高速列车荷载作用下成层饱和软土地基的动力响应

发布时间：2018-04-01 02:29

本文选题：移动荷载　切入点：Biot理论　出处：《浙江大学》2017年硕士论文

【摘要】：铁路高速化已成为当今世界交通运输的发展趋势,在高铁规模快速扩大的同时,高铁运行速度也得到了极大的提高。已有文献指出,当列车低速运行时,其在地基中引起的动力响应较小,与按静力方法得到的结果差距较小。然而,随着列车运行速度的增加,下部结构的振动水平以及车辆-轨道结构的动力相互作用都将随之加剧,威胁列车的运行安全。且在我国经济发达的东南沿海地区,广泛分布着饱和软土地基。由于软土中Rayleigh波的传播速度较小,这些地区高速列车较易超过地基的Rayleigh波速而产生剧烈的地基振动,不仅影响铁路的安全运营和旅客的舒适性,还将对周边环境带来不可忽视的影响。因此,非常有必要开展对高速列车荷载作用下饱和软土地基的动力响应的研究。本文首先研究了均质饱和地基的动力响应,基于Biot理论与欧拉-伯努利梁理论,建立了饱和多孔介质半空间上覆单位宽度无限长度梁模型。为确保在施加垂向荷载时,梁与半空间之间可以紧密贴合不会脱离,在梁与半空间的界面处使用了一种改进的光滑接触条件。在将等效刚度的表达式由围道积分解析得出后,计算了不同工况下的等效刚度,从而得出三种体波(P1波,P2波与S波)的Rayleigh极点与散布枝点。而后画出了不同土体渗透系数条件下Rayleigh极点与分枝点的轨迹,研究了梁-半空间界面上连续性条件与土体渗透系数对等效刚度的影响。其次,本文将均质饱和地基推广为成层饱和地基,建立了一个三维成层饱和地基模型,通过在水平方向使用傅里叶变换和正交变换从而将饱和地基Biot动力公式化为Love和Rayleigh模态方程。在竖直方向使用薄层法将地基划分为数个单元,得到单个薄层单元的控制方程后通过组装获得模型总体控制方程,最终推导出了三维成层饱和土地基的频域动力Green函数。数值计算时通过将每两层视作一个周期结构单元,研究了 Love模态与Rayleigh模态在不同激振频率与土体参数下的弥散特性,从而得到了波在周期饱和软土地基中的通带和禁带,并研究了周期结构单元数对通带与禁带分布规律的影响。最后,在第二部分中已建立的三维层状饱和地基模型的基础上建立了铁路高架桥的三维数值模型。该模型为无碴轨道模型,其部件包括无限长的铁轨、铁轨扣件、不连续的轨道板及其垫层和架设于无限多跨弹性支撑梁上的混凝土底座。地基模型使用了已建立的三维层状饱和地基模型,桩则离散为欧拉-伯努利梁。使用一系列移动简谐点荷载模拟了列车荷载。通过数值计算,首先研究了饱和土地基中群桩基础的阻抗,其次研究了不同速度下地表振动速度与孔压的空间分布规律以及列车速度的变化对地表最大振动速度与地下最大孔压的影响,最后研究了荷载激振频率对地基动力响应的影响。以上研究为铁路高架桥引起的地基振动提供了理论分析模型和方法,可丰富饱和土体波动理论,对铁路高架桥周边建筑的设计与施工具有重要的指导意义。
[Abstract]:High speed railway has become the development trend of world transportation, high-speed rail in the rapid expansion of the scale at the same time, high-speed rail running speed has been greatly improved. It has been pointed out that, when the train is running at low speed, the dynamic response of the smaller caused in the foundation, according to the gap with the static method results in smaller. However, with the increase of train speed, the dynamic substructure vibration level and vehicle track structure interaction will be intensified, a threat to the safe operation of the train. And in China's economically developed southeast coastal areas, widely distributed in saturated soft soil. Because of the transmission speed of the smaller Rayleigh wave in soft soil these areas, high-speed trains more easily than Rayleigh wave velocity of the foundation caused severe ground vibration not only affects the safe operation, and the railway passenger comfort, will not bring to the surrounding environment Ignored. Therefore, it is necessary to carry out research on the power of the high-speed train load response of saturated soft soil. This paper studies the dynamic response of homogeneous saturated soil, Biot theory and Euler Bernoulli beam based on the theory of saturated porous media was established with unit width of half space infinite length beam model. Ensure the applied vertical load, between the beam and the half space can be tightly not out, at the interface in the beam and a half space using an improved smooth contact conditions. The formula of equivalent stiffness by contour integral analysis, equivalent stiffness calculation under different working conditions, so that three kinds of body waves (P1 wave, P2 wave and S wave) Rayleigh pole and branch point spread. And then draw the different permeability coefficients of soil under the condition of Rayleigh pole and branch point trajectory of beam - half space interface. The continuity conditions and soil permeability coefficient affecting equivalent stiffness. Secondly, the foundation for the promotion of homogeneous saturated layered saturated soil, a three-dimensional layered saturated soil model, by using Fourier transform and orthogonal transformation in the horizontal direction and the saturated soil Biot dynamic formula for Love and Rayleigh modal equations. Using the thin layer method in the vertical direction the foundation is divided into a plurality of units, the governing equations are obtained by assembling the single layer unit model overall control equation, we deduced the three-dimensional domain layer saturated soil dynamic Green function. Numerical calculation by each of the two layer as a periodic structure unit, dispersion characteristics study on the Love mode and the Rayleigh mode in different vibration frequency and soil parameters, thus obtained the periodic wave in saturated soft soil in the passband and stopband, and study The number of units through periodic structure influence and the band gap distribution. Finally, the foundation has been established in the second part of the three-dimensional layered soil model was established on the three-dimensional numerical model of railway viaduct. The model for ballastless track model, its components including infinite rail fastening, discontinuous rail plate and cushion and erected in the infinite multi span concrete base beam on elastic support. The foundation model uses the established three-dimensional layered saturated soil pile model, discrete Euler Bernoulli beam. The train load was simulated using a series of harmonic moving point load. By numerical calculation, firstly studies the impedance of pile group foundation of saturated soil in the medium, then the speed speed and the hole surface vibration pressure distribution and train speed variation of the maximum vibration velocity of surface and underground maximum pore pressure. Effect of sound, finally studied the response of vibration frequency on the foundation. The above research foundation for vibration induced by railway viaduct provides a theoretical model and analysis method that can enrich the soil wave theory, which has important guiding significance to the design and construction of the railway viaduct surrounding buildings.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U211;TU435

【参考文献】