Type of Document	Dissertation
Author	Zhang, Chaohan
Author's Email Address	chaohan_zhang@yahoo.com
URN	etd-07022004-110605
Title	The Effect of High Groundwater Level on Pavement Subgrade Performance
Degree	Doctor of Philosophy
Department	Civil and Environmental Engineering, Department of
Advisory Committee	Advisor Name Title W. Virgil Ping Committee Chair Amy Chan Hilton Committee Member Makola Abdullah Committee Member Tarek Abichou Committee Member Xufeng Niu Committee Member
Keywords	Moisture Content Soil Subgrade Resilient Modulus
Date of Defense	2004-06-18
Availability	unrestricted
Abstract High 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. This dissertation presents an experimental study to evaluate the effects of high groundwater and the moisture on determining pavement base clearance for granular subgrades. Full-scale in-lab and test-pit tests were conducted to simulate pavement profile and vehicle dynamic impact on the pavement. Eight types of granular subgrades 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. Multiple regression model will be established to predict soil resilient modulus without doing resilient modulus test. The dominant factor or factors of the effect of moisture to resilient modulus will be discussed. The results showed that a 24-inch base clearance was considered adequate for the base protection of most A-3 and A-2 subgrades against high groundwater tables. The lab resilient modulus and layer resilient modulus have the same trend for each soil according to the moisture content change. The SR-70 A-2-4 (14% fines) soil was the most susceptible to the change of groundwater table than the other soils. The percent of fines or the percent of clays of subgrade soil is not 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 to modulus.
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