Influence Of Pipe Material And Pipe Connection Form On Crystallization Formation Of Dolomite Tunnel Drainage System

Dolomite is easily eroded by water,and its solution is easy to crystallize in the tunnel drainage pipe,and then block the drainage system,which affects the drainage capacity of the tunnel,resulting in large differences in the force and design of the supporting structure,resulting in potential safety and water leakage hazards.Aiming at the problem of crystalline blockage of the tunnel drainage system in the Dolomite area,relying on the Baiyanjiao tunnel of Luzhou-Zhaotong Expressway(referred to as Luzhao Expressway),the crystal samples were scanned by electron microscope,energy spectrum,and X-ray diffraction analysis(XRD)and other tests,liquid chromatography was used to analyze the water sample flowing through the dolomite.Design and apply an indoor simulation test device to simulate the crystallization situation in the actual tunnel drainage system.The influence of tunnel drainage pipe connection method on crystallization and the influence of pipe material on crystallization are studied.According to the test results and the found crystallization laws,the Ca CO₃ fixed deposition device was designed based on the electrodeposition method,and the assembly test was performed to verify the feasibility of the device,and the control factors required for the device were analyzed and discussed.The main work and results are as follows:(1)Through engineering field sampling and analysis,the microstructure,element composition,phase composition of the crystal in the tunnel drainage system and the element composition of the water sample in the tunnel drainage system were obtained.Based on the analysis of the two existing crystallization mechanisms of tunnel drainage systems,combined with sampling point working conditions and sampling analysis results,a third crystallization mechanism that may occur in the tunnel drainage system is proposed.(2)Through carrying out indoor simulation experiments,the influence of the connection mode of the tunnel drainage pipe on the crystallization in the tunnel drainage system was studied.It is found that the location where the reverse slope drainage occurs in the tunnel drainage system and the location of the intersection of the vertical drainage pipe,the horizontal drainage pipe,and the circular drainage pipe are the high-risk areas for crystallization blockage.Combined with the drainage design of the tunnel project,two optimized design schemes for the anti-crystallization of the drainage system are proposed.(3)Through indoor simulation experiments,the influence of drainage pipe materials on crystallization was studied,and it was found that the crystallization quality in descending order was PVC,half-wall corrugated pipe,HDPE,PPR,and combined with the tunnel drainage pipe materials used in the actual project,optimization suggestions were given.(4)Combining the experimental phenomenon and the crystallization situation of the field engineering,the process of crystallization in the tunnel drainage system is divided into:calcite crystallization,calcite shedding and deposition,and calcite consolidation.It is found that the process of calcite shedding is the best period for the treatment of crystallization in the tunnel drainage system.(5)Combined with the electrodeposition method,a device was designed to fix the calcite to a convenient place for daily cleaning.And the feasibility was verified through experiments,and finally the optimized parameters required for the actual application of the device were discussed and analyzed.