特定场地下土工构筑物荷载变形曲线的概率密度分布

Probability Density Distribution of Load Deformation Curves of Geotechnical Structures at a Specific Site

荷载变形测试是评判土工构筑物的极限承载力和安全性的重要技术手段之一。基于现行技术规范,某一特定场地下往往需要评判多个或数十个土工构筑物,当综合分析这些构筑物的荷载变形曲线时,会呈现出较强的离散性。为此,结合京畿地区场地水平下的荷载变形典型测试成果,包括钻孔灌注桩、CFG桩单桩和锚杆,分别探讨了给定荷载下的变形量值的概率密度分布和给定变形下的荷载量值的概率密度分布。拟合优度检验中选用了两参数的概率密度分布形式,如正态、对数正态、伽玛、耿贝尔和威布尔。基于AIC准则,确定了这些量值(变量)的最优分布概型。计算表明,尽管特定场地下的荷载量值或变形量值的最优概率密度分布并不总是服从正态分布,但它与最优分布之间差异不大。结合基桩承载能力的极限状态设计,探讨了基于概率密度分布的可靠性分析方法。

Load deformation test is one of the important technical means to judge the ultimate bearing capacity and safety of geotechnical structures. At a specific site, multiple or dozens of geotechnical structures often are required to evaluate. When a comprehensive analysis is performed for these load deformation curves, a strong dispersion of the curves can be found. In this paper, the typical test results of the load deformation behavior of various geo-structures in Beijing area, including the bored pile, the CFG pile and the anchor were discussed. The probability density distribution of deformation values under a given load was discussed; yet the probability density distribution of load values under a given deformation is presented. The probability density distributions are chosen in the goodness-of-fit test, such as normal, logarithmic normal, gamma, Gumbel and Weibull. The best-fit distribution of these load or deformation values was identified by using the AIC criterion. Although the best-fit distribution did not always obey the normal distribution, it was not very different from the best-fit distribution. Taken the limit state design of bearing capacity of pile as an illustrative example, the reliability analysis method by using the known probability density distribution was discussed.