THE PREPARATION OF SUBGRADES

LOW COST MATERIALS DETERMINE THE FACTORS OF DRAINAGE, CLIMATIC CONDITIONS, AND TRAFFIC IN DESIGNING SUBGRADES. PRELIMINARY INVESTIGATIONS ARE NECESSARY TO OBTAIN INFORMATION ON: (1) THE SOILS AVAILABLE FROM HIGHWAY EXCAVATIONS, (2) LOCAL PITS FOR BASE AND SUBGRADE REINFORCEMENT, AND (3) SUB-SOIL MOISTURE CONDITIONS. SOIL TESTS ARE USED TO IDENTIFY MATERIALS AND TO MEASURE THE BASIC PROPERTIES INFLUENCING SUBGRADE PERFORMANCE. SPECIFICATION REQUIREMENTS, SUBGRADE REINFORCEMENTS, SOIL EXPANSION AND THE CORRELATION BETWEEN TESTS AND ACTUAL PERFORMANCE ARE BRIEFLY DISCUSSED.