Crystallization Blockage Mechanism in Drainage System of Xi'an-Yan'an HSR Tunnel
Based on the on-site survey and investigation of crystallization blockage in the drainage system of Xi'an-Yan'an HSR Tunnel,taking Yijun Tunnel and Wujiayuan Tunnel as examples,this paper samples and analyzes groundwater,crystals,shotcrete outer layer seepage and building materials,and clarifies the main components and formation mechanism of crystals.The study shows that the blockage position of white and gray crystalline deposits is mainly located at the outlet of the circumferential blind pipe,with small water flow at the nozzle and serious blockage.The main component of white crystal is CaCO3,and a small amount of gray crystal is carbonate mixed with concrete.In the crystal,Ca2+mainly comes from the hydration product of cement in shotcrete,and CO32-mainly comes from mineralized ions in groundwater.Therefore,the crystallization process in tunnel drainage pipe includes 3 stages:penetration process of groundwater to shotcrete;dissolution process of calcium in concrete;crystal deposition process in drainage pipe,which provides a theoretical basis for prevention and treatment of crystallization blockage hazards in tunnel drainage system.
Xi'an-Yan'an HSRtunneldrainage system blockagecrystalcrystallization mechanism
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