Applicability evaluation of a two-dimensional piezoelectric transducer to monitor dynamic soil stress in unbound granular materials of road engineering

Abstract

In road engineering, the applications of piezoelectric ceramics on road energy harvesting or electronic sensing have drawn many attentions. However, the application potential of piezoelectric sensor on UGMs (unbound granular materials) in road is unclear. The main problem is the applicability of piezoelectric equation considering that the soil structure of UGMs and the working environment that the transducer may suffer may influence the transferred stress on the piezoelectric transducer and then the electricity generation. In this study, a two-dimensional piezoelectric transducer made by PZT-5H piezoelectric ceramics was installed in the sample of UGMs, and a series of cyclic tests were performed on the UGMs samples by a large-scale triaxial apparatus. This test method is specially designed for the case that the piezoelectric transducer is installed in UGMs of pavement base/subbase layers and then undergo traffic loading under complex working environment. Test results show that the electricity generation is primarily dependent on the magnitude and frequency of cyclic loading, while the influences of other factors are limited. The piezoelectric equation to calculate the open-circuit voltage is deduced and verified under the complex working environment. This indicates that the piezoelectric equation is applicable to the case that the applied stress on the piezoelectric transducer is transferred from the soil medium, and the two-dimensional piezoelectric transducer has a sensor potential to monitor the dynamic vertical and horizontal soil stresses under traffic loading.