The purpose of the compaction during a road construction is to achieve a necessary stiffness level. Therefore, the compaction evaluation process can be regarded as an in-situ shear-wave velocity (Vs) measurement for top, at most, 1-m thickness of roadbeds. Minnesota Department of Transportation (MnDOT) recently launched a feasibility study to use a seismic surface-wave (MASW) method for this purpose. The first field test, conducted at a 153-m-long test site, used a set of four parallel land streamers (12-channel per streamer) with 1-m geophone spacing and 1.2-m streamer separation. Five surveys were conducted at five different compaction stages during a full-depth reclamation (FDR) road construction. Analysis results of cross sections clearly showed velocity (Vs) variations for, approximately, the top 0.3-m thickness between different stages. In addition, depth-slice (DS) maps created from four parallel cross sections delineated velocity variations not only between different stages, but also between different surface locations. Frequency limitations in surface waves measured by using low-frequency (4.5 Hz) geophones and relatively long (11 m) receiver array for depth of interest (<1 m) made overall velocities underestimated. Future adjustment in acquisition system and geometry will significantly increase the resolution of the approach.
Presentation Date: Monday, September 25, 2017
Start Time: 3:30 PM
Presentation Type: ORAL