Compaction of Loose Flooded Granular Masses Using Air Pulses

Spontaneous flows of very loose sands pose a serious environmental problem particularly in mining areas. Conventional compaction methods such as blasting densification and vibrofloatation have no or limited monitoring and/or control devices during their application. Alternative methods with monitoring features are needed to remediate those collapsible wastelands in terms of safety. In laboratory experiments the effects of repeated air pulses in loose sands were investigated, focusing on their densiflcation success and liquefaction potential. Tests in a modified semi-large triaxial cell investigated the effect of induced drainage on liquefied sand. Large scale field experiments using an airgun as pulse source were performed on test sites instrumented with geophones and pressure transducers to consider in situ conditions. The results show that repeated air pulses can liquefy and then compact cohesionless soils. The extent of liquefaction can be monitored on-line and controlled through induced drainage. The proposed method may be useful when careful soil treatment is required because of closeby sensitive structures.