Design highwater clearances for highway pavements appendix : volume II, appendix, August 2008.

694887469Appendix.MPEGTech 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. Base clearance guidelines have been developed to prevent water from entering the pavement system in order to reduce its detrimental effects. In these guidelines a minimum height, the clearance, between a groundwater level and a particular elevation within the pavement system is specified. This report presents an experimental study to evaluate the effects of high groundwater and moisture on determining pavement base clearance for granular subgrades. Full-scale in-lab test-pit tests were conducted to simulate pavement profile and vehicle dynamic impact on the pavement. Eleven types of subgrade were tested for this study. From the 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 of the 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 of most of the A-3 and A-2-4 subgrades against high groundwater tables. The lab resilient modulus and layer resilient modulus had the same trend for each soil according to the moisture content change. The percent of fines or the percent of clays of subgrade soil was not a good indicator to measure the influence of moisture effect on the resilient modulus. The coefficient of uniformity and coefficient of curvature of the subgrade gradations, which better represent the whole shape of the gradation curve, are better indicators of the effect 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 modulus reduction 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 also very significant for the base clearance from 2 ft. to 0 ft. with the equivalent modulus reduction rates in the range of 21% to 45%