6th INTERNATIONAL CONFERENCE ON GROUTING AND DEEP SOIL MIXING
Our C.E.O. and Technical Director Vittorio Manassero will attend the 6th INTERNATIONAL CONFERENCE ON GROUTING AND DEEP MIXING in New Orleans in January 15th through 18th.
During the Conference, as part of the C4 Session “Tunnels, Mines and Dams” - in Salon A-C, 3rd floor, at the New Orleans Mariott - on Tuesday 17th Vittorio Manassero will give a presentation entitled “Soil Improvement for Ventilation Adits at the Naples Subway Line 6”.
The presentation will cover the design and construction of three horizontal ventilation adits connecting ventilation shaft with TBM tunnel at Naples Subway Line 6, using different soil and rock improvement technologies: penetration grouting, jet grouting and artificial ground freezing. The ventilation system of the subway entails underground chambers connected to the TBM tunnel by a vertical shaft and a horizontal adit. The connection adits are below a water table head of 18.0 to 23.5 m; for this reason they had to be excavated using soil or rock improvement as a preventive measure. At one of the three adits penetration grouting was adopted to seal the system of fractures within the Neapolitan Yellow Tuff. At the other two adits a combination of vertical jet grouting columns, installed from the surface, and grouting, performed from the shaft, was at first foreseen. After a field trial the jet grouting activities started. During the installation of the first columns, a phenomenon of systematic soil removal and consequent formation of chimneys was observed, leading to a high risk if instability of the drilling rig operating on the working platform. This occurrence led to seeking alternative design solutions: among them, a solution entailing the preventive formation of a frozen soil shell all around the adit to be excavated was selected and then applied. The result was successful for all the three adits, i.e. tunnelling was safe and almost dry, as well as any effect on the adjacent structures were avoided.