陡坡桥梁桩基及其支护结构振动台试验研究

发布时间：2018-08-19 20:32

【摘要】：四川西部地形复杂,地质活跃,是我国地震灾害最严重的地区之一。这些地区高陡边坡繁多,许多铁路线路的桥梁的墩台基础不可避免的会设置于高陡边坡及滑坡、岩堆等不良地质体上。许多高陡边坡在地震作用下极易发生滑坡,从而对边坡上的铁路桥梁桩基造成严重损害。因此,研究地震作用下陡坡桥梁桩基及其支护结构地震响应特征与结构的内力分布规律显得尤为重要。论文针对高陡边坡铁路桥梁桩基及支护结构在地震作用下的响应特征及内力分布问题,以某铁路线上某工点滑坡体的铁路桥梁工程建设为背景,采用资料调研、振动台模型试验、FLAC3D数值模拟等方法,研究桥梁桩基及其支护结构在地震作用下的动力响应特征及结构的内力分布规律。经过研究,得到主要结论如下:(1)地震作用下,模型边坡会发生剪切变形,从坡顶到坡脚,沿水平方向上,由于抗滑桩的加固作用,各测点水平位移增量幅值越来越小;(2)地震作用下,动力加速度响应被边坡放大,放大效应随高程增加越发明显;加速度时程出现"滞后效应"现象,较高位置点响应滞后于较低位置点;桥梁桩基及抗滑桩加固的临近土体地震加速度响应情况受到明显抑制;(3)在基岩与滑体交界面附近,随着地震荷载作用的增强,考虑桩土相互作用下的桥梁桩基沿桩身自上而下的土压力呈不规则分布,随着埋深先增大后减小;抗滑桩桩背动土压力在滑动面以下沿桩身逐渐变小,而在滑动面以上沿桩身动土压力逐渐变大;随着地震荷载的增大,抗滑桩桩后土体会产生一定的土抗力,桩身滑动面以下部分可能会发生微小旋转或者出现脱空现象,因此,工程设计中应注意转角的控制计算;(4)地震荷载作用下,由于抗滑桩对边坡加固,桥梁桩基的弯矩整体相对较小,且从内侧桩基到外侧桩基,同一高度处桩身弯矩越来越小;部分嵌固在基岩中的抗滑桩类似于悬臂梁,内力分布形式也近似,基岩以上抗滑部分的桩身弯矩随高程的增加而减小;随着地震荷载的增加,弯矩极值点附近桩身会发生塑性铰破坏,因此抗震设计时,应该注意滑动面处桩身的抗弯承载力的设计计算。
[Abstract]:The western part of Sichuan is one of the most serious areas of earthquake disaster because of its complex topography and active geology. There are many high and steep slopes in these areas, and the piers and abutments of many railway bridges will inevitably be set on high and steep slopes, landslides, rock piles and other bad geological bodies. Many high and steep slopes are prone to landslide under earthquake, which results in serious damage to the pile foundation of railway bridges on the slope. Therefore, it is very important to study the seismic response characteristics and internal force distribution of steep slope bridge pile foundation and its supporting structure. Aiming at the response characteristics and internal force distribution of pile foundation and supporting structure of railway bridge on high and steep slope under earthquake, the paper takes the railway bridge construction of a certain work point on a railway line as the background, adopts the data investigation. The dynamic response characteristics and internal force distribution of bridge pile foundation and its supporting structure under earthquake are studied by means of shaking table model test and FLAC3D numerical simulation. The main conclusions are as follows: (1) under earthquake, shear deformation will occur in the model slope, from the top to the foot of the slope, along the horizontal direction, because of the reinforcement effect of anti-slide pile, The increment amplitude of horizontal displacement is becoming smaller and smaller. (2) under the earthquake, the dynamic acceleration response is magnified by the slope, and the amplification effect becomes more and more obvious with the elevation increasing, and the acceleration time history appears the phenomenon of "lag effect". The response of the higher position point lags behind the lower position point; the seismic acceleration response of the bridge pile foundation and the adjacent soil strengthened by the anti-slide pile is obviously restrained; (3) near the interface between the bedrock and the sliding body, with the increase of the seismic load, Considering the pile-soil interaction, the earth pressure of bridge pile foundation is irregular distribution along the pile body from top to bottom, which increases first and then decreases with the depth of burying, and the dynamic earth pressure on the back of anti-slide pile decreases gradually along the pile body below the sliding surface. However, the dynamic earth pressure along the pile body increases gradually above the sliding surface, and with the increase of seismic load, the soil behind the anti-slide pile produces a certain soil resistance, and the slip surface of the pile body may rotate slightly or appear void phenomenon, so, In engineering design, attention should be paid to the calculation of the angle of rotation: (4) under the action of seismic load, the bending moment of bridge pile foundation is relatively small due to the reinforcement of slope by anti-slide pile, and the bending moment of pile body becomes smaller and smaller at the same height from the inside pile foundation to the outside pile foundation; The anti-slide pile embedded in the bedrock is similar to the cantilever beam, and the internal force distribution is similar. The bending moment of the anti-slide part above the bedrock decreases with the increase of elevation, and with the increase of seismic load, The plastic hinge failure will occur in the pile body near the moment extremum, so in seismic design, attention should be paid to the design and calculation of the flexural bearing capacity of the pile body at the sliding surface.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U445.551

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