piles, serious borehole collapse, slurry leakage and other problems occur. Technologies, including strictly controlling the slurry indexes, using polymeric slurry, using wear resistant drill bit with alloy bullet shaped teeth and backfilling high quality soil, are adopted. In the end, the construction of the bored piles has been completed successfully and the pile quality is guaranteed.