冲击荷载作用下的井壁混凝土能量与损伤特性

Energy and damage characteristics of shaft lining concrete subjected to impact

针对深部矿井井壁混凝土产生类似“岩爆”现象的问题,从典型种类混凝土动力学性能角度出发,采用直径为75 mm的分离式霍普金森杆(SHPB)和超声检测装置对普通高强混凝土(NHSC)、钢纤维混凝土(SFRC)和免蒸养活性粉末混凝土(NSC-RPC)进行动力学试验。研究单次和多次冲击荷载作用下,不同种类混凝土的应力、应变行为,能量输入与耗散特征以及损伤程度。分析子弹的冲击速度、混凝土内部能量和损伤程度3者之间的相关关系,探明不同种类混凝土的失效特征与机理。结果表明:3种典型种类混凝土的应力应变、能量和损伤值皆与冲击速度呈正相关性。NSC-RPC的能量承受和耗散能力是NHSC和SFRC的两倍左右,同时NSC-RPC要产生可测损伤值所需要的临界冲击速度亦高于另外两者。多次冲击荷载导致混凝土应力峰值降低,应变增大,材料的承载能力弱化,但多次的冲击行为对NSC-RPC的劣化程度最小,且在多次较低速的冲击荷载下,NSC-RPC仍未出现可测损伤值。在3种典型种类混凝土中,NSC-RPC具有最为优异的抗冲击能力,将NSC-RPC应用为深部地下工程井壁以及关键结构部位材料更具有优势。本工作从应力应变、能量与损伤等多方位因素,揭示深竖井井壁结构在服役期限内的损伤、失效机理,提出深部井筒支护材料的改善措施,为超深井井壁混凝土材料的选择提供可靠的理论依据。

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 diameter 75 mm and ultrasonic testing device.The stress and strain behavior,damage degree,energy input and dissipation 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 dissipative 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 deterioration 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 structures has more advantages.From the mul-ti-directional factors such as stress,strain,energy and damage,this paper reveals 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.