Soil Dynamics

Soil Dynamics is the engineering field that deals with the response of soils subjected to time-dependent (dynamic) loads. The behavior of soil under a dynamic load is critical for any building constructed on top of the ground.

The dynamic loads mainly derive from earthquakes, operation of heavy machinery, blasts, and wave or wind forces, etc. Common soil dynamics topics include the determination of dynamic earth pressures, the analysis and design of foundations under dynamic loads and dynamic soil-structure interaction problems. In civil engineering, earthquakes are the most common phenomena from which dynamic loads affect structures.

Understanding the dynamic behavior of soils is critical to prevent any structural or ground failure under earthquake loads. The properties that are needed to be determined to evaluate the dynamic behavior of soil are the following:

• Dynamic Young’s modulus (E) and dynamic shear modulus (G) and their variation with shear strain (typically referred to as Shear Modulus Reduction curves)
• Damping ratio (ξ) and its variation with shear strain (typically referred to as material damping curves)
• Poisson’s ratio (ν)
• Other parameters related to liquefaction (e.g. cyclic shearing stress ratio and cyclic deformation)

Soil properties are commonly divided into: i) small strain (or linear) properties and ii) large strain properties, that need to be understood depending on the project needs.