基于离散—连续方法的昔格达地层铁路隧道基底动力特性及长期沉降研究

发布时间：2018-04-25 03:30

本文选题：列车荷载 + 动三轴试验　；参考：《西南交通大学》2017年硕士论文

【摘要】：随着中国西部大开发的继续深入,西南地区铁路的建设迎来新的高潮。成昆铁路复线米易至攀枝花段,峨眉山至米易段正在如火如茶的建设中。新建成昆铁路将穿越我国四川攀西地区特有的昔格达地层。昔格达地层质软,易风化剥落,最显著的特点是水稳性差,遇水软化崩解呈现流塑性。在既有老成昆铁路隧道病害调研中发现,穿越昔格达地层的隧道均出现大量翻浆冒泥、道床下沉、衬砌裂损等病害,给老成昆铁路的运营带来极大的安全隐患。本文以国家自然基金项目“昔格达组地层高速铁路隧道围岩承载能力及灾变控制技术研究”为依托,采用文献调研、理论分析、室内动三轴试验、离散-连续耦合方法的数值模拟等多种研究手段,探究了列车荷载作用下昔格达地层隧道基底动力响应规律,并提出了昔格达粘土在循环荷载下的累积塑性应变公式,意在为在建铁路隧道基底施工提供科学依据,改善施工工艺,减少后期运营过程中因列车荷载反复作用引起的各种病害,从而节约大量的后期维护成本。主要研究工作及结论如下:(1)通过多工况的昔格达粘土动三轴试验,研究了其在循环荷载作用下的累积塑性变形、动弹性模量、阻尼比的变化规律,建立了考虑含水率的累积塑性变形模型。研究表明:昔格达粘土累积塑性变形曲线可分为稳定型和破坏型,曲线类型主要受动应力比和含水率的影响。累积塑性变形随着动应力比、静偏应力比、含水率的增大而增大,随着围压和荷载频率的增大而减小。(2)运用试块冲击模拟试验验证了 FLAC3D6.0内置耦合方案在耦合界面应力的连续性,并基于室内三轴剪切试验数据,分别在FLAC3D和PFC3D中建立三轴剪切试验模型,标定了昔格达粘土的细观和宏观参数。(3)运用离散-连续方法分析了列车荷载作用下昔格达隧道基底动力特性,具体方法是仰拱底部附近区域采用离散元进行模拟,其他区域连续介质进行模拟。研究表明:列车振动引起加速度的变化可分为初始加速度和行车中加速度,随着列车车速增大,初始加速度峰值缓慢增大,行车中加速度峰值显著增大,且动应力峰值增大。
[Abstract]:With the further development of China's western region, the railway construction in the southwest region has ushered in a new climax. Cheng-Kun railway line from Miyi to Panzhihua section, Emei Mountain to Miyi section is in the construction of fire as tea. The newly built Kun Railway will cross the Xigeda formation in Panxi area, Sichuan Province, China. Xigeda formation is soft and easy to be weathered and spalling. The most obvious feature is that water stability is poor and water softening disintegration presents flow plasticity. In the investigation and investigation of the tunnel diseases of the existing Laocheng and Kun railway, it is found that a large number of diseases such as mud-breaking, bed sinking and lining damage appear in the tunnels passing through Xigeda, which bring great safety risks to the operation of the Laocheng and Kun Railway. Based on the National Natural Fund project "study on bearing capacity and catastrophe Control Technology of surrounding Rock of High-speed Railway Tunnel in Xigeda formation", this paper adopts literature investigation, theoretical analysis and indoor dynamic triaxial test. In this paper, the dynamic response law of foundation of Xigeda formation tunnel under train load is studied by numerical simulation of discrete-time and continuous coupling method, and the cumulative plastic strain formula of Xigeda clay under cyclic load is put forward. The purpose of this paper is to provide scientific basis for the foundation construction of the railway tunnel under construction, to improve the construction technology, to reduce various diseases caused by repeated train loads in the later operation process, and thus to save a large amount of later maintenance costs. The main research work and conclusions are as follows: (1) through the dynamic triaxial test of Xigeda clay under multiple working conditions, the variation of cumulative plastic deformation, dynamic elastic modulus and damping ratio under cyclic load is studied. A model of cumulative plastic deformation considering moisture content is established. The results show that the cumulative plastic deformation curve of Xigeda clay can be divided into stable type and failure type, which are mainly affected by dynamic stress ratio and water content. The cumulative plastic deformation increases with the increase of dynamic stress ratio, static stress ratio and moisture content. With the increase of confining pressure and load frequency, the test block impact simulation test is used to verify the continuity of the coupled interface stress of the FLAC3D6.0 built-in coupling scheme, and based on the indoor triaxial shear test data, The triaxial shear test models were established in FLAC3D and PFC3D respectively, and the mesoscopic and macroscopic parameters of Xigda clay were calibrated. The dynamic characteristics of Xigeda tunnel foundation under train loads were analyzed by discrete-time continuous method. The concrete method is that discrete element is used to simulate the region near the bottom of inverted arch and continuum medium is used to simulate other regions. The results show that the variation of acceleration caused by train vibration can be divided into initial acceleration and in-train acceleration. With the increase of train speed, the peak of initial acceleration increases slowly, the peak of acceleration increases significantly, and the peak of dynamic stress increases.
【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】：U457.2

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