燃烧热能机械能复合破岩先导性试验研究

为了证实燃烧热能-机械能复合破岩方法的可行性,通过理论分析和室内试验对该破岩方法进行了研究。采用瞬态传热方式对岩石有限元模型进行了热分析,评价了燃烧热能对破岩的作用;并利用自制的钻头和试验台架开展了模拟钻进试验和对比试验,验证了燃烧热能-机械复合破岩的可行性和破岩提速能力。理论分析可知,在不考虑岩石受热而发生热应力裂解的情况下,燃烧热能获得的钻速达18.0 m/h。模拟试验得到,该方法在花岗岩中的平均钻进速度为24.5 m/h,同时钻进中高温改变了井眼周围岩石成分的团聚状态,可形成1.8 mm厚的陶瓷层;在相同试验条件下,该破岩方法获得的钻进速度是常规机械破岩方法的8.3倍。研究结果表明,对于导热系数较小、抗拉强度和剪切强度较低的岩石,燃烧热能形成的热冲击力能引起岩石脆性破坏,降低岩石抗压强度,与机械能复合破岩能明显提高钻进效率。 

Pilot Tests on Thermal-Mechanical Composite Rock-Breaking Methods

In this paper, theoretical analysis and laboratory tests were performed on the thermal-mechanical composite rock breaking method to verify its feasibility. Thermal analysis was conducted on the rock finite element model by means of transient heat transfer to evaluate the effect of heating power on rock breaking. And then, simulated drilling tests and comparison tests were carried out by using the self-made drilling bits and test benches to verify the feasibility and rock breaking velocity increasing capacity of the thermal-mechanical composite rock breaking method. Based on the theoretical analysis, the penetration rate contributed by the heat of combustion was 18.0 m/h if thermal-stress rock cracking due to the heat was not taken into consideration. Based on simulation tests, the average penetration rate in granites was 24.5 m/h. And in the process of drilling, the aggregation state of rock compositions around the borehole was changed under high temperature, and consequently a ceramic layer of 1.8 mm thick was formed. And in the same test conditions, the penetration rate obtained by the thermal-mechanical composite rock breaking method was 8.3 times the conventional one. It was shown that brittle failure occurred on the rocks with lower coefficient of heat conductivity, tensile strength and shear strength under the effect of heat impact caused by heat of combustion, and the compressive strength dropped. And by virtue of the thermal-mechanical composite rock breaking method, drilling efficiency was increased significantly.