基桩承载力自平衡试验中荷载-沉降曲线简单转换法的改进

IMPROVEMENT OF THE SIMPLE CONVERSION METHOD FOR LOAD-SETTLEMENT CURVES IN SELF-BALANCE TESTS

简单转换法是自平衡静载试验Q-s曲线转化为传统静载试验曲线的常用方法,上推桩桩身压缩量的计算精度决定了简单转换法及自平衡静载试验结果的准确性。针对现行简单转换法的不足,对上推桩桩身压缩量的计算方法展开研究,通过对上推桩受力机理的分析和有限元计算,得出桩侧摩阻力分布系数C直接影响上推桩桩身压缩量的计算精度,上推桩在上推力的作用下,桩侧负摩阻力沿桩身向上急剧减小,呈下凹双曲线型分布,且分布系数C随基桩长径比的增大而增大,由此给出了桩身压缩量更为精确的计算式,改进了现行的简单转换法。工程实践证明,改进的简单转换法更为准确、实用。

The simple conversion method is a common method for transform Q-s curves of self-balanced static load tests into curves of traditional static load tests. The calculation accuracy of compression for piles of being pushed-up determined the accuracy of the simple conversion method and the results of self-balanced static load tests.Aimed at the deficiency of the current simple conversion method, the compression calculations of the pushed-up piles were studied. Based on analysis of the force mechanisms for pushed-up piles and the finite element calculations, the distribution coefficient C of the side friction resistance for piles were obtained, which could influence the calculation accuracy of compression for pushed-up piles. Under the action of the thrust, the negative friction on the sides of piles decreased sharply upward along pile shafts, and the distribution of the negative friction was a concave hyperbola. With the increase of aspect ratios, the values of C increased.Therein, the calculation formula of pile compression was more accurate. Engineering examples showed that the improved simple transformation method was more accurate and practical.