Abstract
In order to study the fragmentation energy dissipation characteristics of cemented sand specimens under confining pressure and impact loads, the energy consumption of cemented sand specimens was analyzed through an impact compression and split test performed at different loading rates with different impact pressures by using a variable cross section SHPB (split Hopkinson pressure bar) with an active confining pressure loading apparatus. The results show that (1) the absorbed energy and incident energy were in a linear relationship and the proportion between them was relatively constant under confining pressure, and the absorbed energy had a quadratic relationship with the incident energy under zero confining pressure. (2) The fracture energy ratio increased with the increase in incident energy, the damage energy ratio decreased with the increase in incident energy, and the damage energy ratio were always higher than the fracture energy ratio under confining pressure. (3) The energy absorbed by the cemented sand specimens decreased sharply with the increase of confining pressure under the same incident wave energy conditions, and the reflected wave energy and transmitted wave energy increased. (4) When the incident wave energy was constant, the ratio of the energy causing surface fractures to the energy absorbed by the cemented sand specimens decreased sharply with the increase of confining pressure, while the energy causing crack growth and damage increased sharply. These conclusions may guide similar models of blasting tests in the future.
Highlights
As underground construction work in China continues to increase in depth, their geological conditions are becoming more and more complicated. erefore, deep rock mass mechanics has become a major issue relating to state property and public safety, and this has led to focus on rock mass mechanics and underground engineering in China and around the world [1,2,3,4,5].For the purposes of deep resource exploitation, the creation and growth of cracks in deep surrounding rock caused under dynamic blasting loads are still unclear due to high crustal stress
Is paper establishes a relationship between degree of fragmentation and energy based on the analysis on the degree of fragmentation and energy of cemented sand measured under confining pressure and impact load, obtains the fragmentation energy consumption factor of the cemented sand according to the results of the fragmentation, screening, and energy calculation of SHPB test specimens and energy calculation, and analyzes the relationship between the fragmentation and fracture energy of the cemented sand and the confining pressure. ese research findings are of great importance to guide similar future test models for deep rock mass blasting
Engineering Prototype and Stress Loading Apparatus. e prototype of this simulation test of deep rock mass blasting was a model of extrathick hard roof used in deep coal mines. e crustal stress field of the mining area focuses on the area where the roof was located relative to horizontal tectonic stress. e measured horizontal lateral pressure coefficient of the stress was 1.5. e underground elevation was −706.3 to −760.1 m, and the thickness was 35 to 55 m
Summary
As underground construction work in China continues to increase in depth, their geological conditions are becoming more and more complicated. erefore, deep rock mass mechanics has become a major issue relating to state property and public safety, and this has led to focus on rock mass mechanics and underground engineering in China and around the world [1,2,3,4,5]. Previous research shows that rocks under external force will undergo stages such as microcrack closure, elastic deformation, microdefect evolution and expansion, and catastrophic failure During these stages, the rocks are always exchanging energy with the surrounding environment, converting the mechanical energy from the surrounding environment into strain energy and thermal energy and storing them as their own internal energy. In the similar testing models for deep rock mass blasting (part of the National Natural Science Foundation Program of China), a cemented sand substitute was subject to the dynamic load from explosive blasting and a static load generated by active confining pressure to simulate crustal stress. Its deformation and fragmentation process, just like that of rocks, inevitably resulted in energy exchange with the surrounding environment, and the subsequent degree of fragmentation and energy dissipation featured characteristics of self-similarity. Is paper establishes a relationship between degree of fragmentation and energy based on the analysis on the degree of fragmentation and energy of cemented sand measured under confining pressure and impact load, obtains the fragmentation energy consumption factor of the cemented sand according to the results of the fragmentation, screening, and energy calculation of SHPB test specimens and energy calculation, and analyzes the relationship between the fragmentation and fracture energy of the cemented sand and the confining pressure. ese research findings are of great importance to guide similar future test models for deep rock mass blasting
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