What’s New in the Fourth Edition: The fourth edition further examines the relationships between the maximum and minimum void ratios of granular soils and adds the American Association of State Highway and Transportation Officials (AASHTO) soil classification system. It summarizes soil compaction procedures and Proctor compaction tests. It introduces new sections on vertical stress due to a line load of finite length, vertical stress in Westergaard material due to point load, line load of finite length, circularly loaded area, and rectangularly loaded area. The text discusses the fundamental concepts of compaction of clay soil for the construction of clay liners in waste disposal sites as they relate to permeability and adds new empirical correlations for overconsolidation ratio and compression index for clay soils. It provides additional information on the components affecting friction angle of granular soils, drained failure envelopes, and secant residual friction angles of clay and clay shale.