DYNAMIC RESPONSE ANALYSIS OF WALL RETAINING GRANULAR FILLS WITH PZT PATCHES

Abstract

This thesis focuses on the dynamic response analysis of confined granular fill with PZT (Lead Zirconate Titanate) patches embedded in various geo-structures. The geo-structures consist of machine foundations, pavement, subgrade, bridge abutment, railway track, retaining wall, and contact geo-material. These structures are subjected to ambient mechanical vibration due to dynamic loads. In this study, dynamic loading refers to the input excitations frequency on the confined granular fill with PZT patch. The dynamic response refers to stress and strain in the PZT patch and the wall retaining granular fill due to varied excitation frequencies. The voltage across the PZT patch is produced in response to the dynamic loading. The electromechanical coupling of piezoelectric material is the key factor for the voltage and power output. The coupling techniques of structures and PZT patches are significantly affected by the variables namely fundamental frequency, contact pressure of loading, structure geometry, PZT patch placement, and contact material. The potential of power generation from the mechanical vibration of geo-structures has been classified for a range of power outputs. The coupling parameters improved the efficacy of power generation from the ambient vibration of geo-structures. The study of charge density, voltage output, and power from the PZT patches is affected by alignment of PZT patches, thickness ratio, material properties of the confined granular fill and retaining structure. As a result the voltage output can be obtained directly from the stress-strain response, position of the PZT patch and the engineering properties of the confined granular fill. The modulus ratio of the material, alignment of PZT patches, and gradation of infill material significantly affect the voltage generation. The maximum voltage output was obtained in the range of 0.001–0.5 V for the thickness ratio of 0.2–0.6 for the horizontally and vertically embedded PZT vii patches. The observed voltage output is found appropriate for wide-ranging implements. A relationship between voltage and power output has been proposed for engineering applications. The power output may be up-scaled using multiple patches embedded throughout the confined granular fill and pavements subjected to continuous dynamic loads. Experiments are carried out to capture the dynamic response of confined granular fill in terms of the voltage output from embedded PZT patches. The dynamic response of the system is analysed using the fast Fourier transformation (FFT). A digital static cone penetrometer (DSCP) test is conducted on a granular fill compacted at various excitation frequencies. The cone resistance of compacted granular fill indicates that voltage output (0.8-2.4 V) increased proportionally with varied excitation frequencies. The damping loss factor and natural frequency are determined using the peak pick method. The depth of embedment, excitation frequency, location, and engineering properties of the confined granular fill influences the experimental voltage output from the PZT patch. The peak voltage output at the same embedment depth is observed at 10-50 Hz excitation frequencies in the vertical and transverse directions. The experimental observations show the output voltage in the range of 1.5-3.0 V in the vertical and transverse directions. The results show that the voltage and energy output gradually decay at higher frequencies for increasing the embedment depth of PZT patches. The strain sensitivity of the PZT patch can be maximized at higher excitation frequencies and embedding the patch in a deeper granular fill. At deeper depths for various excitation frequencies, the energy output is obtained in the range of 0.10-1.78 nJ, and power output is obtained in the range of 0.5-14 watts. Thus, the mechanical vibration of the structures can be utilized for power generation using the electromechanical conversion characteristics of the piezoelectric material. This research can lead to viii an increase in the energy output and can thus improve the overall efficiency of the PZT patch embedded in confined granular fills. The findings of this research contribute to advancing the knowledge and understanding of dynamic response analysis in confined granular fill with PZT patches. The results offer valuable insights into the behavior of PZT patches under different excitation frequencies, facilitating the design and optimization of these systems in a wide range of geo-structures. Future research can build upon these findings to further refine the dynamic response analysis techniques and enhance the performance of PZT patches in various applications.