Question

A. Calculate the price of pit-run gravel delivered to the site per cubic yard (bank measure) based on the following data: The pit is located 10 miles from the site. Trucks cost $43.75 per hour including fuel and maintenance; they have 12 cubic yards (loose material) capacity and travel at an average speed of 30 miles per hour. The swell factor for this material is 15%. Trucks take 5 minutes to unload at the site. The loader costs $82.50 per hour and loads material at the pit at the rate of 40 cubic yards per hour. The truck driver’s wage is $45.00 per hour, and the equipment operator’s wage is $54.00 per hour.

Answer 1

Given:

Distance between site and pit = 10 miles

Swell factor of material = 15%

Truck capacity = 12 cubic yards (loose material)

Truck average speed = 30 miles / hour

Unload or dump time = 5 minutes

Truck cost = $43.75 per hour

Truck driver's wage = $45 per hour

Loader productivity = 40 cubic yards / hour

Loader cost = $82.5 per hour

Operator's wage = $54 per hour

Solution:

The number of trucks required to avoid idling of loading equipment should be calculated. From this, the cost of transportation (hauling) of material per hour can be found out. The cost per hour divided by the quantity that can be loaded in one hour will give us the price of soil per cubic yard.

Truck capacity (Bank quantity) = Truck capacity (loose quantity) / Swell factor x 100

= 12 cubic yards / 115 x 100

= 10.435 cubic yards.

Truck cycle time = Loading time + Travel time to the site + Unloading time (dump) + Travel time back to site

Loading time = Truck capacity / Loader productivity

= 10.435 cubic yards / 40 cubic yards per hour

= 0.2609 hour = 0.2609 x 60 minutes

= 15.65 minutes

Travel time to the site = Diatance / Average speed

= 10 miles / 30 miles per hour

= 0.33 hour = 20 minutes

Travel time back to pit = Travel time to the site (because distance is equal)

= 20 minutes

Now substitute the above values to find truck cycle time

Truck cycle time = 15.65 + 20 + 5 + 20

= 60.65 minutes

Number of trucks required = Truck cycle time / Loading time for one truck

= 60.65 minutes / 15.65 minutes per truck

= 3.875 trucks

Consider 4 number of trucks.

Cost per hour = cost of loading + cost of hauling (transport to the site)

Cost of loading = Loader cost + Operator's wage

= $82.5 per hour + $54 per hour

= $136.5 per hour

Cost of hauling (Transport) = ( Truck cost + Driver's wage ) x Number of trucks

= ( $43.75 per hour + $45 per hour ) x 4

= $ 355 per hour

Now substitute the above values to find the cost per hour

Cost per hour = $136.5 per hour + $355 per hour

= $491.5 per hour

Price of delivery per cubic yard of material = Cost per hour / Quantity of material loaded per hour (Loader productivity)

= $ 491.5 / 40 cubic yards

= $12.29 per cubic yards

The price of pit-run gravel delivered to the site is $12.29 per cubic yards.