4 compacting and finishing bach khoa

Construction Methods
110401542

4 – Compacting and
Finishing
Dr. Khaled Hyari
Department of Civil Engineering
Hashemite University

Compacting and Finishing
• Principles of Compaction
• Compaction Equipment and Procedures
• Grading and Finishing

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Principles of Compaction
• Compaction: the process of increasing the density
of a soil by mechanically forcing the soil particles
closer together, thereby expelling air from the void
spaces in the soil.

• Consolidation: an increase in soil density of a
cohesive soil resulting from the expulsion of water
from the soil’s void space
• Consolidation vs. Compaction: Months vs. hours

• Compaction Why?

– To improve the engineering properties of soil
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Principles of Compaction II

• Compaction Advantages:
– Increased bearing strength
– Reduced compressibility
– Improved volume change characteristics
– Reduced permeability

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Principles of Compaction III

• Factors Affecting Degree of Compaction:
– Physical and Chemical properties of the
soil (grain size, cohesiveness, etc.)
– Moisture content of the soil
– The compaction method employed
– The Amount of compactive effort
– The thickness of the soil layer being
compacted
– Soil’s initial density
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Compaction Forces

•

FOUR basic compaction forces:

– Static Weight (Pressure)
– Manipulation (kneading): most effective in
plastic soils
– Impact
– Vibration
• Most compactors combine static weight with
one or more of the other compaction forces
–

Ex: Plate Vibrator combines static weight with
vibration
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Compaction Forces II
• Impact and vibration produce similar
forces (frequency is different)
• Impact or tamping involve blows at lower
frequency (usually 10 cycles per second)
that is more suitable for cohesive soils
• Vibration uses higher frequency (> 80
cycles per second) that is more suitable
for cohesionless soils like sand and gravel

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Optimum Moisture Content I
• Optimum Moisture Content: The moisture content
at which maximum dry density is achieved under
a specific compaction effort
• Proctor Test: A standard laboratory test
developed to evaluate a soil’s moisture – density
relationship under a specified compaction effort
– Compaction tests are performed over a range of soil
moisture contents
– The results are plotted as dry density versus moisture
content
– The peak of the curve represents the maximum
density obtained under the compactive effort supplied

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Optimum Moisture Content II

Proctor
Compaction
Tests

Optimum Moisture Content III
Typical Compaction Test

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Compaction Specifications
• Compaction specifications are intended to ensure
that the compacted material provides:
– The required engineering properties (minimum dry
density to be achieved) and
– A satisfactory level of uniformity (A maximum variation
of density between adjacent areas)
• Typical density requirements are expressed as a percentage
of Proctor (Ex. For the support of structures and for pavement
base courses, requirements of 95 to 100% of Modified Proctor
are commonly used
• A lack of uniformity in compaction may result in differential
settlement of structures or may produce a bump or
depression in pavements
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Measuring Field Density

• Why?
– To verify the adequacy of compaction actually
obtained in the field

• How? Methods available include:
– Traditional methods (liquid tests, sand tests)
– Nuclear density devices

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Compaction Equipment

• Principal Types of
Compaction Equipment:
– Tamping Foot Rollers
– Grid or Mesh Rollers
– Vibratory Compactors
– Smooth Steel Drum
Rollers
– Pneumatic Rollers
– Segmented Pad Rollers
– Tampers or Rammers
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Tamping Foot Rollers
• Utilize a compaction drum
equipped with a number of
protruding feet to achieve
compaction
• These rollers come with a
variety of foot shapes and
sizes and include the classic
sheepsfoot roller
• Achieve compaction through
static weight and
manipulation

• They are most effective on
cohesive soils

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Grid or Mesh Rollers
• Utilize a compactor drum made up of a heavy steel
mesh
• They can operate at high speed without scattering
the material being compacted
• Their compactive effort is due to static weight and
impact
• Most effective in compacting gravel and sand
• Able to crush and compact soft rock

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Vibratory Compactors
• Available in a wide range of sizes and types
– Size: ranges from small hand-operated compactors
through towed rollers to large self-propelled rollers)
– Type: include plate compactors, smooth drum rollers,
and tamping foot rollers

• Most effective in compacting noncohesive soils
• Many vibratory compactors
permit varying the vibration

frequency to obtain the most
effective compaction
• Compactive forces are
principally vibration and
static weight

