The Characteristics of Underground Utility Repairs Made in Asphaltic Roadways – Comparing the Use of Grade D Aggregate as a Viable Backfill Option

Abstract

Given that most utilities are located beneath public right of ways, it is difficult to perform repairs to the utility without significantly disturbing the existing roadway. Currently there are several standard orders of procedure that deal with small-scale repairs on asphaltic surfaces. This study investigates the use of Grade D Aggregate as a backfill during a utility repair versus the condition of the repair. Five East Tennessee utilities provided a total of 60 utility repair locations over three years of age; 30 of which incorporated Grade D Aggregate and 30 incorporated #57 Stone.

The Tennessee Department of Transportation specifies a smoothness criterion of the roadway to regulate any deviation of the surface of the roadway greater than ¼ inch over a 12-foot span. The parameters measured during this study include smoothness, condition of the asphalt topcoat, adjacent stress cracking, depth of repair and disturbed surface area. Multiple linear regression and analysis of variance tests were used to analyze the results.

Results suggest that there is no difference between using and not using Grade D Aggregate except with failures of one inch or greater. The results also suggest that there is little to no relationship between roadway characteristics and the performance of the repair except with failures one inch or greater. There is a correlation between slope and failures that had a deviation of one inch or greater. The results suggest that Grade D Aggregate performs better when significant failures occur. Recommendations include implementation of a cutback area, development and implementation of installation guidelines within the municipality, and implementation of a maintenance program that will address the repair cut failures in a timely manner.