Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources, Yangtze River Scientific Research Institute, Wuhan 430010, China
Abstract:Two in-situ plate-loading creep tests on fracture shale in Goupitan Hydropower Station are conducted, in which the pressure is at the same engineering stress level and is loaded under one cycle pattern and the test durations are 1686 and 2299 h, respectively. Some creep characteristics of the soft rock are revealed as follows: (1) Under the engineering stress level, after decelerating creep at the initial stage and the subsequent constant-rate creep continuing for a period of 682 and 910 h, the creep rate tends to zero instead of occurrence of plastic flow, showing that the creep is the attenuation creep in total. (2) After unloading, there's instantly rebound deformation and anelasticity and residual deformation, which is over 50% of the total deformation. A kind of one-way spring element ([HI]), which will behave as elastic object under pressure but not rebound after unloading, is used to describe the residual deformation. By connecting the [HI] element with the generalized Kelvin model, a changed generalized Kelvin model is established. It has simple components and can comprehensively describe the creep features of soft rock, that is, it is the attenuation creep while loading and there is the residual deformation after unloading. The constitutive equation of the model is derived, and the creep formula is also derived based on the corresponding principle. The model parameters are inversed by taking the creep formula to fit the trial curves.
[1] 刘学增, 王华军, 周 敏, 等. 板岩流变特性试验与模型辨识[J]. 同济大学学报(自然科学版), 2010, 38(5): 664-672. (LIU Xue-zeng, WANG Hua-jun, ZHOU Min, et al. Rheological tests of slates and model identification of rocks[J]. Joural of Tongji University (Natural Science), 2010, 38(5): 664-672. (in Chinese)) [2] 张强勇, 向 文, 杨文东, 等. 坝区岩体蠕变参数反演与边坡开挖流变计算分析[J]. 武汉大学学报, 2008, 41(5): 72-76,96. (ZHANG Qiang-yong, XIANG Weng, YANG Weng-dong, et al. Creep parameters inversion for dam zone rockmass and rheological computational analysys of slope excavation[J]. Engineering Journal of Wuhan University, 2008, 41(5): 72-76,96. (in Chinese)) [3] 周火明, 徐 平. 三峡永久船闸边坡现场岩体压缩蠕变试验研究[J]. 岩石力学与工程学报, 2001, 20(增刊): 1882-1885. (ZHOU Huo-ming, XU Ping. In-situ testing study on compressive creep behavior of rock mass in Three Gorges Project shiplock slopes[J]. Chinese Journal of Rock Mechanics and Engineering, 2001, 20(S0): 1882-1885. (in Chinese)) [4] 熊诗湖, 周火明, 钟作武. 岩体载荷蠕变试验方法研究[J].岩石力学与工程学报, 2009, 28(10): 2121-2127. (XIONG Shi-hu, ZHOU Huo-ming, ZHONG Zuo-wu. Study on methodology of plate-loading creeptest of rockmass[J]. Chinese Journal of Rock Mechanics and Engineering, 2009, 28(10): 2121-2127. (in Chinese)) [5] 陈文玲, 赵法锁, 弓虎军. 基于微观试验的云母石英片岩三轴蠕变机制研究[J]. 岩石力学与工程学报, 2010, 29(增刊2): 3578-3584. (CHEN Wen-ling, ZHAO Fa-suo, GONG Hu-jun. Study of triaxial creep mechanism of mica-quartz schist based on microscopic test[J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(S2): 3578-3584. (in Chinese)) [6] 范庆忠, 高延法, 崔希海, 等. 软岩非线性蠕变模型研究[J].岩土工程学报, 2007, 29(4): 505-508. (FAN Qing-zhong, GAO Yan-fa, CUI Xi-hai, et al. Study o n nonlinear creep model of soft rock[J]. Chinese Journal of Geotechnical Engineering, 2007, 29(4): 505-508. (in Chinese)) [7] 张治亮, 徐卫亚, 王 伟. 向家坝水电站坝基挤压带岩石三轴蠕变试验及非线性黏弹塑性蠕变模型研究[J]. 岩石力学与工程学报, 2011, 30(1): 132-140. (ZHANG Zhi-liang, XU Wei-ya, WANG Wei. Study of triaxial creep tests and its nonlinear visco-elastoplastic creep model of rock from compressive zone of dam foundation in Xiangjiaba hydropower staion[J]. Chinese Journal of Rock Mechanics and Engineering, 2011, 30(1): 132-140. (in Chinese)) [8] 闫子舰, 夏才初, 李宏哲, 等. 分级卸荷条件下锦屏大理岩流变规律研究[J]. 岩石力学与工程学报, 2008, 27(10): 2153-2159. (YAN Zi-jian, XIA Cai-chu, LI Hong-zhe, et al. Study on rheological rules of marble in jinpi ng hydropower station under condition of step unloading[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(10): 2153-2159. (in Chinese)) [9] 蒋昱州, 朱杰兵, 王瑞红. 软硬互层岩体卸荷蠕变力学特性试验研究[J]. 岩石力学与工程学报, 2012, 31(4): 778-784. (JIANG Yu-zhou, ZHU Jie-bing, WANG Rui-hong. Experimental study of unloading creep mechanical properties alternatively distributed soft and hard rockmass[J]. Chinese Journal of Rock Mechanics and Engineering, 2012, 31(4): 778-784. (in Chinese)) [10] 夏才初, 闫子舰, 王晓东, 等. 大理岩卸荷条件下弹黏塑性本构关系研究[J]. 岩石力学与工程学报, 2009, 28(3): 459-466. (XIA Cai-chu, YAN Zi-jian, WANG Xiao-dong, et al. Experimental research on mechanical properties of limestone containing natural joints under loading and unloading conditions[J]. Chinese Journal of Rock Mechanics and Engineering, 2009, 28(3): 459-466. (in Chinese)) [11] 朱杰兵, 汪 斌, 邬爱清. 锦屏水电站绿砂岩三轴卸荷流变试验及非线性损伤蠕变本构模型研究[J]. 岩石力学与工程学报, 2010, 29(3): 528-534. (ZHU Jie-bing, WANG Bin, WU Ai-qin. Study of unloading triaxial rheological tests and its nonlinear damage constitutive model of Jinping station green sandstone[J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(3): 528-534. (in Chinese)) [12] 谌文武, 原鹏博, 刘小伟. 分级加载下薄层状岩石蠕变特性研究[J]. 岩石力学与工程学报, 2009, 28(增刊1): 3076-3081. (CHEN Wen-wu, YUAN Peng-bo, LIU Xiao-wei, et al. Study on creep properties of red-bed soft rock under step load[J]. Chinese Journal of Rock Mechanics and Engineering, 2009, 28(S1): 3076-3081. (in Chinese)) [13] 赵延林, 曹 平, 文有道, 等. 岩石弹黏塑性流变试验和非线性流变模型研究[J]. 岩石力学与工程学报, 2008, 27(3): 477-486. (ZHAO Yan-lin, CAO Ping, WEN You-dao, et al. Elastovisco-plastic rheological experiment and nonlinear rheological model of rocks[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(3): 477-486. (in Chinese))