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Steel Wheel or Smooth Steel drum Rollers
• Widely used for compacting granular bases,
asphaltic bases, and bituminous pavements
• Compaction achieved primarily through static
weight

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Rubber-tired or Pneumatic Rollers
• Well suited for compacting thick soil layers to high
density
• Least suited for compacting sands and gravel

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Segmented Pad Rollers

• Similar to tamping foot rollers except that they
utilize pads shaped as segments of a circle
instead of feet on the roller drum
• They produce less surface disturbance than do
tamping foot rollers

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Tampers or Rammers
• Small impact-type
compactors primarily
used for compaction in
confined spaces
• Some rammers are
classified as vibratory
rammers because of
their operating frequency

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Compaction in Confined Areas
• Confined areas:
– Trenches
– Around foundations

• Equipment examples:
– Vibratory plate compactors

– Tampers or rammers
– Walk-behind static and vibratory rollers
– Attachments for backhoes and hydraulic
excavators
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Compaction Equipment II

Vibratory plate
compactors

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Compaction Equipment III

Walk-behind static and vibratory
rollers

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Compaction Equipment IV

Attachments for
backhoes and
hydraulic
excavators

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Selection of Compaction Equipment

Selection of Compaction Equipment
• Objective:
Obtaining the
required soil
density with a
minimum
expenditure of
time and effort
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Compaction Operation
• After selecting compaction equipment, a
compaction plan must be developed
• Factors to be considered in the plan:
–
–
–
–

–
–
–

Soil moisture content
Lift thickness (layer thickness)
Number of passes used
Ground contact pressure
Compactor weight
Compactor speed
Frequency (for vibratory compactors)
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Compaction Operation II
• Lifts should be kept thin for most effective compaction
– A maximum lift thickness of 15 to 20 cm is suggested for
most rollers

• The compaction achieved by repeated passes of a
compactor depends on the soil/compactor
combination utilized
– The increase in density is relatively small after about 10
passes for most soil/compactor combinations (see Figure
5-12 in the Textbook)

• Trial operations are usually required to determine the
exact values of soil moisture content, lift thickness,
compactor weight and frequency that yield maximum
productivity while achieving the specified soil density
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Compaction Operation III

Number of Pass Effect

Number of Passes

Compaction Production
Production (CCM/h) = (10 x W x S x L x E) / P
Where:
P = number of passes required
W = width compacted per pass (m)
S = compactor speed (km/h)
L = Compacted layer thickness (cm)
E = job efficiency

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Compaction Production II

• Problem 2
Estimate the production in compacted cubic
meters per hour for a self-propelled tamping foot
roller under the following conditions:

–
–
–
–
–

Average speed = 8 km/h
Compacted lift thickness = 15.2 cm
Effective roller width = 3.05 m
Job efficiency = 0.75
Number of passes = 8

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Compaction Production III

• Solution
Production (CCM/h)
= (10 x W x S x L x E) / P
= (10 x 3.05 x 8 x 15.2 x 0.75) /8
= 347.7 CCM/h

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Grading and Finishing
What?

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•

Grading: the process of bringing earthwork to
the desired shape and elevation (or grade)

•

Finishing (or finish grading): Smoothing slopes,
shaping ditches, and bringing the earthwork to
the elevation required by the plans and
specifications

•

The grader is usually the equipment used for
grading and finishing
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Grading and Finishing II
• Graders are used for: stripping, grading,
finishing, backfilling, mixing and spreading
soil, and maintenance of haul roads

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Estimating Grader Production
• Usually calculated on
– Linear basis for roadway projects (kilometers
completed per hour)
– Area basis for general construction projects
(square meters per hour)

• Average speed depends on
– Operator skill
– Machine characteristics
– Job Conditions

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Estimating Grader Production II
• Typical grader operating speed

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Estimating Grader Production III
• Example
24.1 km of gravel road require reshaping and
leveling. It is estimated that 6 passes of a motor
grader will be required as follows:
– 2 passes at 6.4 km/h
– 2 passes at 8.0 km/h
– 2 passes at 9.7 km/h

• Job efficiency is estimated at 0.8
• How many grader hours will be required for this
job?
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Estimating Grader Production IV
• Solution:

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Job Management
• The use of skilled operators and competent
supervision are required
• Use the minimum possible number of grader
passes to accomplish the work
• Eliminate as many turns as possible
• Use grading in reverse for distances less than 305
meters
• Several graders may work side by side if sufficient
working room is available (for large areas)
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