The Liadur noise barriers are usually installed by three methods: through the establishment of bored pillars, anchors drilled into the concrete structure, or with the precast concrete footings.
Installation of columns in the concrete footings is used primarily in the areas with soil characteristics unsuitable for drilling, inaccessible for the drilling rig and places with a frequent occurrence of engineering networks (usually near railroad tracks).
Minimum height of the footing is 80 cm. The footings can be prefabricated or monolithic. Columns are usually fitted into the cup with the depth of 550 mm. In exceptional situations they are installed before the casting. Dimensions of footings, reinforcement and the type of concrete are specified in the project documentation. The footings are usually wrapped in a net only at the bottom surface.
The type of concrete used: C 30/37 – XF4
Borehole diameter and its depth depends on the height of noise barriers, the type of the columns and soil characteristics. This provides a structural analysis for noise barriers.
Steel cage is inserted into the hole and the body of the pillar is filled with concrete (minimum C 25/30) up to the level of the working joint approximately 700 mm below the final top of the face pillar (the pile header), where the center of the column is determined, the hole is drilled and the pin assembly is mounted. This is followed by the column installation, alignment of its verticality and the concreting of the column (C 30/37 - XF4) into its final position.
The borehole is usually reinforced by the steel cage made of Ø 8 mm thick spiral wire, reinforced with Ø 20 mm longitudinal rods. The spiral pitch is typically 300 mm, which at the top of the borehole, in the last 80 cm, thickens to 150 mm. Profiles of the bars are approximate. The exact design of reinforcement is determined by structural analysis and design documentation.
The concrete structure (the pillar, a concrete strip, bridge ledge, retaining wall) is drilled up to the length of 300 m and subsequently the steel column is attached to the anchor through the base plate.