Course Description

Let us begin with the fundamentals. Scour, in the simplest terms, is the removal of soil particles from around foundation elements due to flowing water. This includes bridge piers, abutments, culvert inlets and outlets, and even offshore wind turbine monopiles. As soil is removed, the foundation loses lateral support and bearing capacity, which can lead to excessive settlement, tilting, or catastrophic collapse. In cohesive soils like clays and silty clays, scour behavior is fundamentally different from sands because of electrochemical bonds between clay particles. These bonds create cohesion, which is a true tensile strength that sand does not have. Clay particles are plate-shaped and carry surface charges that attract water molecules and each other, forming a structured fabric. This means that clays do not erode grain by grain like a sand. Instead, they erode in small flakes, larger aggregates, or even as entire blocks when cracks are present. Ignoring the time-dependent nature of scour in clays is one of the most common and dangerous mistakes in practice. Many engineers assume that if a scour calculation shows a certain depth, that depth will be reached during the design flood. But for a stiff clay, that equilibrium depth might take decades to achieve. Conversely, for a soft clay, it might happen in days. Both scenarios require different design responses. Many bridge failures attributed to scour occurred in cohesive formations where the wrong equations were applied. So remember this key point as we move forward: cohesive soils are not just sticky sands. They obey different rules, and we must respect those rules in our analysis and design.

What you'll learn in this course?

• Define scour and distinguish between scour in cohesive versus non-cohesive soils.

• Identify the fundamental mechanisms of erosion in clays and silts.

• Recognize the key hydraulic and geotechnical factors influencing scour depth.

• Explain the role of soil plasticity, shear strength, and hydraulic conductivity in scour resistance.

• Apply commonly used methods for estimating scour in cohesive soils, including the SRICOS and Briaud methods.

• Interpret laboratory test results such as the EFA (Erosion Function Apparatus) and HET (Hole Erosion Test).

• Design practical scour countermeasures for bridges, culverts, and coastal structures.

• Evaluate real-world case studies of scour failure in cohesive soil environments.

Prerequisites

• Basic understanding of soil mechanics, fluid mechanics, and foundation engineering

• Familiarity with bridge, culvert, coastal, or hydraulic infrastructure is helpful