落石冲击下拱形明洞落石冲击荷载及荷载效应研究

发布时间：2018-03-15 09:31

本文选题：拱形明洞　切入点：落石冲击　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：落石冲击下拱形明洞结构的力学响应,与结构特征、落石条件及回填方式等众多因素有关,受力机理复杂,只有将拱形明洞在落石冲击下的结构受力机理研究清楚了,才能使结构设计更加安全和经济,才可能使定性的经验设计过渡到科学的可靠性设计上来。本文以我国新建时速200公里客货共线铁路双线路堑式拱形明洞结构为研究对象,采用离散元和有限元相结合的方法对落石冲击拱形明洞结构冲击力大小影响因素、冲击荷载及荷载效应开展研究。主要研究内容及成果如下:(1)离散元颗粒流数值计算模型的建立。采用离散元颗粒流PFC3D软件,通过三轴试验校准得到与材料宏观物理力学性质一致的细观参数,建立了不同坡度、落石下落高度、回填土厚度、落石重量和坡面性质条件下防落石拱形明洞结构数值计算模型。(2)运用正交设计理论,选择正交表为L_(25)(5~6)的正交试验方案,考察坡度、落石下落高度、回填土厚度、落石重量和坡面性质这五个因素对落石冲击拱形隧道明洞结构的影响,以结构拱顶受到的冲击峰值力作为评价指标,采用极差分析和方差分析进行了影响因素显著水平检验。研究结果表明,回填土厚度对落石冲击拱形隧道明洞结构的冲击力影响最显著。(3)采用ANSYS/LS-DYNA动力有限元仿真软件,对落石冲击下拱形明洞结构力学响应进行研究。首先,从落石与回填土之间的相互作用入手,比较了落石对回填土表面的冲击力、由回填土传递到结构表面的冲击土压力(合力)以及拱顶表面受到的冲击压应力及其对应最大峰值之间的关系,提出应采用拱顶表面受到的冲击压应力作为落石冲击荷载;其次,对落石冲击荷载效应如结构的应力、应变、应变率、位移、加速度等响应进行了分析,对墙脚、仰拱底部地基反力进行了分析,分析得出拱顶是结构受力最不利部位,仰拱处基底反力响应滞后于墙脚基底反力响应;最后,进行了落石不同势能下结构各部位峰值响应最大值的曲线拟合,拟合出响应趋势曲线方程。
[Abstract]:The mechanical response of the open arch tunnel structure under the impact of falling stone is related to many factors, such as the structural characteristics, the condition of falling stone and the way of backfilling, and so on. The mechanical mechanism of the open arch tunnel under the impact of falling stone is studied clearly. In order to make the structure design safer and more economical, it is possible to make the qualitative experience design transition to the scientific reliability design. The method of discrete element and finite element method is used to influence the impact force of rock fall impact arch tunnel structure. The main contents and results of the research are as follows: 1) Establishment of numerical model of discrete element particle flow. PFC3D software of discrete element particle flow is used. Through triaxial test calibration, the mesoscopic parameters consistent with the macroscopic physical and mechanical properties of the material are obtained, and different slopes, falling height and backfill thickness are established. Under the condition of falling stone weight and slope property, the numerical calculation model of the structure of the open tunnel with the arch shape of anti-falling stone. (2) using the orthogonal design theory, the orthogonal test scheme of orthogonal test is selected as L25 / 25 / 5 / 5 / 6) to investigate the slope, the falling height and the thickness of the backfill soil, and to investigate the slope, the falling height of the falling rock, and the thickness of the backfill soil. The influence of rock falling weight and slope property on the structure of open tunnel with rock fall impact arch tunnel is studied. The peak impact force on the roof of the structure is taken as the evaluation index. The significant level test of influencing factors is carried out by means of range analysis and variance analysis. The results show that the thickness of backfill has the most significant influence on the impact force of the open tunnel structure of rock-falling arch tunnel. The ANSYS/LS-DYNA dynamic finite element simulation software is used. The structural mechanical response of the arch tunnel under the impact of falling stone is studied. Firstly, the impact force of the falling stone on the backfill surface is compared from the interaction between the falling stone and the backfill. The relationship between the impact earth pressure (resultant force) transferred from backfill to the structure surface and the impact compressive stress on the surface of the vault and its corresponding maximum peak value is proposed that the impact compressive stress on the surface of the vault should be used as the rock falling impact load. Secondly, the stress, strain, strain rate, displacement, acceleration response of rock fall impact load are analyzed, and the reaction force of the base of wall foot and invert arch is analyzed. It is concluded that the arch is the most unfavorable part of the structure. The counterforce response of the base at the inverted arch lags behind the counterforce response of the base of the wall. Finally, the curve fitting of the maximum peak response of each part of the structure under different potential energy is carried out, and the curve equation of the response trend is fitted.
【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】：U451;P642.2

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