Numerical modeling of composite materials for the alleviation of manhole decrement into pavement

Due to the unevenness produced by utility manholes on road surface, a technique to embed the manholes underneath pavement surface is proposed. A 3-dimensional finite element model is developed to analyze the mechanical behavior of paving material surrounding the manhole under heavy traffic loads. Using the critical strains determined by the model, the potential of pavement distress in the overlaid paving material was assessed. Various overlay material combinations were compared in terms of their expected performance in the pavement/ manhole system. The results show that the fatigue damage of paving materials on buried manhole is consistent with conventional theory, in that the maximum tensile strain at the bottom of the overlay is critical. The maximum compressive strain on the top of buried manhole cover is the determination index of rutting damage while the major cause of ruts is compressive strain on the asphalt overlay resulting from wheel load. Comparing to the single-layer overlay on the manhole, the two-layer overlay was found to be more durable to traffic loading. A suitable combination of the two-layer overlay material for manhole covers consists of a modified asphalt concrete course as the base and a dense-graded asphalt concrete as the surface course.