地下水渗流对冻土区模型桩力学特性的影响分析
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摘要
为了研究冻土区地下水的渗流效应对桩基的荷载传递规律的影响,考虑到桩身轴力、桩侧冻结应力和桩周土温度对桩基承载力均有影响,依据室内模拟试验,分别模拟了无地下水、桩顶水有温度效应、桩底水有温度效应、桩顶水有温度及渗流效应、桩底水有温度及渗流效应5种不同工况下地下水对冻土桩基承载力的影响。试验结果表明:无论是桩顶水还是桩底水,在接近地下水处,同时有温度效应及渗流效应的轴力值变化比仅有温度效应时的小,当地下水为桩底水时加载后的桩轴力小于地下水为桩顶水时的轴力值;桩底水引起的桩侧冻结应力变化幅度比桩顶水大,地下水的温度效应使得部分冻土温度升高而融化,而地下水的渗流效应进一步增大了冻土融化范围,使得桩基力学特性发生改变,进而影响了桩基承载力。
In order to understand the effect of the groundwater seepage on pile foundation in permafrost, considering the axial force and lateral frozen stress of pile, and soil temperature affecting the bearing capacity of pile foundation, a simulation test have carried out. The effects of groundwater on the bearing capacity of permafrost pile foundation under five different working conditions have been simulated, respectively, including there is no groundwater, the pile bottom water has temperature effect only and the pile bottom water has temperature effect and seepage effect both, the pile top water has temperature effect only and the pile top water has temperature effect and seepage effect both. The following conclusions can be drawn: Under the five working conditions, the axial force of the pile is the maximum when there is no groundwater and the axial force decreases downward, when the condition of temperature effect and seepage effect is less than that under the condition of temperature effect only. Compared with no groundwater, the effect of groundwater on frozen stress is more obvious; the water at the top of the pile has a great influence on the lateral frozen stress of the upper half of the pile and the water at the bottom of the pile has a great influence on the lateral frozen stress on the lower half of the pile. As a whole, the variation range of the lateral frozen stress caused by the ground water is larger than that caused by the top water. The temperature effect of water at the pile bottom only is more significant than that the temperature effect together with seepage effect, and the temperature effect and seepage effect of water at the pile top both result in frozen stress on the pile side more serious than that with temperature effect only. At the same depth, groundwater temperature and seepage effect together result soil temperature rise more than only groundwater temperature effect, making frozen stress acting on the pile rapidly decrease, at the same time, the temperature effect of groundwater makes the adjacent frozen soil warm and thawing, and the seepage effect also makes a wider range of frozen soil warm and thawing, the mechanical properties of pile foundation changed, resulting in changing bearing capacity of pile foundation.
In order to understand the effect of the groundwater seepage on pile foundation in permafrost, considering the axial force and lateral frozen stress of pile, and soil temperature affecting the bearing capacity of pile foundation, a simulation test have carried out. The effects of groundwater on the bearing capacity of permafrost pile foundation under five different working conditions have been simulated, respectively, including there is no groundwater, the pile bottom water has temperature effect only and the pile bottom water has temperature effect and seepage effect both, the pile top water has temperature effect only and the pile top water has temperature effect and seepage effect both. The following conclusions can be drawn: Under the five working conditions, the axial force of the pile is the maximum when there is no groundwater and the axial force decreases downward, when the condition of temperature effect and seepage effect is less than that under the condition of temperature effect only. Compared with no groundwater, the effect of groundwater on frozen stress is more obvious; the water at the top of the pile has a great influence on the lateral frozen stress of the upper half of the pile and the water at the bottom of the pile has a great influence on the lateral frozen stress on the lower half of the pile. As a whole, the variation range of the lateral frozen stress caused by the ground water is larger than that caused by the top water. The temperature effect of water at the pile bottom only is more significant than that the temperature effect together with seepage effect, and the temperature effect and seepage effect of water at the pile top both result in frozen stress on the pile side more serious than that with temperature effect only. At the same depth, groundwater temperature and seepage effect together result soil temperature rise more than only groundwater temperature effect, making frozen stress acting on the pile rapidly decrease, at the same time, the temperature effect of groundwater makes the adjacent frozen soil warm and thawing, and the seepage effect also makes a wider range of frozen soil warm and thawing, the mechanical properties of pile foundation changed, resulting in changing bearing capacity of pile foundation.
引文
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[11] Liu Zhen,Guo Chunxiang,Wu Yaping.Numerical simulation analysis of allowance bearing capacity of defected pile foundation in permafrost region[J].Railway Standard Design,2015,59(12):45-49.[刘振,郭春香,吴亚平.冻土区病害桩基容许承载力的数值模拟分析[J].铁道标准设计,2015,59(12):45-49.]
