Rebar
Objective
Our client was tasked to install new
plumbing lines as part of a building
renovation. This task involved drilling 4
inch cores through each floor of the
building. Geoview was contracted to locate
the rebar and post tension cables to
determine safe coring locations.
Method
The geophysical investigation was conducted
using Mala and GSSI ground penetrating radar
(GPR) systems. On site testing determined
that 900 Megahertz and 1.2 Gigahertz
antennas provided the best resolution of the
radar data while also allowing the GPR to
image the entire depth of the 8 inch
concrete floor. Both 2-dimensional and
3-dimensional data was collected at the
site.
Results
The GPR data showed the rebar was located
in an orthogonal grid, with the rebar spaced
7 to 8 inches apart. The post tension cables
were located on an orthogonal grid, with the
cables spaced approximately 60 inches apart.
The GPR survey was conducted on ten floors.
The centers of the proposed safe coring
locations were marked on the surface of the
concrete. As a result of the GPR survey, no
rebar was cut during the coring activity.
Figure 1 - GSSI
Structure Scan GPR System with Optical Scanner used During the
Investigation Figure 2 - Collection of 3-D GPR Data
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