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Tunnel enlargement - A tunnel in a dam accurately enlarged in Spain

The Job:

This operation involved enlarging a tunnel which ran through a dam in Spain. It was necessary to remove a concrete layer precisely 0.5 m thick from the floor, walls and ceiling.

The Requirements:

The operation called for extreme accuracy, since the specified thickness of the removed layer was not to be exceeded. At the same time, severe vibrations inside the tunnel had to be avoided in order not to put the dam at risk.

The Solution:

The tunnel was about 18 m long, 6 m wide and 5 m high, and the concrete was reinforced with 16 mm thick steel. First, 0.5 m deep cuts were made throughout the entire length of the tunnel with diamond tipped saws. Cross-cuts were made every 2 m.
A hole was drilled in each section 1 m from each sawcut, i.e. halfway along. Two Darda C 9 N splitting cylinders and a portable EP hydraulic unit with electric motor then simply split the sections out. The sawcuts ensured that no section was thicker than 0.5 m.