Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts:Insight from laboratory drop test

• Published in: 矿业科学技术学报（英文版） Vol. 33; no. 2; pp. 215 - 231
• Main Authors: Jinfu Lou, Fuqiang Gao, Jianzhong Li, Guiyang Yuan, Mostafa Sharifzadeh
• Format: Journal Article
• Language: English
• Published: State Key Laboratory of Coal Mining and Clean Utilization,Beijing 100013,China%Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Northeastern University,Shenyang 110819,China 2023; CCTEG Coal Mining Research Institute,Beijing 100013,China
• Subjects: Dynamic performance; Residual elastic energy(REE); Energy absorption rate(EAR); Energy-absorbing rockbolt; Drop test; Dynamic capacity envelope
• ISSN: 2095-2686
• DOI: 10.3969/j.issn.2095-2686.2023.02.006

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support,and their ser-viceability is closely related to the frequency and magnitude of seismic events.In this research,the split-tube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1 rockbolts under a wide range of seismic event magnitudes.The test results showed that the impact pro-cess could be subdivided into four distinct stages,i.e.mobilization,strain hardening,plastic flow(duc-tile),and rebound stage,of which strain hardening and plastic flow are the primary energy absorbing stages.As the impact energy per drop increases from 8.1 to 46.7 kJ,the strain rate of the shank varies between 1.20 and 2.70 s-1,and the average impact load is between 240 and 270 kN,which may be con-sidered as constant.The MP1 rockbolt has a cumulative maximum energy absorption(CMEA)of 31.9-40.0 kJ/m,with an average of 35.0 kJ/m,and the elongation rate is 11.4％-14.7％,with an average of 12.7％,both of which are negatively correlated with the impact energy per drop.Regression analysis shows that energy absorption and shank elongation,as well as momentum input and impact duration,conform to the linear relationship.The complete dynamic capacity envelope of MP1 rockbolts is pro-posed,which reflects the dynamic bearing capacity,elongation,and distinct stages.This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engi-neers in robust reinforcement systems design to mitigate rockburst damage in seismically active under-ground excavations.