Numerical simulation of coupled hydro-geochemical behavior induced by tunnel excavation; Preliminary analysis for in-situ test on excavation disturbed zone of the drift in Horonobe URL project

Suzuki, Hideaki; Kimura, Makoto; Fujita, Tomoo 

It is necessary to consider the disturbance around the tunnel caused by the excavation of the realistic numerical simulation regarding the long-term behavior of near-filed after of engineered barrier system. In this paper, it is presented the preliminary analysis for Excavation Disturbed Zone (EDZ) around the horizontal drift at GL.-140m on Horonobe URL project. The coupled analysis, in which the hydraulic disturbance was considered, aiming principally at changes of the geochemical properties in the ground water with excavation was carried out. As a result, changes the pH in the ground water occurred, and it was showed these changes were caused by the gasification of the carbon dioxide in the ground water with enlarging the unsaturated zone, which is reaching up to about 5 meters long from the surface on the drift tunnel.