The strength of London Clay in relation to the design of embedded retaining walls

In the design of embedded retaining walls in stiff clay the lateral earth pressures acting on the wall in limiting equilibrium are derived from the shear strength parameters of the clay. These parameters are usually determined by triaxial compression tests at stress levels greater than those in the field. Consequently they may not realistically represent the actual strength of the soil adjacent to the wall which experiences decreasing effective stress as excavation proceeds in front of the wall. The effect of stress level and stress path on the strength parameters has been investigated in a series of undrained triaxial tests carried out at comparatively low stress levels in compression and extension on undisturbed samples of London clay. The samples were obtained from a site where soil stresses have been monitored adjacent to a propped embedded retaining wall. (Author/TRRL)