The current viewpoints on the modifying coefficient problem of end-bearing resistance of large diameter belled piles are different. The results of four groups contrastive field full-scale axial loading tests investigating the influence of base diameter to end-bearing resistance and settlement behavior of large diameter belled piles in a clay layer site are discussed. Also

a plane finite element model is adopted to analyse the bearing mechanism of large diameter belled piles. Based on the tests and numerical simulation

a study on modifying coefficient of end-bearing resistance of large diameter belled piles is carried out; and some conclusions are drawn as follows. Firstly

the modifying coefficient of end-bearing resistance of large diameter belled piles is essentially a kind of dimension modifying coefficient. The coefficient behave as a modifying coefficient of deformation or strength of base soil layer formally. Secondly

under certain precondition

the relative modifying coefficient method can make piles obtain larger end-bearing resistance in pile foundation design. Finally

other related problems on which attention should be paid are proposed.