Soil Compaction and Field Density

Question 1

A simple ground improvement technique, where the soil
is densified through external compactive effort.

Answer 1

compaction

Question 2

The process of bringing the soil particles closer to a dense
state by mechanical means

Answer 2

compaction

Question 3

The ______ are reduced by
expulsion of air and the soil particles are packed together,
thereby increasing its unit weight.

Answer 3

voids

Question 4

There is no substantial change in the volume of water in soil
during compaction. T or F

Answer 4

T

Question 5

_________ is done to improve the Engineering properties of
soil such as increase of shear, increase the bearing strength,
reduce the compressibility of soil, change the soil properties
like shrinkage, frost susceptibility and permeability of soils.

Answer 5

Compaction

Question 6

To compact a soil,
that is, to place it in a _________.

Answer 6

dense state

Question 7

The __________ is achieved through the reduction of the air voids in the
soil, with little or no reduction in the water content. This process must
not be confused with _________, in which water is squeezed out under
the action of a continuous static load

Answer 7

dense state, consolidation

Question 8

Objective of compaction

Answer 8

(1) Decrease future settlements
(2) Increase shear strength
(3) Decrease permeability

Question 9

_________ in the early 1930’s was building dams for the old Bureau of
Waterworks and Supply in Los Angeles, and he developed the principles
of compaction in a series of articles in Engineering News-Record. In his
honor, the standard laboratory compaction test which he developed is
commonly called the ______

Answer 9

R.R. Proctor, proctor test

Question 10

The purpose of a laboratory compaction test is to determine the _________________ to use when compacting the soil in the field and
the ___________ which can be expected from compaction
at this optimum water

Answer 10

proper
amount of mixing water, resulting degree of denseness

Question 11

The proctor test is an ________. A hammer is dropped several
times on a soil sample in a mold. The mass of the hammer, height of drop,
number of drops, number of layers of soil, and the volume of the mold are
specified

Answer 11

impact compaction

Question 12

Standard Proctor Test
_______ height of drop
_____hammer
______ blows/layer
_____ layers
Mold size: ______
Energy _________

Answer 12

12 in
5.5 lb
25
3
1/30 ft3
12,375 ft·lb/ft3

Question 13

Modified Proctor Test
_____ height of drop
_____ hammer
_____ blows/layer
___ layers
Mold size: _______
Energy ______

Answer 13

18 in
10 lb
25
5
1/30 ft3
56,250 ft·lb/ft3

Question 14

The ________ was developed during World War II by the U.S. Army Corps of Engineering

Answer 14

modified test

Question 15

Several samples of the same soil, but at different water contents, are
compacted according to the ___________

Answer 15

compaction test specifications

Question 16

The ______ of the compaction curve is the point with the maximum
dry density pd max.

Answer 16

peak point

Question 17

Corresponding to the maximum dry density pd max is a
water content known as the ________

Answer 17

optimum water content

Question 18

that the maximum dry density
is only a maximum for a specific compactive effort and method of
compaction. This reflects the maximum dry density
that can be obtained in the field. T or F

Answer 18

T, does not necessarily

Question 19

The curve represents the fully saturated condition (S = 100 %). (It cannot
be reached by compaction)

Answer 19

Zero air voids curve

Question 20

A line drawn through the peak points of several compaction curves at
different compactive efforts for the same soil will be almost parallel to a
100 % S curve, it is called the _________-

Answer 20

line of optimums

Question 21

As the water content increases, the particles
develop larger and larger water films around
them, which tend to “_______-” the particles
and make them easier to be moved about and
reoriented into a denser configuration.

Answer 21

Below wopt (dry side of optimum):, lubricate

Question 22

The density is at the maximum, and it does
not increase any further.

Answer 22

At wopt

Question 23

Water starts to replace soil particles in the
mold, and since pw &laquo_space;ps the dry density
starts to decrease

Answer 23

Above wopt (wet side of optimum):

Question 24

Each data point on the curve represents a single
compaction test, and usually ___________
compaction tests are required to completely determine the
compaction curve.

