Settlement prediction of a pile foundation for bridge abutment · Settlement prediction of a pile foundation for a bridge abutment Rafal Obrzud, GeoMod SA 30.08.2013, Lausanne, Switzerland

Settlement prediction of a pile foundation for bridge abutment

A large scale 3D modelling using ZSoil

Rafal OBRZUD

[email protected]

Claude CHAPPUIS

mailto:[email protected]

Settlement prediction of a pile foundation for a bridge abutment

Rafal Obrzud, GeoMod SA

30.08.2013, Lausanne, Switzerland

Project overview

Project: Replacement of the existing bridge with a new one

Junction A9 motorway and N9 road in Villeneuve (Vaud)

Client: Federal Roads Office (CH)

General project manager: IUB Engineering (CH)

Numerical modelling: GeoMod (CH)

FE modelling of a pile foundation for the new bridge

Content




Bridge replacement at A9 motorway in Villeneuve

Existing bridge

Villeneuve

Dents du midi




Existing old overpass at A9 motorway in Villeneuve

Facts: - 2 spans - abutment founded on micropiles




Concept of pile foundation for the new bridge

Single-span deck

Precast concrete elements




Concept of pile foundation for the new bridge




3D FE mesh at initial state

Drainage along the motorway

Abutement of existing bridge

N09

NB. All natural soils were described with the Hardeninig –Soil model with small strain stiffness extension




T=1 Initial state

NB. Weight of existing bridge neglected Soil overconsolidation taken into account Existing micropiles neglected




T=2 Demolition of the upper part of the existing abutment




Shotcrete h = 10cm

NAILS Ø20mm interval=2.0m, length =8.0m

T=3 Demolition of the existing abutment and realisation of 1st row of nails




Shotcrete h = 10cm


T=4 Demolition of the existing abutment and realisation of 2nd row of nails





Shotcrete h = 10cm

T=5 Demolition of the existing abutment and realisation of 3rd row of nails




Bored piles Ø1200mm

L=18m (under footing level)

Bored piles Ø1200mm

L=16m (under footing level)

f = 2.7m

Work platform

Secant piled wall (Ø750mm) ELASTIC SHELLS heq=0.65cm

T=6 Realisation of secant piled wall and bored piles




Anchors: As = 450 mm2

F0 = 100 kN Lf = 11.0 m Lv = 4.0 m Borehole diameter 0.18 mm Interval= 1.3 m

Excavation 1.2m

T=7 1st stage of excavation and installation of anchors




T=8 Excavation down to the bottom of the excavation

Bottom of the excavation




NB. Weightless structural elements because loads related the self-weight were applied at the foundation level

Foundation

Plastic hinge (connection

ensured by NODAL LINK)

T=9 Realisation of the footing and pillars




1st filling subgrade

T=10 Filling inside the excavation




2nd filling subgrade

T=11 Filling inside the excavation




External load applied at the foundation level

T-11.5: Self weigth of the bridge (SLS)

T-12.0 :Traffic load (SLS)

T-13.5: Wind load (SLS)

T-14.0: All loads with ULS security coefficients

Loads at the footing –pillar joint level provided by bridge’s designer (reactions from structural model)




Final backfill

T=13 Final backfilling




Nails Ø20mm e=2.0m, L=8.0m

Secant piled wall (Ø750mm) heq=0.65cm

Bored piles Ø1200mm L = 18.0 m

f = 2.7m in alluvium fluvial

Bored piles Ø1200mm L = 16.0 m

View on structural elements

Anchors: As = 450 mm2

F0 = 100 kN Lf = 11.0 m Lv = 4.0 m Borehole diameter 0.18 mm Interval= 1.3 m







Drainage along the motorway

GWT 1.0m below soil surface

Groud water level at initial state




Pumping below the excavation

1.3m

Groud water level lowering due to pumping




Main results

Excavation stage




X

Y Z

uz = 1.5cm

DT = 8 - 6 Horizontal displacement due to excavation (“average soil parameters” scenario)




