New approaches for modelling subgrade nonlinearity in thin surfaced flexible pavements

Abstract

a griffith School of engineering, griffith university, gold Coast, australia; b Department of transport and main roads (Queensland), Brisbane, australia ABSTRACT The primary objective of this paper is to present new methods in characterising flexible pavements that possess nonlinear subgrade behavior using deflection data from falling weight deflectometer (FWD). The two techniques to be introduced are Simplified Deflection Modeling and Deflection Ratio (DefR) approach. FWD deflection data can be modelled accurately using an exponential curve in a mathematical form of Y = K 1 exp (−r/K 2 ). K 1 is equal to deflection at D 0 in micron and K 2 is the structural parameter at the respective sensor location. K 2 parameter is found to have a direct relationship with the material constant, value of the subgrade and it is taken as a measurement of the nonlinearity of the pavement layer. As K 2 increases and approaches 500, the pavement structure is observed to possess linear elastic behaviour. In the second method, the DefR is defined as the ratio of the FWD deflection of a sensor divided by the deflection of the preceding sensor. For pavements that exhibit nonlinear subgrade behavior, the DefR shows an increasing trend for FWD sensors located at 300mm and beyond. The two techniques have provided alternative approaches for modelling subgrade nonlinearity.

Concept Paper: Developing Pavement Structural Deterioration Curves

“…For pavement design in Australia, D0 is the maximum deflection, D250 / D0 is the deflection ratio, D0 -D200 is the curvature function and the D900 reflects the subgrade response. Note, for subgrade response on thin pavements, recent research by Chai et al [8] should be considered. For calculating the pavement structural the FWD test data can be used.…”

Analyze the impact of flood on road performance and the corresponding maintenance effect

“…The reason to choose the 900 D deflection is that QDMR (1990) has found that it reflects a subgrade response which remains essentially unaffected by the structure of the overlying pavement. Chai et al (2016) pointed out in the study that assessing the moisture content on the road is one of the applications of simplified deflection model. In addition, he plotted the relationship lines between the moisture content and the k2,900 according to SDM, as shown in Figure 9.…”