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University of South Alabama
Department of Civil, Coastal, and Environmental Engineering
CE490-501/590 Pavement Design
Homework #7 (100 points)
Due: 5:00 pm Wednesday March 13
Figure below shows a two-lane highway paved with HMA on the traffic lanes and the shoulders.
(1) Estimate the amount of surface infiltration in ft3/h/ft.
(2) If the native soil above the impervious boundary has a permeability of 0.5 ft/day, determine
the groundwater inflow into the drainage layer in ft3/day/ft, and the lateral inflow into the
longitudinal drains in ft3/day/ft.
(3) If the highway is located in a cold region with severe frost action and the subgrade consists
of a well-graded clayey gravel, GW-GC, with 4% finer than 0.02 mm. Determine the
inflow to the drainage layer due to the melting of ice lenses. Assume that the thickness of
HMA is 4 in, with a unit weight of 120 pcf, and the drainage layer including the filter is 10
in. thick, with a unit weight of 120 pcf, and the subgrade has a permeability of 0.05 ft./day.
(4) The drainage layer has a thickness of 8 in., a cross slope of 4%, a porosity of 25%, and
permeability of 10,000 ft./day. Determine the steady-state capacity of the drainage layer
and the time for 50 and 95% drainage based on a drainage length of 18 ft.
(5) Smooth plastic pipes with 4 in. in diameter and a roughness coefficient of 0.01, are placed
at 2.5% slope in a trench drain. If outlets are provided every 300 ft., what is the maximum
allowable lateral inflow into the plastic pipes in ft3/day/ft.

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