Earlier this year, we offered a lunch-n-learn to our municipal clients titled “Roadway Reconstruction, Soft Subgrade, and Lessons Learned at Gregory Avenue.” This continuing education program was attended by 26 public works professionals representing nine municipalities. The featured project, Gregory Avenue, was a street maintenance project that was in need of reconstruction after several sessions of edge-mill and overlays.
Gregory Avenue had a 12″ to 18″ pronounced crown and exhibited significant linear cracking. The existing east and west curb and gutters were in fair condition with few sags, but the west curb and gutter appeared to have settled and rolled in several areas. Also, record drawings indicated that the existing water line was made of cast iron and had been installed in 1960.
This project consisted of the complete reconstruction of Gregory Avenue from E. Pipeline Road, 1,150 linear feet northward, to Gettysburg Place. The reconstruction included the removal and replacement of the existing concrete curbs, gutters, driveways, valley gutters, and asphaltic pavement. The existing 6-inch water line from Pipeline Road to Gettysburg Place was also replaced with a new 8-inch water line.
Although a relatively small project, the reconstruction of Gregory Avenue proved to be quite challenging. During construction, we encountered an unusual issue: in the middle-half of the overall project, the proof rolling indicated that the subgrade was soft/yielding (also known as pumping subgrade). Further investigation and testing suggested mechanical stabilization may be appropriate. The solution was to replace the 8-inch Cem-Line stabilized subgrade with a 6-inch flex base reinforced with a Tensar BH1200 Triaxial Geogrid.
Our presentation discussed underlying soils, topography, drainage, groundwater, roadway design/cross-section, construction process, Cem-Line for subgrade stabilization, flex base as subgrade, and the use of a geogrid in the subgrade. This presentation was also given at the American Public Works Association, Texas Chapter, 2017 Short Course.
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