Upload
magdyamdb
View
220
Download
0
Embed Size (px)
Citation preview
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 1/96
EELASTICLASTIC SSETTLEMENTETTLEMENT OFOF
SSHALLOWHALLOW FFOUNDATIONSOUNDATIONS ONON
GGRANULARRANULAR SSOILOIL—— BBRAJARAJA M. DM. DASAS
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 2/96
Settlement, S
• , e
•
• Primary, S p
, s
S = Se + S + Ss
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 3/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 4/96
In
his
landmark
paper
in
1927
entitled
The Science
of
Foundations, Karl Terzaghi wrote:
“Foundation problems, throughout, are of such character that
impossible. The only way to handle them efficiently consists
of finding out, first, what has happened on preceding jobs of a
similar character; next, the kind of soil on which the
operations were performed; and, finally, why the operations
have led to certain results. B s stematicall accumulatin
such knowledge, the empirical data being well defined by the
results of adequate soil investigations, foundation engineering
”‐ . . . .“The bulk of the work—the systematic accumulation of
em irical data—remains to be done.”
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 5/96
To evaluate the current state of the art for
settlement redictions of shallow foundations in
sand, in an attempt to promote the use of shallow
foundations.
A FHWA initiative
. e era g way m n s ra on
2. Texas A & M University
.4. American Society of Civil Engineers (ASCE)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 6/96
exas n vers yNational Geotech Experiment Site
Approximately
12m
28m
5 Square Footings: 1m 1m.5m .5 m
2.5m 2.5m
3m 3m (South)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 7/96
Predict the load at 25 mm settlement
In Situ Test Summary
Bore o e s ear test 3
Cross
hole
test
4
Dilatometer test 4Pressuremeter test 4
Step blade test 1Standard penetration test 6
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 8/96
Number of participants: 31
15 consultants
16 academics
Israel – 1 Brazil – 1
Canada – 2 Italy – 1
– – USA – 21
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 9/96
Methods Used for Settlement Prediction
Schmertmann (1970, 1978), Burland and Burbidge (1985)
and FEM being popular
Alpan (3 times) Menard/Briaud (5)
Buisman, DeBeer (3)
Burland & Burbidge (9)
NAVFAC (4)
Oweis (4)Canada Found. Manual (1)
D’Appolonia (4)
DeBeer 1
Parry (1)
Peck (2)
Robertson & Cam anella 1
Decourt (1)
FEM (1)
Schmertmann (18)
Schulze & Sherif (3)
Leonard
&
Frost (4)
Vesic (6)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 10/96
re cte vs. easure a ues o 25
Footing (m)
Item 11 1.51.5 2.52.5 33 33
Pre ct on
range (kN)591100 1162950 2954271 4075600 4156400
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 11/96
, e
Existing methods for predicting settlement may be
grouped into three categories:
A — Methods in which observed settlement of
structures
are
linked
to
in situ test
results
s an ar pene ra on es , cone
penetration test, Pressuremeter tests)
— em ‐emp r ca me oC — Use of theory of elasticity and modulus of
e ast c ty, E s
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 12/96
CATEGORY A Terzaghi and Peck (1948, 1967)
Meyerhof (1956, 1965)
DeBeer and Martens (1957) Hough (1969)
Peck and Bazaraa 1969
Burland and Burbidge (1985)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 13/96
,
21)1(
1 BSe
e
e
BB
Se(1) = sett ement o a test p ate measur ng B1B1
B is usuall of the order of 0.3m to 1m
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 14/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 15/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 16/96
Terzaghi and Peck (1948, 1967)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 17/96
2
60 3.0
BN
qC C S DW e
where q is in kN/m²; B is in m; S is in mm
C W = ground water table correction
=
below foundation
= 2 if de th of water table is less than or e ual
to B
C = correction for de th of embedment
= 1 – (D f
/4B )
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 18/96
va ugan, c ers ey an
analyzed 79 settlement records
of foundations provided by
Je alan and Boehm 1986
and Papadopoulos (1992).
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 19/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 20/96
2BSe
3.0
2
)1( BSe
43.0 )1(SB e
e
32
Bq
Se
13
.
Sq e
4 )1(60 SN ee
75.0)1(Se
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 21/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 22/96
Me erhof
)(kN/m2 2q
)(kN/m3
.
195622
60
BqN
e
.
