發(fā)布時(shí)間：2018-07-28 20:04

【摘要】：目前公路橋梁大直徑鉆孔灌注摩擦樁在設(shè)計(jì)中偏于保守，使得樁基礎(chǔ)尺寸過大，造價(jià)較高。因此，本文依托現(xiàn)場靜載試驗(yàn)，對(duì)大直徑鉆孔灌注樁的承載特性、荷載傳遞規(guī)律以及有效樁長進(jìn)行了系統(tǒng)的理論分析，在此基礎(chǔ)上，采用MATLAB遺傳算法工具箱對(duì)單樁的幾何尺寸進(jìn)行優(yōu)化，從而得到既滿足承載力要求又經(jīng)濟(jì)合理的最優(yōu)樁基設(shè)計(jì)尺寸，并通過實(shí)例進(jìn)行了驗(yàn)證，取得了如下研究成果： 1．依托新機(jī)場高速公路某大橋工程的建設(shè)，對(duì)四根大直徑鉆孔灌注樁進(jìn)行了豎向靜載試驗(yàn)，結(jié)果表明：大直徑灌注樁的荷載-沉降曲線沒有明顯的拐點(diǎn)，呈緩變形，其承載特性有別于中、小直徑鉆孔灌注樁；砂性土中樁側(cè)阻力呈拋物線分布，樁身軸力隨單樁埋置深度遞減。 2．在對(duì)現(xiàn)場試驗(yàn)實(shí)測數(shù)據(jù)分析的基礎(chǔ)上，引入了有效樁長的概念，并利用Mindlin解同時(shí)考慮樁徑的影響，對(duì)單樁有效樁長計(jì)算公式進(jìn)行推導(dǎo)。公式結(jié)果表明：有效樁長與樁徑、土體壓縮模量、泊松比和樁身彈性模量有關(guān)，這為工程中樁基設(shè)計(jì)時(shí)樁長的選取提供了參考依據(jù)。 3．在對(duì)大直徑鉆孔灌注樁豎向荷載傳遞過程分析的基礎(chǔ)上，，探討了單樁的荷載傳遞規(guī)律，并利用改進(jìn)的荷載傳遞法對(duì)荷載傳遞微分方程進(jìn)行求解，分析了大直徑鉆孔灌注樁單樁承載特性的影響因素，認(rèn)為樁周和樁端土體性質(zhì)、幾何尺寸對(duì)大直徑鉆孔灌注樁承載特性的影響是復(fù)雜耦合的，各影響因素相互作用相互加強(qiáng)。 4．在最優(yōu)化準(zhǔn)則非線性規(guī)劃的理論基礎(chǔ)上，采用遺傳算法，通過MATLAB M語言進(jìn)行計(jì)算機(jī)編程，對(duì)大直徑鉆孔灌注樁進(jìn)行優(yōu)化設(shè)計(jì)，得到了最優(yōu)化的樁徑和樁長，同時(shí)經(jīng)實(shí)例進(jìn)行了驗(yàn)證，使得樁基既滿足承載力要求又經(jīng)濟(jì)實(shí)用。
[Abstract]:At present, the design of large diameter bored friction pile of highway bridge is conservative, which makes the size of pile foundation too large and the cost higher. Therefore, based on the field static load test, this paper makes a systematic theoretical analysis on the bearing characteristics, load transfer law and effective pile length of large diameter bored pile. The MATLAB genetic algorithm toolbox is used to optimize the geometric dimension of single pile, and the optimum design size of pile foundation is obtained, which meets the bearing capacity requirements and is economical and reasonable. The research results are as follows: 1. Based on the construction of a bridge on the New Airport Expressway, the vertical static load tests of four large-diameter bored piles are carried out. The results show that the load-settlement curve of large diameter cast-in-place pile has no obvious inflection point, and its bearing behavior is different from that of medium diameter bored pile, and the lateral resistance of pile is parabola distribution in sandy soil. The axial force of the pile decreases with the buried depth of the single pile. 2. Based on the analysis of the measured data of the field test, the concept of effective pile length is introduced, and the influence of the diameter of the pile is considered simultaneously by using the Mindlin solution. The formula for calculating the effective pile length of a single pile is deduced. The results show that the effective pile length is related to pile diameter, soil compression modulus, Poisson's ratio and elastic modulus of pile body. This provides a reference for the selection of pile length in the design of pile foundation. 3. Based on the analysis of vertical load transfer process of large diameter bored pile, the law of load transfer of single pile is discussed. Using the improved load transfer method to solve the differential equation of load transfer, the factors influencing the bearing characteristics of single pile with large diameter bored cast-in-place pile are analyzed, and the properties of soil around the pile and at the end of the pile are considered. The influence of geometric dimensions on the bearing characteristics of large-diameter bored piles is complex coupled, and the interaction of various factors is strengthened. 4. On the basis of the theory of nonlinear programming of optimization criteria, genetic algorithm is used. Through computer programming in MATLAB M language, the optimization design of large diameter bored pile is carried out, and the optimum diameter and length of pile are obtained. At the same time, an example is given to verify that the pile foundation can not only meet the requirement of bearing capacity but also be economical and practical.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U443.154

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