Anti-Blocking Mechanism of Flocking Drainage Pipes in Tunnels Based on Mathematical Modeling Theory

Crystalline pipe plugging in tunnel drainage systems is one of the causes of tunnel lining cracking and water leakage. Therefore, effective prevention of crystalline pipe blockage in tunnel drainage systems is very important to ensure the safety and stability of the lining structure during tunnel operation. Combined with the theories of fluid mechanics, structural mechanics and basic physics, the flocking and anti-blocking mechanism of drainage pipe was comprehensively analyzed by using the method of mathematical modeling, including: (1) the calculation expression of average velocity of the flocked section of a flocked drainage pipe v = Q/(C₁ − C₂(r + r′)) and the calculation formula of flowing water pressure under the action of groundwater F_w =  KAγQ²/(2g(C₁ − C₂(r + r′))²); (2) the flow velocity v₀ in the flocked drainage pipe shall meet v² < 4gπrlτ₁/γKA, crystals will be attached to the fluff and the crystals will maintain dynamic balance; (3) the flow velocity v₀ in the flocked drainage pipe shall meet v² ≥ 4gπrlτ₁/γKA, crystals will not adhere to the fluff and the flocked drainage pipe will remain unobstructed. The research on the mechanism of preventing blockage of flocking drainage pipes fills the gap in research theory in this regard, contributes to the popularization and application of blocking prevention technology of flocking drainage pipes, reduces the maintenance cost during operation of tunnel drainage systems and ensures the safe and normal operation of tunnels.