Answer 24

four or five individual

Question 25

At least two specimens wet and two specimens dry of optimum, and water contents varying by about ____.

Answer 25

2%

Question 26

Optimum water content is typically slightly less than the plastic limit (___________)

Answer 26

ASTM suggestion

Question 27

Typical values of maximum dry density are around _________ with the maximum range from about __________.

Answer 27

1.6 to 2.0 Mg/m3, 1.3 to 2.4 Mg/m3

Question 28

Typical optimum water contents are between _________, with an outside maximum range of about ________

Answer 28

10% and 20%, 5% to 40%

Question 29

Five factors affecting compaction

Answer 29

1. Physical & chemical properties 2. Moisture content 3. Method of compaction 4. Amount of compactive effort 5. Thickness of layer or “lift” being compacted

Question 30

The ______-that is, grain-size distribution, shape of the soil grains, specific gravity of soil solids, and amount and type of clay minerals present.

Answer 30

soil type

Question 31

As the___________ increased, the max dry unit weight of compaction is also increased and the optimum moisture content is decreased to some extent.

Answer 31

compaction effort

Question 32

The _________ is not directly proportional to the compaction effort.

Answer 32

degree of compaction

Question 33

The_________ generally yield a somewhat lower optimum water content than the actual field optimum

Answer 33

laboratory curves

Question 34

The majority of field compaction is controlled by the ______________

Answer 34

dynamic laboratory tests.

Question 35

For a given compactive effort and dry density, the soil tends to be more ________ (random) for compaction on the dry side as compared on the wet side.

Answer 35

flocculated

Question 36

For a given __________ content, increasing the compactive effort tends to disperse (parallel, oriented) the soil, especially on the dry side

Answer 36

molding water

Question 37

Increasing the water content results in a decrease in permeability on the dry side of the optimum moisture content and a slight increase in permeability on the wet side of optimum. T or F

Answer 37

T

Question 38

At low stresses the sample compacted on the wet side is less compressible than the one compacted on the dry side. T or F

Answer 38

F, more

Question 39

At the high applied stresses the sample compacted on the dry side is more compressible than the sample compacted on the wet side. T or F

Answer 39

T

Question 40

________ of compacted clays is greater for those compacted dry of optimum. They have a relatively greater deficiency of water and therefore have a greater tendency to adsorb water and thus swell more

Answer 40

Swelling

Question 41

the ratio between resistance required to penetrate a 3-in^2 piston into the compacted specimen and resistance required to penetrate the same depth into a standard sample of crushed stone.

Answer 41

The CBR (California bearing ratio)

Question 42

Because of the differences between lab and field compaction methods, the maximum dry density in the field may reach ________

Answer 42

90% to 95%.

Question 43

* 100% coverage under the wheel * Contact pressure up to 380 kPa * Can be used on all soil types except for rocky soils. * Compactive effort: static weight * The most common use of large smooth wheel rollers is for proof rolling subgrades and compacting asphalt pavement.

Answer 43

Smooth-wheel roller (drum)

Question 44

* 80% coverage under the wheel * Contact pressure up to 700 kPa * Can be used for both granular and fine-grained soils. * Compactive effort: static weight and kneading. * Can be used for highway fills or earth dam construction.

Answer 44

Pneumatic (or rubber-tired) roller

Question 45

* Has many round or rectangular shaped protrusions or “feet” attached to a steel drum * 8% ~ 12 % coverage * Contact pressure is from 1400 to 7000 kPa * It is best suited for clayed soils. * Compactive effort: static weight and kneading.

Answer 45

Sheepsfoot rollers

Question 46

* About 40% coverage * Contact pressure is from 1400 to 8400 kPa * It is best for compacting fine grained soils (silt and clay). * Compactive effort: static weight and kneading.

