Kashima
Developed an expanded-bottom pile construction method using Japan’s largest expanded-bottom bucket to support skyscrapers.
“Earth-LEX(TM) construction method” that can be constructed using conventional excavators, plants, and materials and equipment ……
Kajima Corporation (Minato-ku, Tokyo, President: Hiromasa Amano; hereinafter referred to as Kajima) and Toyo Techno Co., Ltd. (Shibuya-ku, Tokyo; President: Yoshiharu Watanabe; hereinafter referred to as Toyo Techno) have announced that they will be constructing a skyscraper over 300m tall. We jointly developed the Earth-LEX* construction method, a large-diameter cast-in-place concrete expanded-bottom pile construction method. The “Earth-LEX construction method” uses the newly developed largest expanded-bottom bucket in Japan, which is the same construction method used to construct expanded-bottom piles with a diameter of 4,800 mm or less, which has been widely used. Expanded piles can be constructed. In addition, this method achieves a high bearing capacity of 100 MN class, which is 1.6 times the tip bearing capacity of the conventional expanded bottom pile construction method.
In the future, we will respond to the demand for construction of skyscrapers by proposing and adopting this construction method. *Earth stands for earth drill method, and LEX stands for Large Expansion. [Image 1
Development background
In recent years, the load on columns has increased as buildings have grown taller and spanned, making design difficult because the conventionally widely used expanded-bottom piles with a diameter of 4,800 mm or less cannot secure the necessary supporting capacity. The number of cases is increasing. In this case, a different
high-bearing-capacity pile construction method would be adopted, but this would require new materials and equipment, leading to increased costs and an extended construction period. Therefore, Kajima and Toyo Techno have been developing an expanded-bottom pile method that can be constructed using the same construction method as the conventional expanded-bottom pile method, but has a higher bearing capacity. Overview of “Earth-LEX construction method”
The “Earth-LEX construction method” is a highly versatile and easy-to-implement construction method that can be constructed using the excavators, plants, and materials and equipment commonly used in the earth drill type expanded bottom pile construction method. Specifically, the shaft of the pile is excavated to the specified depth of the support layer using an excavator used in the normal cast-in-place concrete pile construction method, and the expanded bottom part is made into Japan’s largest dedicated expanded-bottom bucket (KT Bucket), which has been developed this time. By using a method of enlarging excavation using a special widening bucket (TST bucket) at the rising part, it is possible to construct widening piles with a maximum diameter of 6,100 mm.
For excavating the bottom expansion part, use a KT bucket to excavate the entire bottom expansion part (slanted part rising part height 500mm). If the height of the rising part of the bottom expansion section exceeds 500mm, excavate the rising part using a KT bucket or TST bucket.
In addition, analysis verified that the soundness of the expanded bottom section could be ensured, and construction experiments confirmed that there was no risk of earth and sand collapsing during excavation.
In August 2022, this construction method received a rating from the Building Center of Japan (BCJ rating-FD0619-01).
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Future outlook
In the future, Kajima and Toyo Techno will continue to adopt this construction method and accumulate results, as well as proceed with studies aimed at further improving workability and reducing costs. Contact information
Kajima Corporation Public Relations Office 03-6438-2557
Toyo Techno Co., Ltd. Technology Headquarters 03-3473-9481