Measurement of Unit Weight of Dry Sand Using Piezoelectric Sensor

Recently, an electro-mechanical impedance (EMI) technique has found wide application in the monitoring of concrete structures. This EMI technique was employed for measuring the unit weights of various grain sizes of sand and the relevant process is reported herein. A piezoelectric sensor (PZT, i.e., lead zirconate titanate sensor) was imbedded into small, medium, and large-sized grains of the Nakdong river sand and a surcharge was applied. The effect of an increase in unit weight owing to the surcharge was investigated in terms of the resonant frequency (peak frequency) and corresponding conductance at resonant frequency (peak conductance). A ceramic-coated PZT sensor was used to prevent the occurrence of a short circuit. The measured peak frequency and conductance from the PZT sensor were correlated with the unit weight of sand. With an increase in the unit weight of sand, the peak PZT frequency was found to have increased, however, the peak conductance was seen to have decreased. The peak PZT frequency and conductance were seen to be strongly correlated with the unit weight of Nakdong river sand except for the peak conductance of large grain sized sand.