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Successful first use of compensation grouting for Soletanche Polska in Łódź!

As part of the construction of a new underground railway line in Łódź, our subsidiary Soletanche Polska carried out successfully its first compensation grouting project to ensure the safe passage of a TBM under historic residential areas.


Compensation grouting is not a very commonly used technology in Poland. Underground tunnels are designed to pass under existing streets, but rarely under buildings.

The construction of the new underground railway network in Łódź, which will connect the two stations Łódź Kaliska and Łódź Fabryczna, is particularly complex: it includes the completion of the cross city tunnel, built with a TBM under a residential area.

Soletanche Polska was mobilized to stabilize the ground and reduce settlement of the houses located directly above the tunnel under construction. For the first time in its history, our BU used compensation grouting. This technology involves injecting a cement slurry into the ground to fill voids and cavities in the native soil.

After a thorough preparation, including boreholes drilling, injection rods installation, and testing pre-injection phase, the Soletanche Polska teams proceeded with the final phase of active grouting, which was carried out while the TBM machine was working on a particular section of the work. The work consisted in observing the passage of the tunnel boring machine and the displacement of the surrounding buildings. If subsidence occurred, grout was injected to stabilize the soil.

A precise observation method

The observational method was used: the compensation grouting was performed based on the displacement of the building recorded by a continuous geodetic monitoring system carried out by Sixense Polska. Control over the performed injection was exercised based on specialized GROUT IT® software (which includes SPHINX for design and management of injection parameters with analysis of results and SPICE for computerized pump control and automatic data recording).

This computerized control allowed real-time observation of parameters, pressure checks and preparation of daily reports, which helped to make decisions to start injection in a particular area.

Temporary shafts

As a result, active grouting phase was carried out 24/7 in two working shifts. For safety reasons and the specifics of the work, the injections were carried out from a temporary 12.0 m diameter shaft located as close as possible to the buildings.

Congratulations to all the teams involved in this first for Soletanche Polska!

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