Study On The Drilling Process Of Anchorage Hole With Weak Intercalated Layer In The Roadway

The Coal-bearing strata have obvious characteristics of layered structure.Roadway arranged in these places usually appears floor heave when drived or used.The technique of bolt and cable support has become the preferred way of layered rock reinforcement for significant technical and economic advantages.Anchor hole drilling is the key link to realize the anchoring,the majority of the floor heave contains weak intercalated layer,physical mechanics characteristic of hole-wall is the internal cause of the stability of drilling system through the weak intercalated layer.The site research that there are parts of local rock fall and collapse phenomenon in the drilling floor roadway containing weak intercalated layer and the large volume of slag discharge difficulty.This paper adopted the combination of theoretical analysis,numerical simulation and experiment in the lab.Study shows that the expansion phenomenon mainly appeared in the position of weak and broken rock strata;stress state has greater influence on the expansion of anchor hole;it is no obvious that the effect of drilling force on the extent of expansion.Based on the principle of energy conservation,the energy in the drilling process of anchorage hole is analyzed.Under certain dynamic condition,energy curve changes obviously and energy response is strong when the drill bits drilling through the interfaces of rock strata and the weak intercalated layer;when using drilling speed and rotary velocity analyze the work of axial force and the rotary torque,the response relationship of drilling speed,rotary velocity and work of drill bits cutting rock was found.More than 95% of the energy of the drill bits cutting rocks is from the work of the torque,while the work of axial thrust force is relatively small and less than 5% of the total energy output of the drill system,the change of total energy curve is basically consistent with the work change of rotary torque.The larger the particle size of drilling slag is,the more difficult it is to discharge out of the hole under the action of gravity.The increase of the angle of the anchorage hole makes the slag easily accumulated at the wall of the lower hole,and in contrast to the vertical hole,the increase of the angle of inclination is in fact more beneficial to the slag discharge.The local expansion of the anchorage hole has a great influence on the whole slag discharge process,the greater the degree of enlargement,the more serious the retention of the drills.The research reveals the stability of roadway floor of small diameter anchor hole,providing theoretical support for drilling high quality anchor hole.