考虑桩身压缩的高承台超长群桩沉降计算

Settlement Calculation for Extra-long Pile Groups with High Cap Considering Pile Compression

针对两类高承台超长群桩基础的沉降计算问题,基于苏通大桥主塔群桩基础下的地基条件,根据离心模型试验所得到的各基桩平均端阻比推导了高承台超长群桩桩身弹性压缩量的计算公式,并介绍美国路桥规范对超长桩桩身弹性压缩量的估计方法,然后再按照国内现行规范方法对压缩土层进行沉降计算,最后将总沉降理论计算值与试验值相比较。研究结果表明,考虑桩身弹性压缩量的高承台超长群桩总沉降理论值与试验值比较接近,桩身弹性压缩量占总沉降量的10.3%,可见不能忽略桩身弹性压缩量对高承台超长群桩总沉降的贡献;此外,采用美国规范对其估计的简便方法也是可行的。

In order to calculate the settlement of tow types of extra-long pile groups with high cap, the average ratio of end pile resistance to top pile load gained by centrifugal model tests is used to deduce the formula for the elastic compression of the piles based on the soil layers under the main tower of Sutong Yangtze Rive Highway Bridge, and the simple estimation of the compression is introduced by using American highway bridge code. The settlement of the compressed soil layers under end piles is calculated through the method used in Chinese codes, and the calculated total settlement of the extra-long pile groups with high cap is compared with the settlement from tests. The results indicate that the calculated total settlement including pile compression are close to the settlement from tests, and the ratio of the pile compression to total settlement is up to 10.3%. It is necessary to consider the elastic compression of piles which influences the total settlement of the extra-long pile groups with high cap, and it is also feasible to utilize the concise method to estimate pile compression used by the American code.