茅草街大桥桩基试验研究

针对洞庭湖区软土的工程地质特征，以湖南省茅草街大桥桩基试验为依托，探讨了该类地区大直径超长钻孔灌注桩的竖向及水平静载荷试验方法。在此基础上，对湖区超长钻孔灌注桩的承载机理、变形特性等开展深入研究，提出相应的承载力确定方法．最后，通过对试验数据的综合分析，指出超长灌注桩的荷载-沉降曲线一般为缓变型，其拐点不明显，且可能出现桩身失稳破坏，其设计计算与传统桩基也有所不同．

In-site Load Test of the Piles in the Foundation of Maocaojie Bridge

Considering the characteristics of engineering geology in the soft clay area of the Dongting Lake in Hunan Province, vertical and horizontal load tests were carried out on a super-long and large-diameter bored test pile of the Maocaojie Bridge.The ways of loading were also discussed. Based on the test results, the bearing mechanism and the deforming characteristics of super-long bored piles were thoroughly analyzed, and the relevant formulae to calculate the vertical and horizontal capacities were provided. Analysis of the measured data from the in-site loading test by the present method shows that the load-displacement curve is smooth without obvious inflexion and the buckling failure of the pile shaft is possible for super-long bored piles in soft clay area. Therefore, the design methods for this type of pile should be different from traditional rules for common piles.