Soil testing and investigation involve analyzing soil properties to determine its suitability for construction and foundation design. The process includes tests such as grain size analysis, Atterberg limits, specific gravity, compaction tests, shear strength, permeability, and consolidation tests. These assessments help identify soil bearing capacity, stability, drainage characteristics, and potential settlement issues, ensuring safe and sustainable construction practices. Proper soil investigation minimizes risks like soil liquefaction, uneven settlement, or foundation failure, providing critical data for designing appropriate foundations and mitigating construction hazards.