Study on the crystallisation formation mechanism and breakage of tunnel drainage system in dolomite area

Abstract

AbstractDolomite is a soluble salt rock, and in dolomite locations, tunnel drainage systems are frequently clogged by crystallisation, resulting in tunnel leaks. This research starts with a field survey to investigate the environmental conditions that influence crystal formation and sample collection. Afterward, the crystals underwent examination using EDS, scanning electron microscopy (SEM) and XRD, which enabled the analysis of crystals' elemental composition, matter composition and microstructure. Finally, a measure for crystal removal using ultrasound is proposed. The feasibility of ultrasonic crystal removal was verified by the indoor model experiment. The results show that the crystals contain mainly metallic elements such as Ca, Mg and Al. The main component of the crystals is CaCO3. The crystals also contain small amounts of Mg (OH)2, Al (OH)2 and CaAl2(SO4)3(OH)2‐26H2O. As the ultrasonic frequency increases, the de‐crystallisation effect becomes more pronounced. At ultrasonic frequencies greater than 50 kHz, the growth in crystal break‐up efficiency tends to level off. Therefore, the ultrasonic frequency based on this parameter will be used to remove the crystals.