with a Frozen Crust

plantcitybusinessUrban and Civil

Nov 26, 2013 (3 years and 6 months ago)

93 views

Abstract

3
-
D Dynamic Base Shaking Model

Conclusion

Introduction

References

2
-
D Static BNWF Pushover Model

The

BNWF

(Beam

on

Nonlinear

Winker

Foundation)

Pushover

method

is

a

simplified

approach

to

analyzing

piles

in

laterally

spreading

ground,

which

has

the

potential

to

serve

as

a

practical

tool

for

engineers
.

Using

BNWF,

a

model

for

frozen

soil

were

developed

and

implemented

into

OpenSees
.

Summary
:

A

3
-
D

Finite

Element

simulation

of

a

single

bridge

pile

embedded

in

liquefiable

soils

overlain

by

a

frozen

crust

was

carried

out

using

OpenSees
.

The

BNWF

Pushover

method

was

used

to

evaluate

the

pile

performance

with

a

newly

developed

frozen

soil

p
-
y

curve
.

The

simplified

BNWF

model

generated

accurate

results

and

can

be

used

to

develop

guidelines

for

engineers
.

Time

histories

recorded

during

the

2002

Denali

earthquake

at

Trans
-
Alaska

Pipeline

System

Pump

Station

#
10

were

input

at

the

base

in

X

direction
.

The

record

has

an

82

second

duration

and

peak

acceleration

of

0
.
3
g
.

P
-
y,

t
-
z

and

q
-
z

springs

were

used

to

represent

soil

lateral

behavior,

friction

in

soil
-
pile

interface,

and

end
-
bearing

capacity,

respectively
.


Displacement

was

imposed

on

a

frozen

crust

spring
.

(
Brandenberg

et

al
.

2007
;

OpenSees

Example

Page)

for y<=
y
u


To

approximate

liquefaction

effects

on

p
-
y

behavior

one

must

apply

a

p
-
multiplier

to

drained

p
-
y

resistance
.

A

p
-
y

curve

for

frozen

silt

was

proposed

based

on

the

p
-
y

curve

model

for

weak

rock

(Reese,

1997
)

and

clay

(Matlock,

1970
)

and

calibrated

by

field

test

data

(Li,

2011
)
.

This

was

used

in

a

2
-
D

Static

BNWF

Pushover

Model
.


3
/
1
2









m
u
y
y
p
p
u
p
p

)
25
.
0
5
.
1
(
b
x
b
q
p
r
u
u


b
q
p
u
u
5
.
4

for y
>
y
u


for
0

x
r

2b

for
x
r
>12b

b
k
y
m
m

A frozen soil p
-
y model was proposed based on
an experiment
conducted in Fairbanks, Alaska
.

In

March

1964
,

Alaska

experienced

one

of

the

largest

earthquakes

in

recorded

history
.

In

November

2002
,

the

Denali

Earthquake

struck

Interior

Alaska
.

These

two

winter

earthquakes

caused

extensive

ground

failure

and

structural

damage,

including

substantial

damage

to

bridges
.

Alaska’s

population

has

increased

from

226
,
167

in

1960

to

710
,
231

in

2010

(
2010

Census),

making

t
he

topic

of

potential

earthquake

damage

more

important

than

ever
.

Brandenberg

S

J
.

and

Boulanger

R

W
.

(
2007
)
.

"Static

Pushover

Analyses

of

Pile

Groups

in

Liquefied

and

Laterally

Spreading

Ground

in

Centrifuge

Tests
.
"

Journal

of

Geotechnical

and

Geoenvironmental

Engineering

133
:

9
.

OpenSees

Example

Page,

http
:
//opensees
.
berkeley
.
edu/wiki/index
.
php/Laterally
-
Loaded_Pile_Foundation,

Retrieved

on

2011
-
05
-
01
.

Reese,

L
.

C
.

(
1997
)
.

"Analysis

of

laterally

loaded

piles

in

weak

rock
.
"

Journal

of

Geotechnical

and

Geoenvironmental

Engineering

123
:

1010
-
1017
.

Matlock,

H
.

(
1970
)
.

"Correlations

of

design

of

laterally

loaded

piles

in

soft

clay
.
"

Proc
.
,

Offshore

Technology

Conf
.

1
:

577

594
.

“Resident

Population

Data



2010

Census”

(
2010
.
)

http
:
//www
.
c
ensus
.
gov
.

Retrieved

on

2011
-
05
-
29
.








Liquefaction

and

associated

ground

failures

are

common

in

major

earthquakes

in

Alaska

and

have

caused

extensive

infrastructure

damage
.

To

model

ground

failures

in

cold

regions

and

their

effects

on

infrastructure,

it

is

necessary

to

account

for

frozen

ground

crusts,

which

have

drastically

different

physical

properties

(including

stiffness,

shear

strength

and

permeability)

than

unfrozen

ground
.

