Experimental study on EPRD(effectiveness for a given period to resistance dynamic load)of bolted rock under dynamic load

The impact failure of bolted rock under dynamic load is a prominent problem in coal mining. It is of great significance to study the failure mechanism of rock with bolt support under dynamic load disturbance. The impact failure responses of four kinds of bolted rock specimens (No bolt,End anchor,Full anchor and Flexible bolt) under dynamic load were studied by using split Hopkinson pressure bar. The dynamic stress-strain laws of bolted rock specimens with different anchoring types were obtained. The influence of anchoring types on the dynamic crack growth on specimens was analyzed. According to the dynamic strain evolution characteristics of bolt and rock mass,the concept of EPRD was proposed based on the sliding failure mode of bolted rock. Based on the principle of coordinating the deformation of bolt and rock mass,reasonable suggestions were put forward to ensuring the stability of anchored surrounding rock under dynamic load. The results show that：① the stress-strain curve of bolted rock specimen under dynamic load is “closed-shape”,the dynamic strength and peak strain of bolted specimens is：No bolt < End anchor < Full anchor < Flexible bolt; ② the deformation between bolt and rock under dynamic load could be divided into “collaborative deformation stage”,“no cooperative deformation stage” and “failure stage”. The effectiveness of bolted rock in “coordinated deformation stage” and “no cooperative deformation stage” is EPRD; ③ EPRD of bolted rock is related to the uncoordinated deformation among rock,anchoring agent and bolt. Improving the anti sliding characteristics and coordinating deformation capacity of rock mass,anchoring agent and bolt can prolong the duration of EPRD,and reduce the effect of dynamic load on the anchored surrounding rock. The research results have a certain theoretical guidance and reference significance for deep roadway bolt support.