Joint Project with Ohmoto-gumi: Developed 'Automated Soil Removal Equipment Technology' for Pneumatic Caisson Method

Actio Co., Ltd. (Headquarters: Nihonbashi, Chuo-ku, Tokyo; President & COO: Naoto Konuma), a general construction machinery rental company, in collaboration with Ohmoto-gumi Co., Ltd. (Headquarters: Kita-ku, Okayama; President: Keiichi Miyake), has developed a system to automate soil removal work in the pneumatic caisson method. This development aims to solve labor shortages and skill transfer challenges in the construction industry. Field tests of this technology confirmed an approximate 11% reduction in cycle time compared to manual operation, achieving both improved construction efficiency and safety.

The pneumatic caisson method is widely used for foundations of bridges and buildings, underground structures, and the installation of shield launching/arrival shafts. 'Pneumatic' refers to air, and 'caisson' means a box. This method involves constructing a main body on the ground (with a sealed working chamber at the bottom), injecting compressed air to prevent groundwater intrusion, excavating, and installing it to a predetermined depth.

While this method ensures high construction accuracy under deep and high-water pressure conditions, the harsh working environment has been a challenge. For soil removal, skilled dedicated operators were required for each task: lifting buckets with a soil removal crane, opening and closing pressure-resistant doors within the material lock (*1), and precise pressure adjustment operations.

Furthermore, in the construction industry in recent years, the utilization of ICT and automation technologies has become a critical issue, in addition to addressing the shortage of skilled workers and improving safety.

Against this background, Actio and Ohmoto-gumi have combined their respective pneumatic caisson construction technologies and construction equipment automation technologies to develop automated soil removal equipment.

By introducing this technology, safety is improved by minimizing worker entry into high-altitude spaces, and labor saving and efficiency are achieved through automated soil removal. Furthermore, it is expected to stabilize construction quality by suppressing operational variations.

*1 A material lock is equipment used to discharge excavated soil from within the caisson to the ground.

■ Features of 'Automated Soil Removal Equipment Technology' for Pneumatic Caisson Method
① Advanced Automatic Position Detection and Correction
Various sensors (rotary encoder, load cell, position measurement camera, etc.) installed on the soil removal crane and material lock measure and correct 'deviations' due to crane deflection, wire expansion/contraction, and caisson tilt in real-time, enabling accurate loading and unloading.

② Stable Operation with Anti-Sway Control
An anti-sway inverter is adopted, reducing the swing amplitude of suspended loads by approximately 95%. This achieves smooth automatic stopping and loading without sway into the narrow permissible range (within ±20cm of the center) inside the material lock.

③ Seamless Automatic Operation Flow
Integrated control covers bucket lifting, door opening/closing, pressure adjustment, and tipping discharge by the soil removal device. 'Seamless operation' that efficiently transitions between steps ensures greater efficiency than manual operation.

④ Thorough Fail-Safe Design
Equipped with functions to ensure the safety of 'internal caisson pressure management,' which is most crucial in the caisson method, such as automatic valve shutdown during communication failures and setting an upper limit for exhaust time to prevent erroneous exhaust.

■ Verification Results and Future Outlook
The results of the field test proved that automated operation has less variation in cycle time compared to manual operation, enabling stable construction. It was also confirmed that the constant presence of material lock operators, previously required, is no longer necessary, and the risk of contact with suspended loads is reduced, improving safety. Going forward, the companies aim to further verify its practicality through actual site application and contribute to promoting 'work style reform' in construction sites where labor shortages are becoming severe.

■ Patent Application
Patent Application Number: JP 2025-201717

■ Inquiries regarding this product
Actio Co., Ltd. Crane Business Division
TEL: 03-6854-1423