Page 99 - Moving the Earth_ The Workbook of Excavation

SURVEYS AND MEASUREMENTS

SURVEYS AND MEASUREMENTS 2.49

In dredging, the volume of water handled is computed by multiplying a cross section of the
stream in the pipe by the rate of flow. This production in cubic feet or cubic yards of water per
minute is then multiplied by the percentage of solids in the water—usually 10 to 20 percent—to
obtain useful production.
Each belt or pipe might be considered to be a container with a measurable capacity. However,
this capacity is related to haul distance rather than rate of production. A conveyor belt carrying a
load with a cross section of 2 square feet and traveling 500 feet per minute will deliver 1,000 cubic
feet per minute, regardless of whether it is a 10-foot feeder belt or a half-mile-long hauler. The
only production difference is the extra time—practically 5 minutes—that it will take to reload the
longer belt after unloading it at the end of a shift.
The cost of belt construction and maintenance varies almost directly with the length if width,
load, and support requirements remain the same.

Intermediate. This class of machines requires individual methods of study to determine pro-
duction.
A grader is a continuous flow machine in sidecasting until it reaches the end of a work area
and must turn or reverse. If the area is very short, or it is pushing material bulldozer fashion, it
has a cycle. Most grader work is measured by the area processed, either as square yards or as lin-
ear feet of roadway of a specified width. Production may be figured on a basis of width processed
times speed.
A drill will cut continuously to the end of its stroke, but steels are changed and/or new holes are
started frequently. Measurement is by speed in feet per minute or per hour, less nondrilling time.
A hopper often serves to convert intermittent cycle loads to continuous flow, as in a dragline
feeding a conveyor belt. Its production rate is usually that of either the excavator or the belt, as it
can be adjusted to almost any rate of feed within its capacity.
A special application is in speeding up truck loading. A 2-yard excavator might load sand into a
hopper at the rate of 3 yards a minute, and the hopper might be able to fill a 15-yard truck in 1
minute. It serves to convert a rapidly repeated 2-yard shovel cycle into a slower 15-yard truck cycle.

Noncycle Time. There is almost always a wide gap between production that should be obtained
on a basis of cycle speed and capacity, and what is actually produced. Checking the cause of these
delays is a drawn-out matter that can usually be best done by studying lost-time reports made out
by operators or checkers. Some, however, are frequent enough to be included in brief time studies.
For a shovel there are cleanup and move-up operations, and waits for trucks. Trucks wait to
get into loading position, are delayed by traffic, and get stuck. Scrapers wait for pushers, have
traffic problems, and sometimes get stuck.
If a breakdown occurs, it is useful to make a note of its nature, and of how long how many
machines are put out of action or slowed down.

SWELL AND SHRINKAGE

Swell. When soil or rock is dug or blasted out of its original position, it breaks up into particles
or chunks that lie loosely on each other. This rearrangement creates spaces or voids and adds to
its bulk. This increase from bank yards to loose yards is called “swell.”
1
Swell is expressed as a percentage of the bulk in the bank. If 1 bank yard puffs up to 1 ⁄ 4 loose
1
yards, the swell is ⁄ 4 100 percent, or 25 percent.
When converting bank yards to loose yards, the measurement is increased by the percentage
of swell. In the above example, 10 bank yards could be converted to 10 10 .25, or 10 1.25,
giving 12.5 loose yards.
Swell Factor. The swell factor is the percentage of bank yards in loose yards. The contractor
uses it to make a conversion on paper of the loose yards being hauled back to the bank yards for