青藏铁路多年冻土区桥梁桩基础地震响应的试验研究与数值分析
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摘要
基于对负温条件下青藏铁路高温不稳定多年冻土区桥梁桩基础的缩尺模型振动台试验,明确了动荷载作用下模型桩-土界面和两桩中间土体存在温度升高响应。在此基础上,考虑天然状态和地震荷载作用下地温升高两种条件,运用动力有限元方法,对青藏铁路清水河特大桥桩基础进行了地震响应分析。计算表明,在高温状态下(-1℃以上),多年冻土的地基及桩基础在地震荷载作用下的动态响应对温度的升高异常敏感;在50年超载概率2%的青藏人工波作用下,因桩基础的相对位移增大了地基与桩基础间的滑移、脱离现象,特别是高温状态下地基与桩基础间的变形出现了明显的不稳定滑移,影响了整个桩基础的稳定性。
Based on shaking table tests for scale model of pile foundation,which belongs to bridges at the unstable permafrost regions of high earth temperatures along the Qinghai-Tibet Railroad,on condition that the soil temperature around pile was below 0 ℃,it discovered that temperature increased at the spot of soil between piles and the interface of the piles and soil under seismic dynamic motions.Moreover,under the conditions of natural state and soil temperature increase,the characteristics of seismic response of pile foundation of the Qingshui River Bridge were analyzed by dynamic finite element analysis.It indicated that seismic response of the permafrost layer and pile foundation,under seismic motions,was obviously sensitive to the increase in temperature,while earth temperature above -1 ℃.Under artificial wave with exceedance probability of 2% in 50 years loading,the slippage and escape,between pile foundation and soil layer around,were enlarged due to relative displacement of pile foundation.Especially,on condition that temperature above -1℃,the slippage was so obvious that it influenced the stability of whole pile foundation.
Based on shaking table tests for scale model of pile foundation,which belongs to bridges at the unstable permafrost regions of high earth temperatures along the Qinghai-Tibet Railroad,on condition that the soil temperature around pile was below 0 ℃,it discovered that temperature increased at the spot of soil between piles and the interface of the piles and soil under seismic dynamic motions.Moreover,under the conditions of natural state and soil temperature increase,the characteristics of seismic response of pile foundation of the Qingshui River Bridge were analyzed by dynamic finite element analysis.It indicated that seismic response of the permafrost layer and pile foundation,under seismic motions,was obviously sensitive to the increase in temperature,while earth temperature above -1 ℃.Under artificial wave with exceedance probability of 2% in 50 years loading,the slippage and escape,between pile foundation and soil layer around,were enlarged due to relative displacement of pile foundation.Especially,on condition that temperature above -1℃,the slippage was so obvious that it influenced the stability of whole pile foundation.
引文
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[13]徐学燕,仲丛利,陈亚明,等.冻土的动力特性研究及其参数确定[J].岩土工程学报,1998,20(5):77-81.XUE Xu-yan,ZHONG Cong-li,CHEN Ya-ming,et al.The dynamic characteristic of frozen soil and determination of parameters[J].Chinese Journal of Geotechnical Engineering,1998,20(5):77-81.
[14]朱元林,张家懿.冻土的弹性变形及压缩变形[J].冰川冻土,1982,4(3):29-39.ZHU Yuan-lin.ZHANG Jia-yi.The elastic and compressive deformation of the frozen soil[J].Journal of Glaciology and Geocryology,1982,4(3):29-39.
[15]吴紫汪,马巍.冻土强度与蠕变[M].兰州:兰州大学出版社,1994.
[2]吴志坚,马巍,王兰民,等.地震荷载作用下温度和围压对冻土强度影响的试验研究[J].冰川冻土,2003,25(6):648-652.WU Zhi-jian,MA Wei,WANG Lan-min,et al.Laboratory study on the effect of temperature and confining pressure on strength of frozen soil under seismic dynamic loading[J].Journal of Glaciology and Geocryology,2003,25(6):648-652.
