the demolished asphalt concrete and existing base. Therefore, if
Alternative 1 is applied, the need for removing the existing road
is eliminated, and construction schedule would be reduced by at
least 10 months.
Alternative 2
Alternative 2 involves PBD installation without removing the
existing road (Fig. 5). Similar to Alternative 1, Alternative 2 would
result in a significant reduction in the quantity of embankment
by 500,000 m3, but because of the same longitudinal grade as
the original design, it would require additional embankment. The
PBD installation on the existing road would require additional
construction cost not only for the installation itself but also for
the treatment of the disturbed soil during installation. For those reasons, the schedule reduction by Alternative 2 is not as significant as
Alternative 1.
Alternative 3
Alternative 3 involves using expanded polystyrene (EPS) to reduce the weight of embankment on the existing road, so that the
PBD installation would not be needed (Fig. 6). Like Alternative
2, Alternative 3 shares the benefit of reducing the quantity of embankment by 500,000 m3 but still requires additional embankment
because of the same longitudinal grade as the original design. Like
Alternative 1, Alternative 3 would reduce the quantity of PBDs by
1,140,000 m, and subsequently eliminate a need for the treatment
of the disturbed soil during the PBD installation. However, the installation of EPS would require a significant increase both in construction cost and operation, so the benefit from schedule reduction
is not comparable to Alternative 1.