公路桥梁大直径钻孔灌注桩轴向承载力优化设计研究
发布时间：2018-07-28 20:04
【摘要】：目前公路桥梁大直径钻孔灌注摩擦桩在设计中偏于保守，使得桩基础尺寸过大，造价较高。因此，本文依托现场静载试验，对大直径钻孔灌注桩的承载特性、荷载传递规律以及有效桩长进行了系统的理论分析，在此基础上，采用MATLAB遗传算法工具箱对单桩的几何尺寸进行优化，从而得到既满足承载力要求又经济合理的最优桩基设计尺寸，并通过实例进行了验证，取得了如下研究成果： 1．依托新机场高速公路某大桥工程的建设，对四根大直径钻孔灌注桩进行了竖向静载试验，结果表明：大直径灌注桩的荷载-沉降曲线没有明显的拐点，呈缓变形，其承载特性有别于中、小直径钻孔灌注桩；砂性土中桩侧阻力呈抛物线分布，桩身轴力随单桩埋置深度递减。 2．在对现场试验实测数据分析的基础上，引入了有效桩长的概念，并利用Mindlin解同时考虑桩径的影响，对单桩有效桩长计算公式进行推导。公式结果表明：有效桩长与桩径、土体压缩模量、泊松比和桩身弹性模量有关，这为工程中桩基设计时桩长的选取提供了参考依据。 3．在对大直径钻孔灌注桩竖向荷载传递过程分析的基础上，，探讨了单桩的荷载传递规律，并利用改进的荷载传递法对荷载传递微分方程进行求解，分析了大直径钻孔灌注桩单桩承载特性的影响因素，认为桩周和桩端土体性质、几何尺寸对大直径钻孔灌注桩承载特性的影响是复杂耦合的，各影响因素相互作用相互加强。 4．在最优化准则非线性规划的理论基础上，采用遗传算法，通过MATLAB M语言进行计算机编程，对大直径钻孔灌注桩进行优化设计，得到了最优化的桩径和桩长，同时经实例进行了验证，使得桩基既满足承载力要求又经济实用。
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.154
本文编号：2151431
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.154
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