Automated Construction of Underground Tank

An automated landslide protection wall construction system and an automated concrete placing system were developed and applied in an underground LNG tank construction project at the Negishi plant of Tokyo Gas. The underground LNG tank is a huge vertical shaft storage of liquefied natural gas. This tank is a concrete structure of internally cylindrical shape lined on the inside with thermal insulation material and membrane. The structure has an inside diameter of 50m and depth of approximately 40m.Conventionally, landslide protection work and concrete placing work entailed in construction of an underground tank have involved operations in adverse environments of great height, dirtiness, noisiness, etc., and have required much effort for improvement of productivity and quality.The landslide protection work automation system introduced for this project is composed of a “Mesh Setter” equipped with a nailing machine for anchoring reinforcing mesh and a mesh anchoring apparatus which automatically positions and fixes mesh at a wall surface, a “Gunite shooter” which pneumatically applies mortar to the wall surface moving a revolving nozzle up and down, right and left, and further, a “Rock Bolt Setter” which automatically performs a series of operations consisting of drilling holes in the reinforced, mortar-lined walls, injecting grout in the holes, and inserting rock bolts in the holes. The automated concrete placing system comprises an “Automatic Placing Apparatus” capable of placing concrete to a uniform height at a concrete side wall, an “Compaction Robot” which automatically compacts the concrete placed, and a “Placing Management System” which manages concrete placing operations in timely fashion to allow work to be done more smoothly. The number of workers required has been reduced to less than one-third compared with before, while the working environment has been improved through adoption of these systems.