土体强度的空间分布形式对单桩承载力的影响

土体参数可能服从不同类型的分布，而在考虑土性空间变异性的桩基础承载特性的研究中一般将随机变量假定为服从对数正态分布。以土体的不排水强度为随机变量，考虑不同的变异系数和相关距离，采用随机有限元法分别模拟了竖向和水平向荷载作用下单桩基础的承载性状，对比分析了土体不排水强度分别服从对数正态分布、Beta分布和Gamma分布条件下单桩的承载力均值和标准差。结果表明，土体强度的分布形式对单桩竖向承载力的均值没有影响，而服从对数正态分布的随机场中单桩水平承载力均值最大，服从Beta分布的随机场中单桩水平承载力均值最小；竖向荷载和水平荷载作用下Beta分布得到的承载力标准差均为最大。当地基土强度空间分布形式未知时，建议采用Beta分布确定单桩承载力。

Influence of the spatial distribution of soil strength on the bearing capacity of single pile

The soil parameters may obey different types of distribution. However, the lognormal distribution is generally chosen in the probability analysis of pile foundations. The undrained strength of soil is taken as the random variable, and it is assumed to obey Lognormal distribution, Beta distribution and Gamma distribution, respectively. Then the bearing behavior of single pile foundation under vertical and horizontal loads is simulated by stochastic finite element method, in which the different coefficient of variation and correlation distance are considered. The mean value and standard deviation of bearing capacity of single pile are analyzed. The results show that the average vertical bearing capacity of single pile is not affected by the distribution of soil strength. The average horizontal bearing capacity of single pile is the largest when the lognormal distribution is adopted, while the bearing capacity is the smallest when random field obeys the Beta distribution. The standard deviation of bearing capacity obtained by Beta distribution under vertical and horizontal loads is the largest. It is recommended to use Beta distribution to determine the bearing capacity of single pile foundation when the spatial distribution of soil strength is unknown.