Abstract: 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.

Key words: large-diameter, cast-in-situ tubular pile, vertical bearing capacity, inner friction, obstruction effect