现浇混凝土-冻土接触面冻结强度直剪试验研究
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摘要
关于混凝土-冻土接触面的力学强度研究多集中于预制成型混凝土样(块)与冻土接触面的力学试验研究,而与工程实际更为接近的冻土中现浇混凝土、冻结稳定后混凝土-冻土接触面的力学强度研究则少有涉及。基于冻土中现浇混凝土的试验方式,开展了不同水灰比、含冰量及冻土温度条件下,混凝土-冻土复杂接触面冻结强度的直剪试验研究。结果表明:试验条件下,由于混凝土中粗、细骨料导热系数及水化热侵蚀强度不同,冻土中现浇混凝土会导致混凝土-冻土接触面发生起伏变化。受该因素影响,粗糙接触面较光滑接触面的冻结强度增大71.9%。粗糙接触面引起的应力集中,使得剪应力在剪切破坏过程中出现间歇性增大、跳跃。在冻结强度构成中,随接触面粗糙程度的增大,φ值对冻结强度增长的贡献要大于c值。水灰比由0.4增至0.6,混凝土导热系数降低,生成接触面趋于光滑,冻结强度减小;土体含水量由15%增大至30%时,冻结强度增大,含水量继续增大至40%时,冻结强度减小;在不同温度条件下,整体呈现冻土温度降低冻结强度相应增大的趋势。基于上述结果,多年冻土区灌注桩设计时,建议混凝土采用0.4~0.5水灰比。
Previous experimental study of interface strength between concrete pile and frozen soil has focused more on the mechanical properties of the interface between precast concrete block or specimen and frozen soil with less information about direct shear test of freezing strength between cast-in-situ concrete and frozen soil.Based on a new specimen preparation method,a series of laboratory direct shear tests of the interface between cast-in-situ and frozen soil were performed. The results show that because of difference in thermal parameters of concrete,the interface between cast-in-situ concrete and frozen soil appears irregular model. Freezing strength of rough interface will increase by 71. 9% as compared with that of smooth interface. Stress concentration occurs on the rough interface,resulting in stress intermittently increasing and jumping in the shear failure process. With the increase of roughness at the interface,φ contribution increase more than c contribution increase by degree. Thusφ can play more important role in the growth of freezing strength. When water cement ratio increases from 0. 4 to0. 6,with the thermal conductivity of concrete decreasing,the interface becomes smoother and the freezing strength will decrease; when water content increases from 15% to 30%,freezing strength will increase first and then decrease; when water content increases to 40%,freezing strength will decrease. Thus,it is recommended that 0. 4 ~ 0. 5 is a reasonable water cement ratio,according to this study.
Previous experimental study of interface strength between concrete pile and frozen soil has focused more on the mechanical properties of the interface between precast concrete block or specimen and frozen soil with less information about direct shear test of freezing strength between cast-in-situ concrete and frozen soil.Based on a new specimen preparation method,a series of laboratory direct shear tests of the interface between cast-in-situ and frozen soil were performed. The results show that because of difference in thermal parameters of concrete,the interface between cast-in-situ concrete and frozen soil appears irregular model. Freezing strength of rough interface will increase by 71. 9% as compared with that of smooth interface. Stress concentration occurs on the rough interface,resulting in stress intermittently increasing and jumping in the shear failure process. With the increase of roughness at the interface,φ contribution increase more than c contribution increase by degree. Thusφ can play more important role in the growth of freezing strength. When water cement ratio increases from 0. 4 to0. 6,with the thermal conductivity of concrete decreasing,the interface becomes smoother and the freezing strength will decrease; when water content increases from 15% to 30%,freezing strength will increase first and then decrease; when water content increases to 40%,freezing strength will decrease. Thus,it is recommended that 0. 4 ~ 0. 5 is a reasonable water cement ratio,according to this study.
