ASSESSMENT OF BRIDGE PIER SCOUR USING IMPULSE RADAR.

The use of impulse sub-surface radar in detecting the presence of scour holes in river beds is described in this paper. The basic theory of radar signal emission is briefly described to show the theoretical limits of a system. This is followed by a review of surveys carried out in lakes and rivers, with the values of the limits actually attained. Transmission line equipment developed at Liverpool University to measure the electrical properties of river water, mud and silt suspensions is described. The variation of these properties along the length of a river is shown for River Dee water and silt samples. Computer modelling of radar signals has also been developed, and the results obtained are compared with signals measured at both Liverpool University swimming pool and a small-scale model of a scour hole. Finally, the field results obtained during on-site testing on the River Severn at Gloucester are presented. (A)