Mechanism of aggregate start-up process and coupling of two-phase flow in hydrodynamic roadway

In order to study the relationship between the aggregate accumulation state in the roadways with hydrodynamic water and the inclination angle of the roadways, the criterion for the start of aggregate particles in the inclined roadways were established. A numerical mechanics model(CFD-eDEM) describing the process of aggregate infusion was established using computational fluid dynamics and discrete element method, the start-up velocity and water carrying capacity of 5-10 mm, 10-30 mm and 30-50 mm aggregate particle groups under different accumulation thickness were tested, and the static water accumulation angle and dynamic water accumulation shape of each particle group in different inclined roadways were simulated. The results are as follows:The starting speed decreases in order of ascending roadway, horizontal roadway and descending roadway, and the ratio of the square of starting speed was (tanΩcosθ+sinθ):tanΩ:(tanΩcosθ-sinθ). It was found that the shape of the accumulation is determined by the dynamic equilibrium state of the flow field and the pouring capacity. When the carrying capacity of the flow field is much smaller than the pouring capacity, it is easy for the accumulatiom to connect the top, and vice versa. It shows that the inclination angle of the roadway has no effect on the accumulation angle. Under the same flow velocity, the accumulation form of aggregate in the downhill roadway is "stretched" and not easy to connect to the top, while it is "compressed" in the uphill roadway and relatively easy to connect to the top. During the construction process, the uphill section should be selected as much as possible to reduce the construction difficulty. After the site of the project is determined, the particle size in the downhill should be appropriately increased, and reduced correspondingly in the uphill, so as to achieve rapid closure and reduce ineffective perfusion engineering.