In civil engineering, foundational theories underpin various practices. These include principles of mechanics, materials science, and structural analysis. For instance, in structural engineering, theories like elasticity, plasticity, and structural dynamics are fundamental for designing safe and efficient structures. Geotechnical engineering relies on theories of soil mechanics to understand soil behavior and its interaction with structures. Transportation engineering employs theories of traffic flow and transportation planning. In essence, theories serve as the backbone of civil engineering, guiding engineers in designing, constructing, and maintaining infrastructure projects.