Experimental Study on Prevention and Control of Calcium Carbonate Crystallization in Tunnel Based on the Yijun Tunnel

The occurrence of crystallization plugging in the tunnel drainage system will lead to cracking and leakage of the tunnel lining. Therefore, it is very important to take effective measures to prevent the blockage of the crystallization pipe of the tunnel drainage system and ensure the safety and stability of the lining structure during the operation of the tunnel. In this study, we conducted field surveys and laboratory tests to analyze the relationship between the crystals in the Yijun tunnel blind pipeline and the concentration of various ions in the groundwater. X-ray diffraction (XRD) analysis confirmed that the main component of the crystalline sediment was calcium carbonate. The formation mechanism of crystallization was explored by using the environmental water chemical equilibrium software, Visual MINTEQ 3.1. Considering that the preparation of cleaning agent has less corrosive effect on tunnel concrete materials, the cleaning efficiency test of various acid cleaning agents on tunnel crystals was carried out to determine the optimal concentration of cleaning solution. Finally, it is determined that the mixture of formic acid: citric acid: corrosion inhibitor: surfactant: water = 1:0.5: 0.5:0.5: 5 is used as the cleaning agent of tunnel blind pipe. The experimental results show that the cleaning agent has a 92.4% CaCO₃ dissolution rate, and the pH is controllable (4.7-7.9), which meets the environmental protection standards, and has little damage to the concrete (strength loss of 3.4 Mega Pascal, control group 6.2 Mega Pascal).