North Sitra Sewage Scheme microtunnel breakthrough

8 February 2018

Bahrain - Joseph Gallagher successfully installed its first microtunnel of 2018 in Bahrain. The project was to install a short drive, some 35m, of 600mm steel pipe underneath a road to form part of a new sewer network, the North Sitra Sewage Scheme.

Geology was a mixed face with rock at the bottom of the horizon, but the rest comprising sands and gravels. Overburden was up to 5m, underneath a busy junction. The Iseki TBM was set up for a 10mm overcut.

The carrier pipe for the sewer was a 14mm-thick steel wall pipe which was installed in 6m-long sections with a complete weld at each joint. Once the carrier pipe was in place, the GRP sewer pipe was installed, again in 6m-long sections.

The machine launched from a specially designed thrust wall from a shaft that was a sheeted pit, driven to depth with a vibro hammer. A steel I-beam frame was then built and welded into pace. The same setup was used for the reception pit.

A spokesperson said, “Despite encountering some unexpected ground conditions the brand new TCS 600 Rock machine dealt extremely well with the rock, boulder and sand interface.”