3.060 BNe
m)22.1(
)(kN m25.1(mm)
196560
BN
qSe
m)22.1(
3.0)(kN/m2(mm)
60
BB
BN
qSe
Note: q increased by about 50%
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 23/96
m)22.1( 25.1
(mm) Bq
C C S DW e
andkN m2
22 Bm.
3.0mm
60
BN
DW e
0.1W C
B
DC
f D
40.1
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 24/96
eyer o s na ys s
StructureB
(m)AverageN60
q(kN/m2) )observed(
)predicted(
e
e
SS
T. Edison, Sao Paulo
Banco do Brasil, Sao Paulo
I aran a Sao Paulo
18.3
22.9
9.15
15
18
9
229.8
239.4
220.2
1.95
0.99
1.29
C.B.I. Esplanada, Sao Paulo
Riscala, Sao Paulo
14.6
3.96
22
20
383.0
229.8
1.20
1.56
,
Ministry, Dusseldorf
Chimney, Cologne
.
15.9
20.4
20
10
.
220.4
172.4
.
0.98
3.30
Average ≈ 1.50
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 25/96
DeBeer and Martens (1957)
3.2
C o
e
10
‘o = effective overburden pressure at a depth
= increase in pressure due to foundation loadingH = thickness of layer considered
cqC 5.1
Field Test Results:o 9.1predicted eS
o servee
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 26/96
DeBeer (1965)
−
sand
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 27/96
Hough (1969)
log
110H
eS
o
o
o
ce
)( beaC oc
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 28/96
Value of
Type of soilconstant
a b
(uniformity coefficient C u ≤ 2)Clean gravel 0.05 0.50
Coarse sand
Medium sand
Fine sand
0.06
0.07
0.08
0.50
0.50
0.50Inorganic silt 1.00 0.50
Well‐graded cohesionless soil
Silty sand and gravelClean, coarse to fine sand
Coarse to fine silt sand
0.090.12
0.15
0.200.35
0.25
Sandy silt (inorganic) 0.18 0.25
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 29/96
Peck and Bazaraa (1969)
)(kN/m2
(mm)22
BqC C S DW e
where B is in m
.601
(N1)60 = corrected standard penetration number
C = ‘ at 0.5B below the bottom of foundation o = total overburden pressure
‘ = effective overburden ressure
C D = 1.0 – 0.4(D/q) 0.5
=
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 30/96
Peck and Bazaraa (1969)
kN m754 260
NN
01.025.3 o
)kN/m75(
04.01
4)( 260
601
o
o
NN
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 31/96
Peck and Bazaraa’s Method
a ter ppo on a et a .
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 32/96
GRANULAR SOILBurland and Burbidge (1985)
60)(60 25.1 ravel sand
or gravel For NN a
)15(6.015 water ground the
below sand silty
60)(60 NN a
an 60
where N60(a) = adjusted N60 value
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 33/96
'
If
N60(a) [or
N60(a)]
is
approximately
constant
(or
increasing) with depth,
75.0
4.1
Bz
where
RR
BR = reference width = 0.3m
B = width of the actual foundation m
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 34/96
Depth of Stress Influence, z'
If N60(a) [or N60(a)] is decreasing with depth, calculate
z‘ = 2B and z‘ = distance from the bottom of the foundation to the bottom of the soft soil layer (z“ ).
‘ = ‘ = “
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 35/96
Depth of Influence
12factor,Correction
zz
H = thickness of compressible layer
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 36/96
S 71.1
aR NNB
4.1
)(6060 ]or[
.
qBB
L7.025.1
aR pB
B
L25.0
where L = length of the foundation
pa = atmospheric pressure (= 100 kN/m2)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 37/96
For
Overconsolidated
Soilpressure)idationoverconsol ;( ccq
S 57.0
aR NNB 4.1)(6060 ]or[
.
qBB
L7.0
2
25.1
aR pB
BL25.0
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 38/96
For Overconsolidated Soil
:)( cq
eS 57.014.0
aR NNB ]or[
2
.)(6060
cq
B
B
LB 67.0
25.1 7.0
B.
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 39/96
Probability of Exceeding 25‐mm Settlement in the Field
Predicted methods
Predicted
settlement Terzaghi & Peck Schmertmann
Burland &
Burbidge
1
5
0.00
0.00
0.00
0.00
0.00
0.0310
15
0.00
0.09
0.02
0.13
0.15
0.25
2530
.
0.260.31
.
