Scour Monitoring

Monitoring Countermeasure Performance Using Sonar

Authors: Jerry Shen (FHWA) , Frank Jalinoos (FHWA)

Abstract

Current policy in the US considers riprap placed at bridge piers to be only a temporary countermeasure against pier scour. Federal guidance requires that riprap placed at bridge piers to be monitored periodically by visual inspection or by fixed instruments. This policy stems from the challenge in adequate sizing of riprap to withstand the turbulence and hydraulic stress generated in the vicinity of a bridge pier under flood-flow conditions.

Moreover, the design philosophy in HEC-18 to estimate scour at bridge piers does not recommend using countermeasures to protect the pier as part of the design. The reason for this approach is that important data to evaluate the performance of countermeasures on a continuing basis is missing. Comprehensive data on monitoring the performance of scour countermeasures for pier protection is needed before a change in design philosophy can be considered.

This paper discusses the use of various sonar technologies for monitoring the performance of scour countermeasures. Case studies using both sector-scanning and multi-beam imaging technologies will be presented.

The countermeasure monitoring can be beneficial in:

1. Gaining confidence by the bridge owners in the use of countermeasure by monitoring their performance and positions; especially post-flood events.
2. Long-term countermeasure performance monitoring can eventually lead to change the design philosophy in HEC-18.
3. Providing preliminary data for developing AASHTO LRFD specifications for countermeasures.
4. Sonar imaging at the abutments and piers can be used as a quality assurance (QA) measure for inspecting new countermeasure installations and for performance monitoring after extreme events.

Keywords:

How to Cite: Shen, J. & Jalinoos, F. (2014) “Monitoring Countermeasure Performance Using Sonar”, National Hydraulic Engineering Conference 2014. 1(2014).