###### Abstract  
This paper presents the effect of confined granular fill on the efficiency of embedded _PZT_ (Lead Zirconate Titanate) patches. The experiments are carried out to capture the dynamic response of confined granular fill and voltage output. The dynamic response of the system is analysed using the fast Fourier transformation (_FFT_) of vibration and digital static cone penetrometer (DSCP) test at various excitation frequencies. The peak pick method is used to determine the damping loss factor and natural frequency. The efficiency of voltage generation of embedded _PZT_ patches is influenced by the depth of embedment, excitation frequency, location, and engineering properties of the confined granular fill. The results show that the influence of vibration frequency and placement of _PZT_ on the output voltage should be considered. The thickness and engineering properties of granular soil affect the efficiency of voltage output. This study emphasizes the utility of _PZT_ patches in the subgrade and structural health monitoring  
Despite abutting material properties, the output efficiency of the \(PZT\) patch is also influenced by the frequency of mechanical vibrations. [PERSON] et al. [11] indicated that the amplitude and frequency of the loading condition significantly affect the output power. [PERSON] et al. [12] investigated the energy harvesting from the bridge under varied loading conditions. The energy harvester showed a peak voltage response at the natural frequency. [PERSON] et al. [13] studied the effect of piezoelectric energy harvesting under traffic load vibrations. They investigated the influence of vibration frequency and excitation load on power output.  
[PERSON] and [PERSON] [14] studied the influence of confined granular fill on horizontally and vertically embedded granular fill. They concluded that the alignment of the \(PZT\) patch influences the voltage output. The research indicates that the dynamic response of the system significantly affects energy harvesting. These studies considered the effect of the pavement surface and traffic loads on the efficiency of _PEHs_. They did not consider the influence of subgrade on the performance of the piezoelectric energy harvesters. However, the influence of various subgrade materials and engineering properties on converting vibration energy for \(PZT\) patches under various excitation frequencies has not been clearly understood.  
This paper aims to explore an experimental analysis of the influence of the abutting material's properties and the excitation frequency on the voltage output of \(PZT\) patches. Some experiments were conducted on confined granular fill at varying depths to analyse the effect of embedment depths. This paper shows the effect of both vertical and transverse mechanical vibrations of varied excitation frequencies. The dynamic responses of the experimental data were analysed using fast Fourier transformation (\(FFT\)) in the frequency domain. The system's natural frequency was investigated experimentally using the peak pick method from the frequency response (\(FRF\)) function of the system. An analysis of the influence of excitation frequency, embedment depth, and displacement on voltage output is presented based on experimental data. Further, a set of static cone penetration tests was carried out to monitor the effect of confinement under various excitation frequencies. This effort emphasizes the utility of \(PZT\) patches in granular fills with vibration and their uses in piezoelectric energy harvesting from the ambient vibration from civil structures.