Answer 46

Tamping foot roller

Question 47

* 50% coverage * Contact pressure is from 1400 to 6200 kPa * It is ideally suited for compacting rocky soils, gravels, and sands. With high towing speed, the material is vibrated, crushed, and impacted. * Compactive effort: static weight and vibration.

Answer 47

Mesh (or grid pattern) roller

Question 48

Vertical vibrator attached to smooth wheel rollers. * The best explanation of why roller vibration causes densification of granular soils is that particle rearrangement occurs due to cyclic deformation of the soil produced by the ________ of the roller. * Compactive effort: static weight and vibration. * Suitable for granular soils

Answer 48

Vibrating drum on smooth-wheel roller, oscillations

Question 49

________ and ______ correlate well with the engineering properties, and thus they are convenient construction control parameters.

Answer 49

Dry density, water content

Question 50

Since the objective of compaction is to stabilize soils and improve their engineering behavior, it is important to keep in mind the desired engineering properties of the ______, not just its dry density and water content. This point is often lost in the earthwork construction control.

Answer 50

fill

Question 51

_______ are conducted on samples of the proposed borrow materials to define the properties required for design.

Answer 51

Laboratory tests

Question 52

After the earth structure is designed, the compaction specifications are written. Field compaction ________ are specified, and the results of these become the standard for controlling the project

Answer 52

control tests

Question 53

This specification is used for most highways and building foundation, as long as the contractor is able to obtain the specified relative compaction , how he obtains it doesn’t matter, nor does the equipment he uses

Answer 53

End-product specifications

Question 54

The type and weight of roller, the number of passes of that roller, as well as the lift thickness are specified. A maximum allowable size of material may also be specified. It is typically used for large compaction project. From

Answer 54

Method specifications

Question 55

Field Compaction depends on:

Answer 55

· Weight of roller · No of passes of roller

Question 56

_________ is given in specification for field compaction, which is the ratio of field dry density to the maximum lab density, whereas the ________ is determined by Standard or Modified AASHTO tests.

Answer 56

Relative compaction, Lab dry density

Question 57

Typical required R.C.

Answer 57

90% ~ 95%

Question 58

Typical specifications call for a new field test for every _________ or so, or when the borrow material changes significantly.

Answer 58

1000 to 3000 m2

Question 59

Field control tests, measuring the dry density and water content in the field can either be ________

Answer 59

destructive or nondestructive

Question 60

Destructive Methods

Answer 60

(a) Sand cone (b) Balloon (c) Oil (or water) method

Question 61

compaction test is usually done on materials finer than ________

Answer 61

corrected maximum dry density, 4.75 mm

Question 62

· sample contains coarse grained sized particles– gravel in a soil composed mainly of fine grains can be compacted to ________ of their theoretical maximum density– assuming gravel RD=____

Answer 62

90%, 2.65

Question 63

Sometimes, the laboratory maximum density may not be known exactly. It is not uncommon, especially in__________, for a series of laboratory compaction tests to be conducted on “representative” samples of the borrow materials for the highway. If the soils at the site are highly varied, there will be no laboratory results to be compared with. It is time consuming and expensive to conduct a new compaction curve. The alternative is to implement a ___________, or _______

Answer 63

highway construction, field check point, 1 point Proctor test.

Question 64

The measuring error is mainly from the determination of the volume of the ___________.

Answer 64

excavated material

Question 65

Nondestructive Methods

Answer 65

Nuclear density meter (a) Direct transmission (b) Backscatter (c) Air gap

Question 66

The _________ is scattered by the soil particles and the amount of scatter is proportional to the total density of the material. The ___________ is typically provided by the radium or a radioactive isotope of cesium.

Answer 66

Gamma radiation

Question 67

The ____________ can be determined based on the neutron scatter by hydrogen atoms. Typical neutron sources are __________

Answer 67

water content, americium-beryllium isotopes

Question 68

____________ against compacted materials of known density is necessary, and for instruments operating on the surface the presence of an uncontrolled air gap can significantly affect the measurements.

Answer 68

Calibration