Abstract
This paper aims to reveal the mechanical properties, energy evolution characteristics, and dynamic rupture process of preflawed granite under impact loading with different rock bridge angles and strain rates. A series of dynamic impact experiments were conducted along with the separate Hopkinson press bar (SHPB) testing system to analyze and study the overall rock fracture process. Under the impact load, the peak stress of granite increases with the increase of rock bridge angle and strain rate, but the increase gradually decreases. The peak strain also increases gradually with the increase of rock bridge angle, but there is an upper limit value; the total input strain energy increases with the increase of strain rate and rock bridge angle. It is shown that the higher the strain rate, the higher the unit dissipation energy, and the greater the degree of rock fragmentation. For rock under impact loads, the crack first initiates from the wing end of the prefabricated flaw, the preflaw closes gradually, and finally the crack propagates at the locking section leading to the coalescence of rock bridge. With the increase of strain rate, the fragmentation degree of the specimen increases asymptotically, and the average fragmentation size of the specimen decreases with the increase of strain rate. It is suggested that the stability of large rocked slopes is controlled by the locked section, and understanding the fracture evolution of the rock bridge is the key to slope instability prediction.
Highlights
Most of the studies on the mechanical properties of jointed rocks are conducted by means of static loading tests; in addition, most of the studies on the characteristics of jointed rock masses under impact dynamic loading are focused on intact rock. e damage and fracture mechanism of the preflawed rock subjected to dynamic impacting loads are not well understood. erefore, in order to reveal the effects of different joint angles and strain rates on the dynamic response of rock materials, separate Hopkinson press bar (SHPB) impact testing was conducted on fissure-prefabricated specimens with different angles to analyze the effects of different joint angles and strain rates on the dynamic stress-strain analysis, energy evolution, and dynamic fracturing process
The peak stress increases with increasing strain rate, but the increase is smaller and smaller. is is because there is a certain delayed response of the rock under the impact load, and the strength of the rock will increase with the increase of strain rate, tending to the upper limit of strength
Granite specimens with prefabricated different rock bridge angles were dynamically loaded using the SHPB loading method to investigate the stress-strain and energy as well as their dynamic rupture processes
Summary
In the current mining process, blasting is an important means of extraction, and along with the effects of exiting, excavation, and blasting operations, the rock masses in the open pit slope are disturbed by dynamic loads to varying degrees; it is necessary to reveal the influence of impact dynamics on rock instability [1,2,3]. e natural fractures in the mine rock are not continuous, and the discontinuous fractures form a kind of rock bridges (i.e., rock-locked sections) [4, 5]. e stress conditions at rock bridges are often more complex due to the greater shear stresses, and the presence of rock bridges can increase the strength of the weak surfaces of the rock mass, which is called the locking effect of rock bridges on intermittent jointed rock masses [6, 7]. e fracture of rock bridges leads to the connection of joints, and destabilization damage will occur only when all rock bodies are connected by the previous fractures [8]. erefore, the fracture mechanism of rock bridges needs to be studied to ensure the stability of rock masses in open pit mines and the safety of mining. E impact compression test of these three types of rocks was conducted to compare the stress wave propagation characteristics, dynamic stress-strain relationship, degree of fragmentation, and energy dissipation law. Most of the studies on the mechanical properties of jointed rocks are conducted by means of static loading tests; in addition, most of the studies on the characteristics of jointed rock masses under impact dynamic loading are focused on intact rock. Erefore, in order to reveal the effects of different joint angles and strain rates on the dynamic response of rock materials, SHPB impact testing was conducted on fissure-prefabricated specimens with different angles to analyze the effects of different joint angles and strain rates on the dynamic stress-strain analysis, energy evolution, and dynamic fracturing process Most of the studies on the mechanical properties of jointed rocks are conducted by means of static loading tests; in addition, most of the studies on the characteristics of jointed rock masses under impact dynamic loading are focused on intact rock. e damage and fracture mechanism of the preflawed rock subjected to dynamic impacting loads are not well understood. erefore, in order to reveal the effects of different joint angles and strain rates on the dynamic response of rock materials, SHPB impact testing was conducted on fissure-prefabricated specimens with different angles to analyze the effects of different joint angles and strain rates on the dynamic stress-strain analysis, energy evolution, and dynamic fracturing process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