Y Z

uz = 3.3cm

DT = 8 - 6 Horizontal displacement due to excavation (“unfavourable parameters” scenario)




X

Y Z

uz = 0.6cm

uz = 1.1cm


with a strut in the middle




Y

un = 3.3cm

un = 2.0cm





X

Y Z

uz = 1.1cm

uz = 0.6cm

Strut






NB. P0=100kN

fc 235MPa

FHEB400 2440kN

AHEB400 19800mm2

FHEB400

AHEB400

123MPa

1.35 166MPa <fc

1.1214MPa






Mmax = 204 kNm / m’

Mmax = -132 kNm / m’

T = 8 Horizontal displacement due to excavation (“unfavourable parameters” scenario)






T = 8 Horizontal displacement due to excavation (“unfavourable parameters” scenario)





Main results

Construction of bridge and external loads stages




DT = 11 – 8 Filling accomplished




DT = 11.5 – 8 Self weigth of the bridge

36




DT = 12 – 8 Traffic load




DT = 13 – 8 Backfilling




DT = 13.5 – 8 Wind load




DT = 14 – 8 Load increment from SLS to ULS level




DT = 11 – 8 Filling accomplished




DT = 11.5 – 8 Self weigth of the bridge








DT = 13 – 8 Backfilling




DT = 13.5 – 8 Wind load




DT = 14 – 8 Load increment from SLS to ULS level








Settlement at the pillars – footing level Settlement [m]

Reali

sati

on

of

foo

tin

g

Filling up to the

motorway level

Self

weig

ht

of

bri

dg

e

Tra

ffic

lo

ad

Realisation of

final

backfilling

Win

d l

oad

Lo

ad

in

cre

men

t fr

om

SL

S t

o U

LS

Min J11

Max J16

J11

J17 J27

0.45cm




Horizontal displacement at the pillars – footing level

[m]

Reali

sati

on

of

foo

tin

g

Filling up to the

motorway level

Self

weig

ht

of

bri

dg

e

Tra

ffic

lo

ad

Realisation of

final

backfilling

Win

d l

oad

Lo

ad

in

cre

men

t fr

om

SL

S t

o U

LS

Min J27

Max J14

J11

J17 J27




Drainage

Pore pressure excess after stopping

pumping

GWT 1.0m below soil surface

T=13.5 Ground water level (all SLS loads applied)




2.0m of ground water lowering

T=13.5 Ground water lowering (all SLS loads applied)




Settlement at the pillars – footing level (GWT lowering scenario for “unfavourable parameters”)

Settlement [m]

Reali

sati

on

of

foo

tin

g

Filling up to the

motorway level

Self

weig

ht

of

bri

dg

e

Tra

ffic

lo

ad

Realisation of

final

backfilling

Win

d l

oad

« D

rou

gh

t » s

cen

ari

o:

2.0

m o

f G

WT

lo

weri

ng

0.65cm




Settlement at the pillars – footing level (overloading scenario)

[m]

Vertical load /

Vertical load ULS [%]

100

200

300

0

Settlement

100 % of

ULS load

200 % of

ULS load




X

Y

Z

Mzmax = 1043 kNm

X’ Y’

Z’

Local axes for piles

Bending moments




X Z

Mymax = 1171 kN

X’ Y’

Z’


Bending moments




X

Y

Z

X’ Y’

Z’


Normal forces




Tymax = 545 kN

X’ Y’

Z’


Shear forces




Summary

Numerical model allowed to account for :

Actual geometry of both, excavation and foundation

Actual subsoil stratigraphy and hydro-geological conditions

Realistic behaviour of soil (HSS)

Earthwork and construction stages

Soil-structure interaction

FE modelling revealed :

Small horizontal displacements at the foundation level

Expected bridge settlements: 1.7 et 2.2cm (3.0cm)

Internal forces in the piles are not excessive




Thank you for your attention

GeoMod® 2013

Documents

Settlement prediction of a pile foundation for bridge abutment · Settlement prediction of a pile foundation for a bridge abutment Rafal Obrzud, GeoMod SA 30.08.2013, Lausanne, Switzerland