Evaluating the Effectiveness of Rolling Impact Compaction at a Brownfield Site with High and Low Frequency Seismic Surface

An effective procedure has been developed for guiding environmental sampling and verification of the effectiveness of impact rolling compaction for ground improvement at a brownfield site. Extensive surface wave testing within an uncontrolled fill area have demonstrated good correlations between S-wave velocities obtained from high frequency surface wave measurements using a modified MASW system, CPT and in-situ densities This generally increases with increasing number of machine passes but by very little after a certain number of passes. On average, post-compaction in-situ densities increased by 6% to 10% and S-wave velocities increased by up to 40%, clearly demonstrating the sensitivity of S-wave velocities to soil and fill modulus. The S-wave velocity sections also illustrated the consistency achieved in the landform created by the impact roller. A statistical approach was used to develop a linear relationship between S-wave velocity and Dry Density Ratio (DDR). This formed the basis for the compaction specification for the entire brownfield site. Electromagnetic and improved surface wave geophysics provide alternatives to costly excavation, removal and re-engineering of soils at brownfield sites and represent an advance over current practice.