Difficulties in Jetting Inside a Underground Station in Paris Sand Layers-Video

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Video Summary

The presentation describes jet grouting for the underground section of the Porte Maillot station, part of the RER E extension in Paris. The 225-metre station lies among existing metro lines, an underground car park and historic buildings, with ground comprising marls, limestone and sand. To avoid delaying excavation when groundwater drawdown slowed, jet grouting was carried out from two adjacent galleries. The works involved 351 columns, about 5.5 kilometres of drilling and nearly 3 kilometres of jetting, using a primary-secondary sequence.<br /><br />A major challenge was removing spoil through a long, constrained route shared with other contractors. Unexpected lignite in the spoil absorbed water, making it dry and difficult to pump; blockages threatened the schedule. Traditional hose filters helped only partly. Additional screening and a deflocculating synthetic polymer improved filtration and pumping without adversely affecting the grout’s viscosity, bleeding or strength.

Keywords

jet grouting

Porte Maillot station

RER E extension

groundwater drawdown

spoil filtration