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8/2/2019 Week 6 and 7 - Design and Analysis of Shallow Foundation
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TOPIC 3: DESIGN AND ANALYSIS OF SHALLOWTOPIC 3: DESIGN AND ANALYSIS OF SHALLOW
FOUNDATIONFOUNDATION
WEEK 6 and WEEK 7WEEK 6 and WEEK 7
SETTLEMENT OF FOUNDATION ON SOILSETTLEMENT OF FOUNDATION ON SOIL
REVIEW OF VERTICAL STRESS DISTRIBUTIONREVIEW OF VERTICAL STRESS DISTRIBUTION
FOUNDATION ON FILLFOUNDATION ON FILL
Learning OutcomesLearning Outcomes
Students should be able to:Students should be able to:
Determine the type of foundation on fill (CO2Determine the type of foundation on fill (CO2--PO10)PO10)
SETTLEMENTSETTLEMENT OF SHALLOW FOUNDATIONOF SHALLOW FOUNDATION
Total settlement = Immediate Settlement + Consolidation Settlement
Immediate settlement (elastic) takes place during or immediately after
the construction of the structure.
Consolidation Settlement occurs over a period of time. Consists of:
Primary squeezing of water from its void
Secondary slippage and reorientation of soil particles
** Refer to ECG433** (Geotechnics II)
Topic Chapter 1:
Stress Distribution in soil and Immediate Settlement
Calculation of Vertical Stress IncreaseCalculation of Vertical Stress Increase
A) Stress Increase due to Concentrated Load
** Refer to ECG433**(Geotechnics II)
Topic Chapter 1:
Stress Distribution in soil
B) Stress due to Circularly Loaded AreaB) Stress due to Circularly Loaded Area Simple Method or Method 2:1Simple Method or Method 2:1
))(( zLzB
Qz
++=
Stress at depth z under
rectangular footing with
dimensions BxL
8/2/2019 Week 6 and 7 - Design and Analysis of Shallow Foundation
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))(( zLzB
Qz
++=
Simple Method or Method 2:1Simple Method or Method 2:1OTHER METHODSOTHER METHODS
NewmarksNewmarks ChartChart
FadumsFadums ChartChartPressure Bulbs ChartPressure Bulbs Chart
** Refer to ECG433**(Geotechnics II)
Topic Chapter 1:
Stress Distribution in soil
FOUNDATION ON FILLFOUNDATION ON FILL
Type of FillType of Fill
Non engineered fillNon engineered fill
Engineered fillEngineered fill
Reclaimed landReclaimed land
Foundation SelectionFoundation Selection
May use raft for engineered fillMay use raft for engineered fill need toneed to
confirm before constructionconfirm before construction
Ground improvement for reclaimed landGround improvement for reclaimed land
PVD,PVD, VibroVibro compaction, Dynamiccompaction, Dynamic
ompactionompaction, stone column etc, stone column etc
Piling for non engineered fill.Piling for non engineered fill.
TOPIC 3: DESIGN AND ANALYSIS OF SHALLOWTOPIC 3: DESIGN AND ANALYSIS OF SHALLOW
FOUNDATIONFOUNDATION
WEEK 7WEEK 7
Theoretical and Empirical Method for EstimatingTheoretical and Empirical Method for EstimatingSettlement.Settlement.
Total and Differential Settlement to Limit DamageTotal and Differential Settlement to Limit Damage
Learning OutcomesLearning Outcomes
Students should be able to:Students should be able to:
Able to estimate settlement (CO2Able to estimate settlement (CO2--PO10)PO10)
Able to determine angular distortion (CO2Able to determine angular distortion (CO2--PO10)PO10)
Able to discuss on tolerable settlement. (CO2Able to discuss on tolerable settlement. (CO2--PO10)PO10)
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Elastic SettlementElastic Settlement
Settlement of Rigid Foundation
Empirical Methods
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Method based on Standard Penetration TestElastic Parameters of SoilElastic Parameters of Soil
Correlation
TOTAL SETTLEMENT, ST.
isT SSS ++=(1) Primary consolidationsettlement
(2) Secondary
consolidation settlement
(3) Immediate
settlement
I
EpB
i
21=
p
se
eHS
+
=
1
+=
1
2log1 t
tH
e
CS
p
s
Normally consolidated clays:
++
=0
0
0
log1 p
pp
e
HCS c
He
eS
01+
=
Over-consolidated clays:
If po + p pc.
+
+=
0
0
0
log1 p
pp
e
HCS s
Case 1
If po < pc < po + p
+
++
+=
c
c
o
cs
p
pp
e
HC
p
p
e
HCS 0
00
log1
log1
Case 2
Primary Consolidation Settlement
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Primary Consolidation Settlement Calculations
Secondary Compression Index
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Angular DistortionAngular Distortion
Angular distortion is used to get a limit to prevent theAngular distortion is used to get a limit to prevent the
cracking of structures and architectures finishes an alsocracking of structures and architectures finishes an also
for serviceability of building facilities.for serviceability of building facilities.
A rigid structures would have to limit its angular distortionA rigid structures would have to limit its angular distortion
to less than requirement for a more flexible structures.to less than requirement for a more flexible structures.
Uniform SettlementUniform Settlement Differential SettlementDifferential Settlement
stst2
st1
L
Table 3.1 Apparent Tolerable Differential Settlements
StructureStructure Max Differential SettlementMax Differential Settlement
SingleSingle--storey masonry buildingsstorey masonry buildings 0.0015 L*0.0015 L*
HighHigh masonarymasonary wallwall 0.001 L0.001 L
Continuous steel frameContinuous steel frame 0.002 L0.002 L
Reinforced concrete buildingReinforced concrete building 0.005 L0.005 L
Smokestacks and towersSmokestacks and towers 0.004 L0.004 L
300
112
L
ss tt
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Tolerable Settlement of BuildingsTolerable Settlement of Buildings Guideline for Tolerable SettlementGuideline for Tolerable Settlement
Limiting Angular Distortion
Field Load TestField Load Test
Test in Clay, qu(F) = qu(P)
Sand, qu(F) = qu(P) BF/BP
INTERPRETATION OF IN SITUBEARING CAPACITY
TESTS.
Plate Bearing Test
Estimated immediate settlement of a foundation
(Terzaghi and Peck, 1967) is given by theexpression :
where
sb = settlement of a test plate of side dimension b
sB = settlement of a foundation of side dimension B
at the same intensity of loading.
2
+=
bB
2Bss bB
GEOTECHNIQUES (ECG433) ARM - 2007
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For a given qo
Terzaghi and Peck:
For sand, SF/SP = 4/ (1 +BP/BF)2
Clay, SF = SP. BF/BP
Calculate the average Stress Increase for the clay layer and the
Consolidation Settlement
Example:Example: