Geotechnical contractor Kasktas has also taken precautions against earthquakes beneath the Uzel car factory near Duzce, 100km east of Golcuk, installing jet grout columns to improve the ground.
The factory is set in a basin among mountains formed by the North Anatolian Fault. Geology comprises grey silty clay with lenses of sand and gravel, with mainly sands and gravels at the basin edge.
In 1999, while Kasktas was carrying out the ground investigation for the project, the site was struck twice by earthquakes. Both measured over 7 on the Richter scale. As a result ground conditions and seismic risk of the site was re-evaluated and a ground acceleration factor adopted in the engineering design.
Working for main contractor Uzel and consultant Enar Muhendislik Mimarlik Danismanlik, Kasktas installed 800mm diameter, 8m long jet grout columns to control settlements of ground slabs. And to support the footings of the steel frame building the firm put in 650mm diameter, 14m long bored piles.
Working parameters were determined by four, 6m long test jet grout columns which were also excavated for visual inspection. During the main works, quality of the jet grout columns was monitored by coring the heads of one in every 200 columns and integrity testing one in every 50, with six pull-out tests on production jet grout columns.
Geotechnical work on the £2. 5M contract began in November 1999, with a total of 60,700m of jet grouting and 14,000m of bored cast insitu piles installed.