江西岩溶地区桥梁桩基承载性能数值分析研究

发布时间：2018-07-07 21:57

本文选题：嵌岩桩 + 数值模拟　；参考：《南昌大学》2015年硕士论文

【摘要】：岩溶(karst)是一种由地下水长期溶蚀可溶性岩石而产生岩石内部的空洞现象,对建设工程的基础有着很大影响。岩溶地质情况在我国有广泛分布,贵州、云南存在着可溶性岩石,同时也有普遍的溶蚀现象,广西地区的岩溶则已经普遍到能作为旅游景点。江西地区同样也存在着这样的情况,岩溶在江西的分布主要在上高、宜春、萍乡一带,它分布的广泛和发育程度已经对桥梁、建筑等的建设产生了很大的影响。江西省是中部的欠发达地区,其基础设施尚未建设完善,高速公路、铁路、城市桥梁的建设规模会增大,经过岩溶地区的公路将越来越多,桥梁桩基工程需要应对溶洞的情况也会越来越多。然而我国规范中对于建立在溶洞以上的嵌岩桩的承载力的计算方法并不统一和明确,也就是说,规范中仅有常规条件下嵌岩桩承载力的计算式,而缺少存在溶洞情况下的计算式,这对于影响因素颇多、争议很大的岩溶地区显然是不合理的。为指导岩溶地区桥梁下部结构的设计,给桥梁嵌岩桩极限承载力的计算提供可靠的依据,对岩溶区嵌岩桩承载力的研究应该达到一个通用的、公式化的水平。本文将基于江西地区的岩溶地质特征,对下伏溶洞的嵌岩桩承载特性做了一些分析和研究,主要内容包括:(1)对江西某高速公路设计路线上穿过岩溶区的桥梁地质情况、溶洞分布和发育特征做了一个比较详细的统计和总结;(2)查阅文献,分析岩溶区嵌岩桩承载和破坏机理;(3)参考资料,选用扩展的DP模型作为岩土本构模型,并利用有限元软件ABAQUS对嵌岩桩力的传递机理进行了有效的模拟;(4)对溶洞的数个几何与物理参数进行了敏感性数值分析,结论表明:a)嵌入溶洞顶板的桩基破坏模式主要分两种:顶缘受桩端压力破坏和底缘受拉破坏,当桩基和溶洞边界在平面上比较接近时,还容易发生顶板岩石的剪切破坏;b)溶洞的竖向尺寸对桩基承载力的影响并不明显,其水平尺寸的影响较为突出;c)嵌岩桩在4m及以下厚度的顶板上时,其前沿深度宜浅不宜深,在5m至8m厚度的顶板,最佳嵌岩深度宜为0.5m~1.0m;d)溶洞顶板上的嵌岩桩极限承载力依溶洞几何特征的变化规律可以用二元三次多项式来表示,且本文尝试了拟合其结果。(5)对当下溶洞地区基础设计做出了个案分析,并提出了施工上的合理的建议。
[Abstract]:Karst (karst) is a kind of cavitation phenomenon in the rock caused by the long-term dissolution of the groundwater soluble rock, which has great influence on the foundation of the construction project. Karst geology is widely distributed in China. There are soluble rocks in Guizhou and Yunnan, but also widespread dissolution phenomenon. The karst in Guangxi has been widely used as a tourist attraction. The distribution of karst in Jiangxi is mainly in Shanggao, Yichun and Pingxiang. Its wide distribution and development degree have had a great influence on the construction of bridges and buildings. Jiangxi Province is an underdeveloped region in the middle of the country. Its infrastructure has not yet been built. The scale of construction of highways, railways and urban bridges will increase, and more highways will pass through karst areas. The bridge pile foundation engineering needs to deal with the karst cave situation will also be more and more. However, the calculation method of bearing capacity of rock-socketed pile built above the cave is not uniform and clear in the code of our country, that is to say, the calculation formula of bearing capacity of rock-socketed pile under conventional conditions is only in the code. However, the lack of calculation formula in the presence of caverns is obviously unreasonable in karst areas where there are many influencing factors. In order to guide the design of bridge substructure in karst area and to provide reliable basis for the calculation of ultimate bearing capacity of rock-socketed pile in karst area, the research on bearing capacity of rock-socketed pile in karst area should reach a general and formulaic level. Based on the characteristics of karst geology in Jiangxi province, this paper makes some analysis and research on the bearing characteristics of rock-socketed piles in buried caverns. The main contents include: (1) the geological conditions of bridges passing through karst areas on the design route of a highway in Jiangxi Province. The distribution and development characteristics of karst caves are summarized in detail. (2) the literature is consulted to analyze the bearing capacity and failure mechanism of rock-socketed piles in karst areas. (3) the extended DP model is selected as the constitutive model of rock and soil. The finite element software Abaqus is used to simulate the transfer mechanism of rock-socketed pile force effectively. (4) the sensitivity numerical analysis of several geometric and physical parameters of the cavern is carried out. The results show that there are two main failure modes of pile foundation embedded in the roof of the cavern: the top edge is damaged by the pressure at the end of the pile and the bottom edge is damaged by tension, when the boundary between the pile foundation and the cave is close in plane, The vertical dimension of the cavern has no obvious effect on the bearing capacity of pile foundation, and the horizontal dimension has a prominent effect on the bearing capacity of pile foundation. When the rock-socketed pile is on the roof with thickness of 4 m or below, the forward depth should be shallow rather than deep. At the thickness of 5 m to 8 m, the optimum depth of rock embedding is 0.5 m ~ 1.0 m / d) the variation of ultimate bearing capacity of rock-socketed pile on the roof of a karst cave can be expressed by the binary cubic polynomial, and the variation of the ultimate bearing capacity of the rock-socketed pile on the roof of the karst cave can be expressed as a binary cubic polynomial. This paper tries to fit the results. (5) A case study of the foundation design in the present karst cave area is made, and some reasonable construction suggestions are put forward.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U443.15

【参考文献】