A contractor is planning to use 3 Caterpillar 631G single-engine wheeled tractor-scrapers to construct a 2-foot compacted fill that is needed to build a parking lot adjacent to a new hospital. Site plans for the project show the compacted fill to measure 400 feet by 350 feet. The contractor has identified a suitable borrow site for the fill material that is located 1.5 miles from the project site. The haul road generally has a 3% uphill grade when traveling from the borrow site to the fill site. Soil tests on the fill material indicate a bank unit weight of 100 pounds per cubic foot. The swell for the soil has been determined to be 15%, and the shrinkage when compacted to the design density has been determined to be 9%. The contractor plans to use a Caterpillar D9 crawler tractor to push load the scrapers to their rated heaped or weight capacity, whichever governs. The rolling resistance of the haul road is estimated to be 75 pounds per ton, and the coefficient of traction is estimated to be 0.6.
1. How long will it take the contractor (in days) to complete the fill, if he operates his equipment 50 minutes per hour and 8 hours per day? Assume scraper productivity determines the productivity of the entire task. Performance characteristics of the 631G scraper are provided in Caterpillar Performance Handbook (Edition 45).
2. Discuss what factors will affect the productivity of the entire task.
3. Provide detailed solution(s) if the contractor plans to shorten the project duration.