$14\mathrm{.}1.$ A flexible pavement is to be designed for a heavy$-$load military airfield. The subgrade

is a sandy silt with a design $CBR=12.$ Subgrade conditions are extremely variable relative

to changes in soil type and ground water level. The anticipated depth of frost is $58$ inches.

Design a Type A traffic area for these conditions. Assume that all materials used meet standard

military specifications and that all granular base and subbase is non$-$frost susceptible. Design

CBRs for these materials are CBR $=100($base$),$ CBR $=45($subbase No$.2),$ CBR $=25$

$($subbase No$.1).$