2D/3Danalysis of soldier pile wall(„Berlin”type

2D / 3D analysis of
soldier pile wall („Berlin” type).
Case study of a disaster
Aleksander Urbański (aurbansk@pk.edu.pl)
Michał Grodecki
Cracow University of Technology

Soldier wall („Berlin” type). Phases of construction
steel
tube
soft fill
concrete
insertion of steel profile
gradual excavation and lining
anchoring
- optional

a (=2.5m)
Problem:
Deformation and stability
of the system
depends mainly on the
bearing capacity of the
ground surrounding piles
loaded with large horizontal
forces
How to deal in ZSoil with generic 3D periodic structure in
2D (plane strain) model, not loosing its essential 3D features?

Idea of modeling in ZSoil :
� 2D (plane strain, M-C) continuum+beam system
� fictitious e-p connectors
g = 1m
3 zones
on depth
h1
h2
h3
e
k+
L
k-
connectorselasto-plastic
truss,
properties
from 3D problem:
A , E , f ,
σ
C
t
f
c
ε

Subsidiary 3D problem
�one layer of B8 el.
�M-C model
�displacement control
�large deformation
�contact (in large def.)
loads:
h
γ ⋅ h
t
a
2
h0
U
z
x
X
R ( ) X U X
y
U
E,
ν , c',
φ'
( h + h)
γ ⋅ 0
sought function
and its aprox.:
RMAX
MAX
U
X

Subsidiary 3D problem
R
X ( X U
Functions for:
� 3 different depth
� 2 directions + / -
)
h=1.5m, k.-
h=0.5m,k.h=2.5m,k.- h=0.5m, k.+
h=1.5m, k.+
a/2
+
t
charakte rystyki Rx-Ux
k- ! k+
3
2
1
h=2.5m, k.+
0
Ux [m]
-0.15 -0.1 -0.05 0 0.05 0.1 0.15
-1
-2
-3
-4
Rx [kN]
U X RX
-

Identifaction of connectorsas
elasto-plastic truss el.,
from 3D problem:
averaged lateral stresses in t*a:
q
R =
( U )
X
=
2 ⋅ 2 ⋅ RX
t ⋅ a
( U )
static equivalency:
force in truss = force in section e*g:
tensile / compressive strength:
X
truss el. stiffness:
R
X
( U )
X
X
σ ⋅
q
U
qMAX
MAX
A = q ⋅e
⋅
g
U
± ft ⎫ qMAX
⋅e
⋅ g
⎬ =
fc
⎭ A
qMAX
⋅ e ⋅ g ⋅
A⋅
EC
=
U
MAX
X
L

Section I
5kN/m 2
soil (c’=8kPa,φ‘=22 o )
frictional interface μ=0.158
silt(c’=30kPa,φ‘=18 o ,E=10kPa)
no-friction interface
concrete
initial state,
before excavation,
connectors
IPE 360 , a=2.5m
IPE 360+pile CFA d=0.5m

Section I
unloading f.
excavation -
4.8m
raft 0.7m
added „after”
struts
HEA 160 a=2.5m
foundation
additional
connector

Section I
ux=0.2909m (0.32)
ux =0.3466m (0.21-0.41)
(measured)
SF=1.012

Section I
SF=1.012.
bending moments in structural el. (IPE 360)
148.2 kNm
phase 5:
SF=1.0
216.0 kNm
SF=1.26

Section II
5kN/m 2
soil (c’=8kPa, φ‘=22 o )
silt(c’=30kPa,φ‘=18 o )
no-friction interface
initial state,
before 1–st phaze of excavation
piles CFA d=0.5 m

Section II
1 phase of
excavation 2 phase of
excavation
unloading f.
struts
HEA 160 a=2.5 m raft 0.7m

Section II
M MAX=57.0kNm/1pile
M MAX =138.9kNm/IPE360
ux=0.6768m (measured 0.645 m)
ux=0.3794m
SF=1.007
-

Section III
5kN/m2 63kN/m
SF =1.55 2
2.5
connectors
1.0
excavation –4.80
IPN 360 a=2.5m
IPN 360 +CFA a=2.5m
support
HEA 160 2.5m
raft 0.7m
| u | ≅
0.
002m
SF=1.55

Averaged horizontal soil pressures
h [m]
-60 -40 -20 0 20 40
q [kPa]
h [m]
Section I
Section II
bearing capacity
-60 -40 -20 0 20 40
q [kPa]
h [m]
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Section III
qmax=3.0kPa
-0.5 0 0.5 1 1.5 2 2.5 3 3.5
q [kPa]

Conclusions
� Limit state was achevied (s.I and II) by unsupported soldier
pile wall, causing excessive displacements. In s. III safety was
assured. Undertaken measures prove to be satisfactory.
� Mixed 2D/3D method was fast and accurate enough,
in this practical case, for:
�explaining observed phenomena (failure mechanism)
�assessment of stability of the system (safety factors)
�prediction of displacement (~5% accuracy )
More research needed to generalize
Thank you for your attention