{"id":19798,"date":"2025-12-19T09:03:12","date_gmt":"2025-12-19T08:03:12","guid":{"rendered":"https:\/\/www.darda.de\/?page_id=19798"},"modified":"2026-05-22T07:48:02","modified_gmt":"2026-05-22T05:48:02","slug":"segment-tunnel","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/segment-tunnel","title":{"rendered":"Segment tunnel"},"content":{"rendered":"
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Segment tunnels are tunnel tubes assembled from precast concrete elements and produced by mechanized excavation with tunnel boring machines. The individual segments, often referred to as tubbings<\/em>, form ring-shaped sections of the inner tunnel lining. This construction approach is precise, fast, and proven in urban settings, beneath water bodies, and in complex geological formations. In the planning, construction, maintenance, and deconstruction of a segment tunnel, selective demolition and adaptation works play a key role-for example when creating openings, niches, or cross-passages. Depending on the task and boundary conditions, tools such as concrete pulverizers<\/strong> or hydraulic wedge splitters<\/strong> from Darda GmbH are considered in the application areas of concrete demolition and deconstruction<\/a>, gutting works and cutting, as well as rock demolition and tunnel construction<\/a>. Thanks to standardized ring geometry, high dimensional accuracy, and early watertightness, the method enables controlled settlement behavior and predictable construction sequences with low emissions in densely built environments.<\/p>\n

Definition: What is meant by a segment tunnel?<\/h2>\n

A segment tunnel is a tunnel with a ring-shaped inner lining made of precast, reinforced concrete segments. These segments are placed, bolted, and sealed immediately after each advance under the protection of a tunnel boring machine (TBM) using a segment erector. The resulting tunnel lining provides watertightness, structural stability, and load transfer to the surrounding ground and groundwater. In practice, terms such as tubbing tunnel<\/em>, segmented inner lining<\/em>, or segmental lining<\/em> are common. Typical rings consist of several standard segments plus a closing or key segment; geometry and joint configuration are optimized to achieve repeatable assembly, gasket compression, and long-term durability in the final lining.<\/p>\n

Construction method and components of a segment tunnel<\/h2>\n

The typology of the segment tunnel is based on precisely fitting precast concrete elements that are assembled into closed rings. Each component fulfills a defined function to ensure that assembly, sealing, and load transfer are safe and reproducible. Tight manufacturing tolerances, documented quality checks, and coordinated logistics between factory and TBM are essential for consistent performance.<\/p>\n

Tubbings and ring assembly<\/h3>\n

A ring consists of several identical segments and a wedge or closing piece. Shape, number, and thickness depend on geometry, load assumptions, and the shield used. The joint faces are machined, often with tongue-and-groove profiles and inserted seals. Dimensional accuracy and surface quality are critical for ring geometry and subsequent watertightness. Depending on alignment, tapered rings and defined ring rotation patterns are used to realize curves; staggered joints between rings minimize continuous weak planes and enhance structural continuity.<\/p>\n

Sealing and joints<\/h3>\n

Elastic sealing profiles are inserted in the segment joints to create a watertight joint under axial and radial pressure. Shear forces and moments are transmitted via shear dowels, locating pins, or interlocking teeth. The annular space<\/em> between the outside of the tubbing and the ground is filled after assembly with annulus grouting<\/strong> (cementitious or hybrid) to minimize settlements and establish load transfer. For high groundwater pressures, combined sealing concepts with hydrophilic strips or double-gasket systems are specified; bolt pockets and longitudinal joints are detailed to prevent leakage paths and allow safe grout return.<\/p>\n

Connectors and reinforcement<\/h3>\n

Segments are joined by bolted connections, anchors, or coupling plates to form a force-locked assembly. Reinforcement is designed for crack width control, shear and flexural tension capacity, and durability. Local embedded components (e.g., inserts, lifting anchors) serve for assembly and later retrofitting. Where applicable, corrosion-protected bolts and localized fiber reinforcement can improve impact resistance during handling and reduce spalling at edges and bolt holes.<\/p>\n

Construction process: excavation, assembly, and annulus grouting<\/h2>\n

In mechanized tunneling, the tunnel boring machine supports the tunnel cross-section with the shield skin and a support medium (EPB, slurry shield). After each advance stroke, one ring is assembled:<\/p>\n