Study On Technology And Device For Improving Pre-tightening Force Of Rockbol

Boosting the bolt pre-tightening force is an important way to improve theeffectiveness of bolting. In china, bolt supporting is mostly applied in coal mineroadway, but too weak pre-tightening force will seriously restrict the application ofbolt supporting in difficult conditions. As for the boost of the bolt pre-tightening force,many scholars in our country resort to two means to achieve this end: The first is toimprove the nut installation torque M; the second one is to reduce the conversioncoefficientkbetween nut installation torque and bolt pre-tightening force. In orderto increase the bolt pre-tightening force, my tutor has suggested a bolt pre-tighteningdevice which has been granted national patent. This paper conducts research based onthis patent.In this paper, theoretical analysis, laboratory experiments and field tests werecombined to look at the feasibility of this technology and the device. The results wereas follows:(1) Analyzed the role of bolt pre-tightening force in bolting, with factors thatinfluence bolt pre-tightening force obtained and new model of bolt pre-tighteningtechnology and device developed.(2) Summarized the technology of applying bolt pre-tightening; proposed theidea of bolt preload technology and devices; get their good friction reduction bymechanical analysis.(3) Designed bolt pre-tightening device and made a trial product.(4) Conducted an experiment on bolt test platform, culminating with a graph ofthe relationship between torque and bolt preload: when pretension torsional momentgoes below80N·m, bolt pre-tightening force has little effect; while pretensiontorsional moment is increased to200N·m, pre-tightening force is largely increased bypre-tightening device.(5) Achieved good result on the spot.