In assessing the safety of geological disposal of high-level radioactive waste, groundwater chemistry is an important factor influencing the performance of engineered materials and the behavior of radionuclides. It is essential to understand the hydrochemical changing process and stable condition after the closure of the disposal facilities. In this study, a simulated experimental drift was constructed in granite at a depth of 500 m at the Mizunami Underground Research Laboratory, and the hydrochemical condition and related processes after drift closure were observed. The groundwater flow and chemistry around the excavated drift changed owing to water inflow along fractures into the drift. The redox potential increased owing to the infiltration of oxygen from the drift. After closing the drift, the groundwater evolved chemically with time owing to mixing of the groundwaters derived from surrounding rocks, dissolution of shotcrete, and microbial reactions. The redox potential plunged to the initial baseline value in three months owing to the reducing activity of microbes, while the groundwater became alkaline owing to the influence of the dissolved shotcrete. If the content of a pH-buffer mineral in a rock is small compared with the cementaceous materials used, the alkaline groundwater probably spreads broadly in surrounding

. In the , it is necessary to verify the water chemistry evolved by the interaction between the alkaline groundwater and granite minerals.

抄録全体を表示

地層処分場での地下環境は、地下岩盤（岩石・鉱物）と地下水で満たされた地下地質環境とグラウト材やコンクリート支保材など、人工材料とのインターフェースであり、また操業に伴う力学的擾乱や酸化還元反応などといった物理的・化学的変化を伴う環境（場）である。これまでの我が国の性能評価の概念モデルにおいては、これらの複合状態（より現実的な状態）の理解が明確ではなく、信頼性の高い安全評価体系を整備するためには、実環境をより現実的に示すことのできる情報（データ）と調査技術を早急に準備することが必要と考えられる。今回の報告では、このような背景のもと、我が国の地下研をはじめとする地下環境研究の今後の課題と進め方について、とくに理解すべきニアフィールドでの地球化学的現象との相関を念頭にその考え方を提示する。

抄録全体を表示

To investigate deterioration rate of rocks, the authors conducted measurements of the physical properties of naturally weathered Kimachi sandstone and forcedly deteriorated Kimachi sandstone. The naturally weathered Kimachi sandstone was obtained by boring from a surface after excavation which had not been touched for approximately 100 years. From the Measurement results of the physical properties of the naturally weathered Kimachi sandstone, the relationship between these properties, depth and time was obtained. The forced deterioration experiments were carried out by repeated drying-wetting and drying-wetting-freezing-thawing cycles. The experiment results revealed that the decrease in ultrasonic wave speed with each cycle approximated well with the logarithmic function.

抄録全体を表示

物理探査法による地表探査法は古くより活用されてきたが,採掘活動への応用がされるようになったのは近年のことである。採掘活動における物理探査法は,鉱床探査から岩種識別まで多岐にわたる。これによるコスト削減効果の極めて大きことは各国で報告されている。物理探査法の効果的活用には,岩種による物理的性質の違いを正確に把握することが重要である。例えばKambaldaにおける鉱床の特徴は高導電性であるため,鉱床探査は電気・電磁法が主体である。これに対して,金鉱床では一般に顕著な物理的性質の違いが現れないが,多くの成功例が報告されている。本論文では,西オーストラリアにおけるニッケル・金鉱床における物理探査法の適用について具体的な例を通じて,有効性・経済効果などについて紹介する。

抄録全体を表示

2009年7月に，富士山5合目で落石災害が発生した。この災害発生斜面は比較的緩勾配であるにもかかわらず，落石が被災個所まで到達し重大災害に発展している。災害発生後、現地調査をもとにした落石経路のシュミレーションを行い，今後想定される落石規模に対応できる対策工として，高エネルギー落石に対応でき景観にも配慮できる落石防護補強土擁壁工（ジオロックウォール工法）が施工された。本論文では実際施工された落石防護補強土擁壁工の事例を，災害発生メカニズムの調査から対策工選定までの設計手順を踏まえ報告する。

抄録全体を表示

軟岩中に掘削された洪水調整のための大規模地下空洞の掘削中に, ベンチ掘削ステップが進むにつれてトンネル側壁部分の岩盤変形量が予期せず増大する現象が計測された. 支保工の事前設計の階段で用いられた簡便な設計解析によれば, このような変形挙動は事前に予測できなかった. そこで, 本論文は, 軟岩トンネル掘削のための異なる数種類の解析法を採用し, 上記の挙動を再現できるかどうかについて研究した. 具体的には, まず, それらの解析方法について詳述し, 大規模地下空洞の岩盤変形挙動計測データとそれらの解析結果を比較することにより, 個々の解析手法によりどの程度まで変形予測性を改良できることが可能かについて考察し, 個々の解析モデルの軟岩への適用性を概略検証することができた.

抄録全体を表示

Geographic Information System (GIS) is a tool for managing, processing and analyzing the spatial digital data and one of the new information technologies. It has the possibility of solving various difficult problems. Considering the future development of rock engineering, it still remains a lot of problems such as social and environmental engineering problems, which can not be solved using the current technology. In this paper, the state of arts of GIS technology is introduced, and then some advanced application examples in the rock engineering field are shown. Finally, the possibility of GIS applied in the rock engineering is discussed and the future vision of utilizing GIS technology in rock engineering field is mentioned. It is concluded that the environmental impact assessment, the protection of life and properties against the natural disaster and the creation of better environment and health will be the important issues of the rock engineering in the future. In order to solve these difficult problems, the utilization of GIS technology can expect an effective and useful technology for decision making of them. On the future prospect of GIS application to rock engineering, the followings are important: 1) preparation of data, 2) coupling of GIS with various analysis, 3) establishment of synthetic assessment method and 4) temporal and spatial phenomenon analysis in GIS. And, to develop the future GIS application for rock engineering, not only the progress in GIS technology itself, but also the action of the rock engineers and the researchers are also important.

抄録全体を表示

The purpose of this study is to clarify the relationship between mechanical stability of rock block and its vibration characteristics for arbitrary shape and material properties of rock block so as to propose a new method of rock stability evaluation by measuring the vibration of rocks using a remote vibration measuring system. To detect unstable rock masses that are at risk of falling onto railroads, research on safe, efficient, and quantitative evaluation of such risk using a laser Doppler velocimeter (U-Doppler) capable of contactless remote measurement is conducted. In the study, block models representing rocks with different geometries, masses and material properties were used to assess the effects of rock shapes and scales based on the relationship between the dominant frequency and mechanical stability of the model through 2-D FEM analysis. The result of the analysis shows that the relationship between the dominant frequency and mechanical stability is affected by aspect ratio of rock block and dominant frequency reaches a peak when the aspect ratio is around 0.6-0.7 for same stability of the rock block. To further verify the applicability of this block-model simulation, another model representing actual rock-mass geometry randomly defined from 2D-profiled spectra for on-site rocks was included in the analysis. Using this model, the relationship between the dominant frequency and mechanical stability was simulated to determine its acceptability based on comparison of the results.

抄録全体を表示