Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads
ObjectiveDeep rock masses are usually in varying damage degrees induced by excavation disturbance before dynamic catastrophes appear. The complex and ever-changing occurrence environment in deep areas places higher demands on the stability of deeply buried rock masses and the prevention and control...
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Editorial Department of Journal of Sichuan University (Engineering Science Edition)
2025-01-01
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| Series: | 工程科学与技术 |
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| Online Access: | http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202400700 |
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| author | ZHENG Qiangqiang LI Pingfeng XU Ying YIN Zhiqiang HU Hao |
| author_facet | ZHENG Qiangqiang LI Pingfeng XU Ying YIN Zhiqiang HU Hao |
| author_sort | ZHENG Qiangqiang |
| collection | DOAJ |
| description | ObjectiveDeep rock masses are usually in varying damage degrees induced by excavation disturbance before dynamic catastrophes appear. The complex and ever-changing occurrence environment in deep areas places higher demands on the stability of deeply buried rock masses and the prevention and control of dynamic disasters. In response to the dynamic response of damaged rock masses during dynamic catastrophes, the mechanical characteristics of pre-compressed sandstone under impact compression and splitting tensile loads are studied.MethodsFirstly, acoustic emission is used to monitor the damage degree of sandstone after different upper limit static loads, and tomography was employed to verify the damage degrees. The upper limit of static load is 20%, 40%, 60%, and 80% of the uniaxial compressive strength of sandstone, and the lower limit of cyclic load is uniformly set to 2kN with 6 cycles. Then, the dynamic strength, fracture process, and energy evolution of damaged sandstone under impact compression and splitting tensile loading at impact pressures of 0.30, 0.35, and 0.40 MPa are studied by the split Hopkinson pressure bar (SHPB) and high-speed camera. Finally, the strain field evolution of the damaged sandstone under impact splitting tensile loading and the fragmentation characteristics of the damaged sandstone under impact compressive loading are investigated by adopting digital image correlation (DIC) and fractal dimension, respectively.Results and Discussions Sandstone exhibits varying degrees of damage after being subjected to cyclic static loads with different upper limits. The time-lapse double-difference tomography, based on acoustic emission monitoring, provides clear evidence of this phenomenon and further confirms the heterogeneous distribution of damage within the loaded rock. Due to the effects of cyclic static loads, internal defects in the damaged sandstone influence the propagation of stress waves under impact loads. This results in significant variations in dynamic compressive strength, dynamic splitting tensile strength, and dissipated energy density, with the dynamic strength decreasing as the degree of sandstone damage increases, while the energy dissipation density exhibits the opposite trend. High-speed camera footage of the fracture process of damaged sandstone under impact load reveals four stages: initial deformation, crack initiation, formation of fractured rock blocks, and ejection of fractured rock blocks. The degree of damage significantly affects the fracture process, particularly under high-strain rate impact loads. As the impact pressure or degree of sandstone damage increases, the number and scale of crack initiations also increase, during the crushing and fragmentation stage, the number of broken rock blocks rises, and circumferential cracking may occur. Moreover, the degree of fragmentation of the sandstone also increases, while the fragmentation size decreases, and the quantity of fragmented pieces increases after the application of impact compression load. The stress wave propagates through the sandstone under impact splitting tensile load, creating a strain concentration zone at the center, which then expands radially toward the rock-to-rod contact surface. During this expansion in the strain concentration zone, cracks initiate at the center of the specimen and progressively develop, eventually penetrating the entire sandstone specimen. As impact pressure or the degree of damage increases, the strain caused by initial cracking at the specimen's center also increases. Furthermore, both the strain and the extent of its influence grow with higher impact pressure or greater damage.ConclusionsThe change of dynamic mechanical properties of damaged sandstone is closely related to the damage degree of sandstone after static load. With the increase of impact air pressure or the damage degree of sandstone, the dynamic strength reduction rate and the growth rate of energy dissipation density of the damaged sandstone under impact loading (impact compression and impact split tension) are both Weibull cumulative distribution functions related to the ratio of static load upper limit to static strength. The fragmentation degree of damaged sandstone after impact compression loading and the strain at the center of the specimen at the same moment under impact splitting tensile loading increase with the increase of sandstone damage degree, and the higher the impact air pressure, the smaller the variability of the crushing degree and strain concentration caused by the distinct damage degrees. Moreover, sandstones with higher damage degrees showed circumferential rupture and spall under higher impact compression and split tensile loading, respectively. The research results provide some references for studying dynamic strength, energy evolution, and fragmentation characteristics of damaged rock masses and risk mitigation when dynamic catastrophes manifest. |
| format | Article |
| id | doaj-art-7b4c8f01a51e46b3a2fe4ac174a129f9 |
| institution | DOAJ |
| issn | 2096-3246 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | Editorial Department of Journal of Sichuan University (Engineering Science Edition) |
| record_format | Article |
| series | 工程科学与技术 |
