考虑场地效应的高陡岩质斜坡地震失稳机制
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摘要
以金沙江乌东德水电站右岸的鸡冠山梁子高陡斜坡为典型实例,在斜坡表层地震动监测基础上,通过在斜坡弹性模型底部分别输入水平、竖向Ricker子波,发现:斜坡顶部低模量岩体材料在水平Rick子波激励下,易产生放大效应;而当输入竖向Rick子波时,易在模型表层地形凸起部位产生共振放大,其顶面表层卓越频率也与现场实测值基本一致。其次,对比分析了在分别输入汶川八角什邡加速度记录、典型鲁甸地震加速度记录时的斜坡弹塑性模型的稳定性和动力响应特征,发现:(1)斜坡在静力条件下可能存在3种不同位置潜在滑面,但输入两种地震波后,变形破坏区仅发生在顶部滑面位置;(2)输入汶川地震波时,斜坡顶部滑面剪应变增量明显大于输入鲁甸地震波时对应值,且前者的滑面出现明显整体拉破坏区,滑面上部水平、竖向残余变形也不收敛,处于震后斜坡失稳状态。后者滑面底部无明显的拉破坏区,滑面上部残余变形收敛,处于震后斜坡稳定状态;(3)斜坡水平、竖向加速度都在斜坡顶部低模量材料表层出现明显的放大现象,场地效应明显。此外,表层加速度普遍大于斜坡内部相应值,尤其是地形凸起位置。输入汶川地震波时斜坡顶部水平向加速度放大系数大于鲁甸地震波相应值,但竖向加速度放大系数两者基本一致。
The Jiguanshanliangzi high-steep slope is taken as a typical case study in Wudongde hydropower station near Chin-sha River. Based on seismic monitoring of the slope surface, firstly, after inputting horizontal and vertical Ricker wavelets at the elastic slope model bottom, it is found that the low modulus of rock mass materials at the slope top is easily amplified after the excitation of the horizontal Rick wavelet. The surface convex topography is easy to produce resonance amplification when the vertical Rick wavelet is excited. The predominant frequencies of the top surface are consistent with the measured values. Secondly, comparative analysis of the slope stability and dynamic response characteristics are performed when inputting the real Wenchuan and Ludian earthquake acceleration records. It can be found that the slope may have three different potential slip surfaces at different locations under the static condition. However, when inputting the above two seismic waves, the deformation and failure occur only at the slope top position. When inputting the Wenchuan seismic wave, the shear strain increment of the top slip surface is significantly greater than that when inputting Ludian seismic wave. The tension failure zone is observed at the slip surface and the horizontal and vertical residual deformation is not convergence. The slope is at the state of instability after the earthquake. When inputting the Ludian seismic wave, there is no tensile failure zone observed at the slip surface and the residual deformation is convergence, which means that the slope is stable after the earthquake. The slope of horizontal and vertical acceleration at the slope top surface appears significantly enlargement due to a low modulus material, showing obvious site effect. In addition, the surface acceleration is generally greater than the corresponding values within the slope, especially at the location of convex topography. The amplification factor of horizontal acceleration at the slope top after inputting the Wenchuan seismic wave is greater than that after inputting the Ludian seismic wave, but the vertical acceleration amplification factors are essentially the same.
The Jiguanshanliangzi high-steep slope is taken as a typical case study in Wudongde hydropower station near Chin-sha River. Based on seismic monitoring of the slope surface, firstly, after inputting horizontal and vertical Ricker wavelets at the elastic slope model bottom, it is found that the low modulus of rock mass materials at the slope top is easily amplified after the excitation of the horizontal Rick wavelet. The surface convex topography is easy to produce resonance amplification when the vertical Rick wavelet is excited. The predominant frequencies of the top surface are consistent with the measured values. Secondly, comparative analysis of the slope stability and dynamic response characteristics are performed when inputting the real Wenchuan and Ludian earthquake acceleration records. It can be found that the slope may have three different potential slip surfaces at different locations under the static condition. However, when inputting the above two seismic waves, the deformation and failure occur only at the slope top position. When inputting the Wenchuan seismic wave, the shear strain increment of the top slip surface is significantly greater than that when inputting Ludian seismic wave. The tension failure zone is observed at the slip surface and the horizontal and vertical residual deformation is not convergence. The slope is at the state of instability after the earthquake. When inputting the Ludian seismic wave, there is no tensile failure zone observed at the slip surface and the residual deformation is convergence, which means that the slope is stable after the earthquake. The slope of horizontal and vertical acceleration at the slope top surface appears significantly enlargement due to a low modulus material, showing obvious site effect. In addition, the surface acceleration is generally greater than the corresponding values within the slope, especially at the location of convex topography. The amplification factor of horizontal acceleration at the slope top after inputting the Wenchuan seismic wave is greater than that after inputting the Ludian seismic wave, but the vertical acceleration amplification factors are essentially the same.
引文
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[15]YIN Yue-ping,WANG Fa-wu,SUN Ping.Landslide hazards triggered by the 2008 Wenchuan Ms8.0Earthquake,Sichuan,China[J].Landslides,2009,6(2):139-152.
[16]黄小福,张迎宾,赵兴权,等.地震条件下危岩崩塌运动特性的初步探讨[J].岩土力学,2017,38(2):583-592.HUANG Xiao-fu,ZHANG Ying-bin,ZHAO Xing-quan,et al.A preliminary study of kinetic characteristic of rock-fall under seismic loading[J].Rock and Soil Mechanics,2017,38(2):583-592.
[17]LYSMER J,KUHLEMEYER R L.Finite dynamic model for infinite media[J].Journal of the Engineering Mechanics Division,1969,95(4):859-878.