[3]王昭今.冻土退化与青藏高原冻土环境问题探讨[C]//第五届全国冰川冻土大会论文集.兰州:甘肃文化出版社,1996:11-17.
[4]WANG L,WU Z,ZHANG D,et al.The influence of earth temperature on dynamic characteristics of frozen soil and the parameters of ground motion at the sites of permafrost in the Qinghai-Tibet Plateau[C]//Proceedings of the16thInternational Conference on Soil Mechanics and Geotechnical Engineering.Osaka Japan:[s.n.],2005.
[5]吴志坚,张鲁新,马巍,等.青藏铁路冻土区土体冷生过程对路基变形影响分析[J].岩土力学,2007,28(7):1309-1314.WU Zhi-jian,ZHANG Lu-xin,MA Wei,et al.Influence of soil's cryogenic course on deformation of roadbed in permafrost region of Qinghai-Tibet Railway[J].Rock and Soil Mechanics,2007,28(7):1309-1314.
[6]张淑娟.静动荷载及冻融作用下冻土力学性质研究[博士学位论文D].北京:中国科学院研究生院,2007.
[7]史聪慧.青藏铁路清水河高温高含冰量冻土区“以桥代路”工程稳定性研究[博士学位论文D].北京:中国科学院研究生院,2007.
[8]车爱兰,岩楯敞广,葛修润.关于地铁地震响应的模型振动实验及数值分析[J].岩土力学,2006,27(8):1293-1298.CHE Ai-lan,Iwatate Takahiro,GE Xiu-run.Dynamic behaviors of subway structure subjected to strong earthquake motions using shaking table tests and dynamic analyses[J].Rock and Soil Mechanics,2006,27(8):1293-1298.
[9]吴志坚,王兰民,马巍,等.地震荷载作用下冻土的动力学参数试验研究[J].西北地震学报,2003,25(3):210-214.WU Zhi-jian,WANG Lan-min,MA Wei,et al.laboratory study on dynamics parameters of frozen soil under seismic dynamic loading[J].Northwestern Seismological Journal,2003,25(3):210-214.
[10]何平,朱元林,张家懿,等.饱和冻结粉土的动弹模和动强度[J].冰川冻土,1993,15(1):170-174.HE Ping,ZHU Yuan-lin,ZHANG Jia-yi,et al.The dynamic elastic modulus and dynamic strength of saturated frozen silty clay[J].Journal of Glaciology and Geocryology,1993,15(1):170-174.
[11]赵淑萍,朱元林,何平,等.冻土动力学研究的现状与进展[J].冰川冻土,2002,24(5):681-685.ZHAO Shu-ping,ZHU Yuan-lin,HE Ping,et al.Recent progress and suggestion in the research on dynamic response of frozen soil[J].Journal of Glaciology and Geocryology,2002,24(5):681-685.
[12]赵淑萍,何平,朱元林,等.冻结粉土的动静蠕变特征比较[J].岩土工程学报,2006,28(12):2160-2163.ZHAO Shu-ping,HE Ping,ZHU Yuan-lin,et al.Comparison between dynamic and static creep characteristics of frozen silt[J].Chinese Journal of Geotechnical Engineering,2006,28(12):2160-2163.
[13]徐学燕,仲丛利,陈亚明,等.冻土的动力特性研究及其参数确定[J].岩土工程学报,1998,20(5):77-81.XUE Xu-yan,ZHONG Cong-li,CHEN Ya-ming,et al.The dynamic characteristic of frozen soil and determination of parameters[J].Chinese Journal of Geotechnical Engineering,1998,20(5):77-81.
[14]朱元林,张家懿.冻土的弹性变形及压缩变形[J].冰川冻土,1982,4(3):29-39.ZHU Yuan-lin.ZHANG Jia-yi.The elastic and compressive deformation of the frozen soil[J].Journal of Glaciology and Geocryology,1982,4(3):29-39.
[15]吴紫汪,马巍.冻土强度与蠕变[M].兰州:兰州大学出版社,1994.
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