Study on Elastic-Plastic Damage Constitutive Relation of Strongly Weathered Argillaceous Silt

In order to study the constitutive relationship of fully weathered argillaceous siltstone under the influence of seepage, based on the fully weathered argillaceous siltstone under the Nanchang subway tunnel, according to the triaxial undrained shear test, the mechanical response mechanism under static load is revealed. At the same time, with the support of the data of the test results, combined with the existing elastic-plastic constitutive model, the initial crack damage variable and the seepage sub-damage variable are introduced to construct the applicable constitutive model, and the secondary development is carried out through the program. Finally, the correctness of the self-developed elastic-plastic damage model of fully weathered argillaceous siltstone is verified by comparison. The findings indicate: (1) By considering the coupling damage variable relationship under the combined action of initial damage and seepage secondary damage, the constitutive relationship suitable for the rock sample is established. (2) The corresponding constitutive integration algorithm is deduced, and the secondary development of the constitutive model is completed through the UMAT interface program. (3) Based on the secondary developed constitutive model, the fully weathered argillaceous siltstone considering damage is numerically simulated by finite element software. Through numerical verification, it is found that the model can better describe the stress-strain relationship under different confining pressures and different stress levels, and to a certain extent, it can also reflect its strain accumulation.