Page 264 - Civil Engineering Formulas

198 CHAPTER EIGHT

The load, or amount of material a machine carries, can be determined by
weighing or estimating the volume. Payload estimating involves determination
of the bank cubic yards (cubic meters) being carried, whereas the excavated
material expands when loaded into the machine. For determination of bank
cubic yards (cubic meters) from loose volume, the amount of swell or the load
factor must be known.
Weighing is the most accurate method of determining the actual load. This is
normally done by weighing one wheel or axle at a time with portable scales,
adding the wheel or axle weights, and subtracting the weight of the vehicle when
empty. To reduce error, the machine should be relatively level. Enough loads
should be weighed to provide a good average:
weight of load, lb (kg)
3
Bank yd (8.50)
3
3
density of material, lb/bank yd (kg/m )
Equipment Required
To determine the number of scrapers needed on a job, required production must
first be computed:
3
3
quantity, bank yd (m )
3
Production required, yd /h (m /h) (8.51)
3
working time, h
3
3
production required, yd /h (m /h)
No. of scrapers needed (8.52)
3
3
production per unit, yd /h (m /h)
scraper cycle time, min
No. of scrapers a pusher can load (8.53)
pusher cycle time, min
Because speeds and distances may vary on haul and return, haul and return
times are estimated separately.
haul distance, ft return distance, ft
Variable time, min (8.54)
88 speed, mi/h 88 speed, mi/h
haul distance, m return distance, m

16.7 speed, km/h 16.7 speed, km/h
Haul speed may be obtained from the equipment specification sheet when the
drawbar pull required is known.

VIBRATION CONTROL IN BLASTING

Explosive users should take steps to minimize vibration and noise from blasting
and protect themselves against damage claims.