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Título

MULTICHANNEL ANALYSIS OF SURFACE WAVES WITH A PASSIVE ROADSIDE APPROACH AT A TAILINGS DAM

Resumo

The MASW (Multichannel Analysis of Surface Waves) method is a geophysical procedure to obtain the velocity profile of shear waves (S waves) in the subsurface stratigraphical layers. It is a piece of significant information in geotechnical studies because of the direct association of the S waves with the modulus of rigidity. Different types of sources can be employed to generate seismic waves. The choice of the source is critical for obtaining high-quality results from both shallow and deep layers. Active sources (e.g. sledgehammers and weight droppers) generate higher frequency S waves, providing insights into shallow layers. In contrast, passive sources (e.g. ambient noise) generate lower frequency waves, presenting details about deep layers. Ideally, combining active and passive data can yield a comprehensive survey response. However, in practice, there are logistical problems with passive sources since the seismic sensor array must be arranged in two dimensions. In addition, we need to assume that the ambient noise is reasonably well-distributed in all directions, which is not always the case. Therefore, an alternative source strategy is the so-called Passive Roadside, which uses vehicle traffic as a source that can generate lower frequency waves than traditional active sources. We used a vehicle passing over a portable speed bump to generate the seismic waves, and the strategic positioning of the speed bump allowed us to use a linear sensor array. This work presents an MASW survey conducted at a tailings dam in Brazil using the Passive Roadside approach. The procedure is uncommon in the mining industry, but it has provided superior results compared to sledgehammer (active source) data, which is the standard practice. Therefore, we conclude that Passive Roadside is advisable whenever possible, as it has the potential to yield superior results when compared to active sources.

Palavras-chave

MASW, Passive Roadside, S Waves, Tailings Dam.

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