引文
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[3]Ministry of Housing and Urban-Rural Development of the People's Republic of China.Code for design of soil and foundation of building in frozen soil region(JGJ 5118-2011)[S].Beijing:China Architecture&Building Press,2011:52-57.[中华人民共和国住房和城乡建设部中华人民共和国建设部.冻土地区建筑地基基础设计规范(JGJ 118-2011)[S].北京:中国建筑工业出版社,2011:52-57.]
[4]National Energy Administration.Technical code for foundation design of overhead transmission line in frozen soil region(DL/T5501-2015)[S].Beijing:China Electric Power Press,2015:15-20.[国家能源局.冻土区架空输电线路基础设计技术规程(DL/T 5501-2015)[S].北京:中国电力出版社,2015:15-20.]
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[13]Chen Zhaoyu,Li Guoyu,Mu Yanhu,et al.Impact of molding temperature and hydration heat of concrete on thermal propertied of pipe foundation in permafrost regions along the Qinghai-Tibet DC Transmission Line[J].Journal of Glaciology and Geocryology,2014,36(4):818-827.[陈赵育,李国玉,穆彦虎,等.混凝土的入模温度和水化热对青藏直流输电线路冻土桩基温度特性的影响[J].冰川冻土,2014,36(4):818-827.]
[14]Lei Guo,Yu Qihao,Li Xiaoning,et al.Refreezing of cast-inplace piles under various engineering conditions[J].Sciences in Cold and Arid Regions,2015,7(4):376-383.
[15]Ministry of Housing and Urban-Rural Development of the People's Republic of China.Specification for mix proportion design of ordinary concrete(JGJ 55-2011)[S].Beijing:China Architecture&Building Press,2011:20-22.[中华人民共和国住房和城乡建设部.普通混凝土配合比设计规程(JGJ 55-2011)[S].北京:中国建筑工业出版社,2011:20-22.]
[16]Yi Xiangsheng,Yin Yanyu,Li Guosheng,et al.Temperature variation in recent 50 years in the three-river headwaters region of Qinghai Province[J].Acta Geographica Sinica,2011,66(11):1451-1465.[易湘生,尹衍雨,李国胜,等.青海三江源地区近50年来的气温变化[J].地理学报,2011,66(11):1451-1465.]
[17]Xu Xiaozu,Wang Jiacheng,Zhang Lixin.Physics of frozen soil[M].2nd ed.Beijing:Science Press,2010:75-90.[徐斅祖,王家澄,张立新.冻土物理学[M].2版.北京:科学出版社,2010:75-90.]
[18]He Shiming,An Wenhua,Luo Faqian,et al.Study on heat conductivity coefficient of cement slurry and drilling fluids[J].Journal of Southwest Petroleum Institute,2007,27(4)53-55.[何世明,安文华,骆发前,等.水泥浆与泥浆热导率的测定研究[J].天然气工业,2007,27(4):53-55.]
[19]Ma Wei,Wang Dayan.Mechanics of frozen ground[M].Beijing:Science Press,2014:146-150.[马巍,王大雁.冻土力学[M].北京:科学出版社,2014:146-150.]
[20]Xiao Jianzhuang,Song Zhiwen,Zhang Feng.An experimental study on thermal conductivity of concrete[J].Journal of Building Materials,2010,13(1):17-22.[肖建庄,宋志文,张枫.混凝土导热系数试验与分析[J].建筑材料学报,2010,13(1):17-22.]
[21]Liu Weidong,Tian Bo,Hou Ziyi.Experimental study on thermal conductivity of concrete[J].Journal of China&Foreign Highway,2012,22(1):226-229.[刘卫东,田波,侯子义.混凝土导热系数试验研究[J].中外公路,2012,22(1):226-229.]
[22]Chen Xiaobai,Liu Jiankun,Liu Hongxu,et al.Frost action of soil and foundation engineering[M].Beijing:Science Press,2006:288-294.[陈肖柏,刘建坤,刘洪绪,等.土的冻结作用与地基[M].北京:科学出版社,2006:288-294.]
