The source is a comprehensive guide to the various tests used in geotechnical investigations, focusing on the Atterberg Limits tests and their applications in soil classification and engineering. The document first introduces the Atterberg Limits, which are a group of tests that determine the water content at which soil transitions between different states, like liquid, plastic, and solid. This information is crucial for understanding how soils behave under different moisture conditions, and for classifying them into different categories based on their plasticity. The document then dives into a detailed explanation of each individual test, including the Liquid Limit, Plastic Limit, and Shrinkage Limit tests, providing a step-by-step description of the procedures involved. Finally, the document concludes by summarizing the importance of these tests in various engineering applications such as foundation design, slope stability analysis, and construction projects.