Abstract
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.
Highlights
Piezoelectric materials (PZT, i.e., lead zirconate titanate) often find varied applications in civil engineering projects
The unit weights of sand after application of different surcharge levels were determined via consideration of the settled surface
Three grain sizes of the clean Nakdong river sand were poured into a small compaction mold
Summary
Piezoelectric materials (PZT, i.e., lead zirconate titanate) often find varied applications in civil engineering projects. The electro-mechanical impedance (EMI) technique employing PZT sensors has been widely used as a non-destructive testing technique for monitoring concrete structures. When using this technique, the PZT material is usually attached to the surface of concrete and steel bridges and other such concrete structures to monitor their strength or deformation [5,6,7]. The degree of soil compaction can be determined by measuring the unit weight (density) of compacted soils. Three methods are usually used to determine the in situ density of compacted soils: (a) The sand-cone method; (b) the rubber-balloon method; and (c) the nuclear method. Soil densities around pipes or retaining walls could be reduced owing to soil washing due to leakage or groundwater flow [11]
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