Abstract
Before the rock mass in the engineering is broken under load, it is usually in a state of varying degrees of damage. Aiming at the fracture characteristics of damaged sandstone under impact load, this paper adopts a method of the cyclic static load to cause the sandstone specimens to have varying degrees of damage. Then, the wave velocity of sandstone before and after the damage is measured using the nonmetallic acoustic velocimeter, and the change rule of damage factor is analyzed. Finally, the split Hopkinson pressure bar (SHPB) is used to test the impact dynamics of sandstone with different damage degrees. The broken rock block is screened by a vibrating screen, and the crushing characteristics are analyzed. The results show that not only the damage factor of damaged sandstone but the growth rate increases, with the raising upper limit of stress. Under the impact load of the same incident energy, the fragmentation degree of the damaged sandstone increases with the increase of the upper stress limit, while the average diameter of the broken rock block decreases gradually, and the reduction rate increases first and then decreases.
Highlights
Rocks are widely found in geotechnical engineering, such as coal mine roadways, tunnel engineering, roadbed engineering, water conservancy dams, and rock slopes [1, 2]. e natural rock is a complex geological fractured medium, with randomly distributed defects, such as joints and fractures [3, 4]
To analyze the fracture characteristics of sandstone with different damage degrees under the same strain rate, this paper focuses on the damage degree of sandstone as a variable
Many scholars use static load, dynamic load, and dynamic-static coupled loading methods to study the fracture characteristics of rock masses, but the fact that rock masses are often in different damage states affected by mining activities is ignored in most cases. ere are obvious differences in the scale and scale of internal cracks in rock masses with different degrees of damage
Summary
Rocks are widely found in geotechnical engineering, such as coal mine roadways, tunnel engineering, roadbed engineering, water conservancy dams, and rock slopes [1, 2]. e natural rock is a complex geological fractured medium, with randomly distributed defects, such as joints and fractures [3, 4]. The influence of cyclic load on the rock is considered, and the fracture characteristics under dynamic load based on different damage levels of the rock are analyzed. For the sake of exploring the fracture characteristics of damaged rocks under impact load, based on the Kaiser effect of rocks [19], the author uses cyclic loads applied on sandstone specimens with different upper stress limits to cause them to have different degrees of damage. The broken rock block is analyzed by a geometric fractal method, and the breaking characteristics of sandstone with different damage degrees under impact load are explored. The SHPB is adopted to study the breaking characteristics of the rock, and a geometric fractal test is performed on the broken rock blocks with a vibrating screen to analyze the fragmentation distribution of the damaged sandstone under impact load. It is assumed that any plane in the specimen remains flat during the propagation of the stress wave in the sandstone specimen, and there is only uniformly distributed axial stress on the cross section. rough the dynamic stress balance verification of the stress wave of each sandstone
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