煤矿巷道底板锚固孔钻渣尺寸特征实验研究

Experimental study on the size characteristics of rock fragments during borehole drilling in coal mine roadway floors

长期以来,煤矿巷道底板小孔径锚固孔钻进排渣困难是高质量成孔的瓶颈问题。因此,明晰钻渣尺寸分布规律对排渣的顺利进行至关重要。利用理论分析及实验室实验方法研究两翼式钻头在底板锚固孔钻进过程中钻渣的尺寸特征。结果表明:底板岩石强度及钻头刀翼间距是影响钻渣平均尺寸的主要因素,岩石的单轴抗压强度越高,钻进过程中产生的大粒径钻渣比例越大,从而造成了钻渣整体的平均尺寸随岩石单轴抗压强度的增加而增加;钻机动力参数(转速及钻速)对钻渣平均尺寸不会产生规律性影响。此外,钻渣平均尺寸随着钻头刀翼间距的增加而增加。因此,通过减小两翼式钻头刀翼间距可以降低钻渣平均尺寸,在钻进至较坚硬地层时,由于大尺寸钻渣产出量增加,应及时调整排渣动力参数,保证钻渣顺利排出。研究成果可为底板锚固孔钻进过程中钻具结构优化以及排渣参数设定提供一定理论依据。

The difficulty of rock fragment discharging from small diameter boreholes drilled at a downward angle in coal mine roadway floors has long been the major factor that reduces borehole quality. Therefore,fuller understanding of rock fragment sizes is absolutely essential to fragments discharging. In this study,theoretical analysis and laboratory experiments were adopted to analyze the size characteristics of rock fragments formed by two-wring drill bits. The results indicate that the strength of rocks and bit blade spacing are the two keys factors that affect the mean fragment size. The proportion of larger-size fragments increases with the uniaxial compressive strength,which makes the mean fragment size increase with the uniaxial compressive strength as well. The rotation rate and drilling rate have no influence on the mean fragment size. In addition,the mean fragment size increases with the blade spacing. Therefore,the mean fragment size can be reduced by reducing the spacing between two wings. When drilling through high strength rock strata,the mean size of the fragments will increase and the discharge power should be enhanced to prevent fragment discharge blockages. This paper may provide a theoretical basis for discharge power settings and drilling tool optimization.