Application of Ground Penetrating Radar and Hilbert transformation helps revealing anomalous body of leakage in a concrete structure; A case history at Huai Mae Tor, Tak province, Thailand

Ground Penetrating Radar (GPR) measurement plays a key geophysical investigation to delineate rebar, thickness of concrete lining on a horse-shoe spillway, and condition of rock foundation of an earthen dam, Huai Mea Tor, Tak province, Thailand. By applying 2-D GPR, more than a hundred line at concrete floor of spillway, processing results particularly show rebar at depth 20 centimeter and thickness of concrete at 1.6 meter, as well as anomalies in several lines. Subsequence, applying Hilbert transform [5] to the 2-D data, the result displays clearer than original that easy to interpretation. In consequence, applying 3-D processing, the result reveals gridding rebar of 20×20 centimeter at depth between 20 and 40 centimeter as well as anomalous bodies at lower part of concrete floor. The anomalies can be interpreted as potential open cracks or fracture or partial property-lost concrete which may possibly be the weak zone or leakage path that water can approach to the spillway structure under pressure. Finally, treatment at spillway was performed by engineer and for a while after the leakage problem was completely stopped.