Abstract: Post-grouting technique has a wide range application to piled foundations. The principle of post-grouting technique is as follows: through grouting cement into bottom of bored pile or around pile body, the loose material such as deposit and slime during pile construction can be strengthened; and it can highly increase frictional resistance and end bearing capacity of pile. Post-grouting technique was successfully employed in the piled foundation of Su-Tong Bridge, a huge bridge under construction which connects Suzhou City and Nantong City in Jiangsu Province, China. According to the results of static load tests, the U-shape grouting pipe was used in the project for the piles’ bottom grouting. After grouted, values of the ultimate bearing capacity of the tested piles were increased up to1.48-2.0 times the ones of un-grouted bored piles. For end bearing capacities, their values were increased up to 2.46-7.21 times. It can be drawn a conclusion that through using post-grouting technique, it saves investment, improves construction quality and reliability, and brings considerable economic benefits and well social environment effects as well.

Key words: bored pile, post-grouting technique, Su-Tong bridge, pile tip resistance, side friction