作者机构：
[刘红娟; 谢水波] Institute of Nuclear Science and Technology, University of South China, Hengyang;Hunan;421001, China;Key Discipline Laboratory for National Defence for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang;[张希晨; 刘迎九; Zeng, Tao-Tao] Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, University of South China, Hengyang
通讯机构：
[Xie, S.-B.] I;Institute of Nuclear Science and Technology, University of South China, Hengyang, Hunan, China
通讯机构：
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
通讯机构：
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
通讯机构：
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
通讯机构：
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
作者机构：
[王清良; 陈鹏; 胡鄂明; 李乾] Nuclear Resources Engineering College, University of South China, Hengyang;Hunan;421001, China;Coorperative Innovation Center of Hunan Province for Nuclear Fuel Cycle Technology & Equipment, Hengyang;[王红强] Environmental and Safety Engineering College, University of south China, Hengyang
作者机构：
[Dai Bing] Univ South China, Nucl Resources Engn Coll, Hengyang 421001, Peoples R China.;[Zhao Guo-yan; Dai Bing] Cent S Univ, Sch Resources & Safety Engn, Changsha 410001, Hunan, Peoples R China.;[Konietzky, H.; Wasantha, P. L. P.; Dai Bing] TU Bergakad, Geotech Inst, D-09599 Freiberg, Germany.
通讯机构：
[Dai Bing] U;[Dai Bing] C;[Dai Bing] T;Univ South China, Nucl Resources Engn Coll, Hengyang 421001, Peoples R China.;Cent S Univ, Sch Resources & Safety Engn, Changsha 410001, Hunan, Peoples R China.
关键词：
damage evolution;loading and unloading;granitic rock;triaxial testing
摘要：
In-situ rock failures can result from stress changes due to pure loading and/or unloading. Understanding of the damage evolution behavior in brittle rocks during loading and unloading is imperative for the designs of rock structures. In this paper, we investigate the damage evolution characteristics of a granitic rock during loading and unloading after a series of triaxial experiments performed at different confining pressures. The axial stress-axial strain variations of the tested specimens revealed that the specimens undergoing unloading fail with a lower axial strain compared to the specimens failed purely by loading. Higher confining pressures were observed to exacerbate the difference. Volumetric strain versus axial strain curves indicated that the curves reverse the trend with the beginning of major damage of specimens. We suggest here a new form of equation to describe the secant modulus variation of brittle rocks against the axial stress for the unloading process. Failure mechanisms of tested specimens showed two distinct patterns, namely, specimens under pure loading failed with a single distinct shear fracture while for the unloading case specimens displayed multiple intersecting fractures. In addition, analysis of the evolution of dissipation and elastic energy during deformation of the specimens under loading and unloading conditions showed differentiable characteristics. Moreover, we evaluated the variations of two damage indices defined based on the energy dissipation and secant modulus evolution during deformation and observed that both of them satisfactorily distinguish key stages of damage evolution.
通讯机构：
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
作者机构：
[章求才; 贺桂成; 张志军] School of Nuclear Resources Engineering, University of South China, Hengyang;Hunan;421001, China;[黄炳香] State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou;Jiangsu
通讯机构：
[He, G.] S;School of Nuclear Resources Engineering, University of South China, Hengyang, Hunan, China
作者机构：
[彭贯军; 朱忠华; 陶干强] Nuclear Resources Engineering College, University of South China, Hengyang, Hunan 421001, China;[代碧波] Sino Steel Maanshan Institute of Mining Research CO., LTD, Maanshan, Anhui 243000, China
