冻融条件下模型桩基水平动力试验研究
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摘要
基于自制的冻土-桩动力相互作用模型试验系统,对-5℃、-3℃及上层融化多年冻土中模型桩基进行了水平向动力试验,主要研究了冻结及上层融化冻土中模型桩基的桩头位移-荷载关系、桩基水平动刚度变化及桩身弯矩分布情况。结果表明:冻土中桩基动力响应特性与土体温度密切相关;正冻土中桩基有较大的侧向刚度,当冻土与桩接触面出现较大间隙时,桩头位移-荷载曲线呈反S形;桩基动力性能随多年冻土温度降低将有所改善;当冻土上部出现融化层时,桩基动响应变化显著,桩头动刚度明显减小,桩基在较小动载下可发生较大侧向位移,同时桩身最大弯矩值较正冻土中偏大,且此弯矩点埋深较大。对于多年冻土区桩基工程,应特别重视夏季上层冻土融化时可能出现的震害。
Based on the self-made model experimental system of dynamic frozen soil-pile interaction,experiments about dynamic property of model pile foundation under lateral dynamic loads in-5℃,-3℃ and partially thawed permafrost were conducted.This paper mainly studies the displacement-force relationship of pile head,dynamic stiffness of pile foundation in horizontal direction and bending moment distribution of pile body in different permafrost mentioned above.The results show that the dynamic response character of pile foundation and frozen soil temperature is closely related.Pile foundation has a lager lateral stiffness in frozen soil,and the displacement-force curve of pile head presents a reverse S-shaped when the gap between soil and pile interface becomes larger.The dynamic property of pile will improve with the decrease of permafrost temperature;and it will decrease significantly when a thawed layer presences in the top of frozen soil;in this case,dynamic stiffness of pile head will reduced greatly;and the pile could generate a larger lateral displacement under relatively small dynamic load;at the same time,the greatest bending moment of pile is larger and the depth of this moment point is bigger than those of pile in completely frozen soil.Therefore,it should pay more attention to the seismic damages of pile engineering in permafrost zone when a thawed soil layer exists in summer.
Based on the self-made model experimental system of dynamic frozen soil-pile interaction,experiments about dynamic property of model pile foundation under lateral dynamic loads in-5℃,-3℃ and partially thawed permafrost were conducted.This paper mainly studies the displacement-force relationship of pile head,dynamic stiffness of pile foundation in horizontal direction and bending moment distribution of pile body in different permafrost mentioned above.The results show that the dynamic response character of pile foundation and frozen soil temperature is closely related.Pile foundation has a lager lateral stiffness in frozen soil,and the displacement-force curve of pile head presents a reverse S-shaped when the gap between soil and pile interface becomes larger.The dynamic property of pile will improve with the decrease of permafrost temperature;and it will decrease significantly when a thawed layer presences in the top of frozen soil;in this case,dynamic stiffness of pile head will reduced greatly;and the pile could generate a larger lateral displacement under relatively small dynamic load;at the same time,the greatest bending moment of pile is larger and the depth of this moment point is bigger than those of pile in completely frozen soil.Therefore,it should pay more attention to the seismic damages of pile engineering in permafrost zone when a thawed soil layer exists in summer.
引文
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[2]王兰民,张冬丽,吴志坚,等.地温对冻土动力特性及其场地地震动参数的影响[J].中国地震,2003,19(3):195-205.WANG Lan-min,ZHANG Dong-li,WU Zhi-jian,et al.The influence of earth temperature on dynamiccharacteristics of frozen soil and the parameters of groundmotion on the sites of frozen soil[J].EarthquakeResearch in China,2003,19(3):195-205.
[3]孙学先,张慧,田明.多年冻土区灌注桩竖向抗拔承载力试验研究[J].岩土力学,2007,28(10):2110-2114.SUN Xue-xian,ZHANG Hui,TIAN Ming.Experimentalstudy on vertical pullout capacity of cast-in-site pile inpermafrost region[J].Rock and Soil Mechanics,2007,28(10):2110-2114.
[4]汪仁和,王伟,陈永锋.冻土中单桩承载力模型试验研究[J].冰川冻土,2005,27(2):188-193.WANG Ren-he,WANG Wei,CHEN Yong-feng.Modelexperimental study on compressive bearing capacity ofsingle pile in frozen soil[J].Journal of Glaciology andGeocryology,2005,27(2):188-193.
[5]NEUKIRCHNER R J.Analysis of laterally loaded pilesin permafrost[J].Journal of Geotechnical Engineering,1987,113(1):15-29.
[6]CROWTHER G S.Analysis of laterally loaded pilesembedded in layered frozen soil[J].Journal ofGeotechnical Engineering,1990,116(7):1137-1152.
[7]FORIERO A,ST-LAURENT N,LADANYI B.Laterallyloaded pile study in permafrost of northern Québec,Canada[J].Journal of Cold Regions Engineering,2005,19(3):61-84.
[8]SULEIMAN M T,SRITHARAN S,WHITE D J.Cycliclateral load response of bridge column-foundation-soilsystems in freezing conditions[J].Journal of StructuralEngineering,2006,132(11):1745-1754.
[9]SRITHARAN S,SULEIMAN M T,WHITE D J.Effectsof seasonal freezing on bridge column-foundation-soilinteraction and their implications[J].EarthquakeSpectra,2007,23(1):199-222.
[10]WOTHERSPOONA L M,SRITHARAN S,PENDER M J.Modelling the response of cyclically loaded bridgecolumns embedded in warm and seasonally frozensoils[J].Engineering Structures,2010,32(4):933-943.
[11]STELZER D L,ANDERSLAND O B.Model pile-settlement behavior in frozen sand[J].Journal of ColdRegions Engineering,1991,5(1):1-13.
[12]张建明,朱元林,张家懿.动荷载下冻土中模型桩的沉降试验研究[J].中国科学(D辑),1999,29(增刊1):27-33.ZHANG Jian-ming,ZHU Yuan-lin,ZHANG Jia-yi.Experimental study on settlement of model piles in frozensoil under dynamic loading[J].Science in China(SeriesD),1999,29(Supp.1):27-33.
[13]VAZIRI H,HAN Y C.Full-scale field studies of thedynamic response of piles embedded in partially frozensoils[J].Canadian Geotechnical Journal,1991,28(5):708-718.
[14]HAN Y C,VAZIRI H H,HUBBLE D.Dynamic responseof pile foundations in frozen soils[C]//Canadian Geo-technical Conference.[S.l.]:[s.n.],1991,40:1-7.
[15]STEVENS H W.Viscoelastic properties of frozen soilunder vibratory loads[C]//North American Contribution tothe Second International Conference on Permafrost.[S.l.]:[s.n.],1973:400-409.
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