Geotechnical investigation involves assessing the soil, rock, and groundwater of a site to provide information for the design and construction of civil engineering projects, such as buildings, roads, and bridges. It involves analyzing the physical and chemical properties of the materials and determining their behavior under different loading conditions. Geotechnical investigation is a specialized skill that requires advanced knowledge and expertise in geology, soil mechanics, and engineering geology. The results of the investigation are used to ensure the safety and stability of structures built on the site.