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13-42 Edition 47
Adjusting the Production Estimate
If the assumed conditions are not close to the actual
construction conditions, the production estimates
should be corrected. The production estimate from the
table can be adjusted for ‘actual’ construction conditions
by applying adjustment factors:
Q (actual) = Q (assumed)
×
Fs
×
Ft
×
Fp
Where: Q (actual) = adjusted productivity
Q (assumed) = productivity from table
based on assumed conditions
Fs = adjustment for machine speed
Ft = adjustment for layer thickness
Fp= adjustment for no. of passes
The adjustment factors are determined by compar-
ing the ‘actual’ conditions to the ‘assumed’ ones:
Fs = actual speed/assumed speed
Ft = actual thickness/assumed thickness
Fp = assumed passes/actual passes
Metric example
Actual Conditions —
An 9.15-meter (full road width)
base aggregate job is being completed with a compacted
thickness of 15 cm. A CS44B is being used, operating at
4.0 km/h, and making 6 passes to achieve the desired com-
paction. The roller is overlapping its passes 6 inches.
For a 9.15-meter road base the table gives a CS44B
productivity of 249 m
3
/hr. Since the speed, thickness,
and passes are
different
from the assumed conditions,
we should adjust this estimate:
Assumed
Actual
Speed
6.4 km/h
4.0 km/h
Thickness
10.2 cm
15 cm
Passes
4 passes
6 passes
Fs = 4.0 km/h/6.4 km/h = 0.6
Ft = 15 cm/10.2 cm = 1.5
Fp = 4 passes/6 passes = 0.7
The estimated production is adjusted using these
factors:
Q (actual) = 249 m
3
/hr
×
0.6
×
1.7
×
0.7
= 178 m
3
/hr (233 yds
3
/hr)
English example
Actual Conditions
— An wide area commercial site
development job is being compacted in lifts of 8 inches.
A CP56B is being used, operating at 4.0 mph, and mak-
ing 4 passes to achieve the target density.
First, the table gives a CP56B productivity of 847 yds
3
/hr.
Since lift thickness and passes required are
different
from
the assumed conditions, we should adjust this estimate:
Assumed
Actual
Speed
4.0 mph
4.0 mph
Thickness
12 inches
8 inches
Passes
6 passes
4 passes
Fs = no correction necessary
Ft = 8 inches/12 inches = 0.7
Fp = 6 passes/4 passes = 1.5
The estimated production is adjusted using these
factors:
Q (actual) = 847 yds
3
/hr
×
0.7
×
1.5
= 890 yds
3
/hr (680 m
3
/hr)
Notes on Productivity:
●
For jobs that are relatively narrow, especially road
construction jobs, it is important to understand that
certain widths of construction will be more produc-
tive than others for a given compactor. A productive
construction width will make the most use of each
side by side pass required by the compactor in order
to cover the width.
●
Production estimates should be adjusted further if the
length of the compaction cycles are shorter than 75 m
(250 ft). Refer to the Travel Speed Efficiency chart to
determine efficiency E
TS
. For example, a compactor
traveling at 6.4 km/h (4 mph) operating at cycle lengths
of 150 ft has an E
TS
of 0.91. Multiply Q (actual) by E
TS
.
Production Estimating
●
Single Drum
Vibratory Compactors