The Expander Body (EB) technology has been used successfully to increase the pile toe capacity of bored piles in loose to dense soils. 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 EB 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.

Furthermore, the shaft bearing capacity of the piles can be increased by using a soil displacement auger, instead of drilled piles under bentonite, which avoids the shaft soil decompression and increases lateral soil stress. This paper describes the principle of the EB system and its combination with the full displacement system for the shaft. During the past 20 years, a large number of EB piles have been installed in Bolivia and elsewhere, providing a sound database. Results from field loading tests are presented. A comprehensive study of test piles with and without EB base has been carried out which demonstrates the improvement effects that can be achieved by the EB pile system and the combination with the displacement auger pile method. A design concept for the EB pile system with the full displacement auger pile, based on the cavity expansion concepts, is briefly presented. A high degree of quality control can be achieved by monitoring the entire pile installation process, including the displacement pile and the EB.