Abstract: Many geotechnical problems, such as deep excavation of mine, underground storage of nuclear waste and pervasive application of energy piles, need to consider the effect of temperature on the mechanical properties of soft rock. In order to describe the mechanical properties of soft rock more comprehensively, based on the superloading and subloading concept and the concept of temperature-equivalent stress, a new elastoplastic constitutive model for soft rock, which is able to consider the effect of temperature, intermediate principal stress, structure and overconsolidation at the same time, is proposed in the tij stress space. All parameters of the new model have clear physical meaning. By comparing theoretical curves with the experimental results, the correctness of the proposed constitutive model is verified. Finally, by changing the model parameters, the performance of the new constitutive model is analyzed and discussed. Increasing the value of m which controls development of overconsolidation ratio or reducing the value of m* that controls structural state development will enhance the shear strength of soft rock. With the increase of temperature, the shear strength of soft rock declines. The higher the initial overconsolidation ratio is, the more apparent the dilatancy of soft rock becomes. But when initial structure is large, the volume strain of soft rock presents shear contraction in the final shear stage.

Key words: soft rock, temperature, thermal elastoplastic, constitutive model