[12] Liu Naifei,Li Ning,He Min,et al.Analyzing the factors controlling the bearing capacity of cast-in-place piles based on a thermo-hydro-mechanical coupling model[J].Journal of Glaciology and Geocryology,2014,36(6):1471-1477.[刘乃飞,李宁,何敏,等.基于水热力耦合模型的钻孔灌注桩承载力影响因素分析[J].冰川冻土,2014,36(6):1471-1477.]
[13] Liu Yazun.Model test study of the groundwater on single pile′s mechanical properties in permafrost[D].Lanzhou:Lanzhou Jiaotong University,2015.[刘亚尊.寒区地下水对单桩力学特性影响的模型试验研究[D].兰州:兰州交通大学,2015.]
[14] Wang Xiaoli.Seepage stability and monitoring analysis of deep foundation pit of a subway in Lanzhou under precipitation condition[D].Lanzhou:Lanzhou University of Technology,2016.[王晓莉.兰州某地铁深基坑在降水条件下的渗流稳定性及监测分析[D].兰州:兰州理工大学,2016.]
[15] Wei Xianxiang,Lai Yuanming.The principle and application of similarity method[M].Lanzhou:Lanzhou University Press,2001.[魏先祥,赖远明.相似方法的原理及应用[M].兰州:兰州大学出版社,2001.]
[16] Cui Guangxin.Similarity theory and model test[M].Xuzhou,Jiangsu:China University of Mining and Technology Press,1990.[崔广心.相似理论与模型试验[M].江苏徐州:中国矿业大学出版社,1990.]
[17] Wu Qingbai,Shen Yongping,Shi Bin.Relationship between frozen soil together with its water-heat process and ecological environment in the Tibetan Plateau[J].Journal of Glaciology and Geocryology,2003,25(3):250-255.[吴青柏,沈永平,施斌.青藏高原冻土及水热环境与寒区生态坏境的关系[J].冰川冻土,2003,25(3):250-255.]
[18] Fu Jiangtao.Research on load transfer function of single pile foundation and ultimate bearing capacity in permafrost region[D].Lanzhou:Lanzhou Jiaotong University,2012.[付江涛.冻土地区单桩基础的荷载传递函数与极限承载力的研究[D].兰州:兰州交通大学,2012.]
[19] Xu Yuehai.The comparison of two methods of vertically compress static loading test for pile foundation in Dalian area[D].Dalian,Liaoning:Dalian University of Technology,2013.[许月海.大连地区基桩静载试验两方法对比研究[D].辽宁大连:大连理工大学,2013.]
[20] Wang Ning.The influence of groundwater heating and seepage on single pile′s bearing characteristics in permafrost[D].Lanzhou:Lanzhou Jiaotong University,2016.[王宁.地下水对冻土模型单桩承载特性的温度及渗流效应研究[D].兰州:兰州交通大学,2016.]
[2] Cao Li.Study of water-thermal characteristics and frost heave process monitoring in the roadbed of cutting section in seasonally frozen soil regions[J].Journal of Glaciology and Geocryology,2017,39(5):1065-1074.[曹立.我国季节冻土区路堑段路基水热特性及冻胀发展过程监测研究[J].冰川冻土,2017,39(5):1065-1074.]
[3] Min Dongli,Wei Qingzhao,Wang Lianjun,et al.The study of yard-and-station roadbed′s temperature filed of Qinghai-Tibet Railway in permafrost region[J].Journal of Railway Engineering Society,2004(1):119-122.[闵冬丽,魏庆朝,王连俊,等.青藏铁路多年冻土区站场路基温度场试验研究[J].铁道工程学报,2004(1):119-122.]
[4] Gude M,Dietrich S,M?usbacher R,et al.Probable occurrence of sporadic permafrost in non-alpine scree slopes in Central Europe[C]// Proceedings of the 8th International Conference on Permafrost:vol l.Lisse,the Netherlands:A.A.Balkema Publishers,2003:331-336.
[5] Gao Rong,Wei Zhigang,Zhong Hailing.Relationship between land surface characteristics in the Tibetan Plateau and summer precipitation in China[J].Journal of Glaciology and Geocryology,2017,39(4):741-747.[高荣,韦志刚,钟海玲.青藏高原陆表特征与中国夏季降水的关系研究[J].冰川冻土,2017,39(4):741-747.]
[6] Zhou Yundong,Liu Yunbo,Yang De.Numerical simulation analysis of influence of temperature variations on the pile force in permafrost zone under dynamic loads[J].Journal of Hebei University of Engineering,2016(1):11-15.[周云东,刘云波,杨德.动载下冻土区温度变化对桩基受力影响数值分析[J].河北工程大学学报,2016(1):11-15.]
