Appropriate seals, ground improvement, and compatible shaft construction techniques are vital elements for launching and receiving microtunnel boring machines effectively in wet soil where potential consequences of seal failure are significant. This paper describes seals and ground improvement methods for launch or reception portals. It also discusses probing to verify suitability before the portal eye is cut and a need for redundancy in portal seal design. In addition, case history examples are given from some projects where portal seals failed and lessons were learned.
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