冲击动载作用下加锚岩体抗冲时效试验研究

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

冲击动载作用下巷道围岩锚固承载结构的破坏是深部煤炭资源开采的突出问题,深入研究动载作用下锚固围岩的抗冲机制具有重要意义。采用分离式霍普金森压杆研究了冲击动载作用下无锚、端锚、全锚和全锚+柔性锚杆4种锚固岩石试件的冲击破坏响应,获得了不同锚固岩石动态应力应变曲线,分析了锚固方式对加锚岩石试件动态裂纹扩展发育的影响,通过对比锚固岩石冲击破坏过程中锚杆与岩石的动态应变演化特征,结合锚固界面滑移破坏形态,提出了锚固岩石抗冲时效的概念,并以锚杆与岩体两者协同变形为原则提出冲击动载作用下保障锚固围岩稳定的合理建议。研究结果表明:①冲击动载作用下锚固岩石应力应变曲线呈“闭口型”,锚固岩石动态强度与应变峰值的排序为:无锚岩石<端锚岩石<全锚岩石<全锚+柔性锚杆岩石;②冲击动载作用下锚杆与岩石之间的变形可分为“协同变形阶段”、“不协同变形阶段”和“失效阶段”,其中锚固岩石在前两个阶段抵抗动载冲击的作用为“抗冲时效”;③锚固岩石抗冲时效与岩石/锚固剂和锚固剂/锚杆之间不协同变形直接相关,提高岩石、锚固剂和锚杆的抗滑移特性及协调变形能力可有效延长锚固岩石抗冲时效的时长,降低冲击动载对锚固围岩支护结构的影响。研究成果对深部巷道锚固支护工程具有一定的理论指导和借鉴意义。

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:①the 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;②the 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;③EPRD 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.