Abstract
At the Akaishizawa tunneling work in the sandstone and clay slate regions, the oxygen content of the air in the tunnel decreased to about 18% accompanying a great quantity of seepage water. To investigate the cause of the decrease in the oxygen content, hydrogeochemical investigations of seepage water were carried out. Dissolved oxygen, Eh, pH, electric conductivity, water temperature, ionic composition, tritium, oxygen isotope ratio and hydrogen isotope ratio were analyzed. From the results, it was made clear that the decrease in the oxygen content was induced by the dissolution of oxygen in the gushed water.
