Abstract：The determination of yield function，plastic potential function，hardening law and corresponding hardening parameter is essential when establishing elasto-plastic constitutive model for soils. Consequently，the establishment the calculation formula of hardening parameter is particularly important. In this paper，through the comparison of the stress-strain relationship and strength behavior of normal and over consolidated soils，the construction of the unified hardening equation considering the influence of initial state is presented. Then，based on the mechanism analysis of strength behavior of over consolidated soils under complex stress paths，the strength potential MY which can consider the joint effects of initial state and loading process is introduced. Additionally，the unified hardening equation for soils under complex stress paths is obtained through replacing the Mf with MY in the original unified hardening equation. Finally，the significance of the novel unified hardening equation to the establishment of constitutive model for soils is verified by comparing with the experimental results under various stress paths.
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2023, Vol. 42 
