Vibro Projects is quick off the mark in France

Wednesday, 26 November 2008

Vibro Projects Limited has proven to be a ‘European Champion’ when it comes to vibro ground improvement after going head to head with German and French rigs on a project in Dourges, France. The firm was working on the £750,000 contract on behalf of Soletanche Bachy where it pulled out all the stops, producing over 500m of stone columns per shift; easily making the UK based Vibro Projects top of the league.

Speaking of the contract, Vibro Projects’ Mark Henry explained:
“It was the use of pre-auger assistance which allowed Vibro Projects to produce far more stone columns in a shift compared to the other rigs, proving how efficient our system of stone column bottom feed really is. Our high production rates really impressed our fellow Vibro technicians and also Soletanche Bachy, which is extremely positive for Vibro Projects’ future on international projects.”

The site, which is situated 20km south of Lille on the main A1 motorway, is for a 55,000m2 logistics platform warehouse. To improve the bearing capacity and stability of the ground, the Vibro team was contracted to install 7,400no. stone columns to an average depth of 4.5m.

The most efficient way of completing this was to mobilise one of its bottom feed rigs complete with a larger 600mm diameter tube and a Jean Lutz recorder on site. This new 600mm diameter tube guarantees a 600mm diameter clean stone column from top to bottom. The John Lutz recorder, installed in the bottom feed rig, provides information on depth pressures, installation and stone quality used; details which are essential to the sub-contractors, main contractors and client.

The bottom feed stone column technique utilities a hollow steel tube which is driven into the ground by a top mounted hydraulic vibrator. Slots are equally spaced along the length of the tube and around it, at ground level, is a stone hopper. As the vibroflo tube penetrates into the ground it passes through the hopper and fills under gravity with aggregate. When the required treatment depth is reached, the tube is withdrawn allowing the stone (aggregate) to immediately flow out from the base of the tube. The vibroflo tube is then re-lowered and used to compact the previously placed stone.

The process is repeated until stone reaches the surface – constructing a dense, clean and uncontaminated stone column which interlocks with the surrounding soil. With a suitable soil stratum, Vibro can pre-bore the columns as a time saving measure, which certainly proved to be the case on the Dourges project.

As well as the project in Dourges, Vibro Projects is having a successive run in France, recently installing stone columns at Saint-Amand-les-Eaux and Strasbourg; and is near completion on a project in Hambach.