GPR for river dyke - GSB
GPR for river dyke - GSB
GPR for river dyke - GSB
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Figure 5: Radargram <strong>for</strong> the test on 6 th floor ground<br />
Figure 6: Radargram <strong>for</strong> the test along a verticalwWall of Reshad’s room.<br />
This radargram in Figure 6 has also been collected by 10cm length antenna. Again we use<br />
the red arrow to represent the time reference corresponding to the ground (wall) surface and<br />
the blue arrow to point the time of the reflection from the other side of the wall. The travelling<br />
time between those two reflections is about 3 ns. Assuming the wave speed 12 cm/ns and<br />
using s = v t/2 , we obtain the wall thickness of 18 cm. Here we have used the typical value<br />
of the wave speed in brick material. The actual wave speed can be obtained by a calibration<br />
test on a known thickness material layer. In Figure 6, we have clearly seen the interface<br />
between two layers of bricks (brown arrow).<br />
4.2 <strong>GPR</strong> tests on <strong>dyke</strong><br />
The project area is located in the North and north-western part of the Dhaka city on Turag<br />
<strong>dyke</strong>.This <strong>dyke</strong> is approximately 30 kilometres of earthen embankment along Tongi khal,
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