牙轮钻头是目前世界上设计完善、品种规格多的钻进工具,具有较广泛的适用范围。我们在施工中,用SPJT—300型水文水井钻机,采用牙轮钻头钻进最大粒径达40—50cm的第四系密结卵石地层,成功地完成一口供水井、两口降水井,进尺75.98m,平均台月效率99.37m(见表1)。在另外两口XU300-2型钻机施工的供水井中遇卵石夹层时,用牙轮钻头也顺利钻进通过。第四系卵石地层施工供水井,钻进效率 Tricone bit is the world’s well-designed, more varieties of drilling tools, with a wider range of applications. In the construction, we used SPJT-300 Hydrology and Water Well Drilling Machine to drill a fourth-graded cobblestone layer with a maximum grain size of 40-50cm by using a roller cone drill bit. We successfully completed one water supply well and two precipitation wells, and the footage was 75.98m , The average monthly efficiency of 99.37m Taiwan (see Table 1). In the other two XU300-2 drilling rig construction of water supply wells in the case of pebble interbed, roller cone bit is also successfully drilled through. Quaternary pebble stratum construction water supply wells, drilling efficiency