Mechanics of Small Utility Cuts in Urban Street Pavements: Implications for Restoration

Abstract

The results of a three-dimensional finite element analysis of the impacts of small utility cuts in urban street pavements are presented. The analysis was restricted to flexible pavements for cuts of the order of 915 mm (3 ft) square. Using ANSYS Solid 45 Version 5.2 on a one-eighth area, the excavation process was simulated using a stress relief approach, in which the material was assumed to be removed in successive layers. Starting with gravity loading on the uncut model, the element stress results from the previous removal were used to compute the new effective confining stresses of the respective layers. The in situ material properties were typical of flexible pavements in an urban street. The analysis presented a clear picture of the magnitude and extent of the distress induced on the pavement structure below and surrounding the cut. The analysis also showed how the restraining action of the asphalt layer is reflected in its arching up from heave and granular material thrusting, causing tension at the bottom and compression at the top. The results suggested that for unsupported depths of up to 1524 mm (5 ft), material distress may extend approximately 1068 mm (3.5 ft) into the pavement structure. Implications for methodology and economics of restoration are discussed, including determination of optimum cutback and recompaction of the affected area of pavement.