短螺旋钻头入岩最优切削厚度的理论与实验研究

Theoretical and Experimental Study of Optimal Cutting Thickness of Short Helix Bit while Drilling the Rock

根据岩石的物理力学特性和截齿的破岩机理,建立了单个镐型截齿破岩时受力的数学模型;在此基础上,对安装12个镐型截齿的短螺旋钻头进行整体受力分析,并建立钻头扭矩的数学模型,结合旋挖钻机恒功率钻进的特点,得到钻头转速的数学表达式,从而求得钻头钻进速度关于切削厚度和岩石接触强度的关系式。针对几种不同接触强度的岩层,运用Matlab程序分别求得钻机在不同切削厚度下的钻进速度,并与同等条件下的实验数据相比较。结果表明:若切削厚度过小,钻机钻速达不到最大,钻进效率偏低;若切削厚度过大,钻机提供的扭矩因无法克服负载(即钻速为零),导致钻机损伤。

According to the physical and mechanical characteristics of rock, combining with the working principle of the conical bit while cutting rock, the mathematical model of single conical bit was built. And it was applied in the whole force analysis of the short helix bit with twelve conical bits and the mathematical model of short helix bit＇s torque was built. Also the mathematical expression of rotary speed of short helix bit was obtained because the power of the hydraulic piling rig is constant while drilling rock. Grounded on all these above, it can be deducted to a rela- tional expression among drilling speed, cutting thickness and contact strength of rock. In accordance with rock stra- tum of different contact strength, drilling speed of the machine with different cutting thickness were got by Matlab program, which were compared with those statistics from the practical test under the same condition. From the re- suits, it can be concluded as following： the excessively small cutting thickness will lead to low drilling efficiency because drilling speed isn＇t maximum, and excessively big cutting thickness will lead to the damage of the machine for the torques can＇t get over the load （drilling speed is zero）.