Laboratory Experimental Study On The Mechanism Of Rockburst Prevention By Drilling Pressure Relief

High-stress and high strain energy accumulation under the excavation disturbance of deep rock mass makes geological disasters such as rockburst occur frequently.Drilling pressure relief(DPR)is a widely accepted key technology to eliminate high stress and high energy accumulation in deep rock mass,which has obvious implementation effect in the prevention of rockburst disaster.To investigate the internal mechanism of DPR in preventing rockburst,the SG4500 drilling rig test equipment was independently developed in this work.Combined with the existing INSTRON 1346 servo hydraulic testing system,the uniaxial compression test was carried out on red sandstone specimens with drilling(the prefabricated drilling and real-time drilling).The internal mechanism of DPR was explored from the characteristics of rock mechanical behavior,evolution law of strain energy,and weakening characteristics of rockburst proneness.The main conclusions and laws are as follows:(1)The bearing capacity characteristics and macro failure mechanism of red sandstone specimens under prefabricated drilling and real-time drilling were analyzed.It is found that DPR can effectively weaken the compressive strength and failure release energy characteristics of rock specimen.Besides,different arrangements of prefabricated drillings make the red sandstone specimens present macro failure modes,such as shearing failure,splitting failure and shearing splitting mixed failure.(2)The strain energy evolution law of red sandstone specimens under prefabricated drilling and real-time drilling was investigated.It is found that the prefabricated drilling structure inside the rock specimen has no effect on the linear energy storage and energy dissipation law of rock,but the existence of prefabricated drillings can reduce the energy storage capacity of rock.The energy storage coefficient decreases with the increase of the number of drillings,with the arrangement angle and loading direction of drillings varying 90° to 27° and then to 0°,it first decreases and then increases.When the arrangement angle and loading direction of drillings is 27°,the energy storage coefficient of rock specimens is the smallest.(3)The effectiveness of DPR to weaken rockburst proneness was confirmed.Based on the linear energy storage law of rock under drilling,the rockburst proneness of red sandstone specimens under prefabricated drilling and real-time drilling is quantitatively evaluated by using peak strength strain energy storage index.Besides,the peak strength strain energy storage index decreases with the increase of the number of prefabricated drillings,which firstly decreases and then increases with the angle between arrangement angle and loading direction from 90° to 27°and then to 0°.When the arrangement angle of drillings is 27° to the loading direction,the effect of eliminating rockburst proneness is the best.Additionally,real-time drilling can weaken rockburst proneness more than prefabricated drilling.(4)The differences between high stress real-time drilling and prefabricated drilling in revealing the mechanism of DPR to prevent rockburst were analyzed.It is found that real-time drilling under high stress can more accurately reflect the changes of rock energy state,effectively weaken the elastic strain energy storage capacity and rockburst proneness of rock.In addition,drilling energy relief was found to a significant feature of real-time DPR to prevent rockburst under high stress,and the effectiveness of DPR in reducing rockburst proneness was slao further verified from the perspective of energy.