基于随机场模型的桩基竖向承载力可靠性分析

结合随机场理论和误差传递原理求得了利用CPT确定桩基竖向抗压承载力统计特性的理论公式。为把所得公式应用于工程实际,对相关距离、桩截面尺寸、端阻力计算范围等在程序编制中的协调问题进行了研究,给出了符合实际土层厚薄不均特点的统计原则。最后利用可靠度理论,对上海地区19个预制桩场地和17个灌注桩场地进行了电算,求出了上海地区利用CPT确定桩基竖向抗压承载力的可靠度指标及其统计特性。从而为桩基确定性设计方法向概率极限状态设计方法的过渡提供了理论依据和符合实际的计算结果。

Reliability Analysis of Vertical Bearing Capacity of Pile Based on Random Field Theory

Based on the random field theory, the authors deduced the statistic features of the parameters, fi and Psb , to determine the vertical bearing capacity of pile by using the error propagation theory, and obtained the theoretical formula accordingly. For the application of these formula in the engineering practice, the correlation distance, pile dimensions and the calculating range of the pile tip resistance were analyzed and incorporated in the software, a thumb of role to deal with the unevenness of soil stratum thickness in reality was proposed. The numerical simulation of CPT at nineteen (19) prefabricated pile sites and seventeen (17) cast-in-place pile sites in Shanghai Region was carried out. The reliability index and its statistic properties to calculate the pile capacity by CPT proposed by Shanghai standards were obtained based on simulation results. The research provides the theoretical and data basis for the transition from the determinative design method to probabilistic one.