【作者】 张达政；

【导师】 李红；

【作者基本信息】 长安大学 ， 结构工程， 2011， 硕士

【摘要】 边坡稳定性分析是土力学的三大经典问题之一,也是岩土工程中的重要课题。我国西北地区黄土地层全、类型多、分布广、厚度大,在黄土地区进行公路和铁路建设时,面临着大量高边坡问题,如何保证黄土高边坡的稳定性,公路和铁路建设的关键问题之一。同时处于高边坡上的桥梁墩台桩基,其受力较为复杂。桩基除了承受桩顶传来的上部竖向和水平荷载外,桩侧还要承受坡体的推力作用,兼有主动桩和被动桩的特性。本文以宁夏固原地区的新建铁路工程为背景,以黄土地区典型的路堑高边坡、高边坡上的桥梁桥台和桥墩为对象,通过基于材料非线性的有限元数值仿真技术,系统研究了高边坡的稳定性、桥台—桩基—边坡体系和桥墩承台—桩基—边坡体系最不利荷载下的稳定性和力学行为。通过基于有限元强度折减法的多级黄土路堑高边坡的稳定研究,得出不同的湿陷程度对边坡稳定承载力存在较大影响,因此影响黄土高边坡稳定性的关键是黄土湿陷引起的强度折减。同时多级黄土路堑边坡破坏首先从底层坡脚开始,坡脚应力集中导致土的剪切强度首先达到峰值而破坏,从而导致坡肩开裂并将其不能承担的剪应力向临近点传递,使其强度降低；随着剪应力的依次传递,最后整个滑移面的强度均降低后,滑移面开始整体滑塌而破坏。通过对黄土高边坡上桥台—桩基—边坡体系基于非线性有限元的分析得出,在正常使用的最不利荷载工况下,桥台—桩基—边坡体系失稳的主要原因是桩底土体的破坏；边坡-桥台-桩基体系在加载至最大承载力的过程中,边坡土体没有出现明显的滑移面,说明只要桥台偏离边坡一定距离,可保证边坡的稳定性。当桩侧土体具有明显分层性质时,桩基应力在土层分界部位较大,容易出现了塑性屈服区域,反映出高边坡上桥台承受较大桩后土推力的受力特点。通过对黄土高边坡上桥墩承台—桩基—边坡体系基于非线性有限元的分析得出,正常使用的最不利荷载情况下边坡-承台-桩基体系失稳的主要原因是桩侧黄土破坏,桩身和土体滑移分离,桩基失去竖向承载能力。对于桩侧土体全部为黄土的桥墩桩基,在最不利荷载下桩基应力在桩顶部位较大,且最先开裂,建议应加强桩顶和承台连接部位的配筋和构造设计。同时,桩基应力和位移结果表明,沿纵向和横向不同部位桩基的受力存在较大的差异,反映出较强的群桩受力的非同步效应和桩后土体的土推力作用。更多还原

【Abstract】 Soil slope stability analysis is one of the three classical mechanics, It is also an important subject in geotechnical engineering. In Northwest China loess is all the type、widely distributed、large thickness, in the loess area which road and rail are constructing, it will face with a lot of high slope problems, such as how to ensure high loess slope stability, it is also the key to road and railway construction of which the problems. At the same time, the high slope on the bridge pier foundation, which force is more complex. In addition, come from the under the pile of the upper vertical and lateral loads, the pile side also bear the thrust of the role of the slope, it is that both active and passive pile characteristics.This paper lies in the city of guyuan’s new railway projects area background, it is lies on typical of loess cut slope, high slope on the bridge abutments and piers for the object, through the material nonlinear finite element based numerical simulation, the system The stability of the slope, abutments-pile-slope system and pier cap-pile-slope system stability under the worst load and mechanical behaviorFinite element-based multi-level strength reduction of high slope stability loess cutting research, arrive at different degree of slope stability collapsible capacity there is a big influence, thus affecting the high loess slope stability, the key to loess depression caused by strength reduction. While multi-level damage Loess Slope first start from the bottom foot of the slope, toe stress concentration caused the shear strength of soil and destruction of the first peak, which leads to cracking and its slope can not afford to shoulder the shear stress near the point of delivery to make reduce its intensity; with shear stress were passed, then finally the strength of the slip plane is reduced, as the result,the overall slump and started sliding surface damage。Through the bridge abutment on the high loess slope-pile-the slope system, it based on nonlinear finite element analysis derived in the normal use of the most unfavorable loading conditions, the bridge abutment-pile-instability of the slope system mainly due to the destruction of the soil pile; Slope-abutment-pile system to the maximum load carrying capacity in the process, the slope of the soil without significant slip surface, indicating that as long as the deviation from the slope of a certain distance from abutment which can guarantee the stability of the slope. When the pile has a clear hierarchical nature of the soil, the pile of soil boundaries in the part of a larger is stressing, prone to the plastic yield region, reflecting the high slope on the pile soil behind abutment to withstand greater thrust force characteristics.Through the high loess slope pier cap on-pile-the slope system which based on nonlinear finite element analysis derived, the normal use of the slope under the most adverse load-pile-pile system is the main reason for instability loess pile damage, pile and soil slip separation, loss of vertical bearing capacity of pile. For all of the soil pile pier loess pile, pile foundation under the most unfavorable load stress in the pile at the top bit larger, and the first to crack, with recommendations to strengthen the pile top and cap connected parts of the reinforcement and structural design. Meanwhile, pile the stress and displacement results show that different parts along the vertical and horizontal pile there is a big difference in the force, reflecting the strong force of pile groups and pile of non-synchronous effect of the soil thrust the role of soil mass.更多还原