The Nishimatsu Drilling Company of Japan, part of a large consortium of companies undertaking the three year project, were having major problems supporting horizontal drilling equipment being used to create the initial entry point where the large tunnelling machines being used to drill the tunnel would commence drilling.

Howard Marine Ltd were contacted with what seemed an unusual request to use their jackup barge in a totally non-marine environment.

However, following discussions, loading calculations and tests to prove the Zee Jack Skipper's suitability for the project, Howard Marine was able to supply the jackup and a skilled operator for this part of the contract.

The introduction of the barge proved an enormous success, more than doubling the production of drilling crews working on the face of the tunnel. Lowered down the access shaft as a single unit by a large crane, the jackup was operated in the normal way, raising and lowering itelf hydraulically and thus able to place the drilling equipment at the exact height required for each hole to follow the curvature of the tunnel.

As well as weight loading on the barge, it also had to withstand lateral forces being transmitted by the drilling equipment. This was overcome by using tie bars connected to pre-drilled rock sockets in the area of the tunnel face. Although jacked as high as 14m, the barge experienced no lateral movement from the force of the horizontal drill. Its stability as a working platform gave drilling crews safer working conditions as well as improved productivity.

MJ Information No: 17328