Abstract
Taking the briquette sample as research object, the influence of the incremental impulse (momentum) on the damage of coal-rock under different uniaxial axial pressure was studied by using the self-developed pendulum impact dynamic loading test device, cooperating with the ultrasonic detection device. Meanwhile, the influence of constant impulse on the damage degree of coal-rock was compared. The results show that the damage degree of coal-rock increases with the increase of the impulse, and the damage fitting curve is upward concave, indicating that the coal sample tends to accelerating failure. Moreover, with the increase of axial pressure, the variation gradient of the damage degree of coal-rock tends to moderate and the cumulative damage degree decreases under the same impulse, and the impact resistance of coal-rock increases. When the impulse is constant, the damage degree of coal-rock increases with the number of impact, and the damage curve is upward convex, indicating that coal-rock has a tendency to slow down the damage. The cumulative damage degree of coal-rock decreases with the increase of axial pressure, and the number of impact needed to destroy coal-rock is increased. In addition, the damage model of coal-rock was proposed, and the criterion of coal-rock damage was obtained, which shows that the damage degree of coal-rock increases with the increase of impact load and decreases with the increase of static axial load.
Highlights
Most rocks in nature lie in the complicated environment where there is a combination of confining pressure and dynamic loads, and some are under unidirectional constraints
Viaduct piers suffers dynamic disturbance when a high-speed train is going by on them. All these engineering problems can be simplified to study the effect of dynamic impact on rock under unidirectional constraint. e researches on damage of rock under impact loading have been quite mature so far
The damage degree under the axial compression constraint of 0 is much more obvious, indicating that the greater the axial compression, the smaller the cumulative damage degree. is is mainly due to the fact that when the axial compression is greater, the internal microfractures of the coal-rock close up gradually, which leads to less microfractures in coal-rock and difficult propagation, when the coal-rock is subject to incremental impulse impact load
Summary
Most rocks in nature lie in the complicated environment where there is a combination of confining pressure and dynamic loads, and some are under unidirectional constraints (one-dimensional static loads). Viaduct piers suffers dynamic disturbance when a high-speed train is going by on them All these engineering problems can be simplified to study the effect of dynamic impact on rock (coal-rock) under unidirectional constraint. The research on the coupling relationship between unidirectional static load constraint, impact load, and damage evolution of coal-rock internal structure is still insufficient. It is of great theoretical significance and practical value to study the impact load on coal-rock damage under static load constraint. Erefore, regarding coal-rock as the object, the damage evolution law of coalrock under unidirectional constraint was studied after coalrock was subjected to the impact of incremental impulse, and the effects of constrained static load and impact load on coal-rock damage were analyzed. During the generation of the damage, there will be different acoustic characteristics and ultrasonic transmission parameters. erefore, the quantity change factor of the internal structure of rock-like material after each impact can be calculated by establishing the relationship between the ultrasonic velocity and the damage degree of rock-like material, and the damage degree of rock materials can be calculated by indirect statistics
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