White Papers

Non-Continuous Pressurized (NCP) Tunneling in Rock Tunnels at High Water Pressure: A Comparison with Slurry Tunneling

While Slurry Shield tunneling has a long history of being used in hard rock with high expected water pressures, this method has not always been problem-free and can prove costly. At recent projects around the world, two other methods have proven themselves in hard rock under water pressure: Shielded, Non-Continuous Pressurized (NCP)-TBM tunneling in rock with a comprehensive grouting program, or sequential advance in EPB mode. Both types of tunneling operations have proven themselves safe and cost-effective. In this paper, the authors will analyze machine design and grouting methodology of NCP tunneling using shielded TBMs at projects in the U.S., India, and more and compare these with projects using Slurry Shield TBMs in rock under high water pressures. Recommendations and guidelines will be given in order to establish a clear picture for contractors, consultants and owners to choose the most effective, safest and lowest cost method in these difficult tunneling conditions.


  Download File