0.270.32
.
0.420.49
35
40
0.35
0.387
0.37
0.42
0.44
0.51
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 40/96
CATEGORY B Schmertmann (1970),
.
Briaud (2007)
Terzaghi, Peck and Mesri (1996)
Akbas and Kulhawy (2009)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 41/96
Schmertmann (1970)
])21[()1(
B A
E
qs
s
sz
])21)[(1( B AE
I sssz
z
q
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 42/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 43/96
zE
qC C Ss
ze 21
q = net stress at the level of the foundation
1 = correc on ac or or e ep o e oun a on
= 1 – 0.5(qo /q)
o
foundation
2
= 1+0.2log(t /0.1)
E s = 2qc
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 44/96
The same 79 foundations records
given by Jeypalan and Boehm (1986)
and Papadopoulos (1992)
were anal zed b
Sivakugan et al. (1998).
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 45/96
Schmertmann et al (1978)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 46/96
Schmertmann et al. (1978)
5.0
(peak) 1.05.0
o
zI
Item L/B = 1 L/B 10
Iz at z = 0 0.1 0.2
z p /B 0.5 1.0
zo
. .
E s 2.5qc 3.5qc
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 47/96
Salgado (2008)
20111.01.0)0(at LI zz
Lz ..
BB
41222.02 BBzo
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 48/96
Lee et al. (2008)
FEM Analysis
5.0I
Lz p
6at1of maximumawith
..
L
BB
4315cos95.0 L
BB
o
at4o max mumaw t B
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 49/96
Terzaghi et al.
(1996)
L
Bo
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 50/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 51/96
zzzIo
0z se E
4.1log4.01)1/(
)/(
BLs
BLs
B
L
E
E
5.3)1/( cBLs qE
dayslog1.0
cree oe
t zS
2
c
cc
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 52/96
81 Foundation and 92 Plate Load Tests
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 53/96
81 Foundation and 92 Plate Load Tests
L d S l C
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 54/96
Load‐Settlement Curve
Based on Pressuremeter TestBriaud (2007)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 55/96
Pressuremeter Test
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 56/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 57/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 58/96
],,,[ (mean))/( p f f f f q pd eBL
24.0
R
R
B
Se
functiongamma
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 59/96
SHAPE FACTOR
L
B
f BL 2.08.0)/(
ECCENTRICITY FACTOR
B
e f e Center33.01
eBe f e Edg1
0.5
LOAD INCLINATION FACTOR
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 60/96
LOAD INCLINATION FACTOR
Center90
(deg)1
2
f
Edge(deg)15.0
f
slope1:318.01.0
d f d
15.0
d
,B
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 61/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 62/96
ong‐term sett ement, nc u ng creep =
03.0t
1 t Se
t = design life (in hours)
1 =
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 63/96
L1 ‐ L2 Method
167 Axial compression field load tests
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 64/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 65/96
e(L1) = .
=
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 66/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 67/96
Se
68.169.02
SB
Q
Q
eL
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 68/96
=
≤ m
2
qu
uL Q
BQ
theorysVesic'of portionu NQ
theorysVesic'of portionqqu NQ
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 69/96
Note: Vesic’s theory includes compressibility factor. So
),,,,( BE f Q su
s .
CATEGORY C
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 70/96
Use of Theory of Elasticity andModulus of Elasticit
2 f s
s
soe II
E BqS )(
E s = average modulus of elasticity (z = 0 to z = 4B)
B‘ = B/2
s = Poisson’s ratio
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 71/96
Steinbrenner (1934)
Is = shape factor = f (m, n)
For Se at the center : = 4
B
Lm
B
Hn
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 72/96
Fox 1948
and,factordepth s f
f B
L
B
D f I
center)(flexible,(rigid) 93.0 ee SS
Variation of I f
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 73/96
D f /BL /B
1.0 2.0 5.0
’ s = .
0.20
0.40
0.902
0.808
0.930
0.857
0.951
0.899
.
0.80
1.00
.
0.687
0.650
.
0.747
0.709
.
0.813
0.780
. . . .
Poisson’s ratio s = 0.40
0.20 0.932 0.955 0.970
0.40
0.600.80
0.848
0.7790.727
0.893
0.8360.788
0.927
0.8860.849
.
2.00
.
0.596
.
0.640
.
