Abstract: Based on model test method, pile-soil interaction characteristics of 2×1 and 2×2 belled wedge pile groups embedded in sand under vertical load are carried out. The load versus settlement of pile top, pile tip resistance and the axial force of pile distribution along depth are measured. Meanwhile, model test on vertical bearing capacity of single belled wedge pile are also carried out for comparative analysis. Considering the coefficient values of cap effect and group effect noted in JGJ94 code, the ultimate bearing capacities of belled wedge pile groups are calculated. In this model test conditions, the results show that the group effect coefficients of 2×1 and 2×2 belled wedge pile groups with low cap equal 1.16 and 1.10, respectively; and those of pile groups without cap equal 0.95 and 0.88, respectively. The values of cap effect and group effect coefficients for traditional equal section pile can be used for belled wedge pile.

Key words: pile foundation, pile group, compressive bearing capacity, belled wedge pile, model test