【摘要】：樁基是一種常用的基礎形式,因具有高承載力、可以有效控制沉降和不均勻沉降而得到廣泛使用,其沉降計算是一個非常重要的研究課題。樁基的沉降計算因涉及到樁、土、承臺的相互作用和土體力學行為的非線性而十分復雜,以往的計算方法多假定樁側摩阻力與樁端力互不影響。隨著跨海大橋等大型工程的興建和高層建筑的迅猛增多,超長樁和長短組合樁基在工程上的應用越來越多,但與之相應的理論研究遠遠落后于工程實踐,樁基工程也面臨新的研究課題。本文對豎向荷載作用下,樁基的沉降計算開展了解析與半解析研究,主要工作和創(chuàng)新如下： (1)提出了一種新的樁側摩阻力與樁-土相對位移的指數函數關系,并用于描述樁端力與樁端沉降的關系。 (2)考慮樁-土相對位移與樁-土接觸面上力學行為的非線性,推導了均質土層中由樁端微小位移引起基樁沉降的計算公式。逐步增大樁端位移并按(1)中提出的函數關系計算樁側土體和樁端土的剛度變化,并進一步應用于成層土中單樁的沉降計算。 (3)考慮樁身豎向壓縮變形,建議了超長樁在豎向荷載作用下的沉降計算方法,分析了超長樁的承載特性。通過計算分析指出,超長樁的沉降計算需考慮樁身的非線性壓縮變形�？紤]樁-土接觸面上力學行為的非線性,計算了由位移控制的有效樁長,并對影響有效樁長的因素進行了分析。 (4)基于ABAQUS有限元軟件,分析不同樁長的相互作用,對比了不同樁間距和樁長差對受荷樁與非受荷樁沉降的影響�；赪ong和Poulos建議的計算不同樁長相互作用系數的修正方法,修正了樁-樁相互作用,應用Mindlin位移解計算得到長短樁樁端的相互作用,并應用于長短組合樁基的沉降計算。本文計算結果與ABAQUS計算結果吻合較好。 (5)考慮樁基的承載力隨時間的變化,結合已有的研究成果和實測試驗資料提出了樁基承載力隨時間的計算方法。 (6)提出了長期荷載作用下樁基的沉降計算公式,對其中的影響參數進行分析,并應用已有的實測研究數據證明了本方法的合理性。 (7)結合某實際工程,考慮樁基承載力的時間效應,應用本文建議的長短組合樁基的沉降計算方法對該工程進行計算分析。 最后,對本文工作進行了總結,并建議了進一步的研究方向。
[Abstract]:Pile foundation is a common foundation form, which is widely used because of its high bearing capacity and can effectively control settlement and uneven settlement. Its settlement calculation is a very important research topic. The settlement calculation of pile foundation is very complex because it involves the interaction between pile, soil and cap and the nonlinear behavior of soil mechanics. Most of the previous calculation methods assume that the side friction of pile does not affect the force at the end of pile. With the construction of large projects such as cross-sea bridge and the rapid increase of high-rise buildings, the application of super-long pile and long-short composite pile foundation in engineering is more and more, but the corresponding theoretical research lags far behind the engineering practice. Pile foundation engineering is also facing new research topics. In this paper, analytical and semi-analytical research on settlement calculation of pile foundation under vertical load is carried out. The main work and innovations are as follows: (1) A new exponential function relationship between pile side friction and pile-soil relative displacement is proposed. It is also used to describe the relationship between pile end force and pile end settlement. (2) considering the nonlinear relationship between the relative displacement of pile and soil and the mechanical behavior on the contact surface of pile and soil, the formula for calculating the settlement of foundation pile caused by the small displacement at the end of pile in homogeneous soil layer is derived. The displacement of pile end is increased step by step and the stiffness change of pile side soil and pile end soil is calculated according to the function relation proposed in (1), which is further applied to the settlement calculation of single pile in layered soil. (3) considering the vertical compression deformation of the pile body, the settlement calculation method of the super-long pile under vertical load is suggested, and the bearing characteristics of the super-long pile are analyzed. Through the calculation and analysis, it is pointed out that the nonlinear compression deformation of the pile body should be considered in the settlement calculation of the super-long pile. Considering the nonlinear mechanical behavior on the pile-soil contact surface, the effective pile length controlled by displacement is calculated, and the factors affecting the effective pile length are analyzed. (4) based on ABAQUS finite element software, the interaction of different pile lengths is analyzed, and the effects of different pile spacing and pile length difference on the settlement of loaded pile and unloaded pile are compared. Based on the modified method proposed by Wong and Poulos to calculate the interaction coefficients of different pile lengths, the pile-pile interaction is modified. The Mindlin displacement solution is used to calculate the interaction between long and short pile ends, and it is applied to the settlement calculation of long and short composite pile foundation. The calculated results in this paper are in good agreement with those calculated by ABAQUS. (5) considering the change of bearing capacity of pile foundation with time, combined with the existing research results and measured test data, the calculation method of bearing capacity of pile foundation with time is put forward. (6) the settlement calculation formula of pile foundation under long-term load is put forward, and the influence parameters are analyzed, and the rationality of the method is proved by using the existing measured research data. (7) combined with a practical project, considering the time effect of bearing capacity of pile foundation, the settlement calculation method of long and short composite pile foundation proposed in this paper is used to calculate and analyze the project. Finally, the work of this paper is summarized and further research direction is suggested.
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TU473.1

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