lecture 02 soil compactioncontents.kocw.net/kocw/document/2014/hanyang/parkduhee/4.pdf ·...

CIE_3008 토질역학 및 실험 Lec.2 Soil Compaction 1

Lecture 02

Soil Compaction


Outline

• Compaction – what is it?

• Laboratory tests

• Standard Proctor Test

• Modified Proctor Test

• Compaction - Principles

• Compaction of Clay Soil

• Field Compaction


Compaction – What is it?

Compaction is the densification of soil by removal of air, which

requires mechanical energy.

Different from consolidation

Compaction increases the density of the soils

Increases shear strength

Reduce compressibility

Reduce permeability

Examples of compaction

Highway embankments

Backfilled trench

Sub-foundation soil

Earth dam


Standard Proctor test

ASTM Test Designation D-698, AASHTO Test Designation T-99

Mold : Volume 944 ㎤ ( D=101.6 ㎜ )

Hammer : 2.5kg

Drop : 304.8 ㎜




Ws+Ww = weight of soil inside the mold V = volume of compacted soil w = water content (does not change during compaction)


Modified Proctor test


Comparison

Type Standard

Proctor test Modified

Proctor test

Hammer W

2.5 kg 4.54 kg

Drop H

305 ㎜ 457 ㎜

Layer Num.

3 5


Modified Proctor test

Compaction Test Specifications(ASTM D-698 and D-1557)


Compaction – Principles



Effect of compaction effort

Compaction energy

Compaction energy ↑

↑

OMC ↓

E =

Number

of blows

per layer

æ

è

ççç

ö

ø

÷÷÷

´

Number

of

layer

æ

è

ççç

ö

ø

÷÷÷

´

Weight

of

hammer

æ

è

ççç

ö

ø

÷÷÷

´

Drop height

of

hammer

æ

è

ççç

ö

ø

÷÷÷

Volumeof mold

,maxd

Type Compaction

energy

(Kg cm/cm3)

1 4.77

2 5.96

3 7.16

4 11.93



Efficiency of compactive effort



Effect of soil type

The soil type has a great influence on and OMC

Distribution, Shape, Specific gravity, Amount and type of clay minerals present

,maxd


Structure of compacted clay soil

Soil Structure:

-Flocculated (low water content)

-Orderly arrangement (high water content)

Desired Property:

-100 % compaction ( )

-Practically: 90-98% ( ) compaction

(application specific)

,maxd

,maxd


Effect of compaction on cohesive soil properties

Permeability, Compressibility, Strength

1. Permeability 2. Compressibility

Low Stress

High Stress


Effect of compaction on cohesive soil properties

Permeability, Compressibility, Strength

3. Strength


Field compaction

Compaction Equipment

1. Smooth-wheel roller

2. Pneumatic rubber-tired rollers

3. Sheepsfoot rollers

4. Vibratory rollers


Field compaction

Relative compaction


Field compaction

Design and selection of fill materials


Field compaction

Factors affecting field compaction

1. Moisture content

1. Too wet impossible to compact

2. Too dry difficult to compact

3. Easier to add than remove water! Maintain water

Contents on the dry side

2. Number of roller passes

3. Thickness


Field compaction

Factors affecting field compaction

Typical thickness used is 15 cm


Specification for Field compaction

Relative compaction

( )

(max )

100(%)d field

d lab

R


Determination of field unit weight of compaction

Sand cone method (ASTM Designation D-1556)

W1 = weight of the jar(sand fill)

W2 = weight of the moist soil excavated from hole

W4 = remaining sand in the jar

W5 = weight of sand to fill the hole

23 (%)

1001

w

WW

3d

W

V

5

( )

c

d sand

W WV

5 1 4WW W

lecture 02 soil compactioncontents.kocw.net/kocw/document/2014/hanyang/parkduhee/4.pdf ·...

Documents