Basic Properties Water-Swelling Urethanes as Filling Materials of Ground Improvements
Shinya INAZUMI, Kenji KATO, Hideo KAWABATA, Yoshihiro NAKAGISHI and Kenichi SHISHIDO
Abstract:A variety of methods have been developed and applied to ground improvements, depending on the purpose. For example, surface ground improvement or columnar improvement methods are generally frequently applied to improvements of soft ground. The chemical injection method is commonly selected for the prevention of the collapse of natural ground. Furthermore, in case of ground improvement to solve the problem of liquefaction, forced precipitation or subgrade reinforcement under an existing building, especially when the cavity under the building should be filled in, the injection of urethane (organic), one of the chemical injection methods, is considered. With the injection methods, filling materials can be categorized into mainly two types: chemicals and non-chemicals, and selection should be appropriately made according to the condition of the site. In this study we focused on water-swelling urethanes with a view to applying them to ground improvement, and performed a test for evaluation of their basic characteristics by creating simulated mixing hardening materials of various combinations of water-swelling urethanes and soil materials. As a result, