【作者】 陈波；

【导师】 陈祖煜； 李炎隆；

【作者基本信息】 西安理工大学 ， 水工结构工程， 2017， 硕士

【摘要】 近年来,我国的基础建设发展迅猛,其中水利、公路、铁路、机场、港口以及码头等基础设施正在如火如荼的建设。建设这些基础设施时,其地基的极限承载力问题应该首先考虑。目前现有的地基极限承载力计算方法多为半经验公式,且只针对均质土地基。在工程中的地基多为复杂的层状土地基,现有的层状土地基极限承载力的计算方法尚未形成完善的理论体系。本文首先针对目前层状土地基极限承载力计算缺乏准确的计算方法的问题,应用上限解法,建立基于一般滑裂面的层状土地基极限承载力的数值模拟方法;引入单纯形法并结合随机搜索法确定临界滑动模式及最小加载系数,求解极限承载力;并基于Excel内嵌的VBA语言编写地基极限承载力的计算程序以实现较为复杂函数的计算和计算的自动化;通过与现场试验的对比分析证明了本方法及程序的准确性。计算结果与试验结果表明:对于均质土情况，Vesic方法与本文方法的计算误差最小,误差不足1%, 而Meyerhof以及Terzaghi的方法与上限解的误差最大,均超过20%;对于层状土情况,本文方法与实验结果接近,迈耶霍夫&汉纳理论和扩散角法的计算结果与上限解法的计算结果基本吻合,但扩散角法的计算结果更为接近上限解法的计算结果。而利用汉森加权平均公式得出的计算结果与上限解比较相差较大。本文还探讨了应用强度安全系数法对地基进行稳定分析时，安全系数的取值标准。通过工程结构风险分析和可靠度设计方法对上述问题进行解答,计算结果表明其允许安全系数(1.35)应略大于边坡等同类建筑物的相应值。作者将可靠度理论应用于目标可靠度指标为3.7和允许安全系数为1.35的一个典型地基算例,在土的凝聚力和摩擦系数变异系数分别为0.2和0.1的条件下,获得土的凝聚力、摩擦系数的分项系数的值标定值分别为c=1.041, γf=1.418,与国外规范相近。应用陈祖煜等提出的相对安全率判据,可以发现上述的分项系数标定值通过了普适性考核。更多还原

【Abstract】 In recent years,with the rapid development of Chinese infrastructure,such as roads railways airports ports and docks, the research on the ultimate bearing capacity of foundation is increasing. The existing methods for calculating the Ultimate bearing capacity of foundation are mainly semi-empirical formulas which are only available for Homogeneous soil foundation. In fact, studies on the calculation of the ultimate bearing capacity of layered foundation which is a common kind of ground soil in constructions are not matuare and perfect, have not yet formed a complete theoretical system.In order to solve the problem that there is no an accurate method for the calculation of the ultimate bearing capacity of layered foundation, main work and study of this article are as follow:(1) A numerical simulation method to the calculation of the ultimale bearing capacity of layered foundation is proposed based, on Upper-bound Approach.(2 )This paper introduces the simplex method and integrates the random search method to find the critical sliding surface, obtain the minimum loading factor and calculate the ultimate bearing capacity.(3) The calculation program, by VBA language embedded in EXCEL, for ultimate bearing capacity of foundation is worked out, is worked out to find the Solution of complex frunction and realize in calculating those complicated computations automatically.(4)It is proved that the method and program are accurate by comparing with the field test,The comparison between the calculated results and the experimental ones shows that: for the homogeneous soil, the error between Vesic method and this method is the smallest, the error is less than 1%, and the error between Meyerhof and upper bound solution is larger than 20%.For the layered soil, the upper bound solution is close to the experimental results. Compared with the upper bound solution, the results of Hansen’s method are quite different.Using risk analysis of engineering structure and reliability design method, this paper investigates choosing Value Standards of the safety factor for stability analysis of foundation based on Strength safety factor method. The results show that the allowable safety factor of foundation (1.35) is slightly larger than corresponding values of Slope and other similar buildings. The author applied the theory of reliability analysis on a target example andobtained the calibrated partial factors, being close to the overseas specifications. The calibrated partial factors are further validated by the ’Ratio of safety margin’ theory proposed by the authors’research team.更多还原