基于土拱效应的桩承式路堤承载特性及其变形计算方法研究

发布时间：2019-05-15 00:26

【摘要】：我国高速公路、铁路建设迅猛发展,建设过程中经常会遭遇大面积软土问题,而桩承式路堤作为一种有效适应于该类不良地基的构筑物形式得到普遍应用,同时也引起了学术界的广泛关注,然而桩承式路堤工作机理和应力应变特性非常复杂。在进行土拱效应分析时,主要研究以下几个关键问题:桩土应力比、桩土差异沉降以及基于土拱效应的桩承式路堤设计方法。已有研究提出了不同的土拱模型及相应的计算方法,然而他们对土拱效应的研究主要集中不同的设计参数对其发挥程度的影响,忽略了桩土差异沉降对土拱效应的影响。曹卫平、刘汉龙等人分别通过室内模型试验以及数值模拟分析验证了桩土差异沉降与土拱效应发挥程度密切相关。但是,对于桩土应力比与桩土差异沉降的关系仍然缺乏具体的理论研究。针对这一状况,本文假定等沉面高度,从而判定土拱效应的完整程度。其次,将路堤-桩-桩间土作为整体分析,并基于桩承式路堤的变形协调,提出“桩体向上刺入路堤的体积等于土拱区体积的压缩量”的假设,结合路堤静力平衡和土拱拱脚处土体的极限状态,推导出桩土应力比以及桩土差异沉降的计算公式。接着,对该方法所得结果进行了验证,并分析了桩土面积置换率、填土高度、填土内摩擦角对土拱效应发挥程度以及桩土应力比的影响。为了进一步验证理论的合理性,采用数值模拟软件ABAQUS建立二维分析模型,通过对模型结果的应力应变场分析得到等沉面的高度,即1.4倍桩帽净距,验证了等沉面高度的假设。然后,分别改变桩承式路堤设计参数,得到路堤高度、填土性质、桩间距对桩土应力比以及桩土差异沉降的影响。最后,将数值模型中应力应变场随时间变化的历程输出,可以得到桩土差异沉降对土拱效应发挥程度的影响。最后,建立了一套基于土拱效应的桩承式路堤设计方法,通过调整桩间距及桩帽大小,使路堤达到相应的性能要求,希望对工程实践作出指导。
[Abstract]:With the rapid development of expressway and railway construction in China, large areas of soft soil are often encountered in the process of construction, and pile-supported embankment, as an effective structural form suitable for this kind of bad foundation, has been widely used. At the same time, it has also attracted extensive attention in academic circles. However, the working mechanism and stress-strain characteristics of pile-supported embankment are very complex. In the analysis of soil arch effect, the following key problems are studied: pile-soil stress ratio, pile-soil differential settlement and pile-supported embankment design method based on soil arch effect. Different soil arch models and corresponding calculation methods have been put forward. However, their research on soil arch effect mainly focuses on the influence of different design parameters on the degree of soil arch effect, neglecting the influence of pile-soil differential settlement on soil arch effect. Cao Weiping, Liu Hanlong and others verified that the differential settlement of pile and soil is closely related to the degree of soil arch effect through indoor model test and numerical simulation analysis. However, there is still a lack of specific theoretical research on the relationship between pile-soil stress ratio and pile-soil differential settlement. In view of this situation, this paper assumes the height of equal subsidence surface, so as to determine the integrity of soil arch effect. Secondly, the soil between embankment and pile is taken as the whole analysis, and based on the deformation coordination of pile-supported embankment, the assumption that the volume of pile piercing the embankment upward is equal to the compression of the volume of soil arch area is put forward. Combined with the static balance of embankment and the limit state of soil at the foot of soil arch, the calculation formulas of pile-soil stress ratio and pile-soil differential settlement are derived. Then, the results obtained by this method are verified, and the effects of pile-soil area replacement rate, filling height and internal friction angle on soil arch effect and pile-soil stress ratio are analyzed. In order to further verify the rationality of the theory, a two-dimensional analysis model is established by using the numerical simulation software ABAQUS. The height of the equal sinking surface, that is, 1.4 times the net distance of the pile cap, is obtained by analyzing the stress and strain field of the model results. The hypothesis of equal subsidence surface height is verified. Then, the design parameters of pile-supported embankment are changed respectively, and the effects of embankment height, filling properties and pile spacing on pile-soil stress ratio and pile-soil differential settlement are obtained. Finally, the influence of pile-soil differential settlement on the soil arch effect can be obtained by outputting the stress and strain field in the numerical model with time. Finally, a set of pile-supported embankment design method based on soil arch effect is established. By adjusting the pile spacing and pile cap size, the embankment can meet the corresponding performance requirements, hoping to guide the engineering practice.
【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】：U416.12

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