Assessment of bridge scour and riverbed variation by a ground penetrating radar

Ground-Penetrating Radar(GPR) which is a nondestructive geophysical technique was used to assess the extent and depth of existing and infilled scour thickness, streambed materials, and pre- and post- scour surfaces at bridge piers from July 2002 to October 2002 in Han River, Seoul, South Korea. The GPR acquisition system used for obtaining profiles of the shallow petrology of subsurface deposits was a portable GSSI SIR 2000 system with antennas of frequency 100 and 400 MHz, and the images from GPR gained in the flow direction of the 24 bridge piers and in the surroundings of 5 bridge piers were compared. GPR images collected near bridge piers contain a continuous profile of the water bottom. These sub-bottom reflectors had been correlated to old scour surfaces, pier foundations, old channel beds, or geologic layers. It is concluded that GPR surveys can be effective in determining both the water depth and sub-bottom geological characteristics near bridge piers and abutments provided that the correct instrumentation and operational procedures are applied.