Vysočany Radial, construction no. 0053, 1st phase - Kbelská, SO 211 - Retaining wall

The Zakládání staveb Co. finished in autumn 2006 construction works on a retaining wall securing a sinistral side-hill cut of the A4 branch of the Kbelská crossroads in Prague -Vysočany that is a part of the Vysočany Radial. The A4 branch serves as a slip road to the Radial from the Kbelská Street in the direction from Vysočany. The Vysočany Radial runs from the Kbelská Street in Prague 9 and near Horní Počernice connects with the I/10 road, direction Mladá Boleslav. The retaining wall is connected to a wing wall of the bridge support over the Kbelská Street.

Securing of the A4 branch is carried out with an anchored precast diaphragm wall of 204 m in length, made of separate reinforced concrete prefabricated components - 1980 mm wide, 400 mm thick and 4-16 m long, in the total amount of 102 pieces. The prefabricated components were fixed into an 800 mm wide trench, filled with self-hardening slurry. Excavation of the trench was carried out with an angular hydraulic grab BH 12 250/80 cm, using the Liebherr set on the Unex carrier under the protection of supporting self-hardening slurry.

From the geological point of view the foundation soil on the construction site is variable, including backfills, sandstones, claystones, as well as numerous tectonic disturbances, unconsolidated areas in sandstones and even carbonaceous impurities. The area is affected by block slides. Groundwater level reaches into cretaceous formations below the level of the deepest excavations.

Stability of the retaining wall is secured by permanent strand anchors at 1 to 3 levels depending on the depth of the secured excavation (2 to 11 m). With respect to the above described complicated geological conditions the anchors were designed and carried out to the length of up to 22 m with grouted roots, located outside the potentially sliding area.

At the capital level the prefabricates are tied with base anchors into a reinforced concrete ledge that further contains anchoring of crash barriers, railings, public lighting and other components. The space behind reverse side of precast diaphragm wall is drained at two levels using equipped draining bores run out in front of the wall.

The construction is monitored by geotechnical and geodetic monitoring.

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