OPTIMUM-DEPTH METHOD FOR DESIGN OF FABRIC-REINFORCED UNSURFACED ROADS

Abstract

In recent years, the use of engineering fabric, when placed directly on the subgrade and covered with a single aggregate layer, has been a cost-effective alternative in unsurfaced road construction, especially on soft subgrades. Most fabric-reinforced unsurfaced road design criteria use Boussinesq stress-distribution theory to determine the amount of aggregate cover on the fabric. The research presented in this paper shows that placement of an optimum depth of aggregate on the fabric, when related to the width of the loaded area and independent of subgrade strength and wheel load, will increase strength and deformation resistance of the aggregate cover and produce significant Burmister-type modular ratio stress reductions at the subgrade surface. An alternate method for the design of fabric-reinforced unsurfaced roads, based on the described research, is presented. The method requires significantly less aggregate cover on the engineering fabric than predicted by other current methods of fabric-reinforced road design. (Author)