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Unique Application for Connectable Swellex in Japan


Swellex has long been thought of as a simple and ingenious invention and now in Japan Connectable Swellex has proven to be a viable alternative to cement grouted cable bolts in a pilot tunnel that is part of the second Meishin Highway.

Connectable Swellex, a 200 kN rockbolt, consists of three parts, a lower, middle and an upper section which can be assembled to almost any length. As with all Swellex products, the bolts are made from folded circular steel tubes, which are inserted into the hole segment by segment and then expanded with water using a high-pressure pump. When the water pressure reaches 300 bar the installation is complete.

The Connectable Swellex is being used for pre-pinning in a 5-meter diameter pilot tunnel for the Rito Tunnel, which is part of the Second Meishin Highway. The decision to use it was based on the fact that it was faster and easier to install than traditional cement grouted cable bolts.

In the tunnel, 4-meter long Connectable Swellex sections have been assembled to create 8 and 12-meter complete bolts. The installation time of these long bolts has been relatively short – approximately 5 minutes per bolt in pre-drilled holes and has proven to be trouble free. The bolts have been installed using an Atlas Copco rail drill or have been installed manually.

The Connectable Swellex is installed into the hole using a special extension-adapter which makes it possible to expand the bolt three meters into the rock exactly where the final profile of the tunnel will be once the full section is excavated. This will prove to be beneficial in a number of ways. First, when an excavator, breaker or road-header removes the full section, the bolt will not be in the way of the excavation and; second, it will provide support for the final profile of the tunnel.

Picture: Nr 200205
Connectable Swellex

Fig 1.
The Connectable Swellex will not interfere with with the excavation of the Expansion section and will provide support for the final profile of the tunnel.

Fig 2.
A special extension rod allowed the bolts to be installed quickly and efficiently via an
Atlas Copco rail drill or manually.