a contractor was awarded a contract to excavate

Question

A contractor was awarded a Contract to excavate and haul 200,000-yds³ of silty clay (USCS classification ML) with a bulking factor of 30%.  The contractor's fleet of dump trucks have a capacity of 26-yds³ and operate on a 23-minute cycle. The job must be completed in 5-working days with the fleet working at two 8-hour shifts per day. The number of trucks required is most nearly:

Solution:

• Apply a bulking factor (swell) of 30% to the total volume.
• 200,000-yds³ x 1.30 = 260,000-yds³ (Volume to be trucked off-site)
• 5-wd x 2-shifts x 8-hrs = 80-hrs (Total trucking hours)
• 260,000-yds³ ÷ 80-hrs = 3,250-yds³/hr (Haulage rate per hour)
• (26-yds3/truck ÷ (23-min/cycle ÷ 60-min/hr)) = 67.82-yds³/truck hour
• 3,250-yds³/hr ÷ 67.82-yds³/truck-hr = 47.92-trucks use 48 trucks