Pavement settlement in and around utility cuts results in uneven pavement surfaces, driver annoyance, and further maintenance. A survey of municipal authorities and field and laboratory investigations were conducted to identify factors contributing to the settlement of utility cut restorations in pavement sections. Survey responses from seven Iowa cities indicate that backfill material generally consists of imported granular material, utility cut restorations last less than two years, and quality control during restoration construction is limited. To evaluate the performance of existing utility cuts and construction practices across Iowa, restorations in seven cities were observed. The observations indicate that backfill material varies from city to city, backfill lift thickness often exceeds 12 inches, and backfill is often placed at bulking moisture contents. The backfill materials were investigated in the laboratory to characterize gradation, specific gravity, relative density, and collapse potential. The collapse tests indicate that, at the field moisture contents encountered, the backfill materials have collapse potentials ranging from 5% to 25%. Falling weight deflectometer (FWD) data and elevation shots indicate that the maximum deflection in the pavement occurs in the area around the utility cut restoration. The FWD data indicate a zone of influence around the perimeter of the restoration extending two to three feet beyond the trench perimeter.
Abstract