Comparative study on structural evaluation of flexible pavement using BBD and FWD

Abstract

Flexible pavements undergo deterioration with increase in heavy traffic. Thus, there is a need to evaluate the existing pavement condition and undertake appropriate maintenance measure for safe and efficient flow of traffic. Benkelman Beam Deflectometer (BBD) and Falling Weight Deflectometer (FWD) are the most widely used non-destructive techniques for evaluation and strengthening of flexible pavements in India. There is a need for rational approach of pavement evaluation because of high cost associated with new road construction and limited financial resources for maintenance of roads. Benkelman beam deflectometer involves static loading whereas falling weight deflectometer involves dynamic loading which simulates moving traffic. The main objective of this study is to develop a correlation between FWD and BBD. This paper presents a typical case study on a 5 km length of National Highway from chainage 34+006 to 39+003 in Bangalore, Karnataka. Pavement structural evaluation is conducted using FWD and BBD. The tests were conducted on the same road stretch at the same point of loading. The results are analyzed as per Indian Road Congress (IRC) guidelines and overlay thickness is designed using KGP-BACK and IIT-PAVE. Linear correlation between BBD and FWD is developed using central deflection values and the co-efficient of correlation (R2) is found to be 0.8994. The developed correlation is then validated for present study data and available literature data. The root mean square error is found to be 6.77 and 7.67 respectively. Based on the observations, it is concluded that FWD serves as one of the more reliable method for the structural evaluation of pavements and this method proves to be cost effective by reducing the desired overlay thickness.