Question

A client needs to fill and compact a trench that has the following dimensions 150 x 50 x 1.5 ft. The sub is going to use a dump truck that can carry 12 CY, and travels at an average speed of 40 mph. The borrow pit is located 45 miles from the construction site. The truck driver makes $50/hr and works 8 hours per day. Loading time for the truck is 30 minutes and unloading time is 5 minutes. The sub has to rent the truck at $500 per day + a driver @ $50/hour. The cost of soil $20 per BCY. The soil has a swell factor of 18% and a compaction factor of 12%. What will it cost to backfill this trench if the sheeps foot operator make the same as the driver and fuel cost $1,250.00?

Answer 1

The total volume of soil to be filled in the trench = 150*50*1.5 = 11250 cu.ft.

The compacted volume of soil = loose soil volume * compaction factor

= 11250*1.12 (given in the problem)

=12600cu.ft = 12600/27CY = 466.667 CY

Total time in 1 cycle:

Travel time = distance / speed = 45miles/40mph = 1.125hr =1.125*60 min =67.5min

Loading time = 30 min

Unloading time = 5 min

Total time per cycle = 102.5 min

Workday = 8hrs =8*60 =480 min

No.of cycles per day = 480min/day*1cycle/102.5min = 4.683 cycle /day

Production rate of truck in days =cycles/day*capacity of truck in BCY*swell factor

=4.683*12*1.18

=66.310BCY/day

No. Of days required to fill the trench = 466.667/66.310 =7.037=8days nearly

Cost of truck and driver:

Cost of driver = $50/hr*8hr/day*8days =$3200

Cost of truck = $500/day*8days =$4000

Total cost of truck including driver cost and truck rent = ($3200+$4000) = $7200

Cost of soil =$20/BCY*466. 667 =$9333. 33

Cost of compaction :

Operating cost = $3200 (same as a truck driver as mentioned in the problem)

Fuel cost = $1250. 00

Total cost to backfill the trench =

Cost of soil +cost of a truck (including driver cost and truck rent)+cost of sheep foot compactor+fuel cost

=$9333.33+$7200+$3200+$1250.00

=$20983.33

if the cost of the rent of the sheep foot compactor is also taken as same as the truck rent then the total cost for trench filling = $24983.33 =$25000 nearly