Utilization of Recycled Asphalt as Filling Material for Geobarrier System

Abstract

Abstract A Geobarrier system (GBS) is a retaining structure, made of stacks of geotextile bags filled with fine aggregates laid on a coarse aggregate layer. The near-vertical wall protects steep slopes against rainfall infiltration and failure. The GBS combines the concept of a mechanically stabilized earth (MSE) wall and a capillary barrier system (CBS) which employs the distinct difference in unsaturated hydraulic properties between a fine-grained layer and a coarse-grained layer. Usually, fine and coarse materials are made of natural aggregates. However, in line with current sustainability policy, recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) were used. This study compares the unsaturated properties of RCA and RAP as components of GBS, and the performance of the GBS walls with RCA and RAP as fine and coarse materials. Numerical analyses were conducted using a typical geometry of GBS with a height of 4 m and a slope angle of 70°. Extreme rainfall of 22 mm/hr was applied on the wall for 8 hours. The focus is to evaluate whether the fine aggregates can effectively drain the infiltrated water. Limit equilibrium analyses were performed at various stages during and after rainfall to assess the near-vertical wall stability. The results show that the unsaturated properties of both RCA and RAP are almost similar except for the difference in the coefficient of saturated permeability of fine and coarse aggregates. The initial factor of safety of the wall with RCA is higher than that with RAP due to the higher shear strength of RCA. The transient factor of safety indicates that the fine RCA drains the water more effectively than the fine RAP resulting in a higher Factor of safety after rainfall stops. The study concluded that RAP could be used as filling material for GBS even though it is less effective than RCA.

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