Energy and damage characteristics of shaft lining concrete subjected to impact

In terms of the phenomenon of rock-burst of shaft lining concrete in deep mine,the dynamic tests of three types of concrete,including normal high strength concrete (NHSC),steel fiber reinforced concrete (SFRC) and non- steam cured reactive powder concrete (NSC-RPC),were carried out by using Split Hopkinson Bar (SHPB) with di- ameter 75 mm and ultrasonic testing device. The stress and strain behavior,damage degree,energy input and dissipa- tion characteristics of different types of concrete under single or multiple impacts were studied. The correlations among impact velocity,internal energy and damage degree of concrete were analyzed. Meanwhile,the failure characteristics and mechanism of three kinds of concrete were found out. The results show that the stress-strain,energy and damage values of three typical kinds of concrete are positively correlated with the impact velocity. The energy bearing and dis- sipative capacity of NSC-RPC are about twice of that with NHSC and SFRC,and the critical impact velocity required for NSC-RPC to produce measurable damage is also higher than that of the other two. Multiple impact loads lead to the decrease of the peak stress,the increase of strain and the weakening of the bearing capacity of concrete,but the deteri- oration degree of NSC-RPC caused by repeated impact behavior is the smallest. There is even no measurable damage value in NSC-RPC under multiple low speed impact loads. Among the three typical kinds of concrete,NSC-RPC has the best impact resistance,and the application of NSC-RPC as the material of deep underground engineering struc- tures has more advantages. From the mul-ti-directional factors such as stress,strain,energy and damage,this paper re- veals the damage and failure mechanism of deep shaft lining structure in mine,and puts forward the improvement measures of deep shaft lining material. It provides a reliable theoretical basis for the selection of concrete materials for ultra-deep shaft lining.