This standard provides a code of practice for the design and construction of reinforced concrete diaphragm walls used as retaining walls, load-bearing elements, or impermeable cut-offs. It covers material specifications for concrete and bentonite slurry, design considerations for earth and water pressures, and detailed construction procedures including trenching, slurry control, reinforcement cage installation, and concreting.
Code of practice for design and construction of diaphragm walls
Quick Reference Values
Permissible vertical tolerance1 in 80
Bentonite slurry density (fresh)1.03 to 1.10 g/ml
Bentonite slurry viscosity (Marsh Cone)30 to 90 s
Sand content in slurry before concreting< 6% by volume
Minimum recommended wall thickness500 mm
Minimum concrete gradeM20
Minimum cement content400 kg/m³
Key Formulas
Ka = (1 - sin(φ)) / (1 + sin(φ)) — Active earth pressure coefficient
Kp = (1 + sin(φ)) / (1 - sin(φ)) — Passive earth pressure coefficient
Practical Notes
Bentonite slurry quality control is paramount for trench stability and the integrity of the final concrete wall; regular testing of density, viscosity, and sand content is critical.
The integrity of joints between adjacent panels is crucial for water-tightness. Careful installation and cleaning of stop-ends and water-stops are essential.
Concrete for diaphragm walls must have high workability (slump > 150mm) to ensure it flows properly around reinforcement and displaces the bentonite slurry effectively via tremie placement.