Evaluation of Critical State Line under Cyclic Loadings

The behavior of soils subjected to earthquake and other repeated loadings is becoming a very important area of geotechnical engineering. This is due to increased concern for adequate seismic design procedures that require realistic behavior models. To understand and explain behavior of soils, models based on the theory of a critical state (or critical void ratio) at failure have been developed by Sangrey and used by France and Sangrey. Kirby and Wroth and Esrig have applied the concept of critical state line to study the axial capacity of driven piles in clay. Sangrey used it to study the response of piles to cyclic loading. In the present investigation, the critical state line under static and cyclic loadings was established from an extensive series of drained triaxal tests on Ottawa sand. By applying boundary and elastic energy corrections suggested by Rosecoe, for the Cambridge model, a theoretical critical state line was obtained. The energy corrections suggested by Burland for the modified Cambridge model, were also applied. The theoretical lines so obtained are compared with the experimental data.