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Optimizing Earthwork Operation with CAT 375 Excavator and D30D Articulated Trucks

## Part 1: Optimizing with D30D Articulated Trucks

Please prepare the following assignment. Submit per course schedule and instructions:

You are an earthwork subcontractor designing an operation to excavate 5,000 m3 of clay and haul it to a dump site (the fill location) that is 1,600 m away from the load site (the cut location). You have already decided to use a CAT 375 excavator with a 2.75 m3 bucket and are deciding on the number of CAT D30D articulated trucks that you will use. Each D30D has a capacity of 16.5 m3.

The performance of a D30D on this operation is summarized as follows:

Haul time: Uniform[5,6.75] minutes

Dump time: Uniform[10,20] seconds

Return time: Uniform[1.7,3] minutes

Maneuver time at load site: Uniform[0.1,0.3] minutes

The performance of a CAT 375 on this operation is summarized as follows:

Time to excavate and fill bucket: Uniform[0.1,0.25] minutes

Time to swing loaded bucket: Uniform[0.1,0.14] minutes

Time to dump bucket into truck or hopper: Uniform[0.04,0.10] minutes

Time to swing empty bucket: Uniform[0.09,0.13] minutes

The excavator works on a cycle that includes the actual excavating time to fill the bucket, a 75 degree swing with the loaded bucket, the dumping of the clay in the bucket into a truck that has maneuvered into position at the load site (the excavator has to need to wait for a truck to be present in the correct position before dumping), and a 75 degree swing with the empty bucket.

The following cost data are available:

CAT 375: \$4,750 transportation cost + \$80/h of use

CAT D30D: \$1,300 transportation cost + \$44/h of use

Indirect cost of operation: \$125/h

Part 1:

Prepare a simulation model and experiment with it to determine the number of trucks that will result in the lowest possible cost in \$/m3 for this operation. Show your \$/m3 calculations for all options that you examined before determining the optimum number of trucks. Submit a drawing of the Activity Cycle Diagram, the cost calculations in tabular format, and a written discussion of your approach and results.

Part 2:

A hopper is a large-capacity container mounted on a tall structure that allows a truck to be positioned below it. The hopper is loaded through its open top with material, e.g. clay. As long as there is space in the hopper the excavator can place material into it, even if there is no truck positioned below it. Material is released through an opening in the bottom of the hopper only when a truck is positioned below the hopper. The mechanism controlling this can be controlled precisely and quickly so that a truck with a capacity of 16.5 m3 can be loaded in 15 seconds.

Redesign your operation by including a hopper with a capacity of 20 m3 that costs \$20,000 to purchase, install, use, and dispose of after completing the operation. Prepare a simulation model and experiment with it to determine the number of trucks that will result in the lowest possible cost in \$/m3 for this modified operation. Show your \$/m3 calculations for all options that you examined before determining the optimum number of trucks. Submit a drawing of the Activity Cycle Diagram, the cost values in tabular format, and a written discussion of your approach and results.

Part 3:

Submit a memorandum that describes your approach in solving this assignment, any problems that you encountered while working on it, e.g. understanding the exact nature of the operation, the solutions that you developed in solving these problems, e.g. for debugging the Activity Cycle Diagram, and any other thoughts that you may have had.