Design highwater clearances for highway pavements : volume I, final report, August 2008.

694886360Final report; Oct. 2005-Apr. 2008.PDFTech ReportFL/DOT/RMC/BD-543-13FDOT BD453-13PavementsPavement maintenancePavement designDrainageFloridaFAMU-FSU College of Engineering (Tallahassee, Fla.). Civil & Environmental EngineeringPing, W.V.lLing, Ching-ChinFAMU-FSU College of Engineering (Tallahassee, Fla.). Civil & Environmental EngineeringFlorida. Dept. of Transportation. Research CenterNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceNTL-HIGHWAY/ROAD TRANSPORTATION-DesignNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionHigh groundwater table exerts detrimental effects on the roadway base and the whole pavement. Baseclearance guidelines have been developed to prevent water from entering the pavement system in order toreduce its detrimental effects. In these guidelines a minimum height, the clearance, between a groundwaterlevel and a particular elevation within the pavement system is specified. This report presents anexperimental study to evaluate the effects of high groundwater and moisture on determining pavement baseclearance for granular subgrades. Full-scale in-lab test-pit tests were conducted to simulate pavementprofile and vehicle dynamic impact on the pavement. Eleven types of subgrade were tested for this study. Fromthe test, using layer theory, the results of the resilient modulus for each layer (layer resilient modulus)can be compared with the resilient modulus results from laboratory test. The dominant factor or factors ofthe effect of moisture to resilient modulus will be discussed.The results showed that a 36-in. base clearance was considered adequate for the base protection ofmost of the A-3 and A-2-4 subgrades against high groundwater tables. The lab resilient modulus and layerresilient modulus had the same trend for each soil according to the moisture content change. The percent offines or the percent of clays of subgrade soil was not a good indicator to measure the influence of moistureeffect on the resilient modulus. The coefficient of uniformity and coefficient of curvature of the subgradegradations, which better represent the whole shape of the gradation curve, are better indicators of theeffect of moisture on modulus. The SR70 A-2-4 (14% fines), A-2-4 (30% fines), Oolite A-1, Branch A-2-4 (23%fines) soils were extremely susceptible to the change of high groundwater table; the equivalent modulusreduction rates were more than 50% for lowering the base clearance from 2 ft. to 0 ft. For the Levy A-3 (4%),SR70 A-3 (8%), A-2-4 (12%), A-2-4 (24%), and Spring Cemetery A-2-4 (15%) soils, the reduction rates were alsovery significant for the base clearance from 2 ft. to 0 ft. with the equivalent modulus reduction rates inthe range of 21% to 45%