基于共同作用的短桩—承台式基础设计方法研究
发布时间：2018-10-16 13:05
【摘要】：短桩承台式基础是一种上部为开挖式基础、下部为短桩并且考虑共同受力的新型基础型式。在桩基设计的过程中,通过考虑承台下地基土反力,应用短桩优化桩基设计,从而使得桩基极限承载力有很大提升。该新型基础型式在某些特定地质复杂地区有着重要的实用价值,通过该种型式的桩基优化,使得桩基基础既符合安全性又符合经济性的要求。论文通过资料调研、对比、总结的方式界定了短桩的定义,并通过FLAC3D数值模拟软件模拟了不同桩长(L=2m,3m,4m,4.5m,5m,5.5m,6m,7m,8m,9m,10m,11m)的单桩竖向承载力,当桩长L4m时,其承载力较低;当桩长为4m～6m时,较L4m时其承载力上升幅度较大,大概提高35%左右。而当桩长L6m时,其承载力并没有显著提升。综上,本文界定了所讨论的短桩为长度为4m≤L≤6m,且长径比6L/D20的桩。系统分析了短桩与土共同作用的受力状态,研究了承台与地基土共同作用机理,通过FLAC3D数值模拟进行短桩承台式基础群桩模拟实验,模拟了短桩不同桩长(L=4m、5m、6m),不同桩距(Sa=2d、3d、4d、6d)的短桩群桩承台土反力的变化。得出承台土反力与桩距成正比,当桩距Sa=4d～6d时,承台土能充分发挥作用,承台土反力基本不受桩长影响。承台反力的数值最大处在边柱内侧附近,其次为承台角点,再次为承台边缘处,群桩内部最小。为研究不同土层组合对短桩承台式基础的影响研究,进行在不同土层组合条件下短桩承台群桩模拟实验。测试包括不同承台下土变化(粘土、砂土、圆砾土)、不同桩端土变化(粘土、砂土、圆砾土),分析土层变化对承台分担荷载比例及短桩承台式基础沉降量的影响,及二者之间的联系。实验得出,粘土层承台分担荷载比最大且沉降量最小。通过对不同土层组合Q-s曲线及承台分担荷载比曲线的分析比较,发现沉降量较小的土层组合承台分担荷载比较大。基于以上研究成果,本文认为短桩承台式基础应为浅基础的优化型式,根据整体承载能力和沉降量双重控制标准的设计原则,整体设计思路为:从天然地基设计出发,在满足地基承载力的条件下,为了减少沉降而设置一定数量的短桩。基于此研究共同作用设计方法及关键数据取值,完成短桩-承台-土共同作用设计流程。使用短桩-承台-土共同作用设计方法对实际工程进行重新设计,并通过数值模拟软件予以验证。最后根据以上研究理论及短桩-承台-土共同作用设计方法,使用VB6.0编程软件完成"短桩承台式基础"设计程序的编制,使得该基础型式的设计工程简单高效,提高在实际工程中的应用效率。
[Abstract]:Short pile cap foundation is a new type of foundation which is excavated in the upper part and short pile in the lower part. In the process of pile foundation design, the pile foundation design is optimized by considering the reaction force of foundation soil under the pile cap, so that the ultimate bearing capacity of pile foundation can be greatly improved. This new type of foundation has important practical value in some special geological complex areas. Through the optimization of this type of pile foundation, the pile foundation not only meets the requirements of safety but also meets the requirements of economy. In this paper, the definition of short pile is defined by means of data investigation, comparison and summary, and the vertical bearing capacity of single pile with different pile lengths (L ~ (2) m ~ (3) ~ (3) m ~ (4) ~ (4.5) m ~ (5) ~ (5) m ~ (6) ~ (6) m ~ (?) ~ (8) m ~ (9) ~ (10) m ~ (11 m) is simulated by FLAC3D numerical simulation software. When the length of pile is L ~ (4) m, its bearing capacity is lower. Compared with L _ 4 m, the bearing capacity increases by about 35%. However, when the pile length is L6 m, the bearing capacity does not increase significantly. In summary, this paper defines the discussed short pile as a pile whose length is 4m 鈮，
本文编号：2274453
[Abstract]:Short pile cap foundation is a new type of foundation which is excavated in the upper part and short pile in the lower part. In the process of pile foundation design, the pile foundation design is optimized by considering the reaction force of foundation soil under the pile cap, so that the ultimate bearing capacity of pile foundation can be greatly improved. This new type of foundation has important practical value in some special geological complex areas. Through the optimization of this type of pile foundation, the pile foundation not only meets the requirements of safety but also meets the requirements of economy. In this paper, the definition of short pile is defined by means of data investigation, comparison and summary, and the vertical bearing capacity of single pile with different pile lengths (L ~ (2) m ~ (3) ~ (3) m ~ (4) ~ (4.5) m ~ (5) ~ (5) m ~ (6) ~ (6) m ~ (?) ~ (8) m ~ (9) ~ (10) m ~ (11 m) is simulated by FLAC3D numerical simulation software. When the length of pile is L ~ (4) m, its bearing capacity is lower. Compared with L _ 4 m, the bearing capacity increases by about 35%. However, when the pile length is L6 m, the bearing capacity does not increase significantly. In summary, this paper defines the discussed short pile as a pile whose length is 4m 鈮，
本文编号：2274453
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