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

Shiyang Liu,Feng Gao,Xuefu Zhang

doi:10.3390/coatings11080961

Abstract

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 Fw = 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.

Highlights

As of the end of 2020, there were 21,316 highway tunnels in China, including 1394 extralong tunnels and 5541 long tunnels [1]
With the operation of the tunnels, various types of damage have gradually appeared, especially lining leakage (Figure 1) and cracking (Figure 2) caused by the crystallization-induced blockage of the drainage system of the tunnel in the karst area (Figure 3) [2], which seriously affects the safety of the tunnel lining
A tunnel drainage system blockage caused by crystals can only be dredged by high-pressure gas [3] or excavation, which is costly and affects the normal passage of the tunnel

Summary

Introduction

As of the end of 2020, there were 21,316 highway tunnels in China, including 1394 extralong tunnels and 5541 long tunnels [1]. With the operation of the tunnels, various types of damage have gradually appeared, especially lining leakage (Figure 1) and cracking (Figure 2) caused by the crystallization-induced blockage of the drainage system of the tunnel in the karst area (Figure 3) [2], which seriously affects the safety of the tunnel lining. A tunnel drainage system blockage caused by crystals can only be dredged by high-pressure gas (water) [3] or excavation, which is costly and affects the normal passage of the tunnel. To make the lining structure of the tunnel safe and stable, it is necessary to ensure the effective and smooth operation of the drainage system of the tunnel. It is necessary to prevent the occurrence of crystallization-induced pipe blockage in the drainage system in advance. In view of the problem of crystallization blockage in the tunnel drainage system, the current focus is mainly on three aspects: the analysis of crystal composition, the analysis of crystallization influencing factors and the technology to prevent crystallization

Methods

Results

Conclusion