Class notes of Geotechnical Engineering course I used to teach at UET Lahore. Feel free to download the slide show. Anyone looking to modify these files and use them for their own teaching purposes can contact me directly to get hold of editable version.

1. 1
Geotechnical Engineering–I [CE-221]
BSc Civil Engineering – 4th Semester
by
Dr. Muhammad Irfan
Assistant Professor
Civil Engg. Dept. – UET Lahore
Email: mirfan1@msn.com
Lecture Handouts: https://groups.google.com/d/forum/2016session-geotech-i
Lecture # 15
13-Mar-2018

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RELATIVE COMPACTION
FIELD COMPACTION
Use of compaction curve?
 Not possible to obtain
γd(max) in field.
 In the field, contractor is
usually required to compact
the soil to 90-95% γd(max).
Relative compaction, or percent compaction is defined as the ratio of the
(γd)field to (γd max)lab.
Moisture
Content
Dry Density
γd(max)
(OMC)
ZAV
95% γd(max)

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A family of heavy fill movement and compaction equipment
FIELD COMPACTION EQUIPMENT

4. 4
Motor-scarifier cuts and lays fills in 8 to 24 inch lifts for compaction
FIELD COMPACTION EQUIPMENT

5. 5
FIELD COMPACTION EQUIPMENT
Motor grader levels the ground

6. 6
Water truck used for attaining optimum moisture for compaction
of the subgrade.
FIELD COMPACTION EQUIPMENT

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Field compaction
Common types of rollers:
 Smooth-wheel rollers (or smooth-drum rollers)
 Pneumatic rubber-tired rollers
 Sheepfoot rollers
 Impact rollers
 Vibratory rollers
 Grid rollers
FIELD COMPACTION
→ mostly done with rollers.

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 100% coverage under the
wheel
 Used for all soil types except
for rocky soils.
 Compactive effort: static
weight
 Common use: proof-rolling
subgrades and compacting
asphalt pavement.
SMOOTH-WHEEL ROLLER (DRUM)

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 80% coverage under the wheel
 Used for both granular and fine-
grained soils.
 Compactive effort: static weight
and kneading.
 Typical use: Highway fills or
earth dam construction.
PNEUMATIC ROLLER / RUBBER-TIRED
ROLLER (PTR)

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 Several round or rectangular
shaped protrusions or “feet”
attached to a steel drum
 8% ~12% coverage
 It is best suited for clayey
soils.
 Compactive effort: static
weight and kneading.
SHEEPSFOOT ROLLERS

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 Vibrators can be attached to
smooth, pneumatic rubber-
tired, or sheepfoot rollers to
provide vibratory effect to
soil.
 Particles rearrangement due
to oscillations of roller.
 Extremely efficient in
compacting granular soils.
VIBRATING DRUM ON SMOOTH-
WHEEL ROLLER

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 50% coverage
 Suited for compacting rocky
soils, gravels, and sands.
 Compactive effort: Static weight
and vibration.
MESH (OR GRID PATTERN)
ROLLER

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 Used at places where space
is limited.
 Foundation trenches,
compaction for backfills.
PORTABLE COMPACTORS

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FIELD COMPACTION EQUIPMENT
– SUMMARY

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A- Characteristics of Compactor
(1) Mass, size
(2) Operating frequency
B- Construction procedures
(1) Number of passes of roller
(2) Lift thickness
(3) Towing speed
C- Characteristics of Soil
(1) Initial density
(2) Grain size and shape
(3) Water content
VIBRATORY COMPACTION – EFFICIENCY

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Effect of Compactor Size & Frequency
 Heavier the
compactor, better is
compaction
 Best compaction
achieved at optimum
frequency

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 Increase in density not
significant beyond 5
passes.
 For a given number of
passes, a higher density
is obtained if the vibrator
is towed more slowly.
Effect of Roller Speed & No. of Passes
Passes of roller

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Effect of Lift Height
 Max. density achieved at
around 75% lift height.

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DYNAMIC COMPACTION

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Practice Problem #3
If a sample is saturated at a water content of 30%,
what is its density? Assume Gs=2.70.
Practice Problem #4
The following data are available in connection with the construction of an
embankment:
a) Soil from borrow pit: Natural density = 1.75 Mg/m3, Natural moisture
content = 12%
b) Soil after compaction: Density = 2 Mg/m3, Water content = 18%
For every 100 m3 of compacted soil of the embankment, estimate
i. The quantity of soil to be excavated from the borrow pit, and
ii. The amount of water to be added.

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A borrow pit’s soil is being used as earth fill at a construction project. The
in situ dry unit weight of the borrow pit soil was determined to be 17.18
kN/m3. The soil at the construction site is to be compacted to a dry unit
weight of 18.90 kN/m3. The construction project requires 15,000 m3 of
compacted fill.
Determine the volume of soil required to be excavated from the borrow pit
to provide the necessary volume of compacted fill.
Practice Problem #5

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Practice Problem #6
The natural moisture content of a borrow pit material is 8%.
Assuming 3000 g of moist soil for a standard compaction test,
how much water is to be added to bring the sample to 11%,
15%, and 20% water content?

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Given
The in situ void ratio, e of a borrow pit’s soil is 0.72
The borrow pit soil is to be excavated and transported to fill a
construction site where it will be compacted to a void ratio of
0.42.
The construction project requires 10,000 m3 of compacted fill.
Required
Volume of soil that must be excavated from the borrow pit to
provide the required volume of fill.
Practice Problem #7

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CONCLUDED
REFERENCE MATERIAL
An Introduction to Geotechnical Engineering (2nd Edition)
By R. D. Holtz, W. D. Kovacs and T. C. Sheahan
Chapter #5
Principles of Geotechnical Engineering – (7th Edition)
Braja M. Das
Chapter #6