GSSI StructureScan Mini XT, Руководство пользователя

Страница: 60 / 69

Geophysical Survey Systems, Inc. StructureScan™ Mini XT
Manual
MN 70-813 Rev E 48
Potential Void under Slab
This image shows a wire mesh reinforced
slab. Note the heavy black band below the
wire mesh and shown by the orange
arrows. The black band results from a
pronounced high to low dielectric change
as in concrete to air. While we do not know
how thick the void might be we can tell the
starting and ending point by locating where
the black band starts and ends. Once we
know the location, the next step is to drill a
small hole in the concrete for confirmation.
When searching for voids behind slabs it is
best to collect a long file so that any change
(such as the black band at the right) will be
more readily visible.
Rebar
This image is of #8 (1” diameter) rebar spaced 12” (30 cm) apart. Compare this image to the previous two
examples. Notice that while there is a constant spacing, the spacing is too wide for normal wire mesh.
Also, when surveying over suspected rebar, take two profiles at right angles to each other. You will notice
that the two directions of rebar hyperbolas will show at slightly different depth while wire mesh
hyperbolas will be at the same depth. This is because mesh is welded together as a screen.
Also note the back of the slab as a black band at approximately 8” depth.