How

can

we

predict

the

impact

to

a

bridge

pile

foundation

when

there

is

a

frozen

ground

crust

that

is

resting

on

top

of

the

liquefied

soil
?

Numerical

simulations

were

used

to

address

this

issue
.

A

simplified

method

to

account

for

frozen

crust

was

developed

and

evaluated
.

Depth

(m)

Soil

Type

Status

Mass
density

(kg/m
3
)

Shear
wave
velocity,
V
S

(m/s)

Permeabili
ty

(m/s)

Friction
Angle

(deg)

Cohesio
n (
kPa
)

0
-
0.2

Silt

Frozen

1.8x10
3

500

1.0 x10
-
8

27

100

Unfrozen

200

1.0 x10
-
7

33

0

0.2
-
1.8

Silt

Frozen

1.8x10
3

1,000

1.0 x10
-
9

27

100

Unfrozen

200

1.0 x10
-
7

33

0

1.8
-
2.0

Silt

Frozen

1.8x10
3

500

1.0 x10
-
8

27

100

Unfrozen

200

1.0 x10
-
7

33

0

2.0
-
8.0

Loose

Sand

Unfrozen

1.9x10
3

180

6.6 x10
-
5

29

0

8.0
-
14.0

Medium

Dense Sand

Unfrozen

1.9x10
3

200

6.6 x10
-
5

37

0

14.0
-
24.0

Dense

Sand

Unfrozen

2.1x10
3

250

6.6 x10
-
5

40

0

Damage from the 1964 Alaska Earthquake

The

Open

System

for

Earthquake

Engineering

Simulation

platform

(OpenSees)

was

used

to

conduct

pile
-
soil

interaction

analyses
.

Based

on

general

Alaska

soil

conditions,

an

idealized

soil

profile

with

an

embedded

pile

and

a

surface

inclination

angle

of

3
°

was

used
.

A

reinforced

concrete
-
filled

steel
-
pipe

pile,

commonly

used

in

constructing

Alaskan

highway

bridge

foundations,

was

chosen

for

study
.


-0.4
-0.2
0
0.2
0.4
0.6
Deflection, (m)
Frozen Crust
Loose Sand
Medium
Dense Sand
Dense
Sand
-0.4
-0.2
0
0.2
0.4
0.6
-20
-15
-10
-5
0
5
Frozen Crust
Loose Sand
Medium
Dense Sand
Dense
Sand
Depth (m)
0 sec
10 sec
20 sec
30 sec
40 sec
50 sec
60 sec
70 sec
82 sec
BNWF model
3D model
-4
-2
0
2
4
6
-20
-15
-10
-5
0
5
Shear Force (kN, x10
3
)
Loose Sand
Frozen Crust
Medium
Dense Sand
Dense
Sand
-4
-2
0
2
4
6
-20
-15
-10
-5
0
5
Depth, (m)
x10
3
Frozen Crust
Loose Sand
Medium
Dense Sand
Dense
Sand
0 sec
10 sec
20 sec
30 sec
40 sec
50 sec
60 sec
70 sec
82 sec
3D model
BNWF model
-10
-8
-6
-4
-2
0
2
4
6
8
10
Medium
Dense Sand
Loose Sand
Frozen Crust
-10
-8
-6
-4
-2
0
2
4
6
8
10
-20
-15
-10
-5
0
5
Bending Moment (kN-m, x10
3
)
Frozen Crust
Loose Sand
Medium
Dense Sand
Dense
Sand
Depth, m


0 sec
10 sec
20 sec
30 sec
40 sec
50 sec
60 sec
70 sec
82 sec
3D model
BNWF model
These figures are
comparisons of pile
performance
evaluated from both
models. The graphs
on the left were
obtained from 3
-
D
modeling, the ones
on the right from a
BNWF process (the
final step in a
Pushover analysis.)
As can be seen, the
simplified method
provides accurate
data and has the
potential to be used
in design practices.

Acknowledgement
:

This

research

was

supported

from

Alaska

EPSCoR

NSF

award

#EPS
-
07011898
.


22
nd

National

NSF

EPSCoR

Conference,

Coeur

d’Alene,

Idaho

October

24
-
27
,

2011
.

Theme
:

Water/Environment
.

Represented

Theme
:
:

This

poster

is

entered

in

the

Water/Environment,

as

it

deals

with

naturally

occurrence

elements

and

processes

(i
.
e
.

frozen

soil

and

earthquakes
.
)

Analysis of Laterally Loaded Piles in Liquefiable Soils
with a Frozen Crust

Xiaoyu Zhang
1
, Zhaohui (Joey)Yang
, Ph.D.
1

1. Dept. of Civil Engineering, University of Alaska Anchorage, Anchorage, Alaska