[18]ZIENKIEWICZ O C,HUMPHESON C,LEWIS R W.Associated and nonassociated visco-plasticity and plasticity in soil mechanics[J].Geotechnique,1975,25(4):671-89.
[19]ZHANG Ying-bin,CHEN Guang-qi,ZHENG Lu,et al.Effects of vertical seismic force on initiation of the Daguangbao landslide induced by the 2008 Wenchuan earthquake[J].Soil Dynamics&Earthquake Engineering,2015,73(7):91-102.
[2]陈明,卢文波,李鹏,等.岩质边坡爆破振动速度的高程放大效应研究[J].岩石力学与工程学报,2011,30(11):2189-2195.CHEN Ming,LU Wen-bo,LI Peng,et al.Elevation amplification effects of blasting vibration velocity in rock slope[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(11):2189-2195.
[3]李会中,刘冲平,黄孝泉,等.金沙江乌东德水电站枢纽区高位自然边坡块体安全性评价与处理措施研究[J].资源环境与工程,2011,25(5):468-473.LI Hui-zhong,LIU Chong-ping,HUANG Xiao-quan,et al.Study on block safety evaluation and trearment measures of high natural slope in key region of Wudongde hydropower station of Jinsha river[J].Resources Environment and Engineering,2011,25(5):468-473.
[4]殷跃平,王猛,李滨,等.汶川地震大光包滑坡动力响应特征研究[J].岩石力学与工程学报,2012,31(10):1969-1982.YIN Yue-ping,WANG Meng,LI Bin,et al.Dynamic response characteristics of Daguangbao landslide triggered by Wenchuan earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(10):1969-1982.
[5]殷跃平.汶川八级地震滑坡触发特征分析[J].工程地质学报,2009,17(1):29-38.YIN Yue-ping.Features of landsldies triggered by the Ms8.0 Wenchuan earthquake[J].Journal of Engineering Geology,2009,17(1):29-38.
[6]崔芳鹏,许强,殷跃平,等.基于带状震源破裂机制的斜坡动力响应[J].岩土力学,2018,39(1):320-330.CUI Fang-peng,XU Qiang,YIN Yue-ping,et al.Dynamic response of slope based on fracture mechanism of strip-shape hypocenter[J].Rock and Soil Mechanics,2018,39(1):320-330.
[7]王文沛,殷跃平,李滨,等.不同坡角斜坡动力响应频谱特征研究[J].岩石力学与工程学报,2015,81(1):121-128.WANG Wen-pei,YIN Yue-ping,LI Bin,et al.Study on spectral characteristics of slope dynamic response with different angles[J].Chinese Journal of Rock Mechanics and Engineering,2012,81(1):121-128.
[8]罗永红.地震作用下复杂斜坡响应规律演技[D].重庆:成都理工大学,2011.LUO Yong-hong.Study on complex slopes response law under earthquake action[D].Chengdu:Chengdu University of Technology,2011.
[9]WANG G H,KAMAI TOSHITAKA,HUANG R Q,et al.A large landslide riggered by the 2008 Wenchuan(M8.0)earthquake:insights for seismic motion[C]//Geologically Active,Proceedings of IAEG 2010.[S.l.]:CRC Press,2010:757-764.
[10]HUANG Run-qiu,PEI Xiang-jun,FAN Xuan-mei,et al.The characteristics and failure mechanism of the largest landslide triggered by the Wenchuan earthquake,May 12,2008,China[J].Landslides,2012,9(1):131-142.
[11]王海云,谢礼立.自贡市西山公园地形对地震动的影响[J].地球物理学报,2010,53(7):1631-1638.WANG Hai-yun,XIE Li-li.Effects of topography on ground motion in the Xishan park,Zigong city[J].Chinese Journal of Geophysics,2010,53(7):1631-1638.
[12]HAVENITH H B,STROM A,JONGMANS D,et al.Seismic triggering of landslides,part A:field evidence from the northern Tien Shan[J].Natural Hazards and Earth System Sciences,2003,3(1-2):135-149.
[13]BOURDEAU C,HAVENITH H B.Site effects modelling applied to the slope affected by the Suusamyr earthquake(Kyrgyzstan,1992)[J].Engineering Geology,2008,97(3-4):126-145.
[14]BOZZANO F,LENTI S,MARTINO A,et al.Earthquake triggering of landslides in highly jointed rock masses:reconstruction of the 1783 Scilla rock avalanche(Italy)[J].Geomorphology,2011,129(3-4):294-308.
[15]YIN Yue-ping,WANG Fa-wu,SUN Ping.Landslide hazards triggered by the 2008 Wenchuan Ms8.0Earthquake,Sichuan,China[J].Landslides,2009,6(2):139-152.
[16]黄小福,张迎宾,赵兴权,等.地震条件下危岩崩塌运动特性的初步探讨[J].岩土力学,2017,38(2):583-592.HUANG Xiao-fu,ZHANG Ying-bin,ZHAO Xing-quan,et al.A preliminary study of kinetic characteristic of rock-fall under seismic loading[J].Rock and Soil Mechanics,2017,38(2):583-592.
[17]LYSMER J,KUHLEMEYER R L.Finite dynamic model for infinite media[J].Journal of the Engineering Mechanics Division,1969,95(4):859-878.
[18]ZIENKIEWICZ O C,HUMPHESON C,LEWIS R W.Associated and nonassociated visco-plasticity and plasticity in soil mechanics[J].Geotechnique,1975,25(4):671-89.
[19]ZHANG Ying-bin,CHEN Guang-qi,ZHENG Lu,et al.Effects of vertical seismic force on initiation of the Daguangbao landslide induced by the 2008 Wenchuan earthquake[J].Soil Dynamics&Earthquake Engineering,2015,73(7):91-102.