Performances of negative skin friction of belled wedge pile group under surcharge load

In order to reduce negative skin friction and improve positive skin friction of piles which is are embedded in soft ground, a new pile type, cast-in-place belled wedge reinforced concrete pile (referred to as belled wedge pile), is developed. The design method and construction process of the belled wedge pile are introduced. Based on FLAC^3D, the accuracy is verified by analyzing model test examples, and the properties of negative skin friction of balled wedge pile groups are preliminarily studied. The parametric studies on pile spacing, taper angles, pile-soil modulus ratio and coefficient, and soil layered modulus ratio are carried out and discussed. The conventional equal section pile which is in the same concrete volume is comparatively analyzed. It is shown that 16 % - 20 % of downdrag can be reduced by small taper angles (between 0.4^o – 1.0^o) compareed with the equal section pile, which shows that taper angle can reduce downdrag effectively.