Geotechnical Engineering focuses on the understanding and application of how soil and rock are used as engineering materials within our constructed environment. Soil and rock constitute the largest construction material by volume used, and understanding their behavior as engineering materials is critical to the design of building foundation systems, earth and rockfill dams and embankments, tunnels and other underground structures, and all other facilities constructed of or in contact with soil or rock. In addition, geotechnical engineering is an important component of understanding how our lifeline systems perform, both above and below ground. Research activities rely upon fundamental understanding of stress-strain-strength behavior, probabilistic modeling and reliability-based design, use of geographic information systems (GIS) for reliability evaluation, marine and coastal engineering, earthquake engineering, and use of advanced sensors for monitoring lifeline health and safety.