A constitutive model of rock based on strain cone surface and the parameter calibration method with high efficiency

The elastic and plastic strains of rock during the compression process cannot be accurately identified by common constitutive models. This paper investigated the strain evolution of rock under monotonic compressive load by referring to results from damage-controlled cyclic loading tests, and discussed the contradiction between the flow rule of traditional elastoplastic constitutive models and real plastic strain development. Therefore, a strain cone surface constitutive model was proposed, where the yield surface was replaced with strain cone surfaces for both elastic and plastic strains. The magnitude and direction of vectors regarding elastic and plastic strain increments occurring on these conical surfaces were explored. Then, the proposed model was validated against cyclic loading tests. Furthermore, a robust parameter calibration method was developed based on genetic algorithm, and its ability to search for optimal parameters was verified by comparing the simulated constitutive relationships with the practical stress–strain curves. The results show that the traditional flow rule could be incompatible with the real plastic strain variation. In contrast, the proposed model could accurately simulate the evolution of elastic and plastic strains, demonstrating high precision and applicability. Moreover, the calibration method enables the determination of model parameters with high accuracy and efficiency.