强震崩塌岩体冲击桥墩动力响应研究
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摘要
雅(安)—泸(沽)高速公路YK136+097西冲特大桥16#桥墩岩质边坡发育的陡倾坡外结构面与风化卸荷裂隙构成倒悬危岩体。该区属高地震烈度区(VIII度),运用非连续变形数值分析(DDA)方法,对危岩体在强震作用下的失稳模式、破坏规模、运动轨迹及对桥墩冲击的动力响应进行模拟研究。演进过程如下:强地震力作用产生放大效应,使突出山梁部位岩体首先震裂、抛掷,接续为中下部岩体沿卸荷拉裂面溃崩解体,滑体进而沿主控结构面整体滑塌、冲击桥墩。统计分析坡体及桥墩监测点位移大小和变化特征,表明桥墩上各监测点位移与地震节律呈正相关,在失稳岩块撞击及堆积岩体推挤作用下,系梁与桥墩顶端变形及永久位移较墩身其他位置大,这一过程与"5·12"汶川地震滚石冲击桥梁破坏现象吻合。在对坡体及桥墩变形量化分析基础上,依据强震触发崩塌特征提出了桥梁边坡危岩防治方案。
In the high earthquake region of intensity VIII,dangerous rock mass slope of Xichongte bridge pier #16 at YK136+097 along Ya?an—Lugu highway is selected as studying objects.The geology-dynamics model of dangerous rock bodies is constructed from steep structural plane tilting to the outside slope and weathering-unloading fracture.Monitoring points are placed at important places of slope body and bridge pier.Using the numerical analysis method of discontinuous deformation,the instability model,failure scale,motion trajectory of dangerous rock masses and their impact dynamic response characteristics on bridge pier are simulated.Evolution process is presented as follows:Under intense earthquake,horizontal earthquake force causes enlargement effect,which results in earthquake collapse and ejection of the rock masses at salient position at first.Next,shattering-sliding and disintegrating of the rock masses happens along unloading tension fracture surfaces in the middle of slope.At last,the whole landslide body slumps along controlling structural plane and impacts bridge pier.Statistical analysis of displacement and deformation feature of all monitoring points at slope body and bridge pier shows that the displacement from all monitoring points is positively correlated with earthquake rhythm.Under the influence of the impacting of instability rock and the pushing of accumulation rock,the deformation and permanent displacement of beam and the top of pier are larger than that at other positions,which is the same as phenomenon of bridge failure during "5?12" Wenchuan earthquake.Based on the quantitative analysis of deformation of slope and pier,according to the collapse features induced by intense earthquake,prevention and treatment measurement are put forward for the dangerous rock mass of bridge slope.
In the high earthquake region of intensity VIII,dangerous rock mass slope of Xichongte bridge pier #16 at YK136+097 along Ya?an—Lugu highway is selected as studying objects.The geology-dynamics model of dangerous rock bodies is constructed from steep structural plane tilting to the outside slope and weathering-unloading fracture.Monitoring points are placed at important places of slope body and bridge pier.Using the numerical analysis method of discontinuous deformation,the instability model,failure scale,motion trajectory of dangerous rock masses and their impact dynamic response characteristics on bridge pier are simulated.Evolution process is presented as follows:Under intense earthquake,horizontal earthquake force causes enlargement effect,which results in earthquake collapse and ejection of the rock masses at salient position at first.Next,shattering-sliding and disintegrating of the rock masses happens along unloading tension fracture surfaces in the middle of slope.At last,the whole landslide body slumps along controlling structural plane and impacts bridge pier.Statistical analysis of displacement and deformation feature of all monitoring points at slope body and bridge pier shows that the displacement from all monitoring points is positively correlated with earthquake rhythm.Under the influence of the impacting of instability rock and the pushing of accumulation rock,the deformation and permanent displacement of beam and the top of pier are larger than that at other positions,which is the same as phenomenon of bridge failure during "5?12" Wenchuan earthquake.Based on the quantitative analysis of deformation of slope and pier,according to the collapse features induced by intense earthquake,prevention and treatment measurement are put forward for the dangerous rock mass of bridge slope.
引文
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[4]黄润秋.汶川8.0级地震触发崩滑灾害机制及其地质力学模式[J].岩石力学与工程学报,2009,28(6):1 239–1 249.(HUANG Runqiu.Mechanism and geomechanical modes of landslide hazards triggered by Wenchuan 8.0 earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(6):1 239–1 249.(in Chinese))
[5]SHI G H.Producing joint polygons,cutting joint blocks and finding key blocks for general free surfaces[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(11):2 161–2 170.
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[7]刘洪兵,朱晞.地震中地形放大效应的观测和研究进展[J].世界地震工程,1999,15(3):20–25.(LIU Hongbing,ZHU Xi.Advance on topographic amplification effects of seismic response[J].World Earthquake Engineering,1999,15(3):20–25.(in Chinese))
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