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坑内天端傾斜計測による切羽前方地山評価システムの開発

トンネル天端傾斜計「TT-Monitor(Tunnel Tilt Monitor)」の現場適用

谷 卓也*1・工藤 直矢*2・青木 智幸*1

トンネルの計画段階においては,地質調査の技術的な限界や費用面の制約等から,限定された情報で支保が設計され,施工が開始される。そのため,施工段階に行われる観察・計測で,設計を合理的に確認・修正していく「情報化施工」が行われる。著者らは,切羽近傍のトンネル天端に設置する小型傾斜計により,容易かつ精度の良い地山評価手法を提案してきた。この技術は,日常の計測管理の一つとして天端傾斜計測を実施し,計測箇所の地山状況と切羽前方の地質変化を早期に捉え,着実な進行と施工の安全性を確保することを目的に開発されたものである。本報では,TT-Monitorと称する傾斜計の改良内容と現場運用によりその適用性を確認した結果について述べる。

キーワード:  山岳トンネル,現場計測,地山予測,天端傾斜計,情報化施工

*1 技術センター 土木技術研究所 地盤・岩盤研究室
*2 関西支店 土木工事作業所

Realization of Ground Evaluation Ahead of a Tunnel Face by Inclination Measurement at Tunnel Crown

Field Operation of Tunnel Tilt Monitoring System in Two Mountain Tunnel Projects

Takuya TANI*1, Naoya KUDO*2 and Tomoyuki AOKI*1

In the planning stage of a tunnel, due to limited technology in the geological survey and the financial restriction, tunnel supports are often designed from unsatisfactory information, and the tunnel construction is started. Therefore, "Information-oriented construction" is carried out in the construction stage, in which the design is rationally verified and modified by observations/measurements. The authors have proposed a simple but accurate method of predicting ground condition ahead of the face, with the uses of inclinometers installed at the tunnel crown near the cutting face. To measure inclination at the tunnel crown, this inclinometer was originally developed as a daily control measurement, such that the geological condition and its possible change behind the face could be detected early, and a steady advance and construction safety could be ensured. This paper describes an improvement of this inclinometer called TT-Monitor and the results of field verification programme at a tunnel under construction.

Keywords:  mountain tunnel, field measurement, forward prediction, inclinometer at tunnel crown, information-oriented construction

*1 Soil and Rock Engineering Research Section, Civil Engineering Research Institute, Technology Center
*2 Construction Site, Kansai Branch