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Jonathan Rivera Dungca, D.Eng.

Associate Professor

FOUNDES

Soil Mechanics/Review(Part 2)

De La Salle University -ManilaDepartment of Civil and Engineering



Chapter 3: Soil Mechanics

Lecture No.1

3.1 Soil Composition

Soil-a 3-phase material Soil Characterization (particle size,

soil plasticity)

3.2 Soil Classification 3.3 Groundwater

3.4 Stress (Total vs. Effective)



Chapter 3: Soil Mechanics

Lecture No.2

3.5 Compressibility and

settlementLecture No.3

3.6 Strength



3.5 Compressibility & Settlement

Settlement requirements oftencontrol the design of foundations

This chapter provides a generaloverview of principles involved insettlement analysis

The subject will be dealt with in

greater detail in Chapter 7.



Case Study

Settlement must be withinacceptable limits …..

Palacio de las Bellas

Artes, Mexico CityBuilt 1932-1934



Palace of Fine Arts in Mexico CitySettled 3m!

Lacustrine Clay deposited in former LakeTexcoco

Av. Water content 281%, Void Ratio 6.90Groundwater withdrawal; increase in

effective stress

Resulting Consolidation43-story Tower Latino Americana



Case Study

Tower of Latino

Americana, MexicoCityBuilt ihn 1956

44 stories; 597-ft



Increase in Vertical Effective Stress

Due to a Placement of a fill

Due to an external load

fill fill z zf H

0

induced z z zf 0



VoidsVoids

Solids

H

V v = eV s

V s

c

e

V v = (e - e)V s

V s Solids

z

′

z

′

z0′

z0′

z0′

z0′

} z f ′

} z f ′

Before After

Consolidation



u0

0

Before Loading

Point, P



u0+u

0 +

ImmediatelyAfter Loading

Point, P



0 +

u0+u

u0

0 +

Shortly after LoadingNo settlement

Long after LoadingSettlement Complete



Settlement

Distortion Settlement (Immediate)

Consolidation (Time Dependent)

Secondary Compression time

Settlement



Laboratory Consolidation Test



Consolidation Test



Test Results



Consolidation Plot



Test ResultsIdealizedData



Compression Index andRecompression Index

a zb z

bac

eeC

)(log)(log

c zd z

d c

r

ee

C )(log)(log



Compression Ratio andRecompression Ratio

a zb z

b za zcc

e

C C

)(log)(log

)()(

1 0

c zd z

c zd zr r

e

C

C )(log)(log

)()(

1 0



Normally andOver-Consolidated Soils

c zo ….. Normally consolidated

c zo ….. Over consolidated

c zo ….. Under consolidated



Normal vs. Over-Consolidation



Over-Consolidation Margin & Over-consolidation Ratio

zocm ….. Over-consolidation

Margin

zo

cOCR

….. Over consolidation ratio



Typical Range of OC Margins



Compressibility of Sand andGravels (Table 3.7)



Example 3.3



Settlement PredictionsN.C. Clays

00

log

1 z

zf cc H

e

C



Settlement PredictionsO.C. Clays…… Case I

00

log

1 z

zf r c H

e

C



Settlement PredictionsO.C. Clays…… Case II

c

zf c

z

cr c H

eC H

eC

log

1log

1 000



Ex. 3.4



Example 3.4



Ex. 3.5

E l



Example3.5