Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Deep soil mixing keeps Rotterdam rail tunnel running on time


DEEP SOIL MIXING has been used to combat soft soils on the Botlek rail tunnel project in Rotterdam in the Netherlands.

German contractor Bauer Foundation Engineering, part of the consortium of Ballast Nedam, NGT and Visser & Smit carrying out the ground improvement, suggested using the method instead of a three phase jet grouting process.

The Botlek tunnel runs under the Oude Mass channel in the port of Rotterdam. It replaces a lifting bridge in the harbour and forms part of a Netherlands Railways twin track freight line from Rotterdam to Germany.

Soil improvement was needed on a large section of the tunnel as the alignment runs through saturated soft peat and clay.

Engineer Holland Railconsult's design called for a post treatment stiffness modulus of between 20MPa and 40MPa and a maximum compressive strength of 5MPa.

After successful trials of the wet soil mixing method on site, main contractor BTC awarded the subcontract to the consortium, which began installing 4500, 800mm diameter soil-cement columns up to 23m deep in February this year.

Two fully automated MAT mixing plants and three drilling rigs fitted with mixing tools designed by Bauer were used.

Grout volume, mixing time and rate of penetration were monitored and recorded throughout the work and inclinometers used to check verticality of 10% of the columns. Samples were also taken for laboratory testing.

Soon after the rigs started work, heave occurred. To counteract this and to protect the rail tracks and the numerous services within the harbour, construction speed was adjusted to ground behaviour, which was constantly monitored.

Despite this, work was expected to finish ahead of schedule last month.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.