大直径灌注筒桩单桩竖向承载机理分析

筒桩土芯性状复杂，而筒桩承载力计算还不成熟。分别对黏性土层和砂性土层中筒桩土芯承载机理进行了比较分析，认为土芯与筒桩存在相对位移趋势，相对位移的发生是筒桩内侧摩阻力产生的原因，得到了土芯内摩阻力及土芯端部承担荷载计算公式。黏性土层中土芯承载作用较小，而砂性土层中由于土芯闭塞效应承载作用大大加强，得到了单桩竖向极限承载力的简化计算公式。最后通过工程实例验证了该公式的实用性。

Analysis of vertical bearing mechanism of large-diameter tubular pile using cast-in-situ concrete

Owing to complexity of soil core’s characteristic, the calculation of tubular pile’s bearing capacity isn’t mature. Two kinds of bearing mechanism in clay and in sand are compared. The reason how inner friction appears is that relative displacement or the trend of it exists between the soil core and pile, depending on which the calculation method of the inside friction and of the bearing capacity of soil core top are settled. The conclusion is that the contribution to bearing of inner friction is little in clay and is large in sand for the obstruction effect. At last, predigested calculation formula of vertical bearing capacity of tubular pile is established, Case study are given to validate the method.