Tunnelikerros

Tunnelikerros is a Finnish term that translates to "tunnel layer" or "tunnel lining" in English. It refers to the structural support system that lines the inside of a tunnel. This lining is crucial for the stability and longevity of the tunnel, providing protection against ground pressure, water ingress, and general wear and tear. The materials and design of a tunnelikerros vary significantly depending on the tunnel's purpose, the geological conditions it traverses, and the expected loads.

Common materials used for tunnelikerros include concrete segments, shotcrete (sprayed concrete), steel ribs, and sometimes precast concrete slabs or masonry. In many modern tunnel projects, especially those for transportation, precast concrete segments are often employed. These segments are manufactured off-site to precise specifications and then assembled within the tunnel as it is excavated. Shotcrete is frequently used as a primary support layer, particularly in rock tunnels, to quickly stabilize the excavated surface. Steel ribs may be used in conjunction with shotcrete or as a standalone support system in areas of poor ground conditions.

The primary functions of a tunnelikerros are to prevent the collapse of the excavated space, to manage and direct groundwater flow, and to create a smooth and durable surface for the intended use of the tunnel, whether it be for vehicular traffic, railways, or pedestrian walkways. The design process considers factors such as the in-situ stress, the presence of faults or weak zones in the ground, and the seismic activity of the region. Proper installation and maintenance of the tunnelikerros are vital for the safety and operational efficiency of any tunnel.