Risk Analysis of Permeable Layer in Pavement Subsurface Drainage System

Abstract

The paper presents a framework to predict and consider the risks associated with the permeable layer in a pavement subsurface drainage system and suggests strategies to reduce the risks and improve the performance of the system. The performance of the system is dependent on the inflow characteristics, aggregate gradation, drainage characteristics of unsaturated soils, and geometry of the pavement section. The demand on the system is considered as the required permeability, which is estimated on the basis of total inflow into the pavement system plus the geometric section properties. The discharge capacity of the layer is dependent on the permeability of the drainage layer. The design of the system is examined in terms of capacity-demand models, and a rational design methodology considering variations in demand through rainfall characteristics and capacity in the form of permeability of the permeable layer is presented. Because determination of the exact demand and capacity of the system is a complex and stochastic process, the evaluation of its performance in light of uncertainty is a more realistic process, which should include consideration of the probability of failure and associated risks. The performance measure is analyzed by considering the sensitivity of the design to different variables. The performance of the system can be increased optimally by increasing the layer thickness and/or providing coarser gradation with stabilization.