路基地震峰值加速度响应特性振动台试验研究
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摘要
在采用拟静力法分析公路路基抗震稳定时,需要考虑路基对地震加速度产生动力放大效果的影响。为了研究该放大效果,针对填方路基在强地震动作用下的动力响应,设计并完成了1∶20比尺的路基大型振动台模型试验。通过输入不同类型、幅值、频率的地震波激励,研究地震作用下路基模型边坡地震峰值加速度的放大系数。试验结果表明,路基边坡对输入的水平地震波具有明显的放大作用,而对竖向地震波的放大作用不明显。沿路基高程向上,水平地震波加速度峰值放大系数呈现波动,且坡面的放大系数大于路基内部的放大系数。在不同类型、不同振幅和不同频率的地震波作用下,路基地震峰值加速度放大系数具有明显的差异。试验结果可为确定路基抗震稳定设计的动力荷载提供相应的参考。
Many slopes of subgrades fail during earthquakes.Therefore,it is necessary to evaluate the stability of slopes under seismic loading in the design of the subgrade.The pseudo-static method is one of the most frequently used methods in seismic stability analysis of slopes and is the specified method in the"Specifications of Seismic Designs for Highway Engineering."One of the key factors in this method is the effect of amplification of the peak acceleration of a seismic load.To study this effect,a large-scale shaking-table model was developed with a subgrade model at a scale of 1:20.A series of tests was performed with various inputs of seismic wave type,amplitude,and frequency.Seismic wave type included one type of artificial-seismic wave(sinusoidal wave)and two types of observed seismic waves(EL Centro and Wenchuan seismic waves).The amplitude and the frequency of each wave were determined by the scales of model similarity.In these tests,accelerometers were set at various locations in the subgrade model.Accelerations of the model under seismic loading were then measured in both vertical and horizontal directions.Amplification coefficients were calculated by dividing these accelerations by the measured acceleration at the surface of shaking-table.Test results show that horizontal seismic waves are greatly amplified by the subgrade;amplification of vertical seismic waves was not noticeable.Maximum amplification coefficients of 2.45 and 1.3were located at the surface of the slope for both vertical and horizontal waves,respectively.The amplification coefficient of the horizontal seismic wave varied along the height of the subgrade and was divided into three stages of height increase such as increasing,decreasing,and later increasing again.The maximum amplification coefficient was reached at the highest point of the pavement,and it varied along the pavement.The amplification coefficients were greater at the surface of the slope than those inside for both horizontal and vertical seismic waves.For horizontal waves,the amplifications differed significantly under seismic waves with different frequencies,wave type,and amplitude.The amplification coefficient increased with an increase in frequency in the test.For the three types of input waves,the amplification coefficient was maximum under EL Centro seismic waves and minimum under sinusoidal waves.Moreover,the amplification coefficient decreased with an increase in amplitude.These results show that the amplification varies under different seismic loads and should be evaluated according to actual situations.Further,these results are helpful for determining seismic load in the seismic stability design of subgrades.
Many slopes of subgrades fail during earthquakes.Therefore,it is necessary to evaluate the stability of slopes under seismic loading in the design of the subgrade.The pseudo-static method is one of the most frequently used methods in seismic stability analysis of slopes and is the specified method in the"Specifications of Seismic Designs for Highway Engineering."One of the key factors in this method is the effect of amplification of the peak acceleration of a seismic load.To study this effect,a large-scale shaking-table model was developed with a subgrade model at a scale of 1:20.A series of tests was performed with various inputs of seismic wave type,amplitude,and frequency.Seismic wave type included one type of artificial-seismic wave(sinusoidal wave)and two types of observed seismic waves(EL Centro and Wenchuan seismic waves).The amplitude and the frequency of each wave were determined by the scales of model similarity.In these tests,accelerometers were set at various locations in the subgrade model.Accelerations of the model under seismic loading were then measured in both vertical and horizontal directions.Amplification coefficients were calculated by dividing these accelerations by the measured acceleration at the surface of shaking-table.Test results show that horizontal seismic waves are greatly amplified by the subgrade;amplification of vertical seismic waves was not noticeable.Maximum amplification coefficients of 2.45 and 1.3were located at the surface of the slope for both vertical and horizontal waves,respectively.The amplification coefficient of the horizontal seismic wave varied along the height of the subgrade and was divided into three stages of height increase such as increasing,decreasing,and later increasing again.The maximum amplification coefficient was reached at the highest point of the pavement,and it varied along the pavement.The amplification coefficients were greater at the surface of the slope than those inside for both horizontal and vertical seismic waves.For horizontal waves,the amplifications differed significantly under seismic waves with different frequencies,wave type,and amplitude.The amplification coefficient increased with an increase in frequency in the test.For the three types of input waves,the amplification coefficient was maximum under EL Centro seismic waves and minimum under sinusoidal waves.Moreover,the amplification coefficient decreased with an increase in amplitude.These results show that the amplification varies under different seismic loads and should be evaluated according to actual situations.Further,these results are helpful for determining seismic load in the seismic stability design of subgrades.
