Reducing Road Sinkhole Risks with 500mm Diameter Spheres: Kyowa Rubber Launches Mass Production of Countermeasure Components to Restore Subsurface Cavity Support

Kyowa Rubber Co., Ltd. (Headquarters: Hirakata, Osaka; Representative Director: Tsuyoshi Tarasaka) will launch these spheres for subsurface cavity countermeasures on April 1, 2026.

【Social Background】

On January 28, 2025, a road sinkhole occurred in Yashio City, Saitama Prefecture, believed to be caused by damage to a regional sewer pipe, heightening national interest in subsurface cavities. According to the Ministry of Land, Infrastructure, Transport and Tourism's white paper, approximately 2,600 road sinkholes caused by sewer pipes occurred nationwide in fiscal year 2022.

In response, interest in subsurface cavity surveys has surged. Geo Search Co., Ltd. announced that following the Yashio City accident, they responded to an emergency request from February 3 to 7, 2025, deploying 15 subsurface cavity survey vehicles and 40 teams to cover a total of 1,600 km.

【Development Background】

As a rubber manufacturing company in its 55th year, Kyowa Rubber takes these road sinkhole accidents very seriously. While survey technology is advancing, determining how to repair discovered cavities and reduce risk remains a major challenge on-site.

Subsurface cavities have irregular shapes and may contain protrusions. To minimize traffic impact, it is desirable to perform construction through small holes rather than large-scale excavation.

Leveraging its expertise in rubber processing, Kyowa Rubber developed these "Road Sinkhole Countermeasure Spheres." They are inserted into cavities through small holes drilled in the road and then expanded by injecting fluidized treated soil or concrete.

【Kyowa Rubber's Philosophy】

The key to addressing subsurface cavities is not just filling the entire volume, but designing a solution that restores roadbed support and load transmission to significantly reduce sinkhole risk. Public data from the University of Tokyo's Institute of Industrial Science indicates that even if some voids remain, the risk of collapse can be drastically reduced.

In geotechnical engineering, sinkhole risk should be evaluated based on cavity width, ceiling depth, and impact on the roadbed, rather than just the presence of a cavity. Therefore, Kyowa Rubber designs its products with a focus on: construction through small-diameter holes, adaptability to cavity shapes, and ensuring support restoration and load transmission.

About the Product:

The Road Sinkhole Countermeasure Sphere is a spherical component inserted into subsurface cavities through small holes. By injecting fluidized soil or concrete inside, it expands to restore support and ensure load transmission around the cavity.

Kyowa Rubber's spheres are 500mm in diameter and equipped with a long, thin injection tube. They are custom-designed and manufactured based on data from cavity surveys to match the size, volume, and shape of the specific cavity.

【Product Lineup】

・PVC Tarpaulin Sphere
Material: PVC Tarpaulin
Includes reinforcement base fabric.
Features excellent strength and adaptability.