Adam CS Sandwich wall presentation Sept 2002

VOF Stationseiland is een samenwerkingsverband van

ARCADIS Infra en Holland Railconsult

Sandwich wallunderneath

Amsterdam Central Station

Dr Mazin Alhamrany



Presentation topics

• Introduction and geotechnical longitudinal section;

• Requirements and construction method;

• The composite wall under the Station building;

• Risk profile and position VOF;

• Questions.



Old open port front

Artificial island

The IJ

Track of new

metro line

A bird’s-eye view of the island with Amsterdam Central Station



Longitudinal section of the existing StationStationbuilding Rail-road tracks



Requirements for the building pit

• Minimize disruption to the train operations during construction;

• Minimize inconvenience to the passengers during construction;

• Limit the damage to the existing structures, especially the station building, which is a listed “monumental” building.



The construction method

Various solutions have been considered (10 different preliminary designs)

The adopted solution:

• Make a covered trench underneath the station, filled with water and connected to the waterway (the IJ) behind the station;

• Float in a tunnel element and submerge this in the trench.



The construction process









The final result



Vertical

force

Horizontal force

Forces on the composite wall



Steel Tubex piles with rings

The Sandwich wall elementsJetgrout columns



The principle of the Sandwich composite wall

Shearforce by steel rings

Compression (Steel Tubex pile + Jet Grout)

Tension (Steel Tubex pile)



Specific topics of the trench

x

Floor plan with trench walls

Trench

Jetgrout solid

Screwed steel tubesIsometric view

2.5 m



A

A A

A A A AA AA AA A

A A

The Serviceability Limit State has been calculated with PLAXIS

Horizontal deflection approx.

15 mm.

Excavation

approx. 20 m



Example of the predicted vertical deformations of the building

60

30

40

50

0

10

20

Totaal

Installatie Tubex palen

Puntzakking wand/paal

El verkorting wand/paal

Zakking agv doorbuigen wand

Achtergrondzetting Eemklei

Doorbuiging prim ligger



The pile-driving machine (Top-drill)



Jetgrout columns



Risk profileRisk / fail Consequence Cause

Constructive •Large deformation of the wall

•Groutstrength too low•Inadequate fastening with Tubexpiles•Missing large groutvolumes

Impermeability •Groundwater lowering outside the pit•Groundwater lowering inside the pit not controllable

•Inadequate overlap between Tubex - jetgrout•Inadequate overlap between grout columns

Compactness of the ground

•See impermeability•Earth movement

•See impermeability



Control risk jetgrouting

• Perform of jetgrout test including recommendations;

• Use observation method (anticipate) testconclusions with regards to geometrie and strength;

• Perform probabilistic analyse GeoDelft;

• Perform leakdetection (Texplor) and dewatering test.



Position VOF

• Strength jetgrout is not regarded as a dominant risk;

• Local diameter deviations are compensated through the strength of the design;

• Structural deviations in diameter which does not comply with the requirements constitute the biggest risk, this must be all time checked.



Questions?

Documents

Adam CS Sandwich wall presentation Sept 2002