Geotechnical engineering is a branch of civil engineering that focuses on the behavior of earth materials such as soil, rocks, and groundwater. It involves the study of the physical properties of these materials and how they can be influenced by human activities, as well as natural processes like earthquakes and erosion. Geotechnical engineers use their expertise to design structures such as buildings, bridges, dams, and tunnels that are stable and safe, considering factors such as soil stability, slope stability, and foundation design. They also work to assess and mitigate risks related to ground movements, groundwater flow, and soil erosion. Overall, geotechnical engineering plays a crucial role in ensuring the safety and stability of infrastructure projects, as well as in protecting the environment from potential hazards associated with the use of earth materials.