The coal mined-out areas existed under a section of the main canal of Middle Route Project of South to North Wa-ter Diversion, so the grouting reinforcement was needed. The grout hole passed through hard sandstone layer, during which the problems such as low drilling efficiency, severe equipment wear and tear and frequent pipe sticking occurred. Through analysis of the hardness and fragmentation degree of different layers, the drilling out of different layers by different drilling equipment was determined. The technological process and key points of quality control in the drilling construction were described. The engineer-ing practice showed that the working efficiency was improved, the construction period was shortened and the cost was saved by the combined construction, and the environmental protection effects were gained as well.%南水北调中线一期总干渠某渠段基岩以下存在采空区，需进行灌浆加固，灌浆孔要穿过坚硬的铁板砂石岩层。施工中还存在钻进工效低、设备耗损大、卡钻事故频繁等难题。通过分析不同地层硬度和破碎程度，现场针对各种地层岩性分别采用不同的击破施工方法，且对于不同地层使用不同的钻孔设备。介绍了组合钻孔施工的工艺流程、质量控制要点。工程实践表明，不同钻机的组合使用不仅提高了工效、缩短了工期、降低了成本，而且起到了环保的效果。
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