[23]Wu Ziwang,Ma Wei.Strength and creep of frozen soil[M].Lanzhou:Lan Zhou University Press,1994:98-105.[吴紫汪,马巍.冻土强度与蠕变[M].兰州:兰州大学出版社,1994:98-105.]
[24]Zhang Wen,Zhang Weihong,Pan Qilai.Factors affecting intension of the aged frozen earth[J].Journal of Qinghai University(Nature Science),2005,23(4):26-29.[张文,张卫红,潘起来.青藏高原多年冻土冻结强度的影响因素[J].青海大学学报(自然科学版),2005,23(4):26-29.]
[2]Ruan Guofeng,Zhang Jianming,Chai Mingtang.Risk division of thaw settlement hazard along Qinghai-Tibet engineering corridor under climate change[J].Journal of Glaciology and Geocryology,2014,36(4):811-817.[阮国峰,张建明,柴明堂.气候变化情景下青藏工程走廊融沉灾害风险性区划研究[J].冰川冻土,2014,36(4):811-817.]
[3]Ministry of Housing and Urban-Rural Development of the People's Republic of China.Code for design of soil and foundation of building in frozen soil region(JGJ 5118-2011)[S].Beijing:China Architecture&Building Press,2011:52-57.[中华人民共和国住房和城乡建设部中华人民共和国建设部.冻土地区建筑地基基础设计规范(JGJ 118-2011)[S].北京:中国建筑工业出版社,2011:52-57.]
[4]National Energy Administration.Technical code for foundation design of overhead transmission line in frozen soil region(DL/T5501-2015)[S].Beijing:China Electric Power Press,2015:15-20.[国家能源局.冻土区架空输电线路基础设计技术规程(DL/T 5501-2015)[S].北京:中国电力出版社,2015:15-20.]
[5]Penner E,Gold L W.Transfer of heaving force by adfreezing to columns and foundation walls in frostsusceptible soils[J].Canadian Geotechincal Journal,1971,8(4):514-526.
[6]Sadovsikiy A V.Adfreeze between ground and foundation materials[C]//Proceedings of 2th International Permafrost Conference,Yakutsk,1973:650-653.
[7]Perameswaran V R.Creep of model piles in frozen soils[J].Canadian Geotechnical Journal,1979,16(1):69-77.
[8]Chen Xiaobai,Liu Jiankun,Liu Hongxu,et al.Frost action of soil and foundation engineering[M].Beijing:Science Press,2006:284-296.[陈肖柏,刘建坤,刘洪绪,等.土的冻结作用与地基[M].北京:科学出版社,2006:284-296.]
[9]Ministry of Housing and Urban-Rural Development of the People's Republic of China.Technical code for building pile foundations(JGJ 94-2008)[S].Beijing:China Architecture&Building Press,2008:102-114.[中华人民共和国住房和城乡建设部中华人民共和国建设部.建筑桩基础技术规范(JGJ 94-2008)[S].北京:中国建筑工业出版社,2008:102-114.]
[10]Lu Peng,Liu Jiankun.An experimental study on direct shear tests of frozen soil-concrete interface[J].Journal of the China Railway Society,2015,37(2):106-110.[吕鹏,刘建坤.冻土与混凝土接触面直剪试验研究[J].铁道学报,2015,37(2):106-110.]
[11]Dong Shengshi,Dong Lanfeng,Wen Zhi,et al.Study of constitutive relation of interface between frozen Qinghai-Tibet silt and concrete[J].Rock and Soil Mechanics,2014,35(6):1629-1633.[董盛时,董兰凤,温智,等.青藏冻结粉土与混凝土基础接触面本构关系研究[J].岩土力学,2014,35(6):1629-1633.]
[12]Wen Zhi,Yu Qihao,Zhang Jianming,et al.Experimental study on adfreezing bond strength of interface between silt and foundation of Qinghai-Tibetan transmission line[J].Chinese Journal of Geotechnical Engineering,2013,35(12):2262-2267.[温智,俞祁浩,张建明,等.青藏直流输变电工程基础冻结强度试验研究[J].岩土工程学报,2013,35(12):2262-2267.]
