Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
FREQUENCY POWER LAWS FOR THE DECAY OF THE LEAK NOISE SPECTRUM IN SANDY SOIL WITH DIFFERENT DEGREES OF COMPACTION
Submission Author:
Matheus Proença , SP
Co-Authors:
Matheus Proença, Daniel Henrique de Sousa Obata, Amarildo Tabone Paschoalini, Vinícius de Araújo Salmazo
Presenter: Matheus Proença
doi://10.26678/ABCM.COBEM2023.COB2023-0188
Abstract
Leaks in urban water distribution networks are still a great challenge for several supply companies around the world, and, in this scenario, the vibro-acoustic detection/location techniques have stood out as part of the problem’s solution. However, several factors, such as the geological environment and its compaction, affect the measurement of the leakage signal on the ground surface and, consequently, harm the efficiency of these techniques. In this regard, knowing the attenuation behavior of the soil surrounding the pipe is a significant step towards determining the noise characteristics of the leak at the source, thereby contributing to the development of analytical and numerical approaches as well as in the remote processes of water leak detection/localization through vibro-acoustic methods. Therefore, this manuscript was carried out to numerically investigate the influence of the degrees of compaction of sandy soils upon its power laws of attenuation. The sandy soil was modeled as a viscoelastic solid using a previously validated Kelvin–Voigt model, and the differential equations describing the problem were solved using the Finite Element Method (FEM). The results showed that the frequency-dependent attenuation obeys a specific power law for each degree of compaction of the sandy soil. Therefore, a representative polynomial surface was constructed to predict the attenuation level for each Penetration Resistance Index (NSPT) of any frequency within the worked band interval. It has been found that the leak noise spectra decay with a frequency power law close to 1/ω2 in the soil with a controlled compaction level and equal to 1/ω in the soil with a high compaction level. Furthermore, in an experimental test, an inverse method was applied to predict the temporal signal of an excitation source at the base of a sand massif using only the experimental output signal measured on the ground surface and its calculated numerical attenuation. The compared results agreed very well.
Keywords
Frequency power law, Soil attenuation, Soil compaction, viscoelasticity, Vibro-acoustics
