空隙特征对砂岩水致劣化规律的影响
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摘要
针对南京秦淮东河开挖后的稳定性问题,选取黄马青组(T_(2h))砂岩为研究对象,对砂岩在吸水-干燥循环条件下的单轴抗压、抗拉特性进行试验研究。考虑到未来边坡运营过程中水的影响,试验时分别考虑自然吸水和饱和吸水两种情况。根据试验结果对所研究砂岩的空隙特征、水致劣化特征和劣化机制进行了详细分析。随着吸水-干燥循环次数增加,岩石的抗压、抗拉强度和凝聚力均呈劣化趋势,说明循环次数的增加对岩石的损伤有累积作用。岩石自然吸水条件下(小开空隙未进水时)强度和弹性模量下降速度较慢,而饱和吸水条件下(开空隙被水充满时)强度和弹性模量下降速度较快,表明岩石中小开空隙对岩石的劣化效果显著。微观结构分析结果表明,随着吸水-干燥循环次数增加,岩石中空隙率增大。结合抗剪强度特征分析认为,干-湿循环导致岩石的黏结强度不断下降,而摩擦强度变化较小,表明黏结强度劣化是岩石水致劣化的主要原因,干-湿循环导致水-岩反应,岩石颗粒胶结物发生松散,边缘发生开裂,宏观上表现为岩石劣化。该研究成果对于新开挖河道边坡稳定性分析具有较大的参考价值,为河岸边坡的长期稳定性分析提供了依据。
In this paper, the sandstones of the Huangmaqing Group(T_(2h)) were taken as the study object. The compressive and tensile tests were carried out on the rock samples, considering the influencing factors of the slope along the Qinhuai East River in Nanjing city. Since water is the main factor that affects the stability of the excavated slope, both the natural and saturated soaking-drying cycles were taken into account during the experiments. Based on the experimental results of the sandstones, the void and deterioration characteristics and deteriorating mechanism were analyzed in detail. With the increasing number of the soaking-drying cycle, the compressive and tensile strengths, and the cohesion of the sand rock samples all gradually deteriorate. The more the cycle numbers, the more serious damage of the rock mass, which indicates that the cycles have cumulative damage on the samples. Under the natural water absorption conditions(no water entering the small open voids), the strength and modulus of the rock slowly decrease. However, under the saturated water absorption conditions(the small open voids are filled with water), the strength and modulus rapidly decrease, which indicates that the deterioration effect due to existence of the small open voids is obvious. The micro-structures indicate that the voids in the rock increase with the number of soaking-drying cycle. Combined with the shear strength characteristics results, the declination of the cohesive strength is the main factor of rock strength deterioration, and the frictional strength almost has no change. The cycles lead to the water-rock reaction, causing gradual loss of rock particle cementation and cracking of the edges, and the rock is degraded in macroscopic scale. Research results have an important reference for the study of stability of new excavation slope, and provide favorable evidences for the long-term stability analysis of river bank slopes.
In this paper, the sandstones of the Huangmaqing Group(T_(2h)) were taken as the study object. The compressive and tensile tests were carried out on the rock samples, considering the influencing factors of the slope along the Qinhuai East River in Nanjing city. Since water is the main factor that affects the stability of the excavated slope, both the natural and saturated soaking-drying cycles were taken into account during the experiments. Based on the experimental results of the sandstones, the void and deterioration characteristics and deteriorating mechanism were analyzed in detail. With the increasing number of the soaking-drying cycle, the compressive and tensile strengths, and the cohesion of the sand rock samples all gradually deteriorate. The more the cycle numbers, the more serious damage of the rock mass, which indicates that the cycles have cumulative damage on the samples. Under the natural water absorption conditions(no water entering the small open voids), the strength and modulus of the rock slowly decrease. However, under the saturated water absorption conditions(the small open voids are filled with water), the strength and modulus rapidly decrease, which indicates that the deterioration effect due to existence of the small open voids is obvious. The micro-structures indicate that the voids in the rock increase with the number of soaking-drying cycle. Combined with the shear strength characteristics results, the declination of the cohesive strength is the main factor of rock strength deterioration, and the frictional strength almost has no change. The cycles lead to the water-rock reaction, causing gradual loss of rock particle cementation and cracking of the edges, and the rock is degraded in macroscopic scale. Research results have an important reference for the study of stability of new excavation slope, and provide favorable evidences for the long-term stability analysis of river bank slopes.
引文
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[18]田洪铭,陈卫忠,田田,等.软岩蠕变损伤特性的试验与理论研究[J].岩石力学与工程学报,2012,31(3):610-617.TIAN Hong-ming,CHEN Wei-zhong,TIAN Tian,et al.Experimental and theoretical studies of creep damage behavior of soft rock[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(3):610-617.
[2]谢瑾荣,周翠英,程晔.降雨条件下软岩边坡渗流-软化分析方法及其灾变机制[J].岩土力学,2014,35(1):197-204.XIE Jin-rong,ZHOU Cui-ying,CHENG Ye.Method of seepage-softening analysis and disaster mechanism in soft rock slope under rainfall[J].Rock and Soil Mechanics,2014,35(1):197-204.