| spelling | doaj-art-7b4c8f01a51e46b3a2fe4ac174a129f92025-08-20T02:47:35ZengEditorial Department of Journal of Sichuan University (Engineering Science Edition)工程科学与技术2096-32462025-01-0111385450414Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loadsZHENG QiangqiangLI PingfengXU YingYIN ZhiqiangHU HaoObjectiveDeep rock masses are usually in varying damage degrees induced by excavation disturbance before dynamic catastrophes appear. The complex and ever-changing occurrence environment in deep areas places higher demands on the stability of deeply buried rock masses and the prevention and control of dynamic disasters. In response to the dynamic response of damaged rock masses during dynamic catastrophes, the mechanical characteristics of pre-compressed sandstone under impact compression and splitting tensile loads are studied.MethodsFirstly, acoustic emission is used to monitor the damage degree of sandstone after different upper limit static loads, and tomography was employed to verify the damage degrees. The upper limit of static load is 20%, 40%, 60%, and 80% of the uniaxial compressive strength of sandstone, and the lower limit of cyclic load is uniformly set to 2kN with 6 cycles. Then, the dynamic strength, fracture process, and energy evolution of damaged sandstone under impact compression and splitting tensile loading at impact pressures of 0.30, 0.35, and 0.40 MPa are studied by the split Hopkinson pressure bar (SHPB) and high-speed camera. Finally, the strain field evolution of the damaged sandstone under impact splitting tensile loading and the fragmentation characteristics of the damaged sandstone under impact compressive loading are investigated by adopting digital image correlation (DIC) and fractal dimension, respectively.Results and Discussions Sandstone exhibits varying degrees of damage after being subjected to cyclic static loads with different upper limits. The time-lapse double-difference tomography, based on acoustic emission monitoring, provides clear evidence of this phenomenon and further confirms the heterogeneous distribution of damage within the loaded rock. Due to the effects of cyclic static loads, internal defects in the damaged sandstone influence the propagation of stress waves under impact loads. This results in significant variations in dynamic compressive strength, dynamic splitting tensile strength, and dissipated energy density, with the dynamic strength decreasing as the degree of sandstone damage increases, while the energy dissipation density exhibits the opposite trend. High-speed camera footage of the fracture process of damaged sandstone under impact load reveals four stages: initial deformation, crack initiation, formation of fractured rock blocks, and ejection of fractured rock blocks. The degree of damage significantly affects the fracture process, particularly under high-strain rate impact loads. As the impact pressure or degree of sandstone damage increases, the number and scale of crack initiations also increase, during the crushing and fragmentation stage, the number of broken rock blocks rises, and circumferential cracking may occur. Moreover, the degree of fragmentation of the sandstone also increases, while the fragmentation size decreases, and the quantity of fragmented pieces increases after the application of impact compression load. The stress wave propagates through the sandstone under impact splitting tensile load, creating a strain concentration zone at the center, which then expands radially toward the rock-to-rod contact surface. During this expansion in the strain concentration zone, cracks initiate at the center of the specimen and progressively develop, eventually penetrating the entire sandstone specimen. As impact pressure or the degree of damage increases, the strain caused by initial cracking at the specimen's center also increases. Furthermore, both the strain and the extent of its influence grow with higher impact pressure or greater damage.ConclusionsThe change of dynamic mechanical properties of damaged sandstone is closely related to the damage degree of sandstone after static load. With the increase of impact air pressure or the damage degree of sandstone, the dynamic strength reduction rate and the growth rate of energy dissipation density of the damaged sandstone under impact loading (impact compression and impact split tension) are both Weibull cumulative distribution functions related to the ratio of static load upper limit to static strength. The fragmentation degree of damaged sandstone after impact compression loading and the strain at the center of the specimen at the same moment under impact splitting tensile loading increase with the increase of sandstone damage degree, and the higher the impact air pressure, the smaller the variability of the crushing degree and strain concentration caused by the distinct damage degrees. Moreover, sandstones with higher damage degrees showed circumferential rupture and spall under higher impact compression and split tensile loading, respectively. The research results provide some references for studying dynamic strength, energy evolution, and fragmentation characteristics of damaged rock masses and risk mitigation when dynamic catastrophes manifest.http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202400700impact loaddamaged sandstonedynamic strengthenergy evolutionSHPB. |
| spellingShingle | ZHENG Qiangqiang LI Pingfeng XU Ying YIN Zhiqiang HU Hao Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads 工程科学与技术 impact load damaged sandstone dynamic strength energy evolution SHPB. |
| title | Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads |
| title_full | Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads |
| title_fullStr | Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads |
| title_full_unstemmed | Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads |
| title_short | Energy evolution and dynamic response characteristics of damaged sand-stone caused by pre-compression under impact loads |
| title_sort | energy evolution and dynamic response characteristics of damaged sand stone caused by pre compression under impact loads |
| topic | impact load damaged sandstone dynamic strength energy evolution SHPB. |
| url | http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202400700 |
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