Lovat & Copco successes

Lovat earth pressure balance TBMs recently holed through on Line 1 of Seville’s metro and the second section of the Big Walnut Outfall Augmentation Sewer (BWOAS) in Columbus, Ohio.

In Spain, the 6.05m diameter mixed face EPBM completed the 2334m long drive with the entire alignment below groundwater level with maximum height above the invert of 15m.

Driving mainly through gravel with sandy sections, and blue marls, the EPBM achieved best progress rates of 29.4m in a day, 133m in a week and 333m in a month. Contractor on the project is a JV of Dragados, Sacyr and Cavosa, and the machine is now being prepared for relaunch on the twin tunnel project.

In the US, a Lovat 4.2m diameter mixed face EPBM owned by contractor McNally-Kiewit JV completed the 4084m long drive at Big Walnut with best rates of 24 rings in a day, 79 rings in a week.

Like Seville, the Big Walnut drive was entirely below groundwater but the geology was markedly different: glacial till and glacio-fluvial outwash. Fine sands, gravels, cobbles and boulders were also met. The EPBM was designed for potential gas problems.

* Separately, encountering far more favourable ground and excavating by a different method, Atlas Copco claimed a record for a single face drive by drill and blast at a recently scheduled breakthrough party at the Sauda hydro project, Norway,

Driving in good quality granite without the need for shotcrete but installing rockbolts, contractor AF Anlegg used a Rocket Boomer XL3 C30 to advance the 38m2 face by 165m in one week. Progress was achieved using 33 rounds with, on average, less than four hours between blasts and the contractor installed 199 of the 3m long rockbolts.