Study on construction technology for repository

Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Miura, K.*; Okutsu, Kazuo*; Kobayashi, Masaaki*

JNC TN8400 99-046, 177 Pages, 1999/11

JNC-TN8400-99-046.pdf:6.03MB

For the construction of underground facilities comprising access tunnels, connecting tunnels, main tunnels and disposal tunnels, a large number of tunnels will be excavated in deep rock formations. These excavations will extend hundreds kilometers in total length. Therefore, special attention must be paid, to transporting large volume of debris, ventilation, emergency escape routes in case of accident, and other factors. In addition, special attention must also paid to potential accidents which might in underground excavations, including unstable facing phenomena (such as collapse and swelling of facing at weak layer sections), spring water flow resulting collapse of rock, gas eruption, and rock burst. While considering these factors to be emphasized during the construction of geological disposal facilities, the investigation reviewed the existing working methods on individual construction technologies of access tunnels, main tunnels, connecting tunnels, disposal tunnels, and disposal pit, based on the recognition that the present state deals with a wide range of geological environments, and conducted investigation about the construction methods for each tunnel on the basis current technologies, and described the outline of these methods. Furthermore, for the items to be particulaly emphasized on site characterization koko and siting data such as ground pressure and spring water, the investigation reviewed the current countermeasure works, and made survey on the phenomena appeared during actual tunnel construction works and their countermeasres, and carried out a study on effectiveness of these countermeasures. This constructing of disposal site in deep geological formations is basically possible by applying, or confirming, current excavation technologies for tunnels and underground facilities, A systematic construction system combines separate technologies relating to construction, (excavation technology, tunnel support work method, etc.). Such systems ...

Research for the erosion of buffer material with the vertical disposal concept, 4; Numerical analysis of inflow control into the disposal pits using discrete fracture network model

Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Ishii, Tomoko*; Jo, Mayumi*; Nakayama, Masashi; Ono, Hirokazu

no journal, , 

In the vertical disposal concept of high level radioactive waste, it is important to evaluate influence of the groundwater inflow into the disposal pits against performance of buffer material as an artificial barrier because the inflow might cause the erosion of buffer material. The target of this study was to estimate the inflow control technique (e.g. grouting) around the disposal pits using numerical analysis. The model for the simulation should be a discrete fracture network model when the groundwater mainly flows along the fractures in the rock mass, therefore, the discrete fracture network model was selected to estimate the inflow control technique in this study. The results of numerical flow analysis showed that the effectiveness of grouting for the disposal pits and the impact of grouting for the other disposal pits or surrounding disposal tunnel could be evaluated quantitatively.