Chapter 3- Lecture

Madawalabu
University
Construction Equipment and Plant Management
COTM 4202

General
Definition
 It is the number of units and the
size of equipment that would
permit the constructor to
accomplish the activity with a
duration resulting in the lowest
cost.
 Estimating and planning involves
the judicious selection of
equipment, the careful scheduling
of time and resources, and the
accurate determination of expected
system output and cost.
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COTM 4202

 Haul unit horsepower
 Haul road rolling resistance
 Haul road grades
 Haul unit loaded and empty weight
 Haul unit transmission characteristics
 Haul unit loading time
 Haul unit travel time
 Haul unit delay time
 Altitude of the project site
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 Total power that an engine is capable of
generating is expressed as its horsepower.
 Available horsepower is power that is available
to perform work after taking into account losses
and consumption in other machine functions.
 Rimpull is defined as the tractive force between
the driving wheels and the surface on which
they travel.( V is velocity in mph)
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Power generated by engine
Drawbar Pull
Rolling Resistance
Rimpull

 Rolling resistance is resistance offered to movement of
materials on a plain surface; often expressed in pounds
per ton of materials.
 Rolling Resistance depends upon:
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 The force-opposing movement of a machine up a
frictionless slope is grade resistance.
 The effect of gravitational force in aiding movement of a
vehicle down a slope is grade assistance.
F= 20 lbs/ G% per Ton

 The cycle capacity C of a piece of equipment is
defined as the number of output units per cycle
of operation under standard work conditions.
 The standard production rate R of a piece of
construction equipment is defined as the
number of output units per unit time.
 The cycle time T refers to units of time per cycle
of operation.
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 Time to load a mover for load shifting will
determine loads that can be transferred.
Longer loading time lesser will be
productivity.
 To is loading time
 Te is cycle time for loader/excavator
 Ch is capacity of a hauler (dump truck)
 Ce loading rate/capacity of loader
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 It is time for moving load from production site to
disposal site. Longer time will reduce productivity.
 To determine the productivity of a hauler,
› Let: D be the distance from source to a dump site, S
be the average speed of the hauler, Tt be the travel
time for the round trip to the dump site, To be the
loading time, Td be the dumping time plus other
delays.
 Then the travel time for the round trip is given by:
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 Human and machine system suffer from
inherent delays due to reaction time and
capacity, say Td.
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 For a given dumping time Td, the total cycle
time Th of the hauler is the sum of loading
time, travel time and damping time given by:
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 Optimum number of haul units (N) is
determined by:
 NB: Rounding down will maximize haul unit
productivity.
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 An 16 cubic meter dump truck has a loading
time of 3 min, a travel time of 7 min, and the
dumping and delay times of 5 min. Calculate
the cycle time of the hauler and optimum
number of hauling units.
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 The daily standard production rate Pe of an
excavator is is given by:
 He is the operating hours per day
 Ce is the cycle capacity (in units of volume) of the
excavator
 Te is the cycle time (in hours) of the excavator
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 The daily standard production rate Ph of a
hauler is given by:
 Rh is standard production rate
 Hh is the number of operating hours per day
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 A 1.5 cubic meter front-end loader is going to load
dump trucks with a capacity of 9.0 cubic meter. The
loader takes 0.4 min to fill and load one bucket. The
travel time in the haul is 4.0 min. Dump and delay
times are 2.5 min combined. Calculate:
 The loading time,
 The cycle time of hauler,
 Number of trucks,
 The hourly production rate of haul units, and
 The hourly production of loader
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 A power shovel with a dipper of one cubic
meter capacity has a standard operating
cycle time of 30 seconds. Find the daily
standard production rate of the shovel. Ce
= 1 cu. mtr., Te = 30 sec. and He = 8 hours.
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 A dump truck with a capacity of 6 cubic meter is
used to dispose of excavated materials at a
dump site 4 km away. The average speed of the
dump truck is 30 mph and the dumping time is
30 seconds. Find the daily standard production
rate of the truck. If a fleet of dump trucks of 9
cubic meter capacity is used to dispose of the
excavated materials for 8 hours per day,
determine the number of trucks needed daily.
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 Material properties have a direct effect on the ease or
difficulty of handling the material, on the selection of
equipment, and on equipment production rates.
 Quantities are often measured in volume units.
 Volume of material under different conditions varies
appreciably.
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 Bank: Material in its natural state. Also called in-
place or in-situ. Measurement: BCM (Bank
Cubic Meter)
 Lose: material that has been excavated or
loaded. Measurement: LCM (Lose Cubic Meter)
 Compacted: Material after compaction:
Measurement: CCM (Compacted Cubic Meter)

Swell
Factor
Shrinkage
Factor
 The swell factor is the ratio of the loose dry
weight per unit volume to the bank dry weight per
unit volume.
Loose dry unit weight
Swell Factor (w) = _____________________
Bank dry unit weight
Swell% = ( 1/w – 1 )x100
 The shrinkage factor is the ratio of the compacted dry
weight per unit volume to the bank dry weight per unit
volume:
Compacted dry unit weight
Shrinkage Factor = _________________________
Bank dry unit weight
Shrinkage % = ( SrF – 1 )x100
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 Let w denote the swell factor of the soil
 wPe denote the daily volume of loose
excavated materials.
 Then the approximate number of haulers
required to dispose of the excavated
materials is given by:
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 Equipment productivities at job sites are influenced
by actual work conditions and a variety of
inefficiencies and work stoppages.
 Let F1, F2, ..., Fn, denote factors that lower
productivity, each of which is smaller than 1,
 Then the actual equipment productivity R' at the job
site can be related to the standard production
rate R as follows:
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 The actual cycle time T' at the job site is
related to the standard cycle time T as:
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 A power shovel with a dipper of 1.2 cubic meter
capacity has a standard production rate of 960
cubic meter for an 8-hour day. 4min is consumed to
fill and load. Determine the job site productivity and
the actual cycle time of this shovel under the work
conditions at the site that affects its productivity as
shown below:
 Work Conditions at the Site Factors
Bulk composition 0.954
Soil properties and water content 0.983
Equipment idle time for worker breaks 0.8
Management efficiency 0.7
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 A dump truck with a capacity of 6 cubic meter is used to
dispose of excavated materials. The distance from the
dump site is 4km and the average speed of the dump
truck is 30 kph. The job site productivity of the power
shovel per day is 504 cubic meter, which will be
modified by a swell factor of 1.1. The only factors
affecting the job site productivity of the dump truck in
addition to those affecting the power shovel are 0.80 for
equipment idle time and 0.70 for management
efficiency. Determine the job site productivity of the
dump truck. If a fleet of such trucks is used to haul the
excavated material, find the number of trucks needed
daily.
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 A front-end loader loads a fleet of dump trucks (capacity
18 loose cubic meter each), which haul the earth to a fill
where it is compacted with a shrinkage factor of 10%.
The earth has a percent swell of 20%. The job requires
a volume of 18,000 compacted cubic meter. Distance
between quarry and project site is 5miles connected
with dirt track.
 How many hours will be required to excavate and haul
the material to the fill.
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THANK YOU!
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COTM 4202
31

Chapter 3- Lecture

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Chapter 3- Lecture