An MASW Survey at a Site with High Velocity Uncontrolled Fill - A Case History

Landfill material is not often documented and its thickness and physical properties are largely unknown. The fill materials from general refuge are commonly known to be loose and its S-wave velocity is lower than the natural ground. However, the fill material can vary and there is no guarantee of such common knowledge to be always true. A Multi-Channel Analysis of Surface Waves (MASW) is a seismic survey method used for near-surface investigation. An MASW survey was applied to a proposed construction site with an uncontrolled fill. The survey covered the car park area with 1729m of seismic data collected in two days with a 24-channel landstreamer. A correlation of the result with the borehole data revealed the fill material has a higher S-wave velocity than the natural ground. The MASW method successfully profiled the original ground surface as an interface from high to low S-wave velocity. As this sort of velocity inversion is impossible to detect by more commonly used refraction method, the MASW is perhaps the only way to map the original surface under this environment.