検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

亀裂を有する軟岩の水理・物質移行特性データの取得・解析(委託研究)

Study on flow and mass transport through fractured soft sedimentary rocks (Contract research)

下茂 道人*; 熊本 創*; 前川 恵輔

Shimo, Michito*; Kumamoto, So*; Maekawa, Keisuke

高レベル放射性廃棄物の地層処分サイトの性能評価にあたっては、天然バリアを構成する岩盤中における水理・物質移行特性を適切に評価することが重要である。これまで軟岩における物質移行現象は、粒子間間隙を主な移行経路と考えてきた。しかし亀裂が発達した軟岩では、亀裂が卓越した水みちを形成する可能性がある。本研究は、亀裂を有する軟岩中における水理・物質移行特性の解明を目的とし、軟岩試料を対象とした室内試験及び解析を行った。幌延深地層研究センターの試錐孔(HDB-9$$sim$$11孔)で採取されたコア試料を対象とした室内試験(透水試験,トレーサー試験,拡散試験)を実施し、深度,地層の種類や年代,続成作用等が試験結果に与える影響を検討した。さらにブロック型の自然亀裂試料を用いた透水試験,トレーサー試験を実施し、試験規模の違いによる水理・物質移行パラメータの変化について検討した。また、実スケールの岩盤を想定した亀裂を有する軟岩中の流れと物質移行現象の概念モデルに関する数値解析的検討を行い、岩盤のモデル化手法に関する考察を行った。なお、本研究は旧核燃料サイクル開発機構の成果である。

It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground accurately. Though it is considered that the mass transport in sedimentary rock occurs in pores between grains mainly, fractures of sedimentary rock can be main paths. The objective of this study is to establish a conceptual model for flow and mass transport in fractured soft sedimentary rock. In previous study, a series of laboratory hydraulic and tracer tests and numerical analyses were carried out using sedimentary rock specimens obtained from Koetoi and Wakkanai formation. Single natural fractured cores and rock block specimen were used for the tests and analyses. The results indicated that the matrix diffusion played an important role for mass transport in the fractured soft sedimentary rocks. In this study, the following two tasks were carried out: (1) laboratory hydraulic and tracer experiments of rock cores of koetoi and Wakkanai formation obtained at HDB-9, HDB-10 and HDB-11 boreholes and a rock block specimen, Wakkanai formation, obtained at an outcrop in the Horonobe area, (2) a numerical study on the conceptual model of flow and mass transport through fractured soft sedimentary rocks. Non-sorbing tracer experiments using naturally fractured cores and rock block specimens were carried out. Potassium iodide was used as a tracer. The obtained breakthrough curves were interpreted and fitted by using a numerical simulator, and mass transport parameters, such as longitudinal dispersivity, matrix diffusion coefficient, transport aperture, were obtained. Mass transport simulations using a fracture network model, a continuum model and a double porosity model were performed to study the applicability of continuum model and double porosity model for transport in fractured sedimentary rock.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.