Selection of suitable backcalculation technique and prediction of laboratory resilient modulus from NDT devices

ABSTRACT

This study aims to analyse the backcalculated cohesive subgrade moduli using various backcalculation approaches. A series of in situ and laboratory investigations have been carried out on 190 test locations from 30 pavement sections of cohesive soils using Falling Weight Deflectometer (FWD), Light Weight Deflectometer (LWD), and Repeated Load Triaxial to determine backcalculated resilient moduli (M_{R_back}), composite resilient moduli (M_{R_comp}), and laboratory resilient modulus (M_{R_lab}). The comparative analysis was performed for M_{R_back} by LWD (M_{R_back_LWD}), M_{R_comp} by LWD on subgrade (M_{R_comp_LWD}), and M_{R_back} by FWD (M_{R_back_FWD}) with M_{R_lab} values to assess the level of agreement. M_{R_back_FWD} and M_{R_back_LWD} values of different soils by using Artificial Neural Network and Support Vector Machine techniques have shown the mean percentage variation (1.16–59.63%), correlation in terms of R² value (0.628–0.824), and RMSE value (0.51–20.49%) with M_{R_lab} values. In contrast, M_{R_comp_LWD} values have shown good agreement with M_{R_lab} values among M_{R_back_LWD} and M_{R_comp_LWD}. This study also suggested adjustment factors (0.308–0.974) for predicting M_{R_lab} values from M_{R_back_FWD} and M_{R_back_LWD} for cohesive soils. Thus, this study recommends an appropriate backcalculation technique and suggests adjustment factors to the cohesive type of soils for realistic prediction of resilient characteristics of subgrade.

KEYWORDS:

• Backcalculation
• backcalculated resilient moduli
• cohesive subgrade
• falling weight deflectometer
• light weight deflectometer
• Repeated Load Triaxial Test
• and ANN backcalculation technique

Disclosure statement

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

Additional information

Funding

This work was supported by Ministry of Human Resource Development.