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Shear wave velocities in a construction landfill
| Resumo: | This report presents the Multichannel Analysis of Surface Waves (MASW) on a construction landfill. The main goal of the survey is to determine the shear wave velocities (VS) in order to estimate the dynamic properties of the soil. The velocity of shear waves (VS) were obtained from the Rayleigh wave’s dispersion. The present document reports the acquisition and processing of 28 seismic profiles (approximately 3225 m for MASW data) acquired between March and July 2015. In the acquisition, a linear array of 24 geophones spaced by 1.2 m was used for the active measurements. Since the method uses vertical impulse (PEG 40 and sledge hammer) and vertical recording, it was also possible to determine the compressional wave velocities derived from refraction analysis, using the Rayfract Seismic Refraction & Borehole Tomography software. The 2D compressional wave models were used to infer the thickness/ geometry of the layers, as well as preliminary input for MASW data processing /modeling, since applying an a priori model minimizes the dispersion of the final results. The processing consists of two main stages: imaging dispersion curves of surface waves and the estimation of near-surface shear-wave velocity by inversion of Rayleigh waves. Finally, a 2D S-wave velocity section was generated due to the CMP roll-along acquisition format. For the gridding process, the Golden Software's Surfer was used, placing each S-wave profile (VS versus depth) in the middle of the seismic spread with which it was calculated. Finally, each line was placed in its location and represented Voxler 3 3D software, allowing a better perception of the distribution of the dynamic properties of the soil along the landfill. Shear wave velocities (VS) generally increase with depth, but they can differ due to site conditions, water content, tide levels, landfill operation procedures, like compaction made on site, among others. |
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| Autores principais: | Santos, Joana Filipa Formigo |
| Assunto: | MASW Ondas superficiais Ondas S Aterros Teses de mestrado - 2016 |
| Ano: | 2016 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | This report presents the Multichannel Analysis of Surface Waves (MASW) on a construction landfill. The main goal of the survey is to determine the shear wave velocities (VS) in order to estimate the dynamic properties of the soil. The velocity of shear waves (VS) were obtained from the Rayleigh wave’s dispersion. The present document reports the acquisition and processing of 28 seismic profiles (approximately 3225 m for MASW data) acquired between March and July 2015. In the acquisition, a linear array of 24 geophones spaced by 1.2 m was used for the active measurements. Since the method uses vertical impulse (PEG 40 and sledge hammer) and vertical recording, it was also possible to determine the compressional wave velocities derived from refraction analysis, using the Rayfract Seismic Refraction & Borehole Tomography software. The 2D compressional wave models were used to infer the thickness/ geometry of the layers, as well as preliminary input for MASW data processing /modeling, since applying an a priori model minimizes the dispersion of the final results. The processing consists of two main stages: imaging dispersion curves of surface waves and the estimation of near-surface shear-wave velocity by inversion of Rayleigh waves. Finally, a 2D S-wave velocity section was generated due to the CMP roll-along acquisition format. For the gridding process, the Golden Software's Surfer was used, placing each S-wave profile (VS versus depth) in the middle of the seismic spread with which it was calculated. Finally, each line was placed in its location and represented Voxler 3 3D software, allowing a better perception of the distribution of the dynamic properties of the soil along the landfill. Shear wave velocities (VS) generally increase with depth, but they can differ due to site conditions, water content, tide levels, landfill operation procedures, like compaction made on site, among others. |
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