A REAL TIME SCOUR MEASUREMENT INSTRUMENT

PROPOSED IS A NEW INSTRUMENT BASED ON THE REFRACTION MODE OFSEISMIC SURVEYING TO MEASURE THE DEVELOPMENT OF SCOUR ADJACENT TO A BRIDGE PIER OR ABUTMENT. THE INSTRUMENT USES A REPEATABLE ACOUSTIC SOURCE PLACED NEXTTO THE CONCRETE STRUCTURE AND AN ARRAY OF HYDROPHONES IN A PVC PIPE THAT IS BURIED VERTICALLY IN THE RIVER BED NEXT TO THE PIER. THE ACOUSTIC SOURCE EMITS REPEATED SIGNALS THAT ARE REFRACTED DOWN THE PIER INTO THE SOIL. THE REFRACTED WAVES PROPAGATE TO THE RECEIVER ARRAY ACCORDING TO SHELL'S LAW. SIGNAL ENHANCEMENT THROUGH SUMMING REPEATED EXPERIMENTS IS POSSIBLE BECAUSE THE RATE OF SCOUR IS SLOW COMPARED TO THE TOTAL TRAVEL TIME OF THE REFRACTED ENERGY. SCOUR IS MEASURED AS THE DELAY CAUSED IN THE TRAVEL TIME TO SUCCESSIVELY DEEPER HYDROPHONES AS THE SCOUR ZONE DEEPENS.