[13]Chen Zhaoyu,Li Guoyu,Mu Yanhu,et al.Impact of molding temperature and hydration heat of concrete on thermal propertied of pipe foundation in permafrost regions along the Qinghai-Tibet DC Transmission Line[J].Journal of Glaciology and Geocryology,2014,36(4):818-827.[陈赵育,李国玉,穆彦虎,等.混凝土的入模温度和水化热对青藏直流输电线路冻土桩基温度特性的影响[J].冰川冻土,2014,36(4):818-827.]
[14]Lei Guo,Yu Qihao,Li Xiaoning,et al.Refreezing of cast-inplace piles under various engineering conditions[J].Sciences in Cold and Arid Regions,2015,7(4):376-383.
[15]Ministry of Housing and Urban-Rural Development of the People's Republic of China.Specification for mix proportion design of ordinary concrete(JGJ 55-2011)[S].Beijing:China Architecture&Building Press,2011:20-22.[中华人民共和国住房和城乡建设部.普通混凝土配合比设计规程(JGJ 55-2011)[S].北京:中国建筑工业出版社,2011:20-22.]
[16]Yi Xiangsheng,Yin Yanyu,Li Guosheng,et al.Temperature variation in recent 50 years in the three-river headwaters region of Qinghai Province[J].Acta Geographica Sinica,2011,66(11):1451-1465.[易湘生,尹衍雨,李国胜,等.青海三江源地区近50年来的气温变化[J].地理学报,2011,66(11):1451-1465.]
[17]Xu Xiaozu,Wang Jiacheng,Zhang Lixin.Physics of frozen soil[M].2nd ed.Beijing:Science Press,2010:75-90.[徐斅祖,王家澄,张立新.冻土物理学[M].2版.北京:科学出版社,2010:75-90.]
[18]He Shiming,An Wenhua,Luo Faqian,et al.Study on heat conductivity coefficient of cement slurry and drilling fluids[J].Journal of Southwest Petroleum Institute,2007,27(4)53-55.[何世明,安文华,骆发前,等.水泥浆与泥浆热导率的测定研究[J].天然气工业,2007,27(4):53-55.]
[19]Ma Wei,Wang Dayan.Mechanics of frozen ground[M].Beijing:Science Press,2014:146-150.[马巍,王大雁.冻土力学[M].北京:科学出版社,2014:146-150.]
[20]Xiao Jianzhuang,Song Zhiwen,Zhang Feng.An experimental study on thermal conductivity of concrete[J].Journal of Building Materials,2010,13(1):17-22.[肖建庄,宋志文,张枫.混凝土导热系数试验与分析[J].建筑材料学报,2010,13(1):17-22.]
[21]Liu Weidong,Tian Bo,Hou Ziyi.Experimental study on thermal conductivity of concrete[J].Journal of China&Foreign Highway,2012,22(1):226-229.[刘卫东,田波,侯子义.混凝土导热系数试验研究[J].中外公路,2012,22(1):226-229.]
[22]Chen Xiaobai,Liu Jiankun,Liu Hongxu,et al.Frost action of soil and foundation engineering[M].Beijing:Science Press,2006:288-294.[陈肖柏,刘建坤,刘洪绪,等.土的冻结作用与地基[M].北京:科学出版社,2006:288-294.]
[23]Wu Ziwang,Ma Wei.Strength and creep of frozen soil[M].Lanzhou:Lan Zhou University Press,1994:98-105.[吴紫汪,马巍.冻土强度与蠕变[M].兰州:兰州大学出版社,1994:98-105.]
[24]Zhang Wen,Zhang Weihong,Pan Qilai.Factors affecting intension of the aged frozen earth[J].Journal of Qinghai University(Nature Science),2005,23(4):26-29.[张文,张卫红,潘起来.青藏高原多年冻土冻结强度的影响因素[J].青海大学学报(自然科学版),2005,23(4):26-29.]