Pore pressure characteristics of normal and over-consolidated clays due to excavation of foundation pits

Deformation and strength characteristics for soils depend on the effective stress and stress history of soil skeleton. The successful prediction of pore pressure in soils makes it possible to solve practical engineering problems more effectively based on the effective stress principle.The pore pressure u in undrained triaxial compression tests was normalized with equivalent consolidation pressure p'_e of the Hvorslev Strength Thoery.A bilinear relationship between u/p'_e and stress ratioηwas validated for isotropical over-consolidated clays.A linear relationship passing through the origin of coordinates between u/p'_e andηwas fitted well for the normally consolidated clays.The slope was related with the frication angle in failure.The formulation of the pore pressure coefficient was deduced by use of the linear relationship.The predicted pore pressure coefficients varying withηagree well with those predicted by the pore pressure formulation deduced from the Cam-clay Model.