Use of special jet grouting technologies for tunnel’s crown and core advance consolidation - technical aspects and case studies

摘要

From the early nineties of last century-ADECO-RS tunnel design approach, devised by Rocksoil,rnhas been widely used in Europe, mainly in Italy, for tunnelling in difficult soils. ADECO-RS is based on thernanalysis and control of the deformations both of the tunnel’s surroundings and core. The jet grouting technologyrnis very often applied in the ADECO design for the formation of a series of concentric truncated cone-shapedrncrowns of reinforced consolidated soil on the border. The advance core can be treated, when necessary, withrnfibreglass elements or yet with jet grouting columns.rnApplying jet grouting in sub horizontal assuring the formation of a continuous arch of consolidated soil inrnunstable soil conditions or in the presence of cohesive soil and without causing upheaval on the above structuresrnand ground is not an easy task. To these purposes, very often equipment and jet grouting techniques to be usedrnmust be completely different from the ones used in conventional vertical application.rnThe present paper presents two special applications of said technologies finalized by Trevi Group and appliedrnwith very good results. The first one is named “roto-injection technology” and is a patented technique thatrnallows both to create columns and to install reinforcing steel pipes with large diameter and thickness, and it alsornminimizes the risks of upheaval on the surface.rnThe second one concerns the use of ETJ (Enhanced Trevi Jet) system to substantially improve the efficiencyrnof the jetting in particular soil conditions using special components to increase the disruption power of the jet.rnETJ is often used together with roto-injection.rnBesides a technical explanation of the two technologies, some application case studies are briefly reported.rnIn particular Cassia Tunnel (located in a succession within the works for the renovation of the three lanes of thernGreat Ring Road in Rome) and Cavallo tunnel for the A14 Highway between Bologna and Ancona.