Bridge Foundations in Extremely Hard Rock


In Quebec, a Spanish-Canadian consortium is building the Nouvelle Autoroute 30 highway, bypassing Montreal at the South towards the A20 and A40 in the West.

BAUER Foundations Canada Inc., the local subsidiary of the German company BAUER Spezialtiefbau GmbH, is constructing the foundations of the Beauharnois Bridge, a contract worth about 30 million $. The bridge runs over the Beauharnois Canal, a bypass of the St. Lawrence Seaway.

The waterway forms part of an international network linking the industrial cities of the Great Lakes region with the Atlantic.

The original Beauharnois Canal was built on the south side of the St. Lawrence River, opening in 1843. It was superseded by the Soulanges Canal in 1899 which ran on the north side of the St. Lawrence River.
The present Beauharnois Canal was blasted out of hard rock between 1929-1932. Measuring 24,5 km in length, it was part of a hydroelectric development at Beauharnois which saw a dam and power house built to take advantage of the 24 m drop between Lake St. Francis and Lake St. Louis. Some of the electricity is used to power a large aluminum smelter. In the 1950s, the Beauharnois Canal had 2 locks added as part of the St. Lawrence Seaway project. This in turn superseded the Soulanges Canal for shipping.

The Beauharnois Bridge will be located downstream of the canal. Bauer Foundations Canada has been contracted to build a total of 138 bored piles – 60 on land for the bridge thrust blocks, and 78 in the water, from a pontoon, for the pillars.

Five drilling rigs are being deployed – three BAUER BG 40 and two BAUER BG 28 units. To ensure pinpoint accuracy of the actual drilling, an BAUER IB 10 rig is being used to pre-drill down to 4 m into the rock. The tips of the drilling buckets will then ultimately take over from there. The 2 m diameter piles must socket 4,5 m to 5 m into the rock, sometimes more, depending on the rock quality.

During the geotechnical investigation the rock was proven to be extremely hard. Some rock cores compressive strength was above 300 Mpa. Bauer has a track record of hard rock drilling in Canada with the dam project of Peribonka, also in Quebec, and in Hong Kong, where the initial contact was made with the client back in the spring of 2007. A key factor in subsequent developments was the rock drilling expertise of Egon Stahl, managing director at Bauer Hong Kong Limited.

“So Bauer Hong Kong played a major role in helping Bauer Canada win the contract in March 2009,” says Lars Richter, managing director of Bauer Foundations Canada. “But other Bauer units around the world have been involved too, providing us with equipment, technical support and staff, to ensure the project is handled optimally. It is a great illustration of the Bauer network in action.”

To date, 60 of the 138 piles have been installed. The greatest challenge posed by the project will come later this month, when the piles are driven into the canal itself. The plan is to use two BAUER BG 40 rigs mounted on pontoons to drive 1,80 m piles down to a depth of 4 m.

Source: BAUER Spezialtiefbau GmbH

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