Abstract
Investigation of the damage characteristics of rock material under the combined effect of cyclic load and impact load is extremely crucial for many mining engineering applications. Based on energy dissipation theory, we considered factors such as circulation times, the cyclic stress of a uniaxial cyclic load test, and the impact pressure (strain rate) of a split Hopkinson pressure bar (SHPB) test, studying the damage mechanism of red sandstone under the combined action of a uniaxial cyclic and impact loads. We found that when the load stress is 60%, 70%, and 80% of the uniaxial compressive strength (UCS) of red sandstone, the stress can still promote the development of microcracks and the generation of new cracks in the rock, increasing the inner damage of the rock so that it reduces the rock strength. As the cyclic time increases, the energy dissipation ratio presented a trend of decreasing dramatically and then maintaining basically no change, and the peak strain and the damage variable of the rock both increased first and then tended to remain relatively constant. The damage variable of the rock specimen under the combined action of the uniaxial cyclic loading and impact load had a significant corresponding relationship with the initial damage. As the rock specimen initial damage increases, the damage variable and the peak stress of the rock specimen both decreases almost linearly with initial damage. Meanwhile, the average particle diameter of the rock specimen after breakage gradually increased, showing a positively correlated tendency. The ratio between the fragment quality of the bigger particle diameter in the total rock specimen quality gradually increased. Under the conditions of the same initial damage, a higher impact pressure resulted in smaller rock fragment average particle diameters.
Highlights
Rock masses often suffer from the combined action of cyclic loads and impact loads in many mining engineering applications [1,2,3]
(1) Under the condition keeping the lower limit the generate cyclic stress unchanged, the damage, damage variable of the rock specimen redefined in the cyclic loading test simultaneously considers the reducing of thethe rockrock strength
If theredefined impact load acted on such basis,test rocksimultaneously with damage will more variable specimen inisthe cyclic loading considers the influence of the energy dissipation ratio of the rock under single cycle and the circulation number, so fail than rock without influence of the energydamage
Summary
Rock masses often suffer from the combined action of cyclic loads and impact loads in many mining engineering applications [1,2,3]. The rock bench above slopes in an open pit coal mine are usually subjected to combined action of the cyclic loads of passing heavy trucks and the impact loads of blasting. Energies 2020, 13, 2154 and the shockwave generated by blasting may have a strong load effect on rock slopes [6,7]. Basic research on the rock damage behavior under the combined action of cyclic load and impact load is vital for optimizing engineering designs and preventing geological disasters
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