Rock tunnel cladding structures

We have completed various rock tunnel waterproofing and thermal insulation projects and have extensive experience in applying the required techniques. JIITEE will take care of all work phases required to set up cladding structures in rock tunnels, including anchor bolting and shotcreting. Our comprehensive service offering ensures seamless and efficient project planning and implementation and high-quality results.

The main function of cladding structures is to protect the tunnel from damage caused by changes in temperature, water, pressure differences or other environmental conditions. The structure usually also acts as a waterproofing layer, much like thermal insulation. A cladding structure can include several layers, such as a thermal insulation and waterproofing layer, a fire protection layer and various layers of coatings. The structure also consists of shotcrete, steel reinforcements and rock anchoring. These components strengthen the bedrock surface and improve tunnel safety.

Cladding structures are a key part of making rock tunnels functional and durable. They ensure that the tunnel will remain safe and fit for use for a long time, even if site conditions are difficult. Leaks in the structures may lead to corrosion of metal components, short circuits in electrical equipment, formation of mold and weathering of shotcrete. Our comprehensive service offering covers all working phases related to tunnel cladding structures. We will take care of your project efficiently from start to finish—without compromising on quality, durability or safety.

Cladding structures with membranes and PE mats

Pre- and post-injection techniques are used to prevent water leaks in tunnels. To ensure good results, injection is combined with a cladding structure, or a waterproofing structure. It can be built using either membrane or PE mats. Before the cladding can be installed, the rock must be reinforced with shotcrete and bolts.

Membrane is a thin rubber sheet that is installed on the surface of the rock to prevent water run-off in shafts and tunnels. PE mats are slightly thicker (about 5 mm) foam rubber mats that work in the same way as membrane. Installing both of these types of waterproofing is a very low-tolerance job. The waterproofing sheets are secured into the bedrock with bolts and washers. 

These fixing bolts must be positioned exactly right on the uneven rock surface to ensure that the waterproofing material sits right. If the bolts are too far apart, this may cause various problems: for instance, the material in the tunnel roof may start to sag before long. Determining the correct locations for the bolts and installing the waterproofing material takes experience, a keen eye and a steady hand.

JIITEE has carried out waterproofing and thermal insulation projects in numerous tunnels and shafts. 

Examples of projects that have included different types of cladding structure installations:

• Slussen terminal, Veidekke: installation of membrane on a total surface area of approx. 65,000 m2
• Pepallonmäki train tunnel, R. Ajalin: installation of cladding structures on a total surface area of approx. 2,000 m2
• Karkunvuori tunnels (2 x 180 m), Tampere: cladding structures on a total surface area of 10,000 m2
• VT 12 Tampere coastal tunnel, YIT Infra Oy: installation of cladding structures on a total surface area of 93,000 m2
• Triangular rail junction in Riihimäki, Kreate Oy: cladding structures
• VT 12 Lahti, Liipola tunnel, Skanska Infra Oy: installation of thermal cladding mats on a total surface area of 7,800 m2
• Horizontal displacement and smoke exhaust shafts of the Ring Rail Line: cladding mats on a total surface area of 3,000 m2
• Högbacka train tunnel, R. Ajalin: installation of cladding structures on a total surface area of 600 m2
• Jokeri 2 public transportation tunnel, Destia, YIT: cladding on a total surface area of 17,000 m2