ZEEBRUGGE GAS TERMINAL ZEEBRUGGE - BELGIUM Construction of a circular shaft to take a gas reservoir A s part of the extension project at the Zeebrugge gas terminal, Fontec, the Belgian subsidiary of Solétanche Bachy, was awarded the contract for the diaphragm wall works for a Liquid Natural Gas reservoir. Solétanche Bachy carried out the work as the lead contractor in partnership with Technigaz and MBG working under a design and build contract. The reservoir is a shaft with an internal diameter of 90.50m and a storage capacity of 140,000m 3 . The other three Large shaft Circular diaphragm wall A507 CLIENT: FLUXYS LNG N.V SUPERVISING ENGINEER: FLUXYS LNG-TRACTEBEL CONTRACTORS: TECHNIGAZ - FONTEC - MBG DURATION OF THE DIAPHRAGM WALL WORKS: OCTOBER 2004 TO FEBRUARY 2005 MAIN QUANTITIES : • Diaphragm wall: 11,300m 2 • Diaphragm wall depth: 39,5m • Earthmoving: 166,000m 3 • Reservoir storage capacity: 140,000m 3 Overview of the terminal
Construction of a circular shaft to take a gas reservoir
A s part of the extensionproject at the Zeebruggegas terminal,
Fontec,the Belgian subsidiary ofSoltanche Bachy, was awardedthe
contract for the diaphragmwall works for a Liquid NaturalGas
reservoir. Soltanche Bachycarried out the work as the
leadcontractor in partnership withTechnigaz and MBG workingunder a
design and buildcontract.
The reservoir is a shaft with aninternal diameter of 90.50mand a
storage capacity of140,000m3. The other three
Large shaftCircular diaphragm wall
A507
CLIENT: FLUXYS LNG N.VSUPERVISING ENGINEER: FLUXYS
LNG-TRACTEBELCONTRACTORS: TECHNIGAZ - FONTEC - MBGDURATION OF THE
DIAPHRAGM WALL WORKS: OCTOBER 2004 TO FEBRUARY 2005
reservoirs were constructed bySoltanche Bachy in 1982 using
a1,5m thick diaphragm wall and a800mm thick inner wall. Advances
indesign methodology made possible alighter structural solution for
thisnew reservoir : it uses a 1.20m thickdiaphragm wall down to a
depth of39.50m, with an excavated depth of25m (in part of 28m)
.
As the project is located on a gasstorage site, particular
attention waspaid to safety and procedures weretightened as a
consequence. There were further challengingrequirements: a minimum
concretestrength of 40MPa was needed tomeet the calculated stress
levels inthe arch form wall. This, in turn was
dependent on a 0.5% verticalitytolerance and perfect wall
continuitybetween panels. These requirementsgave rise to a need for
increasedquality control to monitor the workson a continuous and
daily basis.
The walls were constructed using aKS3/2 steerable hydraulic grab
and amechanical grab, both equipped withvertical alignment
recording systems.The circular diaphragm wall construc-tion
comprised 43 panels measuring6.68m in length and 39.5m in depth(the
walls developed length along thecircular wall axis = 287m). The
exca-vation of the diaphragm walls passedthrough fill, clayey sand
and compactsand with a 3m minimum embedmentinto clay.
EarthmovingConstruction of the diaphragm wall
Overview of the terminal 3D study of movement as the diaphragm
wall buckles
CWS joints (stop end with waterstop)were used for the connection
betweenpanels. Vertical alignment, includingany twisting, was very
closely monito-red in order to ensure good circularwall continuity.
Once the diaphragm wall had beencompleted, the construction of
theconcrete capping beam was commen-ced, followed by bulk
excavation insi-de the wall. Nine inclinometer tubes and 24
straingauges were integrated into the wallfor the purpose of
monitoring itsbehaviour during the bulk excavationinside the shaft
and during construc-tion of the LNG tank.
