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Trenchless crossing

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Linear shoring secured the starting pit
Innsbrucker Kommunalbetriebe AG has closed the inner-city pipeline network and increased the security of supply in the city area with the laying of a new underground power line from the middle to the north substation. The scope of the construction work, for the execution of which Kraft & Wärme Rohr- und Anlagentechnik GmbH and, as a subcontractor, TEERAG-ASDAG Aktiengesellschaft were commissioned, includes the crossing of Salurner Straße.

Due to the heavy traffic, which is characterised by a high volume of cars, bus traffic and a tram line, the client had decided to drive the necessary empty conduits for pulling in the 110 kV lines under the busy intersection using a trenchless method.

Contrary to the original planning, the 3.10 metres wide and 7.80 metres long launch pit required for the reception of the drilling rig was not secured with sheet piles but with the linear shoring system from E+S by terra infrastructure. In addition to the economical aspects, a significant technical aspect was crucial for the decision: in contrast to ramming the planks, the linear shoring causes significantly less vibration in the construction environment when driving the linear shoring.

A sensible alternative

With linear shoring, shoring plates are held in vertically installed rails so that they can slide past each other. When fully installed, a stepped shoring system is created. The key design feature of the linear shoring is the rigid roller unit. It ensures that the trench width remains the same during installation and removal in every construction phase – a fact that ensures smooth and economical construction processes.

Sheet piles are usually used to shore the head of the starting pit. Since the struts of the shoring systems may only be subjected to pressure and tension in the longitudinal direction and not horizontally, so-called head shoring adaptors are integrated into the linear shoring system. These are guided in the profile of the linear shoring supports, just like the roller unit, are adjustable in height at any time and are flush with the front edge of the shoring system. This allows the trench sheets to be bracket-supported against the crossbeams, which are capable of bending.

The Salurner Straße crossing was completed on schedule.