Establishing a constitutive model that reflects the local bonding breakage process has always been a core task in soil mechanics and is crucial for solving engineering stability issues. Based on thermodynamic principles and breakage mechanics

this paper proposes a macro-micro thermodynamic constitutive model. This model quantitatively describes the thermodynamic behavior of local bonding breakage and the non-uniform distribution of stress-strain at the microscale. It improves the prediction accuracy of the model for deformation characteristics

which is similar to the Cambridge model in mathematical form. Firstly

based on the law of conservation of thermodynamic energy

the mathematical expression of structural breakage work during compression deformation was determined. It was found that the dissipated energy of breakage can be mainly divided into two parts: the frictional effect between bonded elements and frictional elements

and the irreversible transformation from bonded elements to frictional elements. Furthermore

a macro-micro constitutive model framework considering the thermodynamic behavior of local bonding breakage was established. Secondly

based on the constitutive framework and the deformation mechanism of loess (frictional

bonded

and damaged)

the expressions for free energy

dissipated energy

and damage dissipated energy were determined. The damage yield function and elastic-plastic constitutive model considering the evolution laws of volume breakage and shear breakage were derived. Finally

the established model was used to predict the experimental data of other scholars

and its rationality and simulation advantages were verified through comparison. This model aligns better with thermodynamic principles

and its parameters are easy to determine.