Abstract
The crystalline blockage of tunnel drainage pipes in a karst area seriously affects the normal operation of drainage system and buries hidden dangers for the normal operation of the tunnel. In order to obtain the influencing factors and laws of tunnel drainage pipe crystallization in a karst area, based on the field investigation of crystallization pipe plugging, the effects of groundwater velocity, drainage pipe diameter, drainage pipe material, and structure on the crystallization law of tunnel drainage pipe in karst area are studied by indoor model test. The results show that: (1) With the increase of drainage pipe diameter (20–32 mm), the crystallinity of drainage pipes first increases and then decreases. (2) With the increase of water velocity in the drainage pipe (22.0–63.5 cm·s−1), the crystallinity of the drainage pipes gradually decreases from 1.20 g to 0.70 g. (3) The crystallinity of existing material drainage pipe is: M3 (poly tetra fluoroethylene) > M2 (pentatricopeptide repeats) > M4 (high density polyethylene) > M1 (polyvinyl chloride); M8 (polyvinyl chloride + coil magnetic field) is used to change the crystallinity of drain pipe wall material. (4) When the groundwater flow rate is 34.5 cm·s−1, M1 (polyvinyl chloride) and M8 (polyvinyl chloride + coil magnetic field) can be selected for the tunnel drainage pipe. The research on the influencing factors of tunnel drainage pipe crystallization plugging fills a gap in the research of tunnel drainage pipe crystallization plugging. The research results can provide a basis for the prevention and treatment technology of tunnel drainage pipe crystallization plugging.
Highlights
With the accelerated development and modernization of China, the construction of railways and expressways in China has obviously developed by leaps and bounds
There are numerous tunnels in hard water regions in Southwest China. Water in this geological environment contains nearly saturated bicarbonate and calcium ions, which flow with groundwater into drainage pipes, slowly form calcium carbonate (CaCO3) crystals, and precipitate to clog tunnel drainage systems (Figure 1)
Except for the stable mass of crystals in the pipe using the magnetic field coil (M8), the mass of crystals in the other four pipes using modified materials all showed a negative growth stage, indicating that with the circulation of water flow, the binding force between the CaCO3 crystals and each modified material had an obvious stage of change between attraction and repulsion. It can be seen from the influence experiment of drainage pipe diameter that when the drainage pipe is full of groundwater, the crystallinity increases gradually in the initial stage
Summary
With the accelerated development and modernization of China, the construction of railways and expressways in China has obviously developed by leaps and bounds. There are numerous tunnels in hard water regions in Southwest China Water in this geological environment contains nearly saturated bicarbonate and calcium ions, which flow with groundwater into drainage pipes, slowly form calcium carbonate (CaCO3) crystals, and precipitate to clog tunnel drainage systems (Figure 1). The presence of phosphate ions in the precipitating solution stabilizes the initially formed vaterite by significantly reducing the rate of transformation of vaterite to calcite [2]. Within a certain concentration range of Ca2+ and CO32−, the magnetic field has a significant inhibition effect on the growth and precipitation of CaCO3 crystals [3]. The magnetic field affects the phase equilibrium of CaCO3 polymorphs by influencing the CO2/water interface or through the hydration of CO32− ions [4]. When the pH value is 8~10, the crystallinity of the semi filled pipe is higher
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