Page 386 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

8.48 THE WORK

Basic Factors. Basic factors to be considered in figuring grading for a road may include
1. Clearing costs
2. Topsoil stripping, storage, reclamation, spreading, and planting
3. Amount and type of soil excavation in cuts or borrow pits
4. Amount and type of rock excavation
5. Availability of suitable borrow and cost of purchase
6. Haul road construction and maintenance, and length of hauls
7. Quality of fill required, and processing required of material from cuts and pits
8. Fill compaction, shrinkage, and disposal of surplus
9. Slope finishing and protection
10. Groundwater conditions and drainage requirements
11. Structures such as bridges, culverts, and retaining walls
12. Possession or availability of proper machinery, with necessary parts and supplies; extra costs
of using second-choice or beat-up equipment
13. Availability of construction supplies such as pipe, forms, etc.
14. Labor supply
15. Weather—rain, snow, ice, dust, frozen ground, frozen equipment, mud
16. Time of completion of related structures such as bridges, being built under separate contract
In roadway work, the amount, kind, and location of cut, borrow, and fill, and the length of haul,
may be specified. Haul may be described as normal or free, up to a certain distance, which may be
300 to 1,000 feet, and longer hauls called overhaul. Excavation may be described as unclassified,
or divided into rock yards and dirt yards.
In less formal jobs, these factors may be indicated only approximately, or may be figured by
the contractor from grade or route plans.

Casual Estimating. Where cuts and fills are shallow, and side slopes lacking or moderate, grad-
ing can often be estimated fairly accurately by inspection of centerline stakes. The exact yardage
is sometimes not of primary importance, as stripping topsoil and working over a piece of ground
represent an amount of machine time that may be only moderately increased by the cuts and fills.
Several errors must be watched for, however. Cuts and fills on the stakes may be figured from
the top of the stake, from ground level, or from a line on the stake. The grade indicated may be
subgrade, in which case it is taken at face value, or finish grade when the depth of base courses
and of surfacing must be added to the cuts and subtracted from the fills. The width to be figured
on is not only the road and shoulders, but also gutters and slopes. The depth of topsoil to be
stripped is subtracted from the cuts, added to the fills, and considered separately as an important
cost factor.
When cuts or fills are deep, side slopes exist, topsoil need not be stripped, or when the job is large,
yardages should be carefully calculated. If this is not done on the plans, the contractor can do it.

YARDAGE CALCULATION

Center Profile. The minimum staking for a road is the centerline. When this is done, a profile
is taken, showing the elevation of the ground at each stake. These elevations are plotted on cross-
section paper, usually with the vertical scale 10 times the horizontal, and the points connected by
a line. A profile for the road is then sketched in according to the standards of grade and vertical
curve required, or from some previously formed plan. This line should represent the subgrade
before the addition of any imported material.