Abstract: To investigate the characteristics of crystalline material and the effect of water environment on the drainage path of highway tunnels and analyze the applicability of crystallization change and trend calculation method, a case study is conducted on drainage crystallization disease of tunnels in dolomites. The drainage path of "surrounding rock waterinitial branch waterdrainage pipe water" is regarded as the analysis context to comparatively analyze the variation characteristics of crystalline mineral content, concentrations of the Eight Ions of water, and water environment parameters in the drainage path. In addition, the variation law of crystallization trend in the drainage path is calculated and clarified using the DavisStiff saturation index method and calcite saturation index method. Moreover, the applicability of the recommended methods and the influence of main water environment parameters on the crystallization trend are analyzed. The results reveal the following: (1) The tunnels exhibit calcite drainage crystallization, and the content of calcite in the drainage path increases sharply. The calcites account for 0.6% and 15% of the surrounding rock 〖HJ2.4mm〗and primary support shotcrete, respectively. (2) The primary support shotcrete significantly affect the water environment parameters in the drainage path. It dramatically increases the concentrations of Ca2+ ions, CO2－3 ions, and pH value and sharply decreases the concentration of HCO－3 ions. Salinity, total dissolved solids, and conductivity exhibit an increasing trend. (3) The drainage path initially exhibits an increasing crystallization trend and then stabilizes. The influence of Ca2+ ion and CO2－3 ion concentrations on the saturation trend is greater than that of the temperature 〖WT《TNR#I》〗t〖WT《TNR》〗 and pH value. (4) The calculation results of the crystallization trend of the calcite saturation index method are consistent with the actual situation. Thus, the findings show that the proposed method is suitable for analyzing the crystallization trend of the tunnel water environment in dolomite. 

Key words: dolomite tunnel, drainage crystallization, drainage path, crystallization trend, saturation index