Description
Problem 1 A contractor wants to investigate the production and cost differences of using a 7S blade on a D7H) dozer or an S blade on an 824 dozer. The material is a dry sand, and it is to be moved a distance of 250 ft from the beginning of the cut. The dozing is uphill on a 5% grade. The operator will have average skill, the dozers have power-shift transmissions, and traction is assumed to be satisfactory. The operating technique is slot dozing. The site will be dusty with some visibility loss. The material weighs 103 pcf in the bank state and has a swell percent of 15%. Job efficiency is assumed to be equivalent to a 50-min hour. Calculate the direct cost of the proposed earthmoving operation in dollars per bcy. Assume that the O&O cost for the D7 dozer is $116.00 per hour and $127.00 per hour for the 824. The operator’s wage is $45.00 per hour plus 35% for fringes, workman’s compensation, and other benefits.
Complete the following for each dozer. Round all numbers to the nearest TWO decimals unless otherwise specified. If a number starts with 0, for example 0.45, do not omit the 0, write it as 0.45.
D7H-7S | 824-S | |
1- Ideal production rate (round to nearest whole #) | ||
2- Material-weight correction factor | ||
3- Operator correction factor | ||
4- Material-type correction factor | ||
5- Operating-technique correction factor | ||
6- Visibility correction factor | ||
7- Job Efficiency factor | ||
8- Machine transmission factor | ||
9- Blade adjustment factor | ||
10- Grade correction factor | ||
11- Total correction factor | ||
12- Dozer production in LOOSE CY (round to nearest whole #) | ||
13- Dozer production in BANK CY (round to nearest whole #) | ||
14- Total cost per hour to operate the dozer | ||
15- Direct production cost per bcy Problem 2 A limestone formation, with an average depth of 5 ft is exposed over the full 80-ft width and 23,700-ft length of a highway cut. Preliminary seismic investigations indicate that the rock layer has a seismic velocity of 5,500 fps. The contractor proposes to loosen this rock by using a single-shank ripper on a power shift, track-type tractor. The job conditions relative to lamination and other rock characteristics are average, or midway between adverse and ideal. A 40-min hour working efficiency is possible. The contractor wishes to explore the use of two D10T2 Caterpillar dozers with single shank (for performance data see the CAT Handbook posted on Blackboard and check the assumptions). O&O cost for these tractors is $126.00 per hour including rippers. However, dozers in ripping applications increase O&O cost 30-40%. The operator’s wage & benefits is $74.30 per hour. Q: What is the project duration with two dozers (8 hour work days)? |