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Deep excavation for the new Central Library of LisbonExcavation profonde pour la construction de la nouvelle Bibliothèque Central de Lisbonne

A. Pinto, A. Pereira & M. Villar (Paper number 206)

Alexandre Pinto,

apinto@jetsj.pt

Ana Pereira,

apereira@jetsj.pt

43,80(floor 0)

A 40 m deep excavation was performed for the construction of the new Central Library and Municipal Archive of Lisbon.

Geology:

ZG3 - Heterogeneous fills with thickness varying between 1,5 and 20m, with the major thickness at South - West, close to Álvares Fagundes St;

ZG2 - Miocene sands and clays with fossils, with NSPT values under 60 and a maximum thickness of 19m;

ZG1 - Sands, clays and loam limestones with NSPT values over 60.

Conditions:

- The building could not support the earth pressures caused by the differences of the ground level (30m) at both longitudinal sides of the site (South-West and North-East).

- Streets, services and structures nearby the construction site

- Executive difficulties caused by the topography of the site.

Example of the displacements of the retaining wall in the direction normal to the wall obtained from inclinometer I3 (located in the South-West side).Positive displacements are those occurring towards the excavation.

Plan view of the excavation

Site before excavation

Cross section A-A

Cross section of the South-West side

Cross section of the North-West side

Example of results of staticnumerical calculation for the

South-West retaining wall

Example of results of pseudo-static numerical calculation(seismic coefficient (β) = 0.1) for the South-West retaining wall

South-West side view

Final Excavation (40m depth maximum)

Location of the monitoring equipments

Adopted solutions for the South-West side (maximum excavation depth is 40m, includind 20m of fills):

- Bored pile wall supported by 10 levels of permanent anchors. Jet-grouting columns was performed for protect the soil between the piles in the depth of ZG2 and ZG3. Reinforced shotcrete was used in ZG1.

Adopted solutions for the North-West side:

- Bored pile wall supported by 4 levels of temporary anchors bellow floor 0 with shotcrete to protect the soil between piles.

- Slope stabilization using jet-grouting columns above floor 0, in the depth of ZG3, supported by temporary anchors.

Considering the depth of the excavation (H=40m), the obtained displacements were small (∆h/H = 0.012/40 = 0.03%) and in general lesser than the design prediction.

Measurements were performed the day after each excavation phase

Displacements (mm)

Dep

th (

m)

A

D

C

F

E

36. 65

36.3 0

35.7 5

36.52

33.9 5

34.7 5

33 .43

34.7 6

33.2 2

64.5765 .36

65. 80

66.7 5

37 .02

36.8 5

37 .65

R

M

MMM M

1.00

R

R

M

MMMM

2.00

M M

R

2 xHEB22

0

2xHEB2 40

2 colun as Jet-G routing

Ø12 00 //1.0m2 colun as Jet-Grouting Ø1200 //1.0m

FA

3

2xHEB22 02 xHEB12

0

2xHEB1

20

BE1 BE2 BE3

AB

1A

B2

AB

3A

B4

A

B5

FA

3

FA

2F

A2

FA

1F

A1

Rua do Bar

Rua A

lvare

s Fag

unde

s

Rua Barao de Monte Pedral

Rua Barão M

onte Pedral

2 x 3 colun as Jet-Grouti ng Ø1200 //1.0m c/7 .5m

FA

4F

A4

EF

2 E

F3

EF

4E

F1

EF

2

EF

1

26.8

1

Pav

imen

to T

érre

o(e

=0.1

5)

Ens

olei

ram

ento

Ger

al(h

=1.6

0)

FUN

DAÇÃ

O

26.8

1

Pav

imen

to T

érre

o

(e=0

.15)

Ens

olei

ram

ento

Ger

al

(h=1

.60)

FUN

DAÇÃ

O

2xHEB2

2 0

2xHEB120

2xHEB120

B

Mín.1.00

AB

1A

B2

AB

3A

B4

AB

5

25.0

6

Cot

a de

fund

o da

esc

avaç

ão

Contrafortes(Ver proj ecto de Estabi lidade )

3 colu nas Jet-Grouting Ø120 0 //1 .2m co m 6.0m

3 colun as Jet-Grouting Ø1200 //1.2m com 6.0m

3 colun as Jet-Grouting Ø1200 //1.2m com 6.0m

3 coluna s Jet-Grouting Ø1200 //1.2m com 6.0m

3 colun as Jet-Grouting Ø1200 //1 .2m com 6.0m

Topographic Mark

Topographic Mark

Anchor Load Cells

Topographic Targets

Inclinometers

N

Topographic Mark

Topographic Mark

Anchor Load Cells

Topographic Targets

Inclinometers

I3

MZG2

ZG3

ZG1

Temporary anchors

Jet grouting columns

φ1,2m//1,2m

Concrete Beams

Bored Pile Wall φ0,8m//1,5m

25,06

43,80(floor 0)

66,08 (floor 5)

Micropiles1

2

1

2

56,00

ZG1

ZG2

Aterros

Te

ch

nic

al G

alle

ry

ZG3

BuildingÁlvares

Fagundes St.

Permanent Anchors

Bored Pile wall φ1,0m//1,3m

43,80

25,06

66,08(floor 5)

Static Horizontal Displacements [mm]

Deformed MeshDeformed Mesh

Pseudo-Static Horizontal Displacements [mm]