ABSTRACT
This paper proposes a non-destructive evaluation method for assessing the integrity of geo-structures using transmission lines embedded in concrete. Defects are identified by analyzing variations in electromagnetic wave signals propagating through the lines. Preliminary tests on reinforced concrete columns showed that signal reflections occurred at voids, with amplitudes decreasing as the water content of the soil with voids increased. The wave velocity was also affected by the presence of voids, water content, and curing conditions. Model pile tests were subsequently conducted on bored piles with either centered (intact) or off-center (defective) rebar cages. In the off-center cases, the signal amplitudes increased due to insufficient concrete coverage. In contrast to the proposed method, the conventional cross-hole sonic logging approach failed to clearly detect the misaligned cages. These results demonstrate that the proposed method can identify subtle structural defects that are often overlooked by conventional methods, thereby offering a promising alternative for evaluating the internal condition of concrete structures.
