A multi-field and fluid-solid coupling method for porous media based on DEM-PNM

Many processes in geology and geotechnical engineering fields involve multi-field coupling, fluid-solid coupling and large deformation. The numerical simulation of such complicated processes is still very challenging. Based on the Discrete Element Method, a pore density flow model is proposed to simulate multi-field coupling and fluid-solid coupling, which introduces the Pore Network Model to describe the pores. The fluid properties within a single pore are normalized to reduce the computational complexity and determine the amount of fluid ex-change based on the Darcy's Law. Moreover, an equation including density, pressure and temperature is introduced to simulate fluid state. The pore network changes dynamically with the displacement of elements, which can simulate the cracking and failure process of complex rock and soil mass driven by fluids. This model is implemented in the high-performance discrete element software MatDEM, which can quantitatively analyze the evolution law of fluid-solid coupling in the pore scale. Three examples are given to verify the validity of this model. The simulation results show that this model can not only form an effective network model based on the DEM, but also can reflect the immigration of fluids and heat in the porous medium and the development trend of fluid-driven fractures.