1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; 2. Yanzhou Coal Mining Company Limited, Zoucheng 273500, China; 3. Guizhou Highway Engineering Group Co., Ltd., Guiyang 550008, China
Abstract:The stress relaxation properties of soft rock are an important aspect of its long-term mechanical properties, which are very important to keep soft rock tunnel long-term stability. The triaxial stress relaxation tests on argillaceous siltstone are carried out under confining pressures from 15 to 35 MPa. The relaxation curves can be divided into two stages: the transient relaxation and steady relaxation. When the stress relaxation starts with the initial deviatoric stress, which is much lower than the peak stress of the specimen, the relaxation is mainly composed of transient relaxation. However, when the initial deviatoric stress approaches to the peak stress of the specimen, obvious steady relaxation is observed. The comparisons of relaxation curves obtained from specimens under different confining pressures show that when the initial deviatoric stress is much lower than the peak stress of the specimen, the confining pressure has little effect on the relaxation behaviour of the specimen; and when the initial deviatoric stress approaches to the peak stress of the specimen, the relaxation stress decreases with the increase of the confining pressure. Based on the analysis on the results of triaxial relaxation tests, the Nishihara model is employed to describe the relaxation behaviour of argillaceous siltstone, and the comparisons between numerical and measured relaxation stress indicate the rationality of the Nishihara model.
[1] 孙 钧. 岩土材料流变及其工程应用[M]. 北京: 中国建筑工业出版社, 1999. (SUN Jun. Geotechnical material rheological and its engineering application[M]. Beijing: China Architecture and Building Press, 1999. (in Chinese)) [2] 冯 涛, 王文星, 潘长良. 岩石应力松弛试验及两类岩爆研究[J]. 湘潭矿业学院学报, 2000, 15(1): 27-31. (FENG Tao, WANG Wen-xing, PAN Chang-liang. Stress relaxation tests of rock and research on two types of rockbursts[J]. Journal of Xiangtan Mining Institute, 2000, 15(1): 27-31. (in Chinese)) [3] 唐礼忠, 潘长良. 岩石在峰值荷载变形条件下的松弛试验研究[J]. 岩土力学, 2003, 24(6): 940-942. (TANG Li-zhong, PAN Chang-liang. Experiment study on properties of stress relaxation of rock under deformation at peak load[J]. Rock and Soil Mechanics, 2003, 24(6): 940-942. (in Chinese)) [4] 唐礼忠, 潘长良, 谢学斌. 深埋硬岩矿床岩爆控制研究[J]. 岩石力学与工程学报, 2003, 22(7): 1067-1071. (TANG Li-zhong, PAN Chang-liang, XIE Xue-bin. Study on rockburst control in deep-seated hard ore deposit[J]. Chinese Journal of Rock Mechanics and Engineering, 2003, 22(7): 1067-1071. (in Chinese)) [5] 杨淑碧, 徐 进, 董孝璧. 红层地区砂泥岩互层状斜坡岩性研究[J]. 地质灾害与环境保护, 1996, 7(2): 12-24. (YANG Shu-bin, XU Jin, DONG Xiao-bi. Rheological feature of slope rcomposed of alternating beds of sandstone and mudstone iarea[J]. Journal of Geological Hazards and Environment Press, 1996, 7(2): 12-24. (in Chinese)) [6] 邱贤德, 庄乾城. 岩盐流变特性的研究[J]. 重庆大学学报 (自然学版), 1995, 18(4): 96-103. (QIU Xian-de, ZHUANG Qian-chen. Research on the rheology behavior of rock salt[J]. Journal of Chongqing University (Natural Science), 1995, 18(4): 96-103. (in Chinese)) [7] 熊良霄, 杨林德, 张 尧. 绿片岩多轴受压应力松弛试验研究[J]. 岩土工程学报, 2010, 32(8): 1158-1165. (XIONG Liang-xiao, YANG Lin-de, ZHANG Yao. Stress relaxation tests on green schist speimens under multi-axial compression[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(8): 1158-1165. (in Chinese)) [8] 于怀昌, 周 敏, 刘汉东, 等. 粉砂质泥岩三轴压缩应力松弛特性试验研究[J]. 岩石力学与工程学报, 2011, 30(4): 803-811. (YU Huai-chang, ZHOU Min, LIU Han-dong, et al. Experimental inverstigation on stress relaxation properties of silty mudstone under triaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering, 2011, 30(4): 803-811. (in Chinese)) [9] PENG S, PODNIEKS E R. Relaxation and the behavior of failed rock[J]. Int J Rock Mech Min Sci, 1972, 9: 699-712. [10] ZHANG Z L, XU W Y. Triaxial creep tests of rock from the compressive zone of dam foundation in Xiangjiaba Hydropower Station[J]. International Journal of Rock Mechanics and Mining Sciences, 2009, 46: 1103-1114. [11] 于怀昌, 李亚丽, 刘汉东. 粉砂质泥岩常规力学、蠕变以及应力松弛特性的对比研究[J]. 岩石力学与工程学报, 2012, 31(1): 60-69. (YU Huai-chang, LI Ya-li, LIU Han-dong. Comparative study of conventional mechanical, creep and stress relaxation properties of silty mudstone under triaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering, 2012, 31(1): 60-69. (in Chinese)) [12] 田洪铭, 陈卫忠, 赵武胜, 等. 宜-巴高速公路泥质红砂岩三轴应力松弛特性研究[J]. 岩土力学, 2013, 34(4): 981-986. (TIAN Hong-ming, CHEN Wei-zhong, ZHAO Wu- sheng. Analysis of triaxial stress relaxation properties of red silty mudstone of Yichang-Badong highway[J]. Rock and Soil Mechanics, 2013, 34(4): 981-986. (in Chinese)) [13] 夏才初, 孙 钧. 蠕变试验中流变模型辨识及参数确定[J].同济大学学报(自然科学版), 1996, 21(5): 498-503. (XIA Cai-chu, SUN Jun. Distinction of rheological model and determination of parameters on creep tests[J]. Journal of Tongji University (Nature Science), 1996, 21(5): 498-503. (in Chinese)) [14] 王志俭, 殷坤龙, 简文星, 等. 万州安乐寺滑坡滑带土松弛试验研究[J]. 岩石力学与工程学报, 2008, 27(5): 931-937. (WANG Zhi-jian, YIN Kun-long, JIAN Wen-xing, et al. Experimental research on stress relaxation of slip zone soils for Anlesi landslide in Wanzhou city[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(5): 931-937. (in Chinese)) [15] 李军世. 黏土蠕变-应力松弛耦合效应的数值探讨[J]. 岩土力学, 2001, 22(3): 294-297. (LI Jun-shi. Numerical discussion on coupled effects of creep and stress relaxation of clay[J]. Rock and Soil Mechanics, 2001, 22(3): 294-297. (in Chinese)))