Experimental Study On Influencing Factors Of Crystal Plugging In Tunnel Drainage Pipe

With the rapid development of expressway and high-speed rail in China in recent years,more and more tunnels and underground projects have been built.At the same time,with the blockage of tunnel drainage system,the emergence of cavern leakage and lining cracking has caused experts at home and abroad to pay special attention.In western China,Chongqing,Sichuan,Yunnan,Guizhou and other regions,many rock components are limestone,limestone is mainly rich in Ca CO₃ impurities,and when the tunnel passes through,The drainage pipes of its tunnels can easily form calcium carbonate crystals that accumulate on the drainage pipes,resulting in silt,debris,etc.that can not be discharged normally and block the drainage pipes.The crystal blockage repair of the tunnels will not only cost huge manpower and material resources.Even more serious will affect the comfort and safety of traffic and driving.The tunnel drainage system is like the meridians on the human body.The meridians are blocked and the meridians are blocked.This will cause various discomfort and malaria in the human body.Similarly,the blockage of the tunnel drainage system will affect the service life and safety of the tunnel structure.At present,most of the domestic and foreign studies are aimed at the growth of carbonate crystal nuclei and the growing regularity of grains.However,there is little systematic research on the factors that cause the blockage of carbonate crystals in tunnel drainage pipes.Therefore,we designed and studied the experimental mechanism and factors of crystal blockage in tunnel drainage systems,carried out research experiments on carbonate crystal blockage pipes in limestone areas,and discussed the crystallization laws of carbonate crystals in tunnel drainage pipes.It is of great theoretical significance and practical application value for extending the service life of tunnel,improving the design of tunnel drainage system and avoiding the occurrence of major safety accidents.In this paper,the tunnel diameter,flow rate,pipe material and modified pipe material are studied by means of model experiment based on the research of Chongqing city tunnel,and then relying on the cultivation base and material laboratory of the National key laboratory of bridge and tunnel engineering in the mountainous area of Chongqing Jiaotong University.The main research content is as follows:（1）Study on Optimization of Crystal Design Combination of Pipeline by Orthogonal Experiment.According to the results of the previous investigation,this section is based on the orthogonal principle,and the orthogonal test is designed to analyze the impact of different factors on the crystallization of the tube wall.The three main factors that affect the crystallization efficiency are selected:flow rate,tube material,and coating.Based on three factors and three levels of orthogonal experiment table,according to the minimum combination of crystallization,the main order and the optimal combination that affect the crystallization rate are obtained.（2）Experimental study on the crystallization of tunnel drainage pipes with different diameters.According to the complicated characteristics of different pipe sizes in tunnel drainage system,the effect of different pipe diameters on the crystallization velocity was studied,and the effect of pipe diameters on the blockage was discussed.PVC tubes with diameters of 20mm,25mm and 32mm were studied.（3）Experimental study on the crystallization of tunnel drainage pipes at different velocity.Since the speed of water flow in the tunnel drainage pipe is constantly changing,through the control of the speed of water flow in the tunnel drainage system,combined with specific engineering examples,the method of parallel experiments is used to analyze.The effects of tunnel flow rate on the crystal velocity of 22cm/S,26.5 cm/S,34.5 cm/S,44.5 cm/S,and 63.5 cm/S were studied,and the effect of flow rate on the blockage of drain pipe was discussed.（4）Experimental study on the crystallization of tunnel drainage pipes under different pipe materials and coating.Under actual circumstances,the selection of pipeline materials has a great influence on the crystallization rate.Therefore,it is necessary to study the impact of pipe materials on the crystallization of tunnel drainage pipes.The experimental selection of PVC,HDPE,PPR,and PTFE pipes is four kinds of tubes.The effects of different materials on the crystallization of tunnel were obtained.Further,five coatings of hydrophilic antistatic self-cleaning agents,fluff film,Silicon rubber,polyethylene powder,and magnetic field coils were applied to PVC pipes with a diameter of 32 mm.The effects of different coatings on tunnel crystals were experimentally obtained.（5）Study on Micromechanism of Crystal Blocking Pipeline（Materialized Studio Simulation）.The microscopic study of the crystal blocking mechanism of the tunnel was carried out.Through the method of molecular dynamics simulation,the process of congestion of the drainage pipe was analyzed,and the simulation results were compared with the results of indoor experiments.The binding energy between calcium carbonate crystal and tube wall and the deformation characteristics of polymer and calcium carbonate adsorption were obtained.Secondly,a solid-liquid model was established to explore the microscopic mechanism of crystallization of tube walls by acid and alkali.