0.714
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 74/96
zE E i ss )( average,Weighted
,
s = 60
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 75/96
Mayne and Poulos (1999)
os zk E E
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 76/96
)1( 2s
E RGee
IIIBqS
o
HE ,ac orn uence
BBk ee
G
factorcorrectionrigidityfoundation
IR
5.04 BL
e
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 77/96
24
3 f
R
t E
I
2
.ee
oBk
BE
1
1E I
6.14.022.1exp5.3
f
e
s D
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 78/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 79/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 80/96
Berardi and Lancellotta (1991)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 81/96
s
seE
qBIS
Is = influence factor for a rigid foundation (μs
= 0.15)
(Tsytovich, 1951)
H 1 /B
. . . .
1 0.35 0.56 0.63 0.69
3
.
0.40
.
0.67
.
0.81
.
0.96
10
.
0.42
.
0.71
.
0.89
.
1.06
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 82/96
Berardi and Lancellotta (1991) re‐analyzed field
erformance of 130 structures on redominantl
silica sand as reported by Burland and Burbidge
1963)(Janbu, 5.0
5.0
oaE s
p
pK E
pa = a mosp er c pressure
at a depth B/2 below the foundation ando
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 83/96
npenetratiostandardcorrectedaverage601 Nzonen uencet ennum er
H15 = (1.2 to 2.8)B
25 = . o .
Influence zone for L B ≥ 10:
H15 (1.8 to 2.4)B
. .
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 84/96
Skempton (1986)
2
01.01
2
60601
o
mnso
602601
r D
N
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 85/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 86/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 87/96
P d f C l l i SE ( d)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 88/96
Procedure for Calculating SE (continued)
6. Determine
Is..
calculate Se.
. e . e 9. If so, the calculated Se in Step 7 is the answer.
. , e E .
11. Repeat Steps 5, 7 and 8 until the assumed and
e .
Settlement Prediction in Granular Soils
―
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 89/96
ro a s c pproacSivakugan and Johnson (2004), Geotechnique, Vol. 54,
‐
Predicted Settlement – 25 mm
Probability of
exceeding 25 mm
Method in the field
Terzaghi & Peck (1948) 0.26 (26%)
Schmertmann (1970)
Burland & Burbidge (1985)
0.27 (27%)
0.42 (42%)
erar ance otta .
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 90/96
1. Meyerhof’s relations (1965) simple to use. On the
average, will give Se(predicted)/Se(observed) 1.5 to 2.0.
2. Peck & Bazaraa method (1969) is not superior to
that of Meyerhof (1965).
3. Burland & Burbidge (1965) is an improved method
over that of Meyerhof (1965) and Peck & Bazaraa
(1969).
Difficult to estimate overconsolidation pressure
from field exploration.
.
S h t t l (1978) T hi t l (1996)
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 91/96
Schmertmann et al. (1978), Terzaghi et al. (1996),
Sal ado 2008 and Lee et al. 2008 will ive
reasonable results with proper values of E s .5. Su ested E relations:
BLs LE 4.1log4.01
)/(
cBLs
BLs
qE 5.3)1/(
)1/(
6. The E s (L/B = 1) relationship can be related to N60 via
50 .
7. Pressuremeter method of develo in load‐
settlement relationship is er effecti e b t ma
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 92/96
settlement relationship is very effective, but may
not be cost effective.
8. L1 – L2 (Akbas and Kulhawy) is a good method.
However proper assumption of E and needed to
estimate QL2.
9. Relationshi s
for
settlement
develo ed
usin
theory of elasticity will give equally good results
provided a realistic E s is used.
Use of iteration method is suggested.
If not, used Terzaghi et al.’s relationship
(1996).
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 93/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 94/96
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 95/96
What we have seen is a systematic
accumu a on o now e ge over years.
The
parameters
for
comparing
settlement
reliability.
Reliability is the probability that the actual
settlement would be less than that computed
by
a
specific
method.
In
choosing
a
method
for
design
it
all
comes
8/6/2019 Elastic Settlement a Critical Review
http://slidepdf.com/reader/full/elastic-settlement-a-critical-review 96/96
In choosing a method for design, it all comesdown to keeping a critical balance between
,
at times, knowing the non‐homogeneous
nature of soil in eneral. We cannot be over‐
conservative but, at the same time, not be
accurate.
We need to keep in mind what Karl Terzaghi
sa n e ames orres ec ure a e
Institute of Civil Engineers in London: “
‘an act of God’.”