一种大直径扩底桩端阻力和侧阻力的确定方法

A method for determining tip and side resistances of large diameter pedestal pile

确定大直径扩底桩承载力的最直接的方法是静力载荷试验。但由于加载的困难和试验费用高等原因,静力载荷试验往往不可行。目前进行大直径扩底桩设计时通常借用建筑桩基技术规范的经验参数法,对大直径灌注桩端阻力值和侧阻力值折减确定,容易造成大直径扩底灌注桩的承载能力得不到充分发挥。结合大直径扩底桩的规范编写,对收集的完整试桩资料进行统计分析,并参考《建筑桩基技术规范》及北京、天津、浙江、福建、广东等地方给出的经验值,最终按不同扩底直径给出了端阻承载力特征值和侧阻承载力特征值的经验值表,并与各试桩的承载力实测值以及按桩基规范确定的承载力特征值进行比较,结果表明,本文建议的大直径扩底桩端阻力特征值和侧阻力特征值具有一定的可靠性和较大的适用性。

Static load test is a most direct way to determine bearing capacity of large diameter pedestal pile. Because of the difficulties in loading process and high test cost, load test is not feasible in practical engineering. In general, bearing capacity can be obtained by means of the reduction of pile tip and side resistance based on the empirical parameter method of Technical Code for Building Pile Foundation in large diameter pedestal pile design. In this way, the bearing capacity of large diameter pedestal pile can not be well used. Based on the modifying of technical specification for large-diameter pedestal cast-in-place pile foundation, the test data of piles are statistically analyzed. The characteristic value of tip resistance and shaft resistance are presented using for reference from Technical Code for Building Pile Foundation and empirical values given by local codes of Beijing, Tianjin, Zhejiang, Fujian and Guangdong. The characteristic values of tip resistance and shaft resistance given in the present paper are compared with the measured values of test pile and calculated values obtained by Technical Code for Building Pile Foundation. It is found that the characteristic values proposed in the present paper are reliable and applicable in practical engineering.