Problem $5-3$ from Construction Planning, Equipment, and

Methods, $9^{th}$ ed$.$

Earth $--$ whose in situ weight is $112l\frac{b}{c}f,$ whose loose weight is $95l\frac{b}{c}f,$

and whose compacted weight is $120l\frac{b}{c}f--$ is placed in a fill at the rate

of $250c\frac{y}{h}r,$ measured as compacted earth. The thickness of the

compacted layers is $6$ inches. A roller having a drum width of $84$ in $.$ is

used to compact the material at a speed of $2\mathrm{.}5$ mph $.$ Assume a $55-$min

hour operating efficiency. Determine the number of rollers required to

provide the necessary compaction if eight drum passes are specified for

each layer of earth.