桩基承载力概率研究方法分析.pdf

摘要本文研究了桩基承载力概率分析的方法,对于桩基的可靠性设计将起到积极的推动作用。文章首先分析了按照计算模型进行概率分析的三种不确定性因素,然后分别进行了定量分析。其中土性不确定性的定量分析方法是本文的研究重点,为此建立了有限蜮土性随机场的估计理论,提出了估离方差的概念与计算表达式,并在实验资料的基础上研究了变异函数的特征及其平均值的计算方法,从而正确地解决了与桩基承载力有关的土性变量的概率分析问题。对于几何尺寸的不确定性与计算模型的不确定性,文章根据实测资料的统计分析, 得出了~些有实用价值的结论。文章还指出仅仅依据计算模型进行桩基承载力概率分析是不完善的,并针对桩基设计的特点提出了按照改进的贝叶斯原理进行概率分析的新方法,文章的最后介绍了一个工程实例。毙键词:桩基承载力,概率分析,随机场,变异函数,贝叶斯原理 Research on Probabilistic Analyses Method ofPileCapacity Abstract The paper deals with the probabilistic analyses method ofpilecapacity, which willactively promote the application factors of uncertainty in relation to probabilistic analyses utilizing adesign model were firstdiscussed and then quantitatively analysed one byone,among which the quantitative analysis ofuncertainty ofsoilproperties is themajor point ofthe do so,the estimation theory about random field ofsoil properties infinitedomain was established and,the concept and aexpression of estimate—dispersion variance were thebasis of testinformation, characteristics ofvariogram function were studied,and aestimation program of itsmean value was ,the problem ofprobabilistic ana— lyses ofsoilvariable with regard topilecapacity has been correctly terms oftheuncertainties ofboth geometric sizeand design model,the paper, based on statisticsanalyses of theobserved data,came tosome practical results, Moreover thepaper points out thattheprobabilistic analyses only employing a design model is not connection with thecharacteristics ofpiledesign, anew method ofprobabilistic analyses according totheadvanced Bayes7 theo· rem theend of the paper,a engineering practice isintroduced to illustratewhat we achieved. KEYWORDS:pile capacity,probabilistic analyses,random field,variogram function,Bayes7 theorem Ⅱ 1 引言 】.11桩基设计历史的简要回顾桩基础是目前广泛应用且发展迅速的基础形式,同时也是最古老的一种基础形式。人类采用桩基础建造房屋的历史可以追溯到史前时期,在地基土条件不利的河谷或沼泽地带,我们的祖先就在木桩上盖起了住所(Winterkorn, 1975)。今天,在世界各地我们