Due to reinforce concrete's high strength grade and embedded rebar, it is difficult to obtain an efficient drilling result during the repair and renovation constructions.Besides diamond bit cutters are usually broken during the drilling process, thus leading to diamond bit's short service life.To solve those problems, regulating bit matrix property, optimizing diamond bit structure, as well as adding grinding types are employed within this study.Soft-medium hardness matrix and cubic boron nitride which improves the cutting performance of abrasive particles on the diamond bit workface are used to increased the drilling rate.Optimized bit structures, including diagonal water gap and asymmetric cutters are employed for ensuring a steady drilling process.It can avoid the suddenly full-face encounter between bit cutters and the rebar, which may produce huge transient impact load and cause cutters breaking.Test results indicate that, the average drilling rate and total service life of (Φ)75 mm diamond bit are 1.12 m/h and 28 m respectively under the optimized drilling parameters (i.e., the drilling pressure of 6.5 Mpa, linear velocity of 2.1 m/s and coolant flow of 25 L/min) and there is no cutters broken during the drilling test.Consequently, the diamond bit design methods in this study are proved to be correct, and the diamond bits manufactured following those methods and technologies can satisfy the requirements of construction.%钢筋混凝土结构因内部有钢筋,且自身强度等级较高,在钻孔过程中施工难度大,钻进效率低,经常出现钻头断齿现象.针对这些现象,从调整钻头胎体性能、改进钻头结构和增加磨料种类3个方面进行试验.为提高金刚石钻头钻进效率,采用中软性能的钻头胎体,并添加立方氮化硼(CBN)磨料,提高钻头工作唇面上磨料的切削性能;为使钻头钻进平稳,采用斜水口和奇数齿结构钻头,防止钻齿在孔底与钢筋产生全断面接触,避免钻齿瞬时冲击载荷过大而发生断齿.试验结果表明:使用(Φ)75 mm钻头,钻进压力6.5 Mpa、钻头线速度2.1 m/s、冷却液流量25 L/min时,钻头的平均钻进时效可达到1.12 m/h,钻头寿命28 m,无断齿现象;表明本试验的钻头设计工艺正确,结构合理,可满足施工现场的生产需求.
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