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目前灌注桩孔的施工大量采用回转型钻机进行，但这种钻进方法遇到基岩就很难钻进，效率极低，如应用冲击反循环工艺方法进行钻孔可解决此难题。冲击反循环钻进在孔深50~60 m内效果良好，但在覆盖层中的钻进效率又不如回转钻进，为此我厂研制了具有复合钻进功能的HCF-20型回转─
At present, the construction of bored pile holes is mostly carried out by rotary drilling rigs. However, such a drilling method is difficult to drill when encountering bedrock, and the efficiency is extremely low. For example, the application of impact and reverse circulation drilling methods can solve this problem. Impact reverse circulation drilling is effective in the hole depth of 50 ~ 60 m, but the drilling efficiency in the cover is not as good as rotary drilling. Therefore, our factory developed the HCF-20 rotary drilling with compound drilling function-