Influence of post-grouting and repressing on the base resistance of bored piles

Post-grouting and repressing on bored piles can strengthen the loose debris in pile end and improve the ultimate bearing capacity. A series of well-designed full-scale destructive load tests are conducted to find the bearing characteristics of post-grouted piles and the effect of repressing. The results show that both the shaft and base resistances of the post-grouted piles and repressed piles increase and the ultimate bearing capacity increases with the increase of the pile diameter. The base resistance of post-grouted piles increases sharply at first and changes slowly afterwards. The ultimate unit base resistances of the piles with diameters of 800 mm, 900 mm and 1000 mm are 5265 kPa, 4995 kPa and 4815 kPa, respectively. Thus the corresponding size effect coefficients are 1, 0.95 and 0.91, respectively. The increase rate of the base resistance of the piles in the second loading cycle is larger than that for the post-grouted piles, and their ultimate unit end resistances are 5889 kPa and 5488 kPa, respectively.