超长大直径群桩沉降计算方法探讨

针对苏通长江大桥主塔超长大直径灌注群桩基础,分别采用目前国内铁路桥涵地基和基础设计规范、公路桥涵地基与基础设计规范、建筑桩基技术规范、建筑地基基础设计规范和美国桥梁设计规范中的荷载与抗力系数设计法对其沉降进行计算,然后再与大型离心模型试验沉降值进行比较,提出考虑超长桩的桩身压缩和采用荷载传递系数修正桩端附加应力的沉降计算方法,得到的理论计算值与试验值比较接近,仅相差7.8%;同时用该法所得计算值与内昆线某一大跨刚构连续组合体系特大桥超大规模高墩群桩基础的沉降试验值也比较逼近。最后讨论了现行规范中对群桩沉降计算存在的一些问题并提出一些建议。

Research on Calculating Methods for Settlement of Extra-long Large-diameter Pile Group

The methods specified in four relevant specifications prevailing in China and in the American specifications are applied respectively to calculate settlement of the extra-long large-diameter bored piles group of the south bridge tower of the major Yangtze River Bridge connecting Suzhou and Nantong. The results are compared with the results of the large centrifugal model test. On this basis,the paper presents a settlement calculation method taking into consideration extra-long pile compression and additional stresses at the bottom end of piles corrected with the load transfer coefficient. The theoretical calculation value is close to the test value very much, being only 7.8 % higher. In calculation of the extra-long large-dlameter piles group of the high pier of the large-span rigid-frame extra-long bridge on the Nei-Kun Railway Line, the theoretic value calculated by this method is also close to the test settlement value. Some problems in calculating settlement of piles groups according the current specifications are discussed and some proposals are put forward.