Shear-Wave Seismic Reflection Case Study for Use In The Provision Of Shallow Seismic Profiles For Geotechnical Investigations.

Shear-Wave seismic reflection was utilised to delineate the bedrock within a paleo valley system along with other reflectors within the sediment profile that may be pertinent to a road viaduct construction. The road viaduct construction had planned to socket piles in the bedrock. However, shallower sediment lenses of adequate stiffness within the sediment profile may have utility for friction pile design and provide a design and construction cost advantage. Prior to commencement of the primary field campaign, a trial comparison between compressional-wave seismic reflection utilising explosives and shear-wave reflection utilising shear-wave vibration sources was made. Based on the trial test results and subsequent refinement of collection parameters the primary campaign was carried out using the Shear-wave reflection source. The method was successful in resolving the general bedrock trend in the paleo channel system along with lenses within the sediment profile and distinct variations in sediment Shear-wave velocities. The approximately 1800 m of total survey profiles increased the confidence in the shallow subsurface geological model and provided improved information on the geotechnical parameters.