嵌岩桩单桩竖向承载力计算方法研究

Calculation Method of Vertical Ultimate Bearing Capacity of Rock-socketed Pile

嵌岩桩因其单桩承载力高、群桩效应小等优点,已被广泛运用至工程实践中。而其单桩承载力作为重要参数,常规的静载荷试验方法耗时费力,故而多种计算便捷的估算方法在很多情况下也得到了推广应用。考虑到工程实践中如何选择相适应的嵌岩桩单桩竖向承载力计算方法缺乏系统研究,归纳总结分析了不同的规范法、理论法及经验公式法的优缺点,并结合工程实例对多组实测数据进行不同方法下嵌岩桩承载力的计算应用分析比较。结果表明:3种嵌岩桩承载力估算方法的准确程度和其所表达的嵌岩桩受荷性状和实际受荷性状的接近程度存在较强的关联性,而和需要参数的多少关联性较小。理论分析法由于物理意义更为明确,其计算结果也更为接近实际值。而经验公式方法由于缺乏明确物理意义,计算结果和实际值相差较大。规范中,《建筑桩基技术规范》(JGJ 94—2008)及《公路桥涵地基与基础设计规范》(JTG 3363—2019)规范计算公式体现的桩体受荷性状中最为接近实际且考虑影响因素较为全面,估算准确性较高。根据该研究成果,可对工程实践中嵌岩桩竖向承载力计算方法选择提供可靠的优选建议及误差来源分析。

Rock-socketed piles are widely used in engineering practice because of its high bearing capacity and small pile group effect.As an important parameter,the bearing capacity of single pile is usually time-consuming and laborious to obtain easily through test methods such as static load test.Therefore,there are many convenient methods to estimate the vertical bearing capacity of single rock-socketed pile,such as standard methods,theoretical methods and empirical formula methods.Considering the lack of systematic research on how to select the appropriate method to calculate vertical bearing capacity of rock-socketed pile,the similarities and differences of different standard methods were summarized,theoretical methods and empirical formula methods,and combined with engineering projects the bearing capacity of rock socketed pile under different methods was calculated,analyzed and compared.The results show that the accuracy of these method for estimating the bearing capacity of rock-socketed piles depends more on the similarity between the hypothetical load characteristics of the rock-socketed piles and the actual load characteristics than the number of required parameters.The results of theoretical methods are more accurate than those of empirical formula methods because of its specific physical meaning.Among the standards,the load bearing behavior expressed by calculation formulas of Technical Code for Building Pile Foundation(JGJ 94—2008)and Specification for Design of Foundation of Highway Bridges and Culverts(JTG 3363—2019)are closer to the actual situation,thus,theirs calculational results are more accurate.Finally,according to the analysis,some suggestions for selection of calculation methods for estimating the vertical ultimate bearing capacity of rock-socketed pile and their error source analysis are put forward.