The findings of this research are presented in NCHRP Report 516, "Pier and Contraction Scour in Cohesive Soils." NCHRP Report 516 documents the entire research effort undertaken under NCHRP Project 24-15 and presents a recommended method for predicting the extent of complex pier and contraction scour in cohesive soils.

Scour at bridges founded in or on cohesive materials is a very complex phenomenon that is not completely understood. Conventional approaches to scour prediction were developed from laboratory experiments in cohesionless materials. No methods for predicting scour depths in cohesive material that account for the material's greater scour resistance are available to practicing engineers. The lack of a predictive method results in inadequate design and analysis of bridge foundations in or on cohesive soils. Research investigating the relationship between properties of cohesive material and the erosive power of flowing water is needed to improve scour prediction for bridge foundations in or on cohesive materials.

The research conducted under this project resulted in the development of a procedure to accurately predict pier and contraction scour for bridges founded in or on cohesive materials.

Status: Research is complete.

The NCHRP oversight panel has requested and received an additional $400,000 to investigate abutment scour in cohesive materials. The continuation research will conducted as NCHRP Project 24-15(2).

Product Availability: NCHRP Report 516: Pier and Contraction Scour in Cohesive Soils is available through the TRB website. In addition, the SCICOS-EFA computer program and User's Manual referenced in the final report are available from the Texas Transportation Institute via the internet at: https://ceprofs.tamu.edu/briaud.