Calcium carbonate (CaCO3) precipitation in tunnel drainage system poses serious problems to railway tracks. In this study, the calcification phenomenon identified in Meyssiez tunnel was analyzed through laboratory testing and site water monitoring. In particular, the surrounding soils were investigated in the laboratory. Site water table was regularly monitored in the field and site water was taken for laboratory analyses in terms of pH and electrical conductivity (EC). Examination of the test results showed that the calcification phenomenon was mainly induced by the calcium carbonate dissolution in the fine fractions (d < 0.08 mm) of surrounding soils. Due to this dissolution, the void ratio of fine fractions (ef) and the hydraulic conductivity (k) of soils both increased. Meanwhile, calcium carbonate dissolution increased the pH values and electrical conductivity (EC) of groundwater. However, any recharge of water table by rainfalls decreased both pH and EC. Further analysis showed that a calcium carbonate dissolution degree can be defined in terms of pH and/or electrical conductivity (EC) values. The lower the pH values or the higher the EC, the higher the calcium carbonate dissolution in surrounding soils.