深厚软土中永久全护筒嵌岩灌注桩竖向承载性状研究

发布时间：2018-05-01 20:50

本文选题：永久全护筒 + 嵌岩灌注桩　；参考：《广州大学》2017年硕士论文

【摘要】：我国沿海城市以海相沉积平原地貌为主,这些地区会经常遇到深厚的流塑状软土地质条件,不利于其工程建设。以珠海市横琴区某桩基工程作为例,该工程的中风化花岗岩层平均埋深约28m,软土层平均厚度约24m左右,地质条件尤为特殊。珠海市很多桩基础工程通过改进普通嵌岩灌注桩得到了永久全护筒嵌岩灌注桩的新桩型。实践表明,永久全护筒嵌岩灌注桩能不仅能满足承载力要求还能保证施工质量,很好地适用于这种深厚软土地质条件,解决了深厚软土中的成桩难题。本文将深厚软土中钻孔或清孔、灌注混凝土时使用全护筒护壁,成桩后护筒不予拔出留在土中参与桩身受力且桩端嵌入岩层的钢护筒—混凝土组合结构定义为永久全护筒嵌岩灌注桩。本文先总结了永久全护筒嵌岩灌注桩的施工工艺,然后对其钢护筒厚度选择、承载力及沉降计算方法、承载性状影响因素等展开了研究,其主要内容及成果如下:(1)结合珠海市横琴区某桩基工程实例,总结了永久全护筒嵌岩灌注桩的施工技术、施工要点、质量控制要点及工程应用,并分析了其工程优点。(2)基于静力平衡理论进行施工过程中内外环压下钢护筒稳定性及强度分析,推导了确定永久全护筒嵌岩灌注桩的钢护筒壁厚的计算公式,为工程中全护筒厚度的选择提供了理论依据。(3)分析了永久全护筒嵌岩灌注桩荷载传递的影响因素,然后选择合理的荷载传递模型推导了基于荷载传递函数法的荷载-沉降计算公式;并进一步推导了考虑深厚软土中桩身的压屈失稳影响和强度的竖向极限承载力计算公式,最后以本文所依托的工程的静载试验数据作为依据论证了其合理性。(4)以本文所依托的珠海市横琴区某桩基工程作为背景,通过MIDAS GTS NX有限元软件建立永久全护筒嵌岩灌注桩的三维实体单元模型进行数值模拟,分析了不同桩径、不同桩长、不同钢护筒厚度、不同桩侧土体地质条件、不同嵌岩深度几大主要因素对永久全护筒嵌岩灌注桩承载性状的影响。
[Abstract]:The coastal cities in China are dominated by marine sedimentary plain landforms. These areas often encounter deep geological conditions of fluid-plastic soft soil, which is not conducive to its engineering construction. Taking a pile foundation project in Hengqin District of Zhuhai as an example, the average buried depth of weathered granite layer is about 28m, the average thickness of soft soil is about 24m, and the geological conditions are especially special. Through improving ordinary rock-socketed cast-in-place piles, a new type of permanent hold-in-situ cast-in-place piles has been obtained in many pile foundation projects in Zhuhai. The practice shows that the pile can not only meet the requirements of bearing capacity but also guarantee the construction quality. It is suitable for this kind of deep soft soil geological conditions and solves the problem of pile formation in deep soft soil. In this paper, the hole-hole is drilled or cleared in the deep soft soil, and the wall of the whole protective tube is used when the concrete is poured. The steel-concrete composite structure, which remains in the soil and embraces the rock layer at the end of the pile, is defined as the permanent cast-in-place pile. In this paper, the construction technology of permanent rock-socketed cast-in-place pile is summarized firstly, and then the selection of the thickness of steel retaining tube, the calculation method of bearing capacity and settlement, the factors affecting bearing characteristics, etc., are studied. The main contents and results are as follows: (1) combined with an example of pile foundation project in Hengqin District of Zhuhai City, the construction technology, construction key points, quality control points and engineering application of the cast-in-place pile with rock socketed in permanent retaining tube are summarized. Based on the static equilibrium theory, the stability and strength of steel retaining tube under internal and external ring pressure during construction are analyzed, and the calculation formula for determining the wall thickness of steel casing wall of permanent rock-socketed cast-in-place pile is derived. This paper provides a theoretical basis for the selection of the thickness of the whole retaining tube in engineering) and analyzes the factors affecting the load transfer of the permanent pile with rock-socketed cast-in-place. Then the load-settlement calculation formula based on load transfer function method is deduced by selecting a reasonable load transfer model, and the calculation formula of vertical ultimate bearing capacity considering the influence of buckling and buckling of pile in deep soft soil and the strength of pile is further deduced. Finally, based on the static load test data of the project relied on in this paper, the rationality of the project is demonstrated. (4) the pile foundation project in Hengqin District of Zhuhai City is taken as the background. The 3D solid element model of permanent rock-socketed cast-in-place pile is established by MIDAS GTS NX software, and the geological conditions of different pile diameter, pile length, different thickness of steel retaining tube and different soil around the pile are analyzed. The influence of several main factors of different rock socketed depth on the bearing behavior of permanent rock-socketed cast-in-place pile.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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