Estimating the benefits of improved drainage on pavement performance
The drainage quality is an important parameter which affects the performance of highway pavements. In India, since last few years considerable importance has been given to the drainage as per of pavement. A poor quality of drainage results in premature deterioration of the pavement structure and necessitating large amount of costly repairs or replacement, before they reach their design life. This study presents investigations for premature deterioration of a stretch on National Highway (NH 58) between Rishikesh (km 231) and Shivpuri (km 242) due to poor sub-surface drainage. The sections at km 233.800 and km 235.900 were identified for this study. Investigations were carried out by field measurements and laboratory tests on samples of permeable base (water bound macadam – WBM) and sub-base (granular sub-base – GSB) layer materials. Laboratory investigations included determination of gradation, optimum moisture content, maximum dry density, and permeability. Three samples were prepared for each test for both WBM and GSB material and average results were used. The pavement sections were evaluated structurally by deflection measurements and functionally by measuring the road roughness. In this study, the benefits of providing good drainage over the service life of the pavement were quantified in terms of vehicle operating cost (VOC). Performances in terms of deflection and roughness were predicted for do-nothing and after applying required maintenance. Vehicle operating costs were computed based on the maintenance strategy for good and poor drainage pavement sections and benefits due to maintenance strategy were estimated. Afterwards, economic benefits of good drainage and poor drainage for identified pavement section were compared.
Keywords: Pavement sub-surface drainage, Pavement performance, Vehicle operating cost