■Business Overview

2. Construction business

In the main construction business, steel pipe pile construction and deep ground improvement work account for the majority of sales. The structures targeted by Tenox ＜1905＞ are medium- and low-rise buildings such as detached houses, condominiums, logistics facilities, factories, etc., and civil engineering structures such as road/railway bridges, embankments, water and sewerage facilities, earthworks, retaining walls, steel towers, etc. In addition to supporting buildings, construction purposes include seismic reinforcement, suppression of liquefaction, reduction of environmental load, and suppression of sediment collapse. Construction methods include gantetsu pile method, TN method, TN-X method, NS eco-pile method, ATT column method, etc. for pile construction, and teno column method, pure pile construction method, TOFT method, etc. for ground improvement work. The TN-X method and pure pile construction method target only buildings, but other construction methods are also applied to civil engineering structures. Details of the company's main construction methods are shown below.

(1) Gantetsu pile method (pile)

It is a construction method developed in collaboration with Nippon Steel ＜5401＞ and Kubota ＜6326＞, and it is a synthetic pile construction method in which a steel pipe pile with an outer surface protrusion is pressed into the center of a solid body (soil cement column) formed by injecting cement milk into the ground and stirring and mixing. Features include being able to support a structure with a small number of piles due to the large vertical and peripheral bearing capacity of soil cement columns, being able to obtain large horizontal bearing capacity due to the high toughness characteristic of steel pipes, and being able to reduce the generation of construction residue in order to effectively utilize the ground to form a solidified body. As a result, it was possible to reduce construction costs and shorten construction periods. It is widely used in civil engineering fields such as road and railway bridges, water supply and sewerage facilities, etc.

(2) TN-X method (pile)

It is a construction method developed in collaboration with Nippon Steel, and it is a high bearing capacity steel pipe pile construction method that obtains large bearing capacity by constructing expanded and solidified bulbs at the tip of the pile with a hydraulic expansion and contraction drilling head. It obtained certification from the Minister of Land, Infrastructure, Transport and Tourism in 2005, and is used in important building structures such as logistics facilities, data centers, government facilities, hospitals, and airport facilities that require large pile bearing capacity. The features are that since high tip bearing capacity of up to 17,900 kn*1 can be obtained with a maximum root bearing capacity of up to 17,900 kn*1, it is resistant to large earthquakes due to its high toughness, which is a characteristic of steel pipe piles, and by adopting a medium excavation method, it is possible to construct large diameter steel pipe piles with a diameter of 70m (construction length) compared to site-built piles and concrete piles, and the fact that large diameter steel pipe piles with a diameter of 1,400 mm can be constructed to a depth of 70 m (construction length), excavation depth, drilling speed, cement Quality control is possible by monitoring the amount of milk*2 injected, the diameter of the expansion blade, etc. in real time.

*1 kN (kilonewton): A unit representing load. Roughly 10 kN = 1 t.

*2 Cement milk: A milk-like substance made by mixing cement and water.

(3) ATT column method (pile)

It is a construction method developed in collaboration with Asahi Kasei Building Materials Co., Ltd., and it is a hybrid pile construction method in which a steel pipe pile with a blade is buried in the center of a soil cement column (columnar modification). Features include large peripheral friction and high toughness obtained by the synergistic effect of soil cement columns and steel pipe piles with blades, that large horizontal bearing capacity can be expected even on soft ground, that construction residue can be reduced by applying the teno column construction method described later, and that construction in narrow areas is possible. In addition to being frequently used in low- and middle-rise buildings and as a basis for outframe-type seismic reinforcement, it can also be used on narrow sites such as pedestrian bridge abutments and narrow carry-in roads, and it is highly regarded for being compatible with floating foundations that do not land on a clear support layer.

(4) Teno column construction method (ground improvement)

It is a construction method that pioneered recognition of the use of ground improvement as a basic construction method for buildings, and the company obtained its own patent in 1984. A soil cement column is constructed by injecting cement-based solidifying material (solidifying material liquid) in the form of slurry* into the ground and mechanically stirring and mixing. Features include the ability to construct columns with uniform strength regardless of soil quality, the wide lineup of column diameters and construction machines so they can be adapted to construction specifications and site conditions, construction periods can be shortened and costs reduced by a real-time construction management system, and it is an environmentally friendly construction method without groundwater pollution or secondary pollution in addition to low vibration and low noise. Not only is it used as a foundation for various buildings such as detached houses, condominiums, commercial facilities, middle- and low-rise buildings, factories, etc., but it also has a wide range of uses, such as measures against liquefaction and prevention of arc slippage. At the time of major earthquakes such as the Great Hanshin Earthquake, the Great East Japan Earthquake, and the Kumamoto Earthquake, the structures adopted on the basis of the Teno column construction method were undamaged, so reliability of the same construction method increased once again, and construction results so far are approximately 40,000 cases. Furthermore, the company has developed “TENO Q-be (teno cube),” which is a shallow ground improvement method, and is working towards full-scale commercialization. Since the depth of the support layer is often different even in the same section, combining the two construction methods of a shallow layer “TENO Q-be” and a deep teno column is not only highly convenient for designers and general contractors, but expectations are growing as an environmentally friendly construction method that can also use deep residual soil to solidify shallow layers of ground at sites.

*Slurry: A milk-like substance made by mixing cement and water.

(Written by FISCO Visiting Analyst Miyata Hitomitsu)