The Use of an Expander Body with Full Displacement Piles in Medium-Dense Sandy Soils

The expander body (EB) technology has been used successfully to increase the pile toe capacity of bored piles in loose to medium dense soil. An important advantage of the EB system is the ability to monitor the EB expansion process, which provides important information regarding soil strength and soil stiffness. This information, obtained for each installed pile, can be used to determine the actual shape and pile toe area. The expansion pressure can be used to design the pile base capacity. The expander body system has been recently improved by incorporating the possibility of post-grouting of the soil below the expanded pile toe. This improvement measure provides additional strength and stiffness to the pile toe and reduces pile settlement. Using a soil displacement auger, which avoids soil decompression and increases lateral soil stress, the shaft bearing capacity can increase, mainly in comparison with the traditional bored piles under bentonite. This paper describes the principle of the EB system and its combination with the full displacement system for the shaft. A high degree of quality control can be achieved by monitoring the entire pile installation process, including the displacement pile and the expander body.