Abstract: This paper proposes an improved bounding surface model for remolded clay, which overcomes the defects that it is inconvenience to apply and not related with elastoplastic property in the unloading process of the bounding surface model, by considering elastoplastic loading and unloading processes under cyclic loading. The model uses a simple bounding surface formula, which significantly simplifies the derivation and calculation of the model; which also effectively reduces the empirical dependence in the application process of the improved bounding surface without predefining the bounding surface. It introduces bounding surface expansion and contraction rules, which makes the model consider the elastoplastic property of the soil in the unloading process and then reflects the hysteretic behavior of the soil. This improved bounding surface model is verified by comparison between numerical simulation of remolded clay cyclic triaxial test and the cyclic triaxial lab test. The results show that the improved bounding surface has following advantages: clear physical significance and simple form, parameters easy to determine, high precision of calculation and the calculation results fitting the real test results.

Key words: bounding surface model theory, improved bounding surface model, cyclic triaxial test, hysteretic behavior, bounding surface expansion and contraction