Abstract: Based on the numerical method in modeling the constitutive relations of rock and soil and its four basic steps, the elastoplastic neural network constitutive model of medium sand is set up, the yield surfaces are drawn from test data, and their feasibility and effectiveness are shown through the computed example. The research results show that the model has many advantages. On the one hand, the difficulty for determining the plastic potential in elastoplastic model can be overcome; on the other hand, the ...