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李地元*,肖鹏,谢涛,李夕兵.动静态压缩下岩石试样的长径比效应研究[J].实验力学,2018,33(1):93~100
动静态压缩下岩石试样的长径比效应研究
On the effect of length to diameter ratio of rock specimen subjected to dynamic and static compression
投稿时间: 2016-11-23  最后修改时间: 2017-02-05
DOI:10.7520/1001-4888-16-254
中文关键词:  花岗岩  抗压强度  分离式霍普金森压杆(SHPB)试验  长径比  尺寸效应
英文关键词:granite  compression strength  split Hopkinson pressure bar (SHPB) test  length to diameter ratio  size effect
基金项目:国家自然科学基金(51474250)、国家重点研发计划(2016YFC0600706)和教育部新世纪优秀人才支持计划(NCET-13-0588)
作者单位
李地元* 中南大学 资源与安全工程学院 湖南长沙 410083 
肖鹏 中南大学 资源与安全工程学院 湖南长沙 410083 
谢涛 中南大学 资源与安全工程学院 湖南长沙 410083 
李夕兵 中南大学 资源与安全工程学院 湖南长沙 410083 
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中文摘要:
      利用分离式霍普金森压杆(SHPB)实验装置和INSTRON1346液压伺服试验机分别对直径为50mm,长径比为0.5, 0.6, 0.8, 1.0, 1.2, 1.6, 2.0的花岗岩试样分别进行水平冲击试验和单轴压缩试验,研究岩石试样在动静态压缩下的长径比效应。结果表明:动态冲击试验中,长径比对试样两端的应力平衡状态有显著影响。随着试样长径比的增大(L/D>1.2),应力均匀化条件难以得到满足。试样的SHPB冲击破坏模式具有显著的长径比效应,随着长径比的增大,试样破碎程度降低,破坏模式由轴向劈裂破坏向轴向劈裂和层裂拉伸复合型破坏模式转变。在同应变率水平下,岩石的动态抗压强度随试样长径比的减小而减小(当L/D<1.2时),这与静载作用下岩石单轴抗压强度随长径比的减小而增大的变化规律有明显区别。对岩石类材料来说,长径比的变化对静态抗压强度的影响程度要高于对动态抗压强度的影响,主要是因为静载试验下加载板和试样之间的作用时间长,而动载作用时间很短,导致小长径比试样静载下具有明显的端部效应,从而得到相对更高的名义单轴抗压强度。
英文摘要:
      In this paper,based on split Hopkinson pressure bar (SHPB) and INSTRON1346 hydraulic servo testing machine, horizontal impact experiment and uniaxial compression experiment were carried out for granite specimens with diameter of 50mm and different length to diameter ratios of 0.5, 0.6, 0.8, 1.0, 1.2, 1.6 and 2.0, respectively, to study the effect of length to diameter ratio on rock mechanical behavior under dynamic and static compression. Experimental results show that in dynamic impact experiment, length to diameter ratio has a significant influence on stress equilibrium at both ends of specimen. With the increase of length to diameter ratio (L/D>1.2), the stress equilibrium condition at specimen's both ends is difficult to satisfy. The failure mode of specimen subjected to SHPB impact loading has remarkable length/diameter ratio effect. As the length to diameter ratio increases, the crushing degree of specimen decreases, and the failure mode transforms from axial split failure to axial split and spall tensile failure mixed mode. Under the condition of approximately same strain rate level, the dynamic compression strength of granite decreases with the decrease of length/diameter ratio when L/D<1.2. There is obvious difference between dynamic and static compression, in the later case, the uniaxial compression strength of rock increases with the decrease of length/diameter ratio. For rock materials, the effect of length to diameter ratio on static compression strength is more remarkable than that on dynamic compression strength. The main reason maybe is that under static loading, the loading time between loading plate and specimen is much longer than that in dynamic loading, which results in obvious end effect in static loading for specimen with smaller length/diameter ratio. Thus, relatively higher nominal uniaxial compressive strength is obtained in static loading.
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