断層帯を伴う花崗岩に付随する地下水・湧水の水質について

概要

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Hydrogeochemical investigations were carried out for the water appeared in some pilot tunnels which were under construction in granite regions. The samples obtained are, in general cases, falling water near the cutting face of pilot tunnel and, in another cases, flowing water from horizontally drilled holes for prospecting fissure water. Such water is considered to be conducted through networks of peon discontinuities and fault-sheared zones developed in granitic rock masses above and around the pilot tunnels. Cations, anions and other dissolved substances are analyzed throughout the investigations. Data of hydrogeochemical analysis are compared with each other and with stream and spring water distributed above and around the tunnelling sites. As results, the authors pointed out that mineral water, defined as higher contents of Cl^-, HCO_3^-, SO_^<2-> ions, is distinguished among the water obtained. Mineral water and common water are concealed irregularly and alternatively within the fault-sheared zones. Results of TR (tritium ratio) measurements indicated that large portions of above-mentioned falling water is supplied from the rainfalls before 1955 A.D., but some parts are recharged from the rainfalls after 1955 A.D. So, "intrusion" of rain water is rapid successively to the construction even though the case of pilot tunnel. In one case, 10^<-1> order's TR-value is measured form the cutting face of the central port of the Enasan tunnel.
1981-03-30