基于极限分析上限有限元法的临坡地基承载力研究

发布时间：2018-04-08 08:31

本文选题：临坡地基　切入点：极限分析上限法　出处：《湖南大学》2015年硕士论文

【摘要】：在中部多山地区的建筑、水利、公路、铁路、以及国防等工程中,常常会遇到需把基础设置在斜坡上、临近斜坡顶部或在已有基础附近开挖基坑的情况,又或者在设计跨越沟谷的桥梁时,通常不得不将其桥台或桥墩设置在斜坡上或临坡顶部,还有在城市地铁出口或入口附近的建筑物基础和水利灌溉中渡槽的基础等都需要考虑附近边坡的影响。而在现有的相关规范里,对上述情况中的地基承载力该如何来确定,仍然没给出明确的计算方法。在实际工程中,若遇到斜坡上或临坡地基承载力问题,或采用深基础加以避免,或转换为水平地面承载力问题加以处理,又或者凭借工程经验对其承载力加以折减,但这些方法都缺乏完备的理论依据,就会造成其结果有的偏于保守,不利于资源的节省;有的则安全储备过低,产生潜在的风险。因此,斜坡上或临坡地基承载力问题是一个迫切需要解决的常见工程问题。与水平地面地基土体的对称破坏模式不同,针对临坡地基土体随不同工况呈现出多种复杂破坏模式的特点。本文采用上限分析有限元技术,通过对临坡地基土建模,得到非线性上限规划模型,采用可行弧内点算法对其进行求解。将计算结果转换成相应的速度场和能量耗散图,把临坡地基承载力计算结果转为Terzaghi建议的分项系数叠加形式,并对分项系数Nc、Nγ、Nq的变化规律进行讨论,再与文献结果进行对比分析。本文还在此基础上,分析讨论了采用拟静力分析法来考虑地震作用时其对边坡稳定性和临坡地基承载力的影响。分析结果表明,上限有限元法能够较清楚的模拟出临坡地基破坏的几种模式,并得到合理解。分项系数Nc和Nq变化趋势基本符合现有的单调变化规律,但对于Nγ而言,由于破坏模式的改变造成了破坏体体积的变化,得到的Nγ会发生非单调改变的变化规律。并且地震作用会降低边坡稳定性和造成临坡地基承载力的折损,本文还提出了把临坡基础完全不受斜坡影响的距离a0/B作为绝对安全距离,并给出部分计算图表。
[Abstract]:In the central mountainous area construction, water conservancy, highway, railway, and defense engineering, often need to set up based on the slope, the slope near the top or excavation in the existing near the base of the situation, or in the design of the bridge across the valley, usually have to be set in the pier or abutment the slope or the slope top, and aqueduct near the exit in the city subway or the entrance of the building foundation and the foundation of all irrigation should be considered near slope. In the existing specification, how to determine the bearing capacity of the situation in the foundation, calculation method is still not clear. In practical engineering, when the slope or slope of bearing capacity, or the deep foundation to avoid, or converted to the level of ground bearing capacity problems, or with the engineering experience of its bearing capacity To reduction, but these methods are lack of theoretical basis and complete, it will cause the results of some conservative, is not conducive to resource saving; some safety margin is too low, cause a potential risk. Therefore, the slope or the slope bearing capacity problem is an urgent need to address the common symmetry and engineering problems. The level of the ground soil failure mode in different soil slope with different conditions on the foundation shows a variety of complex failure mode characteristics. This paper uses the upper bound finite element analysis technology, through the modeling of the soil slope, the upper limit of non line programming model, using feasible arc interior point algorithm for solving it. The calculation results convert the velocity field and the energy dissipation diagram, the slope bearing capacity calculation results for partial coefficients of stacking patterns suggested by Terzaghi, and the correlation coefficient Nc, N gamma, Nq change into For discussion, and the literature results were compared and analyzed. This paper is also based on this, discussed using the pseudo static analysis method to consider the impact of the earthquake on the slope stability and the slope of foundation bearing capacity. The analysis results show that the upper limit of the finite element method can better simulate several modes of slope failure of foundation, and get close to understand. The coefficient Nc and Nq changes consistent with monotonic variation of the existing items, but for N gamma, due to the failure mode changes caused changes of damage volume, N gamma will get variation of non monotonic change. And the earthquake will reduce the slope stability and cause break the loss of bearing capacity of slope foundation, this paper also put forward the basis of the slope without slope affects the distance a0/B as absolute safety distance, and gives some graphs.

【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU470

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