Relationship between Surface-Measured Indices and In-Service Pavement Structural Conditions Predicted from Traffic Speed Deflection Devices

Abstract

The rolling wheel deflectometer (RWD) and traffic speed deflectometer (TSD) are continuous deflection measuring devices used for structural evaluation of in-service pavements. Although recent studies have demonstrated the benefits of these devices, state agencies are inclined to believe that surface indices are generally sufficient to describe in-service pavement conditions (functional and structural conditions) and to make cost-effective maintenance and rehabilitation decisions. The main objective of this study was to assess whether the use of surface indices only or the declining rates of these indices to identify structurally damaged sections is feasible instead of relying on RWD and TSD estimated pavement structural indices. Results of the analysis showed that structural deficiency, rates of deterioration, and surface indices were correlated to a certain extent. These results were expected, as pavements that are structurally deteriorated will exhibit surface deficiencies over time. Yet, surface indices cannot be used as a reliable predictor of structural capacity. For RWD, the most accurate surface index, which was the alligator cracking surface index, erroneously identified 35% of structurally sound sections as structurally deficient and 51.5% of structurally deficient sections as structurally sound. Similar results were obtained for the TSD; in this case, the most accurate surface index, which was the random cracking index, erroneously identified 16.7% of structurally sound sections as structurally deficient and 51.0% of structurally deficient sections as structurally sound. The cost implication associated with misinterpreted sections from functional indices was investigated. The incorporation of structural indices is expected to provide significant savings to state agencies.

Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis

“…Recent studies conducted in Louisiana and elsewhere suggest that TSD is a promising device to evaluate pavement conditions at the network level as it can measure deflection at traffic speeds, which enables large spatial coverage and can provide a continuous deflection profile rather than measuring pavement deflection at discrete points, which is the case with FWD ( 4 , 5 ). The tools currently available to backcalculate pavement layer moduli, however, are solely based on FWD deflections ( 6 ).…”

Field and Laboratory Characterization of Subgrade Resilient Modulus for Pavement Mechanistic-Empirical Pavement Design Guide Application

“…Several non-destructive field methods and laboratory test methods have been used to determine the resilient modulus of subgrade soils ( 3 ). Field non-destructive test methods using Dynaflect, falling weight deflectometer (FWD), rolling wheel deflectometer, and traffic speed deflectometer have been used to estimate the resilient modulus of subgrade soils under existing pavements ( 4 – 14 ). Among these non-destructive tests, FWD can be used to back-calculate elastic modulus from pavement deflections and is widely used to predict pavement stiffness ( 15 – 17 ).…”