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| EXPERIMENTAL STUDY OF BEARING CHARACTERISTICS OF LARGE-DIAMETER CAST-IN-PLACE BORED PILE UNDER NON-REFREEZING CONDITION IN LOW-TEMPERATURE PERMAFROST GROUND |
| WANG Xu1，2，JIANG Daijun1，LIU Deren1，HE Fei1 |
| (1. School of Civil Engineering，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China；2. Key Laboratory of Road，Bridge and Underground Engineering of Gansu Province，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China) |
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Abstract For the large-diameter cast-in-place concrete bored piles in low-temperature permafrost ground，a large amount of heat produced by concrete hydration would result in thawing of permafrost soil around the pile，and thus the interface between the pile and the soil would not have enough freezing strength，making it impossible the pile to reach the designed bearing capacity at an early stage after the construction. Thus，the bearing and deformation features of the piles under a non-refreezing state were studied. A series of in-situ ground temperature tests and static loading tests were performed for the pile foundations of the Sonam Dargye Bridge located at the Qinghai-Tibet railway during its construction. The pile-soil-surface thermometer holes，pile-side thermometer holes(30 cm from the pile skin) and reference thermometer holes to measure the ground temperature undisturbed by construction，denoted by SB，SC，and JZ，respectively，were set up to obtain the corresponding temperatures. The temperature distributions for the pile-soil system at various ages were obtained when the piles were cast in summer and the initial concrete temperature was 11 ℃. The refreezing process of the pile-soil system as well as the distribution characteristics of the vertical bearing capacity，vertical deformation and skin friction(or freezing force) of the pile under various ground temperatures were analyzed. Test results show that 30 days after the construction of the pile，the temperature along the pile skin is negative(approximately －0.43 ℃–－1.26 ℃) except in the section 0–2 m below the ground surface；50 days after the construction of the pile，it becomes a bit lower(approximately－1.0 ℃–－1.85 ℃). Compared with the original undisturbed state，the pile-soil system is not fully refrozen. When a maximum vertical load of 7 600 kN is applied，the vertical pile-head displacement is 4.93 mm while the residual deformation after unloading is 1.01 mm. It shows that the pile has a high vertical bearing capacity and a small deformation under a non-fully refreezing condition with the pile age of 30 days.
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Received: 02 May 2013
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| [1] TSYTOVICH H A. 冻土力学[M]. 张长庆，朱元林 译. 北京：科学出版社，1985：152–203.(TSYTOVICH H A. Mechanics of frozen soil[M]. Translated by ZHANG Changqing，ZHU Yuanlin. Beijing：Science Press，1985：152–203.(in Chinese))
[2] 铁道部科技教育司. 国外铁路冻土技术汇编[Z]. 北京：铁道部科技教育司，2002.(Science and Technology Education Department，Ministry of Railways of the People's Republic of China，Frozen soil technology compilations of the foreign railway[Z]. Beijing：Science and Technology Education Department，Ministry of Railways of the People's Republic of China，2002.(in Chinese))
[3] 陈卓怀. 多年冻土地区铁路桥涵基础[C]// 第二届全国冻土学术会议论文选集. 兰州：甘肃人民出版社，1983：412–418.(CHEN Zhuohuai. Railway bridge and tunnel foundation in permafrost regions[C]// Proceedings of Second National Conference on Permafrost. Lanzhou：Gansu People Press，1983：412–418.(in Chinese))
[4] 陈卓怀. 多年冻土地区桩基试验研究[R]. 兰州：铁道部科学研究院西北研究所，1978.(CHEN Zhuohuai. Experimental study of pile foundation in permafrost region[R]. Lanzhou：Northwest Institute，China Academy of Railway Sciences，1978.(in Chinese))
[5] 朱炳泉，励国良. 昆仑山桩基场静载试验研究[R]. 兰州：铁道部科学研究院西北研究所，1982.(ZHU Bingquan，LI Guoliang. Experimental study of pile foundation in permafrost region on Kunlun Mountains[R]. Lanzhou：Northwest Institute，China Academy of Railway Sciences，1982.(in Chinese))
[6] 王 旭，蒋代军，赵新宇，等. 多年冻土区未回冻钻孔灌注桩承载性质试验研究[J]. 岩土工程学报，2005，27(1)：81–84.(WANG Xu，JIANG Daijun，ZHAO Xinyu，et al. Experimental study on bearing features of bored pile under non-refreezing condition in permafrost region[J]. Chinese Journal of Geotechnical Engineering，2005，27(1)：81–84.(in Chinese))
[7] 张军伟，马 巍，王大雁，等. 青藏高原多年冻土区钻孔灌注桩承载特性试验研究[J]. 冰川冻土，2008，30(3)：483–487.(ZHANG Junwei，MA Wei，WANG Dayan，et al. In-situ experimental study of the bearing characteristics of cast-in-place bored pile in permafrost regions of the Tibetan Plateau[J]. Journal of Glaciology and Geocryology，2008，30(3)：483–487.(in Chinese))
[8] 牛永红，刘永智. 桩基施工对冻土区地温影响的试验研究[J]. 铁道工程学报，2004，(1)：30–33.(NIU Yonghong，LIU Yongzhi. Field observation on responses of soil temperature profile to construction of engineering piles in permafrost[J]. Journal of the Railway Engineering Society，2004，(1)：30–33.(in Chinese))
[9] 中华人民共和国行业标准编写组. JGJ118—2011冻土地区建筑地基基础设计规范[S]. 北京：中国建筑工业出版社，2011.(The Professional Standards Compilation Group of People Republic of China. JGJ118—2011 The designing criterion of the foundations in permafrost regions[S]. Beijing：China Architecture and Building Press，2011.(in Chinese))
[10] 铁道部第三勘测设计院. 冻土工程[M]. 北京：中国铁道出版社，2002：225–260.(Third Railway Survey and Design Institute. Frozen soil engineering[M]. Beijing：China Railway Publishing House，2002：225–260.(in Chinese))
[11] 卢世深，林亚超，王帮楣. 桥梁地基基础试验[M]. 北京：中国铁道出版社，1984：235–237.(LU Shishen，LIN Yachao，WANG Bangmei. Bridge foundation base experiment[M]. Beijing：China Railway Publishing House，1984：235–237.(in Chinese)) |
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2013, Vol. 32 
