复杂土层结构黄土场地地震动反应特性
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摘要
基于复杂土层结构黄土场地的振动台缩尺模型试验,揭示了强震作用下场地的地震动响应规律;结合数值仿真模拟,分析了模型场地位移变化规律、地震波传播特征等。结果表明:(1)输入同一地震荷载情况下,峰值加速度(PGA)沿高程方向呈现递增趋势;同一监测点,PGA变化与地震动强度呈现正相关。(2)水平分量PGA大于垂直分量PGA;试验结果和计算所得PGA放大系数变化略有差异。(3)地表位移放大系数在2. 5～3. 5范围内变化;位移峰值的变化趋势与加速度峰值变化相似。(4)地震波传播速度变化与高程之间呈现负相关关系;在上覆土层厚度小于42. 5 m的情况下,地震波传播速度受上覆土层厚度影响较小;地震波在该黄土场地传播的过程中,其水平分量速度较垂直分量速度递减明显。试验与计算结果对黄土场地建筑选址和抗震设防具有一定的参考意义。
Based on shaking table tests for scale model of complex structure loess field,it revealed that the seismic response law under seismic dynamic motion. Combined with numerical simulation,The law of displacement variation and seismic wave propagation characteristics of model site is analyzed. The results show that:( 1) Under the same seismic load,the peak acceleration( PGA) shows an increasing trend along the elevation direction. At the same monitoring point,PGA change is positively correlated with ground vibration intensity.( 2) The horizontal component PGA is greater than the vertical component PGA,there is a slight difference in the change of the PGA magnification coefficient between the test results and the calculated results( 3) The surface displacement amplification coefficient varies from 2. 5 ～ 3. 5. The change trend of displacement peak is similar to that of acceleration peak.( 4) There is a negative correlation between seismic wave propagation velocity and elevation,when the thickness of the overlying soil is less than 42. 5 m,the velocity of seismic wave is less affected by the thickness of the overlying soil layer,In the course of the seismic wave propagation in the loess site,the velocity of the horizontal component is obviously lower than that of the vertical component. The results of the test and calculation have some reference significance to the site selection and seismic fortification of thecomplex structure loess field.
Based on shaking table tests for scale model of complex structure loess field,it revealed that the seismic response law under seismic dynamic motion. Combined with numerical simulation,The law of displacement variation and seismic wave propagation characteristics of model site is analyzed. The results show that:( 1) Under the same seismic load,the peak acceleration( PGA) shows an increasing trend along the elevation direction. At the same monitoring point,PGA change is positively correlated with ground vibration intensity.( 2) The horizontal component PGA is greater than the vertical component PGA,there is a slight difference in the change of the PGA magnification coefficient between the test results and the calculated results( 3) The surface displacement amplification coefficient varies from 2. 5 ～ 3. 5. The change trend of displacement peak is similar to that of acceleration peak.( 4) There is a negative correlation between seismic wave propagation velocity and elevation,when the thickness of the overlying soil is less than 42. 5 m,the velocity of seismic wave is less affected by the thickness of the overlying soil layer,In the course of the seismic wave propagation in the loess site,the velocity of the horizontal component is obviously lower than that of the vertical component. The results of the test and calculation have some reference significance to the site selection and seismic fortification of thecomplex structure loess field.
引文
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[2]石玉成,王兰民,张颖.黄土场地覆盖层厚度和地形条件对地震动放大效应的影响[J].地震工程学报,1999,21(2):203-208.SHI Yucheng,WANG Lanmin,ZHANG Ying. Effects of overburden thickness and topography of loessial sites on earthquake ground motion[J].Northwestern Seismological Journal,1999,21(2):203-208.(in Chinese)
[3]石玉成,王兰民,张向红.黄土场地不同土层结构对地震地面运动参数的影响[J].工程地质学报,2000,8(增刊):355-358.SHI Yucheng,WANG Lanmin,ZHANG Xianghong. The influence of different soil structure on the parameters of seismic ground motion[J]. Journal of Engineering Geology,2000,8(S):355-358.(in Chinese)
[4]吴志坚,王兰民,陈拓,等.汶川地震远场地地震动场地放大效应机制研究[J].岩土力学,2012,33(12):3736-3740.WU Zhijian,WANG Lanmin,CHEN Tuo,et al. Study of mechanism of site amplification effects on ground motion in far field loess during Wenchuan Ms8. 0 earthquake[J]. Rock and Soil Mechanics,2012,33(12):3736-3740.(in Chinese)
[5]陈小云,吴红刚,杨涛.高原地区路基地震液化数值模拟研究[J].地震工程学报,2017,39(4):706-712.CHEN Xiaoyun,WU Honggang,YANG Tao. Numerical simulation of the earthquake liquefaction of a roadbed in a plateau[J]. China Earthquake Engineering Journal,2017,39(4):706-712.(in Chinese)
[6]盛志强,卢玉霞,石玉成,等.河谷地形的地震反应分析[J].地震工程学报,2013,35(1):126-132.SHENG Zhiqian,LU Yuxia,SHI Yucheng,et al. Seismic response analysis of valley topography[J]. China Earthquake Engineering Journal,2013,35(1):126-132.(in Chinese)
[7]肖文静,廖佳名,张亮亮.孤立山体地震动力响应的振动台试验研究[J].地震工程学报,2018,40(3):582-590.XIAO Wenjing,LIAO Jiaming,ZHANG Liangliang. Shaking table on seismic dynamic responses of isolated mountains[J]. China Earthquake Engineering Journal,2018,40(3):582-590.(in Chinese)
[8]陈拓,吴志坚,王平.兰州黄土场地地震动参数量化研究[J].世界地震工程,2017,33(1):166-171.CHEN Tuo,WU Zhijian,WANG Ping. Quantitative analysis of ground motion parameter of Lanzhou loessial sites[J]. World Earthquake Engineering,2017,33(1):166-171.(in Chinese)
[9]王艳茹,苗崇刚,戴君武.土-结构相互作用振动台试验模型简化方法探讨[J].自然灾害学报,2011(2):102-108.WANG Yanru,MIAO Chonggang,DAI Junwu. A simplified model of shaking table test on soil-structure interaction[J]. Journal of Natural Disasters,2011(2):102-108.(in Chinese)
[10]陈国兴,左熹,庄海洋,等.地铁隧道地震反应数值模拟与试验的对比分析[J].自然灾害学报,2007(6):81-87.CHEN Guoxing,ZUO Xi,ZHUANG Haiyang,et al. Contrast analysis of numerical simulation of subway tunnel earthquake response with test results[J]. Journal of Natural Disasters,2007(6):81-87.(in Chinese)
[11] Coetzee,Matthys J,Hart,et al. Flac Basic-An introduction to FLAC and Guide to its Practical Application in Geotechnical Engineering[R]. America:Itasca Consulting Group,Inc.,1998.
[12] Itasca Consulting Group,Inc. Fast Lafrangain Analysis of Continua in 3Dimensions-Theory and Background[M]. Minnesota,2002.
[13]王兰民,石玉成,刘旭,等.黄土动力学[M].北京:地震出版社,2003:202-205.WANG Lanmin,SHI Yucheng,LIU Xu,et al. Loess Dynamics[M]. Beijing:China Seismological Press,2003:202-205.(in Chinese)