Ace the 2026 NCEES FE Civil Exam – Engineer Your Career Success Today!

The term "swell" refers to the increase in volume that occurs when earth or soil is disturbed from its natural state. This phenomenon is primarily due to the loosening of particles when soil is excavated or removed, allowing air to fill the spaces between them. When soil is in its natural state, it is more compact due to the weight of the overlying material and the moisture content acting upon it. Upon excavation, the soil experiences a reduction in density, which causes the overall volume to expand—or swell—when compared to its dense, undisturbed condition.

Understanding swell is crucial in construction and excavation projects because it affects the calculations for material quantities needed, as well as the overall stability and performance of the earth-related structures being built. Recognizing this volume change helps engineers and contractors estimate the amount of material they will need after disturbance, ensuring that earthworks are accurately planned and executed.