Abstract: A discrete element method contact model building method includes: selecting a filling body in a disaster-causing structure to obtain a change rule of cumulative loss of the filling body; performing test simulation, and determining a relation function of each group of corresponding mesoscopic mechanical parameters in each time period and mesoscopic parameters of a DEM contact model representing a change rule of macroscopical parameters of the filling body; embedding each mesoscopic parameter relation function into an existing particle contact model, performing test simulation, and updating a fracture failure criterion of the contact model according to a corresponding relation of macro-mesoscopic strength during model failure; and based on a seepage failure indoor test, building a seepage failure discrete element calculation model, and simulating the seepage failure process of a rock and soil mass by using the obtained particle contact model and the fracture criterion of the particle contact model.

Abstract: A double-channel fluid injection apparatus includes a main shaft, a bearing box, and a sealing box. The main shaft includes an outer tube and an inner tube. An internal channel of the inner tube and a vertical through channel constitute a first fluid passageway. The inner tube and the outer tube form an annular gap, and a channel D is radially formed at a lower part of the outer tube and is in communication with the annular gap, thus constituting a second fluid passageway. The bearing box is mounted on a boss of the outer tube. The sealing box includes a sealing cylinder fixedly connected to a lower end of a lower end cap of the bearing box. A channel E in communication with the second fluid passageway is radially formed at a position of the sealing cylinder corresponding to the channel of the outer tube.