LPWAを用いた無線B計測システム「T-RIPPA® BK」の開発
山岳トンネル工事の計測工Bでは，鋼製支保工応力計・吹付けコンクリート有効応力計・ロックボルト軸力計・地中変位計などの計測機器を支保工あるいは地山に埋設して，多チャンネルロガーによる自動計測を行う。これらの計測器設置作業は，支保工が十分に施されていない切羽近傍で行う必要があり，それに加え多数の配線作業と配線防護工を必要とするため，安全性と効率性に課題があった。
そこでB計測器設置作業の安全性・効率性向上を目的として無線B計測システムを開発した。山岳トンネル現場で施工性に関する検証を行った結果，計測器設置作業時間は従来手法と比較して70%削減し，掘削停止時間の短縮による効率性の向上を確認した。また，支保が一次吹付けのみの環境で計測器設置作業を余儀なくされていたコンクリート有効応力計・鋼製支保工応力計に関して，切羽近傍作業を完全に削減し，安全性を向上させることができた。
キーワード：山岳トンネル，B計測，無線化，LPWA
＊１ 技術センター 生産技術開発部 地下空間技術開発室
＊２ 技術センター 社会基盤技術研究部
＊３ 土木本部 土木技術部
＊４ 技術センター 社会基盤技術研究部 地盤研究室
＊５ 東亞エルメス（株）
Development of Wireless B Measurement System "T-RIPPA" Using LPWA
In B measurement during mountain tunnel construction, measuring instruments such as steel falsework stress meters, shotcrete effective stress meters, rock bolt axial force meters, and underground displacement meters are installed on supports or buried on the ground, and measurements are carried out automatically using a multi-channel data logger. This measuring instrument installation work must be performed near the tunnel face where the falswork is not sufficiently provided, and in addition a large amount of wiring work and wiring protection work is required, so there are problems of safety and efficiency.
Therefore, a wireless B measurement system has been developed for the purpose of improving the safety and efficiency of B measuring instrument installation work. As a result of verifying the workability at a mountain tunnel site, it was confirmed that the measuring instrument installation work time was reduced by 70% compared with the conventional method, and the efficiency was improved by shortening the excavation stop time. In addition, with regard to concrete effective stress meters and steel falsework stress meters, for which the measuring instruments had to be installed in an environment where the support was only the primary shotcrete, the work near the tunnel face could be reduced and safety improved.
Keywords: mountain tunnel, measurement-B, wireless, LPWA
*1 Underground Utilization Technology Development Section, Production Engineering Technology Department, Taisei Advanced Center of Technology
*2 Infrastructure Technology Research Department, Taisei Advanced Center of Technology
*3 Construction Engineering Department, Civil Engineering Division
*4 Geotechnical Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology
*5 Toa Elmes Corporation