A study of low-energy dynamic compaction: field trials and centrifuge modelling

This paper describes research into understanding the efficiency of the low-energy dynamic compaction process, and the development of a novel technique of real-time monitoring that can demonstrate soil improvement in quantitative engineering units during the process, The research, undertaken in the field and using a 500 gTonne geotechnical centrifuge, investigates the validity of applying the principles of the WAK (wave-activated stiffness [K]) test analysis to monitor the progress of compaction, allowing the process to be halted once the required degree of improvement has been reached. The analytical procedures underpinning the interpretation of the compaction process data in the time and frequency domain are presented, including the derivation of dynamic stiffness, depth of compaction, and damping factors associated with the combined footing/soil system. The methods of instrumentation and data acquisition are described for both held and centrifuge test programmes, along,vith the procedures adopted for real-time signal conditioning and data recognition, The results of the field and centrifuge test programmes are discussed, and conclusions are drawn on the effectiveness of the compaction process, confirming the validity of the WAK test analysis in the prediction of improvement in soil stiffness with increasing number of blows.