Backfilling of the underground facilities on a disposal site

Sugita, Yutaka; Fujita, Tomoo; Tanai, Kenji; Hasegawa, Hiroshi; Furuichi, Mitsuaki*; Okutsu, Kazuo*; Miura, K.*

JNC TN8400 99-039, 58 Pages, 1999/11

JNC-TN8400-99-039.pdf:3.19MB

Regarding disposal techniques of high-level radioactive waste (HLW), the HLW is vitrified and then stored for cooling for a period of 30 to 50 years. After cooling, the HLW is isolated in the deep underground. The concept of geological disposal is based on the requirement to enclose the HLW in the deep underground for the long-term durability of the human's environmental safety. Backfilling of a repository is a unique activity on the geological disposal. If underground tunnels excavated to construct the repository are left, they may have significant influences on the barrier performance of an entire repository, such as: the mechanical stability of a tunnel may be damaged by rock stresses and a tunnel may provide a fast pathway for ground water flow. Therefore, the underground facilities are expected to be backfilled with a backfilling material after emplacement of the HLW and a buffer material. The material for the backfilling of the underground facilities is backfilling material. In this report, bentonite-aggregate mixture is considered, as one of the candidate materials for the backfilling material. Aggregate imitates the muck that is generated during construction phase of the underground facilities. The combination of backfilling, plugging and grouting is considered in some underground situations. Plug is composed of concrete material or clay-based one. Grouting material is concrete material or clay-based one, too. In this report, the concept of the backfilling, mechanical and hydrological characteristics of the bentonite-aggregate mixture, the function, work methods and a schedule of the backfilling materials, plugging and grouting are considered, and items of quality control for the bentonite-aggregate mixture, concrete material and grouting are listed.

Physical and chemical properties of bentonite-loam mixture as backfill materials

*; *; *; *

Proc. of the 1989 Joint Int. Waste Management Conf., Vol. 1, p.475 - 481, 1989/10

no abstracts in English

The In-situ verification of performance of engineered barrier system in Horonobe Underground Research Laboratory, 12; Study of quality control method on the in-situ compaction technique for backfilling

Tanai, Kenji; Kikuchi, Hirohito*; Nakayama, Masashi; Ono, Hirokazu; Shirase, Mitsuyasu*; Takahashi, Akihiro*; Niunoya, Sumio*; Kuriyama, Masanori*

no journal, , 

no abstracts in English

Backfilling test in the groundwater recovery experiment, 1; Observation of saturation and swelling process

Takayasu, Kentaro; Takeuchi, Ryuji; Onoe, Hironori

no journal, , 

The Groundwater REcovery Experiment in Tunnel (GREET) is conducted by making the Closure Test Drift (CTD) recovered with water at the depth of 500m. Backfilling test is conducted as a part of GREET to acquire physical property change of the backfill material. Bentonite mixture was constructed into two pits excavated 1m in depth on the floor of the CTD. Hydraulic pressure, soil pressure and moisture content were measured to grasp the groundwater saturation process and the swelling process of backfill material. The moisture content in the pits got almost fully saturated till one month after. During water filling event, both hydraulic pressure and soil pressure reached 3.1 MPa at maximum. The swelling pressure of the backfill was calculated as 0.03-0.09 MPa. Observation inside the pit will be continued, and characteristics of backfill material will be investigated again. Changes of hydraulic pressure and soil pressure will be simulated and the construction method will be validated.