尺寸效应对刚性桩复合地基承载性状影响的研究

发布时间：2018-02-21 00:47

  本文关键词： 刚性桩复合地基 承载性状 尺寸效应 切线模量法 变形协调 沉降控制　出处：《武汉大学》2014年博士论文　论文类型：学位论文

【摘要】：刚性桩复合地基由于沉降小、桩身质量可靠、施工速度快,在工程建设中应用越来越广泛,对沉降变形的可控性已使其在高层建筑中的应用越来越多。为揭示刚性桩复合地基承载性状,科技工作者对此作了大量研究,有力地推动了刚性桩复合地基理论的发展。但目前仍存在一些问题值得进一步探讨,如：不同尺寸基础下刚性桩复合地基桩土受力性状有何规律,工程中用单桩复合地基或多桩复合地基载荷试验进行检测时,其与实际基础下复合地基受力性状存在什么差异；刚性桩复合地基沉降计算采用经验系数修正法还不尽如意,尚需通过研究化经验为理论等,都需进一步深入研究,以更好地认识刚性桩复合地基的作用机理。 为此,本文通过室内模型试验及理论分析开展了系列研究,以获得对刚性桩复合地基受力性状的一些深入认识。具体工作如下： (1)针对刚性桩复合地基承载性状受基础尺寸大小影响的问题,从地基附加应力分布与基础尺寸关系以及地基极限承载力与基础尺寸关系入手进行了分析。介绍了切线模量法的计算理论并提出了应用该理论解决复合地基尺寸效应问题的方法； (2)为研究刚性桩复合地基承载性状受基础尺寸影响的规律,利用自主设计的模型箱试验装置,在4个不同尺寸的压板下分别进行了地基土载荷试验、复合地基载荷试验以及单桩荷载试验等相关模型试验,获得了一套载荷试验测试资料； (3)针对模型试验成果,对刚性桩复合地基的桩土承载性状以及不同尺寸压板复合地基承载性状的差异进行了分析,揭示了以下规律：在基底应力相同和置换率相同时,复合地基沉降随压板尺寸增大而增大,桩土应力比随压板尺寸增大而增大,桩分担的荷载随压板尺寸增大而增大； (4)在以上研究的基础上,针对刚性桩复合地基检测方法确定承载力的问题,对复合地基承载力的评估提出了新的建议,即除了进行单桩和单桩复合地基载荷试验外,尚应进行桩间土载荷试验,先利用桩土组合叠加计算模型方法获得试验压板下复合地基的p-s曲线,再用复合地基试验结果进行检验,然后利用切线模量法计算实际基础下地基土的p-s曲线,与单桩载荷试验的p-s曲线叠加获得实际基础下刚性桩复合地基的p-s曲线,利用该曲线可以对复合地基承载能力进行科学合理的评估； (5)在分析桩土变形协调机制、桩土荷载传递力学性状以及共同作用理论的基础上,利用切线模量法建立了一套按沉降控制的刚性桩复合地基设计计算的系统方法,该方法考虑了桩土变形协调和桩土荷载传递性状。通过工程实例验证,该方法可较好反映实际基础下复合地基承载性状； (6)利用某CFG刚性桩复合地基工程实例,验证了本文提出的刚性桩复合地基承载力评估方法和复合地基设计计算系统方法的合理性和可靠性。同时,实际工程数据与模型试验数据所揭示的刚性桩复合地基承载性状规律是一致的； (7)研究了有褥垫层复合地基的桩土共同作用性状,褥垫层厚度及变形模量在常规值范围内变化时,分析揭示了褥垫层厚度及变形模量对复合地基桩土应力比有影响,但对复合地基总沉降的影响不大。
[Abstract]:Because of the rigid pile composite foundation settlement is small, reliable pile quality, fast construction, in the construction of more and more widely, the controllability of settlement has made it more and more applications in high-rise buildings. In order to reveal the bearing behavior of rigid pile composite foundation, the work of science and technology have made a lot of research effectively to promote the development of the theory of rigid pile composite foundation. But there are still some problems worthy of further study, such as different sizes under the foundation of the rigid pile soil pile composite foundation bearing capacity to any rules, detected by the single pile composite foundation load or multi pile composite foundation test engineering, with the actual composite foundation what are the differences of the stress characters; calculated by empirical coefficient correction method is not satisfactory settlement of rigid pile composite foundation, is required by research experience for the theory, need further study, to The mechanism of the rigid pile composite foundation is better understood.
Therefore, a series of researches have been carried out through indoor model test and theoretical analysis, in order to get some deep understanding of the behavior of rigid pile composite foundation.
(1) according to the basic size effect of bearing capacity of rigid pile composite foundation, the foundation of additional stress and stress distribution and size based relationship based size and ultimate bearing analyzed. This paper introduces the calculation theory of tangent modulus method and proposed the application of the theory method to solve the problem of size effect of the composite foundation;
(2) as basic size influence study on bearing capacity of rigid pile composite foundation of experimental device of the model box is designed, the foundation loading tests were carried out in 4 different sizes of the plate under the model load test of composite foundation and pile load test, get a load test data;
(3) according to the experimental results, the characters of different sizes and pressure bearing capacity of composite foundation of the difference of the analysis of rigid pile composite foundation pile soil bearing, reveal the following rules: in the same substrate stress and the same replacement ratio, and increases with the increase of plate size settlement of composite foundation pile soil stress ratio with the plate size increases, pile load sharing increases with the increase of plate size;
(4) on the basis of the above research, the rigid pile composite foundation test method to determine the bearing capacity problems, evaluation of bearing capacity of composite foundation and put forward new proposals, which in addition to the single pile and single pile composite foundation loading test, through piles of soil load test should be, by combination of pile and soil model superposition calculation method to obtain the test plate under the P-S curve of the composite foundation and composite foundation test results were examined, and then calculate the P-S curve of foundation soil under the actual basis of using tangent modulus method, and p-s curve superposition pile load test p-s curve was the actual foundation of the rigid pile composite foundation, the curve can be used scientific and reasonable evaluation on the bearing capacity of composite foundation;
(5)鍦ㄥ垎鏋愭々鍦熷彉褰㈠崗璋冩満鍒，

本文编号：1520515