Abstract
In this study, we introduce a novel method using longitudinal sound to detect underground soil voids to inspect underwater bed property in terms of effective bulk modulus and effective density of the material properties. The model was simulated in terms of layered material within a monostatic detection configuration. The numerical model demonstrates the feasibility of detecting an underground air void with a spatial resolution of about 0.5 λ and can differentiate a soil firmness of about 5%. The proposed technique can overcome limitations imposed by conventional techniques that use spacing-consuming sonar devices and suffer from low penetration depth and leakage of the transverse sound wave propagating in an underground fluid environment.
Highlights
According to the US Geological Survey in 2014, the average cost of karst collapses in the United States over the past 15 years is more than $300 million per year
By measuring the reflected signal pressure over a roundtrip estimation of the effective bulk modulus and effective density values, the single frequency propagation the wave, a significant difference and wasused found thespeed four cases, as componentof phase velocity should be considered in between place of the of sound shown in value from the pulse envelope
As the listed equations indicated, the amount of reflection time delay back from the rock layer provides a larger effect on the estimated effective bulk modulus and density values than the echo amplitude difference since sound speed is a square term in the equation
Summary
According to the US Geological Survey in 2014, the average cost of karst collapses in the United States over the past 15 years is more than $300 million per year. Noninstructive tests or non-destructive (NDT) such as ground-penetrating radar (GPR) [4,5], spectral analysis of surface waves (SASW) [6,7], multi-channel analysis of surface waves (MASW) [8,9], and micro-tremor array measurement (MAM) [10,11] are useful methodologies to detect underground voids They can provide 2D or 3D subsurface stiffness profiles from the measurements at the ground surface. The density and mechanical properties undergo a clear decrease when the soil became soft Those methods are limited to provide more in-depth engineering information, such as soil type, strength, stability, and so on [12]. The effective bulk modulus and effective density detection (EBME) [15] have been applied to underground soil health monitoring and void detection in a compact monostatic setup
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