Question

We are building a project that includes a fill of 200,000 cubic yards. The unit weight of the soil is 120 lbs per cubic foot. Don't worry about shrink and swell in this problem. Plan to work 8 hours per day. You have two options where you can obtain the soil for this fill:

Pit #1 is located 6,000 feet away at an elevation 200 feet lower than the fill. The rolling resistance of the haul road is 100 lb per ton

Pit #2 is located 8,000 feet away at an elevation 250 feet higher than the fill. The rolling resistance of the haul road is 100 lb per ton

You have access to any number of Caterpillar 725 articulated trucks, the same kind we looked at in class. Use an empty weight of 49,000 lbs. The trucks carry 16 cubic yards. The loaded weight will be based on the volume in the truck and the given unit weight of the soil. A truck with an operator costs $160 per hour.

Your excavator carries 4 cubic yards in the bucket (each cycle is 4 cubic yards). The cycle time is 29 seconds for this excavator. The excavator and operator cost $300 per hour. For this assignment you can rent equipment and pay for labor in fractions of an hour (you do not need to round up to full days or full hours).

When a truck arrives at the fill it takes 90 seconds to dump.

The ultimate question is: Which pit, #1 or #2, will be the least expensive to use? Find the cost per cubic yard to excavate and haul for both options to make your recommendation.down.

I suggest you write your approach now. The following questions are not in a logical order, I don't want to lead you-to the answers.

I suggest you do the problem in a logical order, then go back and clearly label each answer, in whatever order they appear in your solution. Note that you will have to calculate some other intermediate things in addition to what I am asking for below.

"Overtrucking" means you round up the number of trucks from the balance point, "undertrucking" is rounding 1.How fast can you travel from Pit #1 to the fill?

Fig: 1

Fig: 2