This Small Business Innovative Research (SBIR) Phase I project addresses the problem of measuring scour depth around bridge foundations under flood conditions. Flood-borne debris collecting around bridge piers forms bird's nests that aggravate scour by creating excess turbulence and preventing conventional scour detection techniques. The Pneumatic Scour Detection System (PSDS)addresses both problems of measuring scour through a bird's nest of debris and withstanding the ravages of flood-borne debris. This technique is based on the differential resistance to airflow through a vertical array of porous filters made of sintered brass. The array of filters are sealed into the wall of a probe used as a probe and battered through the bird's nest into the river bottom adjacent to the pier like a large nail. Shallow filters are exposed to water, and deeper filters are exposed to competent soil.
The 2002 National Bridge Inventory lists 22, 414 scour-critical bridges, many with bird's nests of debris. Flood-borne debris masks the river bottom surrounding the pier, making ineffective all currently available scour detection instrumentation, such as sonar depth sounders, ground-penetrating radar, and precludes visual inspection, limiting the bridge engineers ability to determine the safety of the bridge during flood events. The PSDS probe is permanently installed adjacent to scour-critical piers with the multiple pneumatic hoses bundled at the top of the probe for easy connection to an off-site portable pressure measurement instrument when flood events are in progress or anticipated. Once installed, the bridge engineers have available real-time information of the scour conditions at the pier, enabling them to close the bridge to traffic when dangerous conditions develop. Additionally, yearly monitoring of the scour conditions provides the bridge engineer the knowledge of depth of scour and is then able to schedule remediation before pier movement occurs, keeping maintenance costs to a minimum.
