Dr. Rehm has been a lecturer at the Institute for Technology and Management in Construction (TMB) at KIT since January 1, 2026, for the Master's course in Tunnel Construction. There, he shares his practical and theoretical knowledge with Master's students through lectures and practical site visits; on February 9, 2026, the highly interesting Rastatt Tunnel construction site was visited with the students (see picture).
Since early 2025, Tunnelling Consultant GmbH has been supporting as a TBM expert within the Ramboll and TYPSA joint venture, working on the tender-stage planning for the new, approximately 7.5 km long, twin-tube metro line (Yellow Line) connecting Fridhemsplan and Älvsjö in Stockholm. The project involves the planned use of shielded hard-rock TBMs to excavate through typical Scandinavian igneous and metamorphic rock formations with very high strengths. The tunnel alignment passes through six Metro-stations, and a key challenge lies in the logistical planning and its implementation amidst the highly constrained urban environment of Stockholm.
TC supports the planning joint venture with expert input regarding TBM excavation and urban logistics, drawing on extensive experience gained from projects such as Crossrail in London or Stuttgart21/Germany.
Since early 2025 until today, Tunnelling Consultant GmbH (TC) has been supporting the GKP joint venture (GIBB KNIGHT PIESHOLD) as a TBM expert during the tender planning phase for the uMkhomazi Water Project. The project involves excavating a total of 34 km of pressurized water tunnel in hard rock—along with two additional, relatively steep access tunnels —preferably using a shielded hardrock-TBM. Beyond the relatively small tunnel profile, the specific challenges regarding excavation logistics include the project area's remote location in rural South Africa and the rock's exceptionally high strength. TC advises the joint venture on all aspects of TBM tunnelling planning, TBM design, site logistics, segmental lining design, contractual matters, and the overall excavation strategy (including TBM performance, tunnelling costs, and schedules).
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For the deployment of the Variable-Density TBM with a 7.2 m excavation diameter—planned to construct the 2nd Ave Subway Phase 2 line beneath New York City's skyscrapers—the HALMAR-FCC-C+P joint venture commissioned Tunnelling Consultant GmbH (TC) to prepare a quality assessment of the TBM's main bearing seals. The mixed glacial geology of the two tunnel sections (each approximately 1.2 km long)—comprising highly abrasive soil and rock—combined with groundwater pressures of around 3 bar, generates significant eccentric forces and moments at the main-drive unit via the cutterhead; the drive unit relies crucially on the main bearing seals for protection. These seals represent the Achilles' heel of any TBM. TC has reviewed the technical and numerical background for the design of the main bearing seals.
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In September 2026, Tunnelling Consultant GmbH (TC) was commissioned by the LIMAK/MAPA joint venture to analyze a highly critical excavation situation—encountered after advancing approximately 7.5 km of the total 13.5 km tunnel length using an 11.3 m diameter EPB TBM—and to propose solutions. The extensive geotechnical challenges associated with tunneling in Southeastern Turkey—a region shaped by the tectonic interaction between the Arabian and Eurasian plates—include the presence of methane gas, stress-induced rock squeezing, and chemo-physical deformation caused by swelling anhydrite within the rock mass. Furthermore, the presence of karstified limestone is anticipated.
TC conducted an extensive analysis of rock mechanics and excavation engineering, and developed proposed technical solutions for construction.
The planned Buksefjorden Hydroelectric Power Plant project aims to expand the hydroelectric power supply for Nuuk, Greenland. The plan involves an additional power plant with a capacity of approximately 76–77 MW. Key components include a water diversion tunnel—roughly 16 km long —designed to connect the lakes Kangerluarsunnguup Tasersua and Isortuarsuup Tasia. The project is exceptionally challenging due to the remote construction site, Arctic climate, extensive tunneling, and highly complex logistics; these factors entail significant risks regarding costs and schedules. Currently, the primary challenges lie in construction costs, risk allocation, logistics, and the contract award process. Tunnelling Consultant GmbH has been commissioned to conduct a feasibility study with a strong focus on timeframes and cost estimates.
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