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Difficult Ground Solutions (DGS): New TBM Solutions carve a Path to Success

In many TBM-driven tunnels, the occurrence of squeezing ground, high inrushes of water, blocky rock, and other challenges is a real possibility. Difficult Ground Solutions (DGS) reduces risk to contractors and owners in these conditions while providing accurate ground investigation. The story of how these methods came into practice involves hardship that tested the mettle of a shielded hard rock TBM on a recent project. What came out of those challenges is a new way to deal with both predicted and unforeseen ground conditions in rock and mixed ground. DGS features such as dual-range cutterhead drives, high pressure grout injection systems for face stabilization, and water inrush control are customizable and should be considered to be built into shielded TBMs. This paper will cover solutions informed by field experiences, the tools it takes to be successful in difficult ground, and how they are applied.

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