引文
[1]陈国兴.岩土地震工程学[M].北京:科学出版社,2007.CHEN Guo-xing.Geotechnical Earthquake Engineering[M].Beijing:Science Press,2007.(in Chinese)
[2]姚令侃,冯俊德,杨明.汶川地震路基震害分析及对抗震规范改进的启示[J].西南交通大学学报,2009,44(3):301-311.YAO Ling-kan,FENG Jun-de,YANG Ming.Damage Analysis of Subgrade Engineering in Wenchuan Earthquake and Recommendations for Improving Seismic Design Code[J].Journal of Southwest Jiaotong University,2009,44(3):301-311.(in Chinese)
[3]薄景山,徐国栋,景立平.土边坡地震反应及其动力稳定性分析[J].地震工程与工程振动,2001,21(2):116-120.BO Jing-shan,XU Guo-dong,JING Li-ping.Seismic Response and Dynamic Stability Analysis of Soil Slopes[J].Earthquake Engineering and Engineering Vibration,2001,21(2):116-120.(in Chinese)
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[6]徐光兴,姚令侃,高召宁,等.边坡动力特性与动力响应的大型振动台模型试验研究[J].岩石力学与工程学报,2008,27(3):624-632.XU Guang-xing,YAO Ling-kan,GAO Zhao-ning,et al.Largescale Shaking Table Model Test Study on Dynamic Characteristics and Dynamic Responses of Slope[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):624-632.(in Chinese)
[7]王建,姚令侃,吴伟.路堤震害模式及路堤动力特性研究[J].岩土力学,2010,31(12):3801-3108.WANG Jian,YAO Ling-kan,WU Wei.Research on Seismic Damage Mode and Dynamic Characteristics of Road Embankment[J].Rock and Soil Mechanics,2010,31(12):3801-3108.(in Chinese)
[8]李金贝,张鸿儒,李志强.高烈度地震区公路填方路基大型振动台模型试验[J].公路交通科技,2011,28(11):1-6.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Large-scale Shaking Table Model Test for Fill Subgrade of Highway in Highintensity Earthquake Area[J].Journal of Highway and Transportation Research and Development,2011,28(11):1-6.(in Chinese)
[9]李金贝,张鸿儒,李志强.填方路基振动台动力破坏试验研究[J].岩土力学,2011,32(10):3075-3081.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Experimental Study of Dynamic Failure of Fill Subgrades Using a Shaking Table[J].Rock and Soil Mechanics,2011,32(10):3075-3081.(in Chinese)
[10]李金贝,张鸿儒,李志强.路基动力响应与动力破坏的大型振动台模型试验研究[J].岩石力学与工程学报,2011,30(增2):3746-3754.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Large-scale Shaking Table Model Test Study of Dynamic Response and Dynamic Failure of Subgrade[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(Supp.2):3746-3754.(in Chinese)
[2]姚令侃,冯俊德,杨明.汶川地震路基震害分析及对抗震规范改进的启示[J].西南交通大学学报,2009,44(3):301-311.YAO Ling-kan,FENG Jun-de,YANG Ming.Damage Analysis of Subgrade Engineering in Wenchuan Earthquake and Recommendations for Improving Seismic Design Code[J].Journal of Southwest Jiaotong University,2009,44(3):301-311.(in Chinese)
[3]薄景山,徐国栋,景立平.土边坡地震反应及其动力稳定性分析[J].地震工程与工程振动,2001,21(2):116-120.BO Jing-shan,XU Guo-dong,JING Li-ping.Seismic Response and Dynamic Stability Analysis of Soil Slopes[J].Earthquake Engineering and Engineering Vibration,2001,21(2):116-120.(in Chinese)
[4]中华人民共和国交通运输部.公路工程抗震规范(JTG B02-2013)[S].北京:人民交通出版社,2014.Ministry of Transport of the People’s Republic of China.Specification of Seismic Design for Highway Engineering(JTG B02-2013)[S].Beijing:China Communications Press,2014.(in Chinese).
[5]刘汉龙.土动力学与土工抗震研究进展综述[J].土木工程学报,2012,45(4):148-164.LIU Han-long.A Review of Recent Advances in Soil Dynamics and Geotechnical Earthquake Engineering[J].China Civil Engineering Journal,2012,45(4):148-164.(in Chinese)
[6]徐光兴,姚令侃,高召宁,等.边坡动力特性与动力响应的大型振动台模型试验研究[J].岩石力学与工程学报,2008,27(3):624-632.XU Guang-xing,YAO Ling-kan,GAO Zhao-ning,et al.Largescale Shaking Table Model Test Study on Dynamic Characteristics and Dynamic Responses of Slope[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):624-632.(in Chinese)
[7]王建,姚令侃,吴伟.路堤震害模式及路堤动力特性研究[J].岩土力学,2010,31(12):3801-3108.WANG Jian,YAO Ling-kan,WU Wei.Research on Seismic Damage Mode and Dynamic Characteristics of Road Embankment[J].Rock and Soil Mechanics,2010,31(12):3801-3108.(in Chinese)
[8]李金贝,张鸿儒,李志强.高烈度地震区公路填方路基大型振动台模型试验[J].公路交通科技,2011,28(11):1-6.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Large-scale Shaking Table Model Test for Fill Subgrade of Highway in Highintensity Earthquake Area[J].Journal of Highway and Transportation Research and Development,2011,28(11):1-6.(in Chinese)
[9]李金贝,张鸿儒,李志强.填方路基振动台动力破坏试验研究[J].岩土力学,2011,32(10):3075-3081.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Experimental Study of Dynamic Failure of Fill Subgrades Using a Shaking Table[J].Rock and Soil Mechanics,2011,32(10):3075-3081.(in Chinese)
[10]李金贝,张鸿儒,李志强.路基动力响应与动力破坏的大型振动台模型试验研究[J].岩石力学与工程学报,2011,30(增2):3746-3754.LI Jin-bei,ZHANG Hong-ru,LI Zhi-qiang.Large-scale Shaking Table Model Test Study of Dynamic Response and Dynamic Failure of Subgrade[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(Supp.2):3746-3754.(in Chinese)
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