Question

A contractor is planning to use an excavator to remove the soil for the construction of the foundation for a new hotel. He has determined from the project plans that 3,000 bank cubic yards must be excavated and that 817 compacted cubic yards will be required to backfill the completed foundation. The contractor plans to stockpile the soil needed for backfill on-site and haul the excess soil off-site using trucks that have a heaped capacity of 30 loose cubic yards. The contractor had the soil tested and determined that the bank density is 2,800 pounds per cubic yard, the loose density is 2,295 pounds per cubic yard, and the compacted density is 3,256 pounds per cubic yard.

The haul road to be used by the trucks has a 6% average uphill grade. The tire penetration is estimated to be 2.5 inches, and the trucks are not equipped with ra­dial tires. The empty weight of the truck is 68,750 pounds. What is the total re­sisting force the truck must overcome when traversing the haul road fully loaded?

What is the maximum usable tractive force that can be generated by the truck when operating fully loaded on the haul road if the coefficient of traction is esti­mated to be 0.5 and 67% of the loaded weight is carried by the rear driving wheels?

Answer 1