A framework for the assessment of contribution of base layer performance towards resilience of flexible pavement to flooding
ABSTRACT Flood induced moisture damage of flexible pavements is a serious concern for many road authorities. Reports from several studies confirm the significant structural damage that is caused by flooding on pavements. In general, there is a consensus to design and construct roads that are resistant to flooding. Simultaneously, the concept of resilience has gained popularity frameworks and specifics are being developed to make civil infrastructure components resilient to natural and manmade disasters. This study provides a framework for quantitatively assessing the resilience of flexible pavements to flooding. The different interlinked steps consist of utilising unsaturated flow through the different layers to estimate drainage, interpretation of the results in terms of stiffness of the relevant layers, estimation of the impact of the change in stiffness on the overall structural condition of the pavement and then translating that change to a resilience index. The paper provides an illustrative example of such an estimation of resilience for a pavement. The results demonstrate the need for providing base course materials with appropriate gradation to ensure adequate hydraulic conductivity, and/or thicker surface layer, to avoid a reduction in service quality and loss of resilience for an extended period of time, in flood prone areas. Abbreviations: CBR: California bearing ratio; D60: diameter corresponding to 60% passing in results of sieve analysis; FE: finite element; FWD: falling weight deflectometer; HMA: hot mix asphalt; k eff: effective hydraulic conductivity; k sat: saturated hydraulic conductivity; MEPDG: mechanistic empirical pavement design guide; M R: resilient modulus; M Ropt: optimum resilient modulus; Q (t) Q: quality; R L: loss of resilience; R: Resilience; S Saturation; SNCratiof: post and pre flood modified structural numbers (SNCs) SWCC: soil water characteristic curve; wPI: percentage passing No. 200 sieve x plasticity index.