Mitigation of Void Development under Bridge Approach Slabs Using Rubber Tire Chips

The problem of void development under bridge approach slabs has been correlated to the use of integral abutment bridges (Schaefer and Koch, 1992). This void development then causes settlement of the approach slabs leading to the formation of a bump at the ends of the bridge. The observation of the occurrence of voids under approach slabs, even in cases where no traffic had yet occurred, led to a hypothesis of thermally-induced movements of bridge beams/abutment walls as the mechanism causing the void development. As a result of identification of the mechanism of void development, changes to the approach system needed to be made to accommodate this mechanism. One approach to prevent the passive failure of the backfill soil due to the movement of the bridge abutments is to place a layer of rubber tire chips between the backfill soil and the back face of the abutments. This compressible layer can deform with the abutment and prevent passive failure of the backfill soil. A scale model study has been performed using shredded tire chips in the backfill system. This paper will present the backfill design, instrumentation, testing methodology and data analysis of this model test. The data analysis includes a comparison of data obtained from this model test with previous tests conducted of a backfill system without the incorporation of rubber tire chips.