Instrumentation in Geosynthetic Reinforced Unpaved Road Models and Laboratory Calibration

The first part of the paper discusses the state-of-the-art literature for the calibration methodology adopted since 1974 and the various instrumentations used in pavement testing by researchers since 1996 like EPC, LVDT, moisture gauge, strain gauge, and temperature sensors. The second part of the paper elaborates on the present work on laboratory calibration procedures performed at COEP Technological University for earth pressure cells, moisture sensors, and LVDT. This paper briefly examines and discusses the status, usage, maintenance, and recalibration of the instruments recovered from the previous study of the fully instrumented road model and the specifications, configuration, calibration, and interfacing of new instruments. The EPC and LVDT considered for the present work were retrieved from the two road models tested by full-scale accelerated pavement testing set up with a standard full axle load of 40kN to the design traffic of one lakh load cycles on unreinforced section and 1.5 lakhs load cycles on geotextile reinforced test section. Herein the cell effectiveness is assessed based on its position in the road model either at the interface or below the interface, and the maximum vertical stress induced during cyclic loading. The results reveal that the magnitude of the deflection on the surface of EPC does not exceed 1/2000 of its overall diameter, and the ratio of deflection to diameter is less than 1/5000. The laboratory calibration procedure for LVDT and earth pressure cells resulted in the calibration factor of (-0.5) for LVDT 07 and EP13, which is 0.9053 when tested for the instrument response until it reaches the maximum physical range with minimum fluctuations.