嵌岩桩竖向承载力计算问题探讨

Discussion on Calculation of Vertical Bearing Capacity of Rock-socketed Pile

在综合分析现有文献的基础上，指出现行各行业规范中嵌岩桩承载力计算公式产生差异的缘由及存在的问题。通过对比分析指出，规范经验公式采用岩石单轴抗压强度计算嵌岩桩承载力具有计算简单、便于推广应用的优点，但也存在对影响因素控制性差的局限，计算结果往往偏保守；理论计算通常较规范经验值更接近于现场实测值，但其参数繁多、计算复杂而不便于应用。建议嵌岩桩设计应在现行国家标准规范的基础上，注重地区经验的积累并建立健全地方标准。通过对嵌岩深度问题的深入分析，提出嵌岩桩设计中可按侧阻或端阻占嵌岩段总荷载约40％～60％的比例来确定最佳嵌岩深度，并通过引入分项发挥系数实现了最佳嵌岩深度下的嵌岩桩承载力的计算。

The formulas for bearing capacity of the rock-socketed pile in current industry standards are different from each other. The cause of the difference is pointed out based on analyzing the existing data comprehensively, and also some of the other problems. The results of comparative analysis show that the standard empirical formu- lae have the advantages as easy calculating and convenient spreading, which are calculated by the use of uniaxial compressive strength, but there is limitation of weak control for the influencing factors, and the calculated results tend to be conservative. Although theoretical analytic solutions are usually more closer to the in-site measured values than empirical values, it is not suitable for engineering works because of the multitudinous variables and complex calculation; so it is recommended that the design and application of the rock-socketed pile should focus on the accumulation of experiences and the establishment of regional standards. Furthermore, a method is proposed to determine the optimal embedding depth, and it is corresponding to the depth when the lateral resistance or end resistance accounting for the total load of the embedded section about 40% to 60%, by the way, the calculation of the bearing capacity of the pile at this depth is achieved by the introduction of partial coefficients.