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Injection walls

Porous soil can be injected with a mixture of water glass (sodium silicate) and a hardener (sodium aluminate). This is done at a relatively low injection pressure. This glues soil grains together to create a solid, stony mass. By injecting overlapping columns, walls can be formed with constructive properties. Injection lances are first inserted to the desired depth using cement/bentonite mixture. The grid, injection speed and injection order all determine the end result. An optimum balance must be sought between the number of injection location and the quantity of injection liquid. After hardening of the cement/bentonite mixture, injection can be performed through the openings in the injection lances. Depending on the available equipment and the location of the injection location, injection is performed simultaneously at multiple injection locations. Injection is performed in accordance with a pre-planned injection schedule, determining the quantity to be pumped at each point and the order of injection. In the control room the progress of injection at each location is registered and presented in a graph.

Application

This technique can only be used for porous soil. The walls are used as:

  • Soil- and water-retaining structures underneath existing adjacent structures to excavate building pits abutting these structures.
  • Soil-retaining structures underneath existing abutments of viaducts and bridges.
  • Soil- and water-retaining structures in confined spaces.
  • Upholding existing buildings.

Ambient factors

  • The technique is vibration-free and low-noise.
  • No soil produced.
  • Limited footprint.

Pros and Cons

  • The soil must be homogeneous and porous, as determined by means of a thorough soil investigation comprising of at least laboratory tests of unmixed samples and cone penetration tests.
  • The irregular shapes of the injection masses must be taken into account

Applicated

Name of project

Client

Leidschenveen, Autobustunnel  Adotunnel 

BAM

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