###### Abstract  
The constitutive model is the crucial part for the finite element analyses. To study the elasto-plastic properties of unbound granular materials (UCMs) under repeated vehicular loads, an elasto-plastic constitutive model called revised spatially mobilized plane (SMP) was proposed and validated. In this study, the revised SMP model was used for the plastic strain analyses of a typical three-layer pavement structure. To make comparisons, the Mohr-Coulomb and Druck-Prager models were employed for the numerical computation. The results show that plastic tensile and compressive strains in the horizontal and vertical directions appear on the top surface of UGM using the revised SMP model, but no plastic strains are produced by the Mohr-Coulomb and Druck-Prager models. The distribution of plastic strains in the revised SMP model had a good relationship with the actual loading areas under the vehicular loading, which related to the rutting. With the Mohr-Coulomb and Druck-Prage models, a great plastic strain was produced during the first several loading cycles and hardly increased in the following loading cycles, while the plastic strain in the revised SMP model presented an obvious increasing tendency with increased loading cycles. The predicted permanent deformations of the revised SMP, Mohr-Coulomb and Druck-Prage models were 0.557 mm, 0.78 mm and 0.155 mm, respectively. Our work reveals that the Mohr-Coulomb model may over-predict and Druck-Prage model may under-predict the rutting of pavement in early loading stage and the results proved that the revised SMP model had advantages in the description of the plastic strain of UMG under repeated loads. unbound granular material; elasto-plastic model; plastic strain; revised SMP model; Mohr-Coulomb; Druck-Prage; repeated loads Article  
Strains Comparisons of Unbound Base/Subbase Layer Using Three Elasto-Plastic Models under Repeated Loads  
[PERSON], [PERSON], [PERSON]; [PERSON], H.  
Strains Comparisons of Unbound Base/Subbase Layer Using Three Elasto-Plastic Models under Repeated Loads  
[PERSON], [PERSON], [PERSON], H.  
Strains Comparisons of Unbound Base/Subbase Layer Using Three Elasto-Plastic Models under Repeated Loads
These models consider various factors which would affect the plastic strains. The accuracy and practicality vary greatly however, according to the different application conditions. Aiming at studying the stress-dependency of UGMs, non-linear and anisotropic models were frequently used to describe the mechanical properties of UGM in the laboratory and field [6; 12; 13; 14; 15]. This kind of model was mostly used for the computation without considering the characteristics of plasticity. These aspects are the main current research directions of UGMs. Although the non-linear and anisotropic models are accepted widely, plastic strains are hardly considered in these models, especially for the repeated vehicular loads [6; 14]. On the other hand, the prediction models of plastic strain are difficult to use for structural analyses calculations, therefore, the most appropriate way is to establish a rational elasto-plastic constitutive model to balance the stress and strain. Considering the stress-dependent and plasticity of UGMs, [PERSON] et al. proposed a nonlinear anisotropic elasto-plastic (NAEP) constitutive model based on the Generalized Drucker-Prager criterion [6; 15]. The model was implemented using the weak form equation-based finite element model without a material subroutine and validated by loading tests performed in a laboratory tank. Compared with the nonlinear anisotropic elastic model, the NAEP model gave similar fatigue life results but predicted greater rutting in the pavement [6]. This model took full account of the characteristics of UGMs, avoiding the complicated hardening law. However, the cumulative plastic strain process seems unclear in this model. Based on shakedown theory and the Drucker-Prager criterion, [PERSON] et al.