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某钻孔临近煤矿采空区,采用正循环气动潜孔锤钻进,钻至110m时发生了钻具断裂事故。针对施工过程中出现的钻杆接头断裂失效情况,结合该孔的施工工况,通过对断口进行宏观分析及理化性能试验,结果表明:钻杆接头断裂的主要原因为岩屑上返过程中在钻具外径突变处发生沉积,造成钻杆接头与岩屑剧烈摩擦,造成接头严重磨损,同时产生高温,致使岩屑与接头基体金属熔结为一体,并使金相组织发生了奥氏体转变。高温奥氏体组织硬度、强度大大下降,而变形能力大大提高。在拉力、扭转等应力的作用下,最终在该处薄弱部位发生了过载断裂。
A hole near the coal mined-out area, the use of positive pneumatic down-the-hole drilling, drill to 110m occurred when the drill fracture accident. According to the fracture failure of the drill pipe joints during the construction process and macroscopical analysis and physical and chemical performance test of the fracture, the results show that the main reason of the fracture of the drill pipe joint is the A sudden change in the outer diameter of the drill pipe occurs, which causes severe friction between the drill pipe joint and the cuttings, resulting in severe joint wear and high temperature, causing the cuttings to fuse with the base metal of the joint and causing the austenite change. High-temperature austenitic tissue hardness, strength decreased significantly, while the deformation capacity greatly increased. In the tension, torsion and other stress under the effect of the final site where the weak parts of the occurrence of overload fracture.