Experimental study on failure characteristics of rock mass with interfacial cracks under impact loading
This study explores the macroscopic dynamic mechanical properties,crack propagation rules and failure mechanisms of plate specimens with prefabricated interface cracks.A separate Hopkinson pressure bar was used to apply impact dynamic loads of different strengths to three specimens with different interface inclination angles,and a high-speed camera system was used to record the crack expansion process.The research results show that the dynamic stress-strain curve shapes of different types of samples are quite different,showing single or double peaks at the stress peak.The smaller the incident wave peak,the greater the influence of the joint plane angle on the dynamic compressive strength of the sample.A total of 6 crack types were identified based on the crack shape,crack initiation position and fracture mechanism.As the incident energy increases,the number of cracks in the sample increases,and the sample changes from a single splitting tensile failure mode to a complex tensile-shear composite failure mode.A"transition zone"of material strength is formed at the specimen interface.Factors such as the interface inclination,the elastic modulus of the rock masses on both sides,and Poisson's ratio determine the stress state and strength characteristics of the transition zone.The sample cracks first at the end of the prefabricated crack and the new cracks will generally expand across the weak-side strengthening zone and the weak-side part.As the peak stress of the incident wave increases,they will transform from type Ⅰ tensile cracks to type Ⅱ or type Ⅲ shear cracks.Far-field cracks appear relatively more on the weak side,while tensile cracks only appear on the strong side.The interface and prefabricated cracks create a complex stress environment and strength conditions in different areas of the specimen,making the crack interface and crack tip jointly dominate the typical crack path.Experimental research on the failure characteristics of rock masses containing interface cracks is the basis for the calculation of crack propagation in layered rock masses at an engineering scale and is of great significance for solving engineering stability problems of layered rock masses.
rock mechanicsdynamic compression testbedded rockinterfacial crackmechanical propertycrack path
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