報告書番号

U98052

タイトル（和文）

グラウチングによる岩盤改良の予測・評価に関する現状と今後の研究課題

タイトル（英文）

Status and Future Prospects for Prediction and Evaluation of Rock Improvement by Grouting

概要 （図表や脚注は「報告書全文」に掲載しております）

本報では、文献資料および現地調査に基いてダムの基礎処理工であるグラウチングの調査・設計・施工の現状を把握し、合理的なグラウチングを行うための技術的課題について検討した。現状では、グラウチングによる岩盤改良の効果を予測するために主に試験施工が実施されており、また、注入完了基準については過去の実績に基づいているが、合理的なグラウチングのためには、以下の技術的課題がある。 (1)グラウチングによる改良効果を予測・評価するための浸透モデルが必要であり、それは①グラウト材の粘性特性、②粘性の時間依存性、③目詰まり特性、④注入圧による岩盤割れ目の開口特性、の４つの特性を考慮する必要がある。また、浸透モデル構築のために、岩盤内の亀裂分布特性を精度よく把握し、亀裂分布のモデル化手法を検討する必要がある。(2)注入完了基準を明確に設定するために、加圧脱水を目的とした「だめ押し」の現象を解明する必要がある。

概要 （英文）

In recent years, attention is paid to predict the degree of rock improvement by grouting, and its evaluation. Because the suitable sites for dam construction decrease, and the grouting to improve rock mass is more important. To make clear technical subjects on predicting and evaluating the grouting effects is so significant in executing the rational grouting that we studied past references. In the first part of this paper, we review the status of grouting design and execution, and investigate some subjects on rock foundation works at the dam. At the present, contractors almost carry out the grouting tests to predict and estimate effects of the grouting. But it cannot reasonably be assumed that only the grouting tests are enough to predict and evaluate grouting effects. And injection of cement pastes into a rock mass finishes by pressing and dehydration. In spite of that, the decisive basis for standards, that is, pressure, velocity and time of the injection, is not always clear for the complete injection. Furthermore, Lugeon test is general to judge the effects of the grouting, nevertheless it does not satisfy a assumption that the state of flow is laminar. Therefore, there are two technical themes to perform the rational grouting. First, a method of predicting and estimating effects of the grouting needs to be developed by using a seepage model. In the model, it has to be expressed a viscosity of cement pastes, time effect of the viscosity, plugging aperture with cement pastes and opening fractures with pressure of the grouting. As a result of investigating five models proposed before, the model does not exist representing all the characteristics. And then, modeling the distribution of fractures in a rock mass is necessary for the method. Second, it is important that the phenomenon of pressing and dehydration is to be made clear. Because costs of the injection usually depend on total time of the injection, the standards are determined appropriately. Finally, we arrange a study flow chart to establish the method of predicting and evaluating a quantitative improvement rate.

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