STUDY ON STRENGTH CRITERION OF INTACT SOFT CLAY AFTER MONOTONIC PRINCIPAL STRESS ROTATION

摘要

Underestimating the influence of principal stress rotation on the foundation soil during the construction is the cause of some engineering accidents. Series of experiments were done to study the strength characteristics of intact soft clay after undrained monotonic principal stress rotation. It was found that compared with the progress of undrained monotonic principal stress rotation, the principal stress direction when samples failed influenced the soils' strength much more obviously. But the pore water pressure generated in the tests including principal stress rotation was much higher than that in the test of fixed principal stress direction shear. It was due to the shearing contraction of intact soft clay caused by principal stress rotation. A modified Lade-Duncan failure criterion was used to normalize these testing results and unify the soil's failure criterion including principal stress rotation. It showed that initial anisotropy was one of the most important determinate factors of intact clay's strength when principal stress rotation occurred during the construction.