SPECIAL WORKS REGARDING THE METRO LINE CONSTRUCTION..

The followings techniques have been used:

• Diaphragm wall, anchors, and shotcrete: execution of 4 stations and 5 ventilations.
• .Grouting for the consolidation of 1600 m section of soils, before excavation of the tunnel.

This site is an important evolution in the management of the grouting technic. This page is dedicated to the grouting works only.

Géology:

• On a 1300 m section length: sand, alterated shale and shale.
• On a 300 m section lenght: mass of fallen rocks (Boulders & sand).

This grouting work site is one of the first to use electronic devices and computers to manage the design, the follow up and the analysis.

• .The whole grouting design was made by the "CASTAUR" program (Soletanche),drawing automatically the drillholes, taking in account the following parameters:
  • the specificatiions
  • the caracteristics of the drilling rigs
  • the locations
  • the geology
  • the existing services
• Daily follow up of the quantities allowing:
  • Establishment of a daily report of the quantities for the client , few hours only after the end of the shift.
  • Daily stastistics of the progress
• Daily controls of used products and follow up of the stocks.
• .A quick interpretation of the geology from the results of the drilling parameters records, allowing the adaptation of the grouting treatment.
• Improvement of the production by the rapidity the electronic and computer.
• The possibility to manage the grouting with local Engineers, without any knowledge of this technique,.
• The organisation of a centralized management allowing a homogeneity of the grouting principles (grouting organisation).

Grouting.

Principles

• All works from the surface (Tunnel depth: between 20 and 45 m).
• Grouting using sleeved pipes (Tubes à machettes) of 0,33 m.
• Drillholes by group, in fan-shaped, in a vertical plan, with a maximum space between drillhole of 1,20 m
• Space between group: 1,20 m.
• Définition of the treatment:
  • future tunnel volume + a peripherical cylinder of 3,00m
  • Sands and alterated shales only.
• Cement bentonite grout.
• Variable proportion of Hard gel (relative to the soils).

Chronology of the works:

• Soil investigation by drilling parameters recording .
  • One drillhole each 5,00 m.
• Investigation by 1,50 m depth trench, to locate existing services (water, sewage and gaz pipes, electrical and telephone cables)
  • At each group of drillholes (every 1,20 m).
• .Definition of the treatment by "the grouting organisation", taking in account the soil and trench investigations:
  • Arrangement and depth of the grouting drillholes.
  • Length of smooth and sleeved pipes (TAM), for each hole).
  • Grouting instructions for each sleeve (section of 0,33m) with the following:
    • Maximum pressure
    • Maximum grouting flow rate.
    • maximum quantity.
    • mix grout type.
• Drilling and pipe equipment for each hole.
• After 7 days grouting of the cement bentonite phase.
• 7 days after this phase grouting of the hard gel phase.
• Daily analysis by the "grouting organisation", of the grouting parameters of each sleeve. This analysis can have the following consequencies:
  • The grouting can be considered satisfactory
  • Full revision of the grouting instructions
  • Decide a new grouting phase on the consiterated sleeve..
  • Drill new hole.

On the whole 95% of the works suceed. However the following facts have to be noted:

• Important deviations for drillholes longer than 45 m depth. This fact occured in the last 30 meters of the tunnel. It was necessary to proceed a new grouting with new instructions with changes:
  • space between holes
  • maximum grouting pressure
• Effect of the soil on the grouted mixes:
  • .Some components of the hard gel mix are affected by a type of soil bacterias and the the hard gel is not setting