The work consisted of building a construction pit for the construction of Venlo's new municipal offices.
The construction pit was formed by a roughly 260 m long diaphragm wall , which was anchored partly with permanent grout anchors and partly with temporary grout anchors.
VSF was contracted for these works by Ballast Nedam Funderingstechnieken for main contractor Laudy Bouw & Ontwikkeling, which was contracted by the municipality of Venlo.
Part of the VSF's scope was to engineer the reinforcement and anchoring of the diaphragm wall. Various other calculations had to be made for executing the diaphragm wall, too, such as trench stability calculations. These calculations and the associated drawing work were made in-house by our engineering department.
Just before New Year 2013, VSF transported the excavation equipment and the bentonite plant to Venlo. The 80-cm-thick diaphragm walls reached to roughly 22-26 m below ground level. The dimensions of the construction pit were approximately 63 x 70 m. The total wall length was more than 260 m.
The varying altitudes of the adjacent roads at the very short distance from the wall to those roads made a graduated installation of the guide beams necessary. In general, the excavation work went according to plan with the odd obstacle here and ther originating from a former construction.
The diaphragm wall was excavated using a Liebherr 875 crawler crane with a 25- tonne slurry wall grab. A Sennebogen 6100 crawler crane was used for fitting the reinforcement and handling the endstop.
Once the diaphragm wall had been installed, VSF anchored the wall by means of partly temporary and partly permanent GEWI anchors. Due to the possible high groundwater level, which fluctuated along with the water level in the River Maas, the anchors could not be installed until the pit was closed.
A special construction was used when installing the anchors to prevent water coming in to the construction pit since the ancho rlevel was below the groundwater level. All anchors were tested and tensioned and Ballast Nedam Funderingstechnieken was able to start the excavation works.