[7] Huang Yizhang,Shi Yujin,Chen Jinjian,et al.Effect of deep underground water recharge on long-term settlements of pile foundations[J].Journal of Shanghai Jiaotong University,2016(3):324-330.[黄亦章,史玉金,陈锦剑,等.深层地下水回灌对高架桩基长期沉降的影响[J].上海交通大学学报,2016(3):324-330.]
[8] Guo Chunxiang,Wu Yaping.Effects of solar radiation and global warming on bearing capacity of single pile in permafrost region[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(Suppl 1):3306-3311.[郭春香,吴亚平.太阳辐射及气候变暖对冻土区单桩承载力的影响[J].岩石力学与工程学报,2014,33(增刊1):3306-3311.]
[9] Wu Yaping,Guo Chunxiang,Pan Weidong,et al.Influences of refreezing process of ground on bearing capacity of single pile and bridge construction in permafrost[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(24):4229-4233.[吴亚平,郭春香,潘卫东,等.冻土区桩基回冻过程对单桩承载力和桥梁施工的影响分析[J].岩石力学与工程学报,2004,23(24):4229-4233.]
[10] Tang Liyun,Yang Gengshe,Ye Wanjun.Pile bearing capacity prediction considering air temperature change in cold regions[J].Chinese Journal of Underground Space and Engineering,2015,11(3):652-657.[唐丽云,杨更社,叶万军.考虑大气温度变化的冻土区桩基承载力预测[J].地下空间与工程学报,2015,11(3):652-657.]
[11] Liu Zhen,Guo Chunxiang,Wu Yaping.Numerical simulation analysis of allowance bearing capacity of defected pile foundation in permafrost region[J].Railway Standard Design,2015,59(12):45-49.[刘振,郭春香,吴亚平.冻土区病害桩基容许承载力的数值模拟分析[J].铁道标准设计,2015,59(12):45-49.]
[12] Liu Naifei,Li Ning,He Min,et al.Analyzing the factors controlling the bearing capacity of cast-in-place piles based on a thermo-hydro-mechanical coupling model[J].Journal of Glaciology and Geocryology,2014,36(6):1471-1477.[刘乃飞,李宁,何敏,等.基于水热力耦合模型的钻孔灌注桩承载力影响因素分析[J].冰川冻土,2014,36(6):1471-1477.]
[13] Liu Yazun.Model test study of the groundwater on single pile′s mechanical properties in permafrost[D].Lanzhou:Lanzhou Jiaotong University,2015.[刘亚尊.寒区地下水对单桩力学特性影响的模型试验研究[D].兰州:兰州交通大学,2015.]
[14] Wang Xiaoli.Seepage stability and monitoring analysis of deep foundation pit of a subway in Lanzhou under precipitation condition[D].Lanzhou:Lanzhou University of Technology,2016.[王晓莉.兰州某地铁深基坑在降水条件下的渗流稳定性及监测分析[D].兰州:兰州理工大学,2016.]
[15] Wei Xianxiang,Lai Yuanming.The principle and application of similarity method[M].Lanzhou:Lanzhou University Press,2001.[魏先祥,赖远明.相似方法的原理及应用[M].兰州:兰州大学出版社,2001.]
[16] Cui Guangxin.Similarity theory and model test[M].Xuzhou,Jiangsu:China University of Mining and Technology Press,1990.[崔广心.相似理论与模型试验[M].江苏徐州:中国矿业大学出版社,1990.]
[17] Wu Qingbai,Shen Yongping,Shi Bin.Relationship between frozen soil together with its water-heat process and ecological environment in the Tibetan Plateau[J].Journal of Glaciology and Geocryology,2003,25(3):250-255.[吴青柏,沈永平,施斌.青藏高原冻土及水热环境与寒区生态坏境的关系[J].冰川冻土,2003,25(3):250-255.]
[18] Fu Jiangtao.Research on load transfer function of single pile foundation and ultimate bearing capacity in permafrost region[D].Lanzhou:Lanzhou Jiaotong University,2012.[付江涛.冻土地区单桩基础的荷载传递函数与极限承载力的研究[D].兰州:兰州交通大学,2012.]
[19] Xu Yuehai.The comparison of two methods of vertically compress static loading test for pile foundation in Dalian area[D].Dalian,Liaoning:Dalian University of Technology,2013.[许月海.大连地区基桩静载试验两方法对比研究[D].辽宁大连:大连理工大学,2013.]
[20] Wang Ning.The influence of groundwater heating and seepage on single pile′s bearing characteristics in permafrost[D].Lanzhou:Lanzhou Jiaotong University,2016.[王宁.地下水对冻土模型单桩承载特性的温度及渗流效应研究[D].兰州:兰州交通大学,2016.]