O sítio controlado de geofísica rasa do IAG/USP: instalação e resultados GPR 2D-3D

Abstract

ABSTRACT. The data interpretation from shallow geophysical survey can be complex because the uncertainty about subsurface targets. To reduce the ambiguity and help in the interpretation of geophysical data, the Shallow Geophysical Test Site of IAG-USP (Sítio Controlado de Geofísica Rasa-SCGR do IAG-USP) was installed inside the campus at USP. Different targets at various depths were installed along seven lines. The targets buried in the Test Site simulate targets found in geotechnical, archaeological, and environmental studies. In this article, the construction methodology of the Test Site and some GPR results along a line characterized by empty metallic tanks are presented. The geophysical characterization in controlled field condition allowed the calibration of geophysical responses due to known targets, such as, metallic tanks. 250 MHz GPR profile showed an excellent agreement with a GPR 2D model determined by finite difference in time domain method. Fk-migration improved the resolution and the spatial position of the metallic tanks. GPR 3D results, such as 3D cube, fence diagrams, and depth slices, were very important to improve the characterization of the targets in subsurface. SCGR-IAG revealed itself as important tool for teaching, research and extension activities in university related to Geophysics, and it will be very important to our community. With the installation of this Test Site, an important step was done in searching the State of Art in Shallow Geophysics in Brazil, were the development of news equipment, modeling and inversion software could be tested and its response calibrated.Keywords: SCGR-IAG, Shallow Geophysical Test Site-IAG, GPR-Ground Penetrating Radar, Modeling GPR 2D, Metallic tanks, Cube 3D, Fence diagrams, Depth slices. RESUMO.A interpretação de dados de investigações geofísicas rasas pode ser complexa devidoàs incertezas a respeito dos alvos em subsuperfície. Para reduzir as ambigüidades e auxiliar a interpretação dos dados geofísicos de superfície foi instalado no campus da USP o Sítio Controlado de Geofísica Rasa do IAG-USP. Diferentes alvos foram instalados em várias profundidades ao longo de 7 linhas. Os alvos instalados no Sítio Controlado simulam alvos encontrados em estudos geotécnicos, ambientais e arqueológicos. Neste artigo são apresentadas as principais etapas envolvidas na construção do Sítio Controlado de Geofísica Rasa do IAG/USP e alguns resultados GPR ao longo de uma linha caracterizada por tambores metálicos vazios. A caracterização geofísica, sob condições controladas de campo, permitiu uma calibração das respostas geofísicas para os tambores metálicos instalados no SCGR-IAG. O perfil GPR de 250 MHz apresentou uma excelente concordância com a modelagem GPR 2D através do método das diferenças finitas no domínio do tempo. A migração-fk melhorou a resolução e o posicionamento espacial dos tambores metálicos. Os resultados GPR 3D na forma de cubo 3D, diagrama de cercas e depth slices, mostraram-se muito importantes para melhorar a caracterização dos alvos em subsupe...

Depth Estimates of Buried Utility Systems Using the GPR Method: Studies at the IAG/USP Geophysics Test Site

“…This interference is routine for data acquisition, and permit the verification of noise for instrumentation uses at the site. Further details about the IAG/USP test site construction can be obtained in [9].…”

“…The targets buried under Line 4 used previously by Porsani et al [9] to characterize the GPR signal reflected by the metal drums using a 270 MHz antenna in conjunction with numerical modeling studies. Porsani and Sauck [12] identi-fied artifices in the radargrams, generated by the reflection of the electromagnetic wave between the metal drums positioned close to each other.…”

“…Information on the physical properties associated with the local geology was taken from Porsani et al [14] and information on the arrangement of metal drums installed in the IAG/USP test site was obtained in Porsani et al [9]. The choice of this model aims to reproduce the real environment where GPR data were acquired, and thus compare the real data with synthetic data.…”

“…Numerical modeling studies were performed aiming to validate the studies with real data. The research was developed at the IAG/USP Geophysics Test Site [9].…”

GPR Tomographic Imaging of Concrete Tubes and Steel/Plastic Tanks Buried in IAG/USP Geophysical Test Site, Brazil

“…To reduce the uncertainties, the GPR study was performed under controlled conditions in the IAG/USP geophysical test site in order to obtain the better understanding the normal reflection patterns caused by different targets in the subsoil. Some GPR results using this line of research can be found in the literature [10] This paper presents some results of GPR modeling, standard processing and microwave tomography application in GPR data, over empty concrete tubes, empty steel tanks and plastic tanks (empty and filled with water) buried in the IAG/USP test site [12] in order to characterization these targets that usually are present in the subsoil of the large cities of the world. The test site is located in a geologic urban context different from other worldwide test sites and it is situated at the border of São Paulo sedimentary basin, in São Paulo city, Brazil ( Figure 1).…”