Study on causes and laws of crystallization blockage for dolomite tunnel drainage pipeline

In order to study the crystallization blockage law and crystallization mechanism of dolomite tunnel drainage system, based on the indoor model test, the simulated crystal blockage and growth process were simulated. The phase composition and microstructure of the crystal were analyzed by energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Combined with the pipeline crystal weighing, the crystal growth law and the internal cause of pipeline blockage were analyzed. The results show that the pipeline crystallization mechanism is divided into the first mechanism, the second mechanism, and the third mechanism. The crystallization blockage of the longitudinal and horizontal pipes are more serious, while the crystallization blockage of the ring pipes are less harmful. The crystallization is positively correlated with ion concentration, crystalline ions having a great influence on the blockage of pipeline crystallization, while noncrystalline ions having little influence. The crystal growth law is fast first and then slow, the crystallization affected by the coupling concentration of Cl⁻-K⁺-Na ⁺ ions, and positively correlated with the coupling concentration of CO₃²⁻-SO₄²⁻-Ca²⁺-Mg²⁺-Al³⁺ ions. Compared with the longitudinal pipes and the ring pipes, the horizontal pipes have more crystallization and higher degree of crystallization blockage per meter, while the crystallization degree of the longitudinal pipes are between the horizontal pipes and the ring pipes.