Effects of underground cavities on Rayleigh waves—Field and numerical experiments |
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| Authors: | A Nasseri-Moghaddam G Cascante C Phillips DJ Hutchinson |
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| Institution: | aInspec-Sol Inc., Waterloo, ON, Canada N2 V 1C2;bCivil Engineering Department, University of Waterloo, Waterloo, ON, Canada N2L 3G1;cGolder Associates, Mississauga, ON, Canada L5N 5Z7;dGeological Sciences and Geological Engineering Department, Queen's University, Kingston, ON, Canada K7L 3N6 |
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| Abstract: | This paper presents the results of a multi-channel analysis of surface waves (MASW) test conducted over near-surface mine workings, with the objective of delineating the underlying. Numerical studies were carried out to explain and extend the results. The displacement time histories at the surface show amplitude changes in the region over the void, and the Fourier spectra show significant energy concentration on and in the vicinity of the cavity. Different numerical models are constructed and the responses at the surface of the medium and around voids of different sizes and embedment depths are monitored. The numerical results show that part of the incident energy is trapped within the void. The trapped energy bounces back and forth inside the void, until it is attenuated by radiation. The effect of the trapped energy is seen as a concentration of energy over the void region in the frequency domain. The amount of trapped energy is a function of the size and embedment of the void, as well as of the frequency content of the source. The void absorbs part of the energy and radiates it as body waves. Therefore, the recorded responses at the surface carry valuable information about the void. The characteristics of the void can be extracted from the surface responses by analyzing the responses in time, frequency, and spatial domains. |
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| Keywords: | Rayleigh waves Finite difference method Void detection Geophysical testing method MASW test Frequency domain analysis |
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