[IMAGEM_CAROUSEL]

This service refers to the GPR (Ground Penetrating Radar) surveys for interference location (pipelines, ducts, cables, etc.) performed in the intersection of Herculano Banderia Avenue with Manuel de Brito Street, in Recife − PE.

These elements served as bases for an adequate plan of expansion and improvement works in the local road system. In this specific case, a tunnel building project.

The execution of these services was performed in to order supplement previous information regarding local interferences. Since there were uncertainties regarding these positions in some locations, GPR mapping has the purpose of clarifying exactly these doubt points, thus increasing the accuracy of locating these interferences.

These surveys were executed from August 08 to 09, 2006. A total of 12 GPR profiles were performed, executed in a network under the abovementioned crossing. Due to the excessive local traffic during the day, by the contractor’s request, surveys were performed during the night, with partial interdiction of the avenue.

Methodology

In this study, data were obtained through continuous profiling, with monostatic arrangement, that is, the same antenna, of 200 or 400 MHz, works as transmitter and receiver of electromagnetic waves. In order to minimize the spherical divergence effect, characterized by the attenuation of waves in the propagated medium, a gain is applied during the acquisition from the analysis of trace amplitude in function of time.

Geographic position of profiles performed was linked to remarkable points, based on maps provided by the contracting party. A survey wheel was also used, coupled to the antenna that automatically creates “marks” at previously defined regular intervals, in a way that, knowing the starting and ending location of each section, it is possible to georeference each point surveyed by the GPR.

Data obtained during the survey are then stored in the central unit, which are subsequently transferred to a computer in order to be processed and interpreted.

Finally, interpretations and editions of the profiles generated are performed. The exhibition is given through variable density, represented by “pixel” lines, according to the amplitude value in each time.

Results Obtained

From the surveys executed with GPR it was possible to state that:

    • Nearly all profiles performed indicate the presence of interferences, these being represented by draining, cables, pipes networks, metallic structures, etc.
    • The representation of these interferences in the profile performed was possible by interpreting the geometry of the various reflectors found. In general, these reflectors are presented as hyperboles, in box, parallel planes, etc.
    • Thus, it can be concluded that GPR was shown as a supplementary, high resolution tool, to map these interferences. It is worthy highlighting that, in addition to the accuracy of these surveys, this methodology is known as indirect or non-invasive, that is, there is no need to physically open ditches and/or trenches, which can directly impact more extensive deadlines and, consequently, adversely affect the local traffic.