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UBC Theses and Dissertations

An evaluation of the Phoenix machine : a new apparatus for the in situ densification of soil Hitchman, Ross


An in situ densification probe which employs the novel technique of simultaneous vibration and drainage has been developed by Phoenix Engineering for the purpose of in situ improvement of loose, granular soils. It is believed that pumping of water during the densification process offers improved densification capability over systems operating with vibration alone. This study evaluates the performance of the Phoenix system and investigates some of the parameters which influence the effectiveness of the densification process. A testing programme was conducted at a site in the Lower Mainland to assess the instrument. The site consists of a pumped fill overlying a natural medium sand. Field tests were accomplished in both materials. Characterization of the site and treatment evaluation were achieved by using in situ tests. Changes to soil parameters due to densification treatment were examined, taking into account the modification of stresses brought about by the vibro compaction process. It was found that relative densities up to 85-90% could consistantly be achieved. The study highlighted the important contribution of pumping water from the soil during compaction operations. It demonstrated that the Phoenix system can offer improved compaction over alternative commercial compaction systems if probe size and spacing are taken into account. The importance of maintaining an adequate supply of backfill is emphasized. It was found that the machine was well suited to compacting silty sands, both natural and fill, but was unable to cause improvement in silt. The influences of changing probe spacing and pattern were examined. The effects of time spent densifying and changes to soil conditions due to time effects are briefly covered. Finally, the limitations of this study are noted, and recommendations for future research are proposed.

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