Estimating Earthwork Factors for Roadcuts Using Surface Geophysics

ABSTRACT: A method utilizing surface refraction seismic geophysical measurements to estimate earthwork factors involving large rock cuts in weathered, fractured rock masses and associated embankments has been developed. The method uses Percolation Theory (PT) concepts to relate rock mass modulus values to rock mass porosity values. Surface refraction seismic measurements are used to estimate rock mass low strain modulus values. Recovered rock core unconfined compressive strengths are used to estimate rock particle modulus values, and unit weights are used to estimate corresponding rock particle porosities. Rock mass unit weights are then estimated from measured seismic velocity profiles through project rock cuts. Embankment fill unit weights are estimated from seismic velocities obtained through existing fills and from Proctor test results of materials sampled on the highway projects. Earthwork factors are determined from the ratios of these in-situ rock mass unit weights and existing or anticipated embankment fill unit weights.