[3]邓华锋,肖志勇,李建林,等.水岩作用下损伤砂岩强度劣化规律试验研究[J].岩石力学与工程学报,2015,34(增刊1):1434-1440.DENG Hua-feng,XIAO Zhi-yong,LI Jian-lin,et al.Deteriorating change rule test research of damage sandstone strength under water-rock interaction[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(Supp.1):1434-1440.
[4]邓华锋,李建林,朱敏,等.饱水-风干循环作用下砂岩强度劣化规律试验研究[J].岩土力学,2014,35(1):3306-3312.DENG Hua-feng,LI Jian-lin,ZHU Min,et al.Experimental research on strength deterioration rules of sandstone under saturation-air dry circulation function[J].Rock and Soil Mechanics,2014,35(1):3306-3312.
[5]刘新荣,傅晏,王永新,等.(库)水-岩作用下砂岩抗剪强度劣化规律的试验研究[J].岩土工程学报,2008,30(9):1288-1294.LIU Xin-rong,FU Yan,WANG Yong-xin,et al.Deterioration rules of shear strength of sand rock under water-rock interaction of reservoir[J].Chinese Journal of Geotechnical Engineering,2008,30(9):1288-1294.
[6]梅华,朱燕,牛传星.饱和-失水循环作用下蚀变岩劣化规律研究[J].工程地质学报,2015,23(6):1039-1044.MEI Hua,ZHU Yan,NIU Chuan-xing.Laboratory study on deterioration law of altered rock under effect of water saturation-dehydration circulation[J].Journal of Engineering Geology,2015,23(6):1039-1044.
[7]潘艺,刘镇,周翠英.红层软岩遇水崩解特性试验及其界面模型[J].岩土力学,2017,38(11):3231-3239.PAN Yi,LIU Zhen,ZHOU Cui-ying.Experimental study of disintegration characteristics of red-bed soft rock within water and its interface model[J].Rock and Soil Mechanics,2017,38(11):3231-3239.
[8]朱凤贤,周翠英.软岩遇水软化的耗散结构形成机制[J].中国地质大学学报,2009,34(3):525-532.ZHU Feng-xian,ZHOU Cui-ying.Forming mechanism of dissipative structure in the softening process of saturated soft rocks[J].Journal of China University of Geosciences,2009,34(3):525-532.
[9]刘镇,周翠英,朱凤贤,等.软岩饱水软化过程微观结构演化的临界判据[J].岩土力学,2011,32(3):661-666.LIU Zhen,ZHOU Cui-ying,ZHU Feng-xian,et al.Critical criterion for microstructure evolution of soft rocks in softening process[J].Rock and Soil Mechanics,2011,32(3):661-666.
[10]郭永春,谢强,文江泉.红层岩土水理性质工程判别准则试验研究[J].水文地质工程地质,2008,(4):71-74.GUO Yong-chun,XIE Qiang,WEN Jiang-quan.Experimental study on engineering criterion of waterphysical property of red beds rock[J].Hydrogeology and Engineering Geology,2008,(4):71-74.
[11]张春阳,曹平,汪亦显,等.自然与饱水状态下深部斜长角闪岩蠕变特性[J].中南大学学报(自然科学版),2013,44(4):1577-1585.ZHANG Chun-yang,CAO Ping,WANG Yi-xian,et al.Creep characteristics of plagioclase hornblende rock under natural and water-saturated conditions in deep underground[J].Journal of Central South University(Science and Technology),2013,44(4):1577-1585.
[12]曾志雄,孔令伟,黄珏皓,等.延吉膨胀岩变形特性的水-力路径效应与机制浅析[J].岩土工程学报,2016,38(增刊2):222-227.ZENG Zhi-xiong,KONG Ling-wei,HUANG Jue-hao,et al.Effect and mechanism of hydro-mechanical path on deformation behavior of Yanji swelling rock[J].Chinese Journal of Geotechnical Engineering,2016,38(Supp.2):222-227.
[13]石旭飞,张文静,王寒梅,等.人工回灌过程中的水-岩相互作用模拟[J].吉林大学学报(地球科学版),2013,43(1):220-228.SHI Xu-fei,ZHANG Wen-jing,WANG Han-mei,et al.Modeling of water-rock interaction during the artificial recharge[J].Journal of Jilin University(Earth Science Edition),2013,43(1):220-228.
[14]XU B T,YAN C H.An experimental study of mechanical behavior for a weak intercalated layer[J].Rock Mechanics and Rock Engineering,2014,47(2):791-798.
[15]刘佑荣,唐辉明.岩体力学[M].北京:化学工业出版社,2008.LIU You-rong,TANG Hui-ming.Rock mechanics[M].Beijing:Chemical Industry Press,2008.
[16]长江水利委员会长江科学院.SL264―2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001.Changjiang River Scientific Research Institute of Changjiang Water Resources Commission.SL264―2001Code for rock tests of hydroelectric and water conservancy engineering[S].Beijing:China Water&Power Press,2001.
[17]LIN M L,JENG F S,TSAI L S,et al.Wetting weakening of tertiary sandstones-microscopic mechanism[J].Environmental Geology,2005,48(2):265-275.
[18]田洪铭,陈卫忠,田田,等.软岩蠕变损伤特性的试验与理论研究[J].岩石力学与工程学报,2012,31(3):610-617.TIAN Hong-ming,CHEN Wei-zhong,TIAN Tian,et al.Experimental and theoretical studies of creep damage behavior of soft rock[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(3):610-617.