Kashima
First in Japan! Automating a 2-nozzle spray machine for mountain tunnel construction
Improve safety and productivity with automatic spraying technology and erection guidance system
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Kajima (President: Hiromasa Amano) is proceeding with the development of the next generation automated mountain tunnel construction system “A⁴CSEL for Tunnel” (Quad Axel for Tunnel). We have recently succeeded in automating the spraying process, which is one of the construction steps, using a two-nozzle spraying machine. This was achieved by combining the 1-nozzle automatic spray system established in January 2023 with a 2-nozzle spray machine equipped with an erector (gripping device). As a result, spraying work using two nozzles, which previously had to be operated by two technicians, can now be performed by a single operator in the cabin (control room). In addition, productivity is dramatically improved as work time is halved. Furthermore, we have developed a “construction guidance system” that applies the know-how cultivated through this system to the
construction work of shoring. By combining this with a two-nozzle spraying machine equipped with an erector, we confirmed that it was possible to erect shoring remotely without having to enter the vicinity of the face. As a result, there is no need to work directly under the face, where there is a risk of skin drop*, dramatically improving safety.
* Peeling off of earth, sand, rocks, etc. from the excavated surface.
[Image 1: https://prtimes.jp/i/116603/87/resize/d116603-87-8819b8739392ab9e9332-0.jpg&s3=116603-87-da137a8018533e0d823509c4a7e663da-3900×2900.jpg] 2 nozzle automatic spray machine
Development background
[Image 2: https://prtimes.jp/i/116603/87/resize/d116603-87-9201e85ffd346a0b1bd5-1.jpg&s3=116603-87-37afcc3b2849a3451819536a5fd7c4c6-955×672.jpg] “A⁴CSEL for Tunnel” concept
In the construction industry, “shortage of skilled workers,” “high incidence of industrial accidents,” and “low productivity” are urgent issues, and mountain tunnel construction is no exception. Therefore, our company is proceeding with the development of “A⁴CSEL for Tunnel” to solve these issues. This method divides the excavation work for mountain tunnel construction into six construction steps: (1) drilling, (2) charging/blasting, (3) shearing, (4) strike removal, (5) spraying, and (6) rock bolt driving. This is a next-generation construction production system that automates the heavy machinery used in each step and centrally manages them. Of these, regarding (5) spraying, in January 2023, at the Kamioka Experimental Tunnel (Hida City, Gifu Prefecture), we achieved a high spraying finish accuracy of ±20 mm between the supports on a rock surface with complex unevenness. We have demonstrated a technology that automatically sprays concrete smoothly and accurately. As a result, although we achieved the desired results in terms of accuracy and quality, the issue of further shortening work time remained. In addition, the erection of the shoring, which was carried out at the same time as the spraying, had to be done near the face, and there was a risk of falling skin. Therefore, there was a need for mechanized and remote technology that would allow shoring to be erected without people having to enter the vicinity of the face.
Overview and results of the 2-nozzle automatic spraying system The “automatic spraying system” determines the optimal spraying pattern to ensure a smooth finished surface based on the measurement results of the face shape by scanning before spraying, and the machine performs the spraying according to plan. It consists of a control program for performing work. We have improved the program so that the left and right nozzles perform their respective spraying operations efficiently by adding limits to the nozzle’s movable range using an erector to this system. Furthermore, in addition to a collision prevention function that monitors the boom behavior of the erector and left and right nozzles to prevent collisions during automatic spraying operations, we have also implemented a conflict prevention function that adjusts the movement speeds of the left and right nozzles when they approach each other. As a result, one operator can perform efficient spraying work using two nozzles, achieving an automatic spraying capacity of 48m3/h. As a result, we have demonstrated that spraying time can be reduced by approximately 50% compared to conventional one-nozzle automatic spraying.
[Image 3: https://prtimes.jp/i/116603/87/resize/d116603-87-b4bd9695b567198bfa3e-2.jpg&s3=116603-87-cd71af119e6603fc785becd770d6939e-3900×2748.jpg] Construction using a 2-nozzle automatic spray machine
[Image 4: https://prtimes.jp/i/116603/87/resize/d116603-87-fdcaceaf372b1489965e-3.jpg&s3=116603-87-2e0ca82b08bbd2aa670de87287e6edeb-3900×2925.jpg] Machine operation status
Overview and results of the built-in guidance system
The “Erection Guidance System” calculates the target posture of the erector boom (joint angle, boom extension/contraction amount, etc.) with respect to the target position for erecting the shoring, and remotely controls the erector based on the calculation results to position the erector boom in a predetermined position. This is a system that realizes the erection of shoring. In addition to this system, by using a special shoring structure pre-installed with a one-touch joint for fastening the crown joint and a fixing anchor, conventionally two operators and three to four technicians working near the face are required. We have demonstrated that it is possible to erect shoring, which used to be difficult, with just one operator. As a result, we can expect significant labor savings in shoring erection and a dramatic improvement in safety.
[Image 5: https://prtimes.jp/i/116603/87/resize/d116603-87-2f514c28c24871223435-6.jpg&s3=116603-87-9313a584af16ddab28c261f9dd796fd1-1947×814.jpg] Situation of shoring construction
the next deployment
In the future, we will further improve the two-nozzle spraying machine equipped with an “automatic spraying system” and plan to use this machine for mountain tunnel construction. Kajima will continue to develop technology to automate six construction steps with the aim of improving safety and productivity in mountain tunnel excavation work. Kamioka test tunnel construction overview
Location: Kamioka-cho, Hida City, Gifu Prefecture Specifications: Tunnel excavation length: 321.3m Excavation cross-sectional area: Approach section 43.9m2, automated construction test section 73.5m2 (Reference) Kashima’s civil engineering technology in the video “Mountain Tunnel”
https://www.kajima.co.jp/tech/c_movies/index.html#anc_mountain_tunnel Development and deployment of two-nozzle spraying machine (twin shot method) (2012 December 20, 2021 Press Release)
https://www.kajima.co.jp/news/press/201212/20c1-j.htm Development of automated construction system “A⁴CSEL for Tunnel” for mountain tunnel construction (2021 June 30, 2023 Press Release)
https://www.kajima.co.jp/news/press/202106/30c1-j.htm Shotcrete automation realized for the first time in an actual tunnel (January 12, 2023 Press Release)
https://www.kajima.co.jp/news/press/202301/12c1-j.htm
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