Unified Description of Thermoelastoplastic Behavior of Geomaterials Considering Interparticle Bonding

In this paper, a thermoelastoplastic constitutive model integrating interparticle bonding is proposed to describe the fundamental thermal and mechanical behaviors for different geomaterials (e.g., soft rock, sand, and clay) within a unified framework. In the proposed model, the concepts of subloading surface and superloading surface are adopted to describe the effects of overconsolidation and structure on the mechanical properties of geomaterials. A state variable characterizing the degree of bonding strength is integrated into the yield function to supplement the description of interparticle bonding effects on the mechanical properties of geomaterials. To consider the effects of temperature, thermal expansion/contraction strain is taken as a part of the total strain, and the bonding strength and structure are correlated to temperature change to describe the mechanical properties of some geomaterials affected by temperature. Except for the conventional thermophysical parameters, the model here employs only eight mechanical parameters, five of which are the same as those in the Cam-clay model. The three additional parameters have clear physical meanings and can be determined by conventional tests. Through the calculation of element tests under different mechanical, hydraulic, and thermal conditions for different geomaterials, it is confirmed that the proposed model here can describe properly the general thermoelastoplastic behaviors for typical geomaterials. Moreover, by calculating a temperature-related boundary value problem (BVP), it is found that under a long-term cycling temperature condition, even thermal expansion/ contraction will cause the degradation of bonding in the soft rock.