Diaphragm wall
Diaphragm wall
A diaphragm wall is a reinforced-concrete wall cast in the ground, built up from contiguous panels. It combines earth retention, water cut-off and bearing capacity in a single permanent structure — the go-to technique for deep urban excavations, underground car parks and infrastructure works.
When to use
- Excavations of considerable (> 6 m) to very large (> 20 m) depth
- Combined permanent retention, water cut-off and bearing function
- Urban sites near existing foundations — attention to panel length, trench stability and sequencing
- Permanent basement walls, multi-storey car parks and infrastructure works
- Nearly all subsoils including rock (using a hydromill or chisels)
What we deliver
- Panel layout, width, depth and reinforcement design
- Trench stability analysis based on experience, calculation (DIN 4126) or a combined approach
- Geotechnical design to Eurocode 7, analogous to sheet pile walls
- Water-tightness class specification (ÖBV / CUR publication 231) and any additional measures — secondary barrier, drainage or concrete quality
- Layout with guide walls, joint profiles and reinforcement details
Technical notes
- Support fluid: bentonite-water (or polymer), level at least 2 m above the highest piezometric head and up to the guide walls
- Concrete: high flowability (S = 200 ± 30 mm), cement 350–400 kg/m³, W/C ≤ 0.6 — concrete rise > 3 m/h, cover ≥ 75 mm in permanent works
- Water-tightness: ÖBV classes 4–5 achievable under ~10 m head, class 3 under low heads; class 1 (fully dry) only without water pressure
- A diaphragm wall is not fully watertight — damp spots and dripping possible; the client sets the required tightness class beforehand
- Tolerances: 25 mm towards the excavation, 50 mm towards the soil, 1 % vertical deviation, 100 mm bulges; minimum 10-day wait before excavation
- Variants: cement-bentonite walls (single-phase, mostly cut-off), barrettes as deep foundation elements
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