大直径薄壁筒桩承载力计算新方法

A NEW CALCULATION METHOD FOR LARGE-DIAMETER-TUBULAR-PILE BEARING CAPACITY

基于ICP方法,提出考虑土芯贡献的大直径薄壁筒桩竖向承载力计算新方法,即不考虑桩内侧摩阻力;桩端阻力按闭口桩端阻的1/2计算,单位桩端反力取桩端上下2倍桩径范围内土体CPT锥尖阻力的平均值;破坏面内摩擦角取直剪试验峰值内摩擦角的1.2倍;用简化公式计算打桩后土体的径向有效应力。该方法综合考虑我国浙江地区软土的特点,比ICP方法简单、实用、参数更易确定,通过工程实例验证,并与计算桩侧摩阻力的α法、R1,R2,R3法及V&F法比较,结果表明,新方法的计算结果最接近实测值。

Based on the imperial college pile（ICP） method, a new method is proposed to calculate the bearing capacity of large-diameter-tubular-pile, in which the contribution of soil plug is considered. However the inner pile friction is not taken into account due to the small value, not full-length distributed and conservative consideration. In this approach, the end resistance is the average value of tip resistance from the pile tip to the depth of 2 times of the pile diameter. In view of the unpopularity of ring shear test, the peak value of direct shear test is used for the friction angle of the interface by amplification of 1.2, which is verified through test results. The radial effective stress is very important in bearing capacity calculation, and a simplified method with a few parameters is put forward. This new approach is much simpler than ICP method, and could have satisfactory estimations if compared with a-method, Randolph methods and V＆F method. The test results prove that the new method is reliable.