冲击载荷作用下岩石动态断裂试验研究

以自行研制的可调速落锤冲击试验机进行加载，通过高速相机搭建数据采集系统，采用数字散斑相关方法作为试验的观测方法，开展5组不同预制裂纹长度的花岗岩试件在冲击载荷作用下的动态断裂试验。并对岩石I型裂纹在冲击载荷作用下的位移场演化、裂纹动态断裂的裂尖张开位移、裂纹尖端的扩展历史、动态断裂的应力强度因子进行了定量研究。试验结果表明：对于单一试件而言，在落锤开始与岩石试件的边界接触到试件的预制裂纹开始扩展整个过程中，裂纹尖端的应力强度因子KI呈递增趋势，KII与KI相比，相差1～2个数量级。对于不同预制裂纹试件，在落锤冲击加载作用下，总体表现为一定的预制裂纹长度范围内，随着预制裂纹的长度增加，裂纹尖端应力强度因子呈增加的趋势。

Experiment study of the dynamic fractures of rock under impact loading

Five groups of impact load-driven fracturing experiments were performed on the granite specimens with different pre-existing crack lengths. The dynamic load was generated by a self-developed impact equipment with an adjustable dropping velocity hammer. The fracturing process of the sample was monitored by using high speed cameras with digital acquisition and the digital speckle correlation method. The characteristics of the dynamic fractures of Type I in the rock specimens under impact loading are quantitatively analyzed, including the development of displacement, the opening displacement of crack tip, expansion history of crack tip and stress intensity factor of dynamic fracturing. Experimental results show that from the moment that the hammer dropped down to the moment when the cracking process began, the crack tip stress intensity factor KI for an individual specimen constantly increase, and the magnitude of KI is greater than that of KII by 1-2 orders. For different specimens with pre-cracks under impact loading, stress intensity factor increases with the pre-cracking length.