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| Author(s): |
Welitom Rodrigues Borges
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) |
| Defense date: | 2007-06-29 |
| Examining board members: |
Jorge Luis Porsani;
José Gouvêa Luiz;
Walter Malagutti Filho;
Carlos Alberto Mendonca;
Shozo Shiraiwa
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| Advisor: | Jorge Luis Porsani |
| Abstract | |
The implantation of the Shallow Geophysical Test Site (SCGR) of the Astronomy, Geophysics and Atmospheric Sciences Institute (IAG), from University of Sao Paulo (USP), is a mark in national geophysical history. It is the first site Shallow geophysical study site installed in Brazil. This Test Site is located next to Physics Institute in front of IAG/USP, comprehending an area of 1500 m2 (50 m x 30 m). In this area, different targets were installed, with varied dimensions and different depths, buried in seven lines of 30 meters. Targets were chosen aiming at reproducing a small sample of main objects found in urban environment. The goal of the study was characterizing targets installed in SCGR by using different geophysical methods with emphasis in Ground Penetrating Radar (GPR), electric and inductive electromagnetic (EM-38) methods. This characterization consisted in evaluating the performance and reliability of geophysical methods, when applied in targets whose physical properties are well-known. Measurements were carried out before the targets installation in subsurface, in order to obtain data from land background or geologic horizons before disturbances. In a second stage, geophysical data were obtained after target installation. Geophysical results were shown in 2D profiles, and depth slices in volumetric blocks, Quasi-3D. Geophysical data from land background showed an earthwork layer, with thickness up to 2.8 meters, above loamy sediments of Pinheiros River. EM-38 enabled the mapping of all metallic targets buried until 1.5 meter of maxim depth. The identification of some metallic targets also buried in the depth of 0.5 meter was possible with chargeability results. Electric resistivity data allowed the identification of a metallic tube buried at the centre of the area, to 0.5 meter of depth, and of representative geological materials targets. GPR results identified of the majority of targets buried in SCGR with better resolution than those ones shown highest dielectric contrast. This research contributes for geophysical method refinement applied to everyday problems mostly in geotechnical, urban planning, archaeological and environmental studies. (AU) | |