Deflection bowl parameters for falling weight deflectometer testing: data collection and threshold benchmarking

ABSTRACT

Deflection Bowl Parameters (DBP) has been used widely to evaluate pavement structural performance based on deflection data from Falling Weight Deflectometer (FWD). However, due to different pavement layers, materials configuration, test load, and climatic temperature, DBP thresholds need to be established for urban streets in tropical countries like Singapore. Around 130 km of field data in the network was collected every 25 m span, processed using Elmod 6 software before regression analysis. Based on the high coefficient of determinations (R-squared > 0.65), the DBP thresholds were proposed mainly for the middle layer condition (using Middle Layer Index, Lower Layer Index and Maximum deflection) and subgrade condition (via Lower Layer Index). In contrast, there were still some uncertainties in parameters related to HMA surface layers (by using Base Layer Index and Radius of Curvature) due to lower levels of R-squared (≅ 0.5). Our results have filled the research gaps of field-validated DBP thresholds for FWD 50 kN on the thick bituminous base pavement: Hot Mix Asphalt 130-170 mm, Graded Granite Aggregate Base 200-250 mm, and infinite subgrade. The findings have contributed to newly established DBP thresholds for immediate implementation in Singapore and other countries sharing similar pavement configurations.

KEYWORDS:

• Deflection bowl parameters
• bituminous base pavement
• falling weight deflectometer
• middle layer index
• lower layer index
• Singapore

Acknowledgments

We acknowledged the Land Transport Authority Singapore (LTA) for supporting this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).