This European Standard establishes general principles for the execution of diaphragm walls as either retaining walls or cut-off walls. NOTE 1 This standard covers only structures constructed in a trench excavated with a support fluid or in dry conditions, where soil is removed and replaced by concrete or slurry and with wall thickness B ≥ 40 cm. NOTE 2 Diaphragm walls can be permanent or temporary structures. NOTE 3 The following types of structure are considered: a) retaining walls: usually constructed to support the sides of an excavation in the ground. They include: 1) cast in situ concrete diaphragm walls; 2) precast concrete diaphragm walls; 3) reinforced slurry walls; b) cut-off walls: usually constructed to prevent migration of groundwater, clear or polluted, or of other contaminants present in the ground. They include: 1) slurry walls (possibly with membranes or sheet piles); 2) plastic concrete walls. NOTE 4 Walls formed shallow vertical trenches (typically excavations with a ratio of depth over thickness D/B < 5 or D < 5 m) are not covered by this standard.