Physical Model Studies of a Real Time Riverbed Scour Measurement System

Abstract

Riverbed scour around bridge foundations has led to numerous bridge failures due to the undermining of piers or abutments during floods. Remote monitoring of scour processes becomes very difficult during flood periods, at which time monitoring is most needed. The objective of the present study was to show that seismic methods could be used as the basis for a real time scour monitor system. These methods are based on using travel times of directly transmitted and refracted waves propagating through and in the vicinity of the bridge foundations. A series of experiments designed to test these concepts was carried out using a physical model. The physical model consisted of a rectangular or solid wall pier partly submerged in water and mounted in a sand layer. The wave generation and detection of the seismic energy was carried out with acoustic transducers. Initial tests showed that refracted waves and direct waves could be generated, propagated, and detected in this simplified model of a bridge pier. The results from the refraction wave tests and the direct wave tests indicate that both these methods could be useful in detecting the presence of scour zones. The experiments also suggested that these techniques could be used in an on-line scour monitor system.