113 Architectural questions - What types of excavation support are there?
What types of excavation support are there?
Excavation pits must be created for the construction of underground car parks and basements. There are basically two ways of excavating, namely by constructing an embankment or by vertical shoring. If space permits, the embankment is usually preferred, as it can be constructed inexpensively and without specialised machinery. The space required depends on the depth of the excavation pit and the angle of the slope, which should not exceed 45°-60° depending on the nature of the subsoil.
Vertical shoring is required on narrow plots or if the building is to be attached to the neighbouring building site or if the building is in groundwater. Depending on the excavation depth, the space required must be taken into account in the planning with approx. 80cm. The most commonly used types of vertical shoring are
Sheet piling: Sheet piling consists of individual steel planks that are connected to each other via interlocks. This connection means that sheet piling can be made watertight and can be removed and reused after the construction work has been completed. The piles are driven, vibrated or pressed depending on the soil conditions. Inserting the sheet piles causes vibrations that can lead to damage to neighbouring buildings. The major advantage of sheet piling is that it is watertight and can be installed quickly and then reused.
Bored pile wall: is suitable for all types of soil and can be installed without major vibration. Bored pile walls are mostly used when it is necessary to build onto the neighbouring structure or when an embankment cannot be realised due to the distances involved. The bored piles also serve as a load-bearing wall for the storeys above and can reach great depths. To construct a bored pile wall, boreholes are drilled, a reinforcement cage is installed and the borehole is filled with concrete. Bored pile walls can be overlapped for structures in groundwater, or they can be constructed as a separate structure.
soldier pile wall: to construct a soldier pile wall, steel profiles are rammed into pre-drilled holes and then filled with wooden planks or precast concrete elements. After completion of the work, this type of excavation support can be dismantled. In contrast to the sheet pile or bored pile wall, the soldier pile wall can only be used above the groundwater level.
Diaphragm wall: works in a similar way to the bored pile wall, but the diaphragm walls are made up of individual lamellae, which significantly reduces the number of joints compared to the bored pile wall. Diaphragm walls can be constructed with low noise and vibration levels, but are also more cost-intensive than other excavation stabilisation methods, which is why they are rarely used in residential construction. As diaphragm walls can absorb very high loads and reach enormous depths, they are often used for underground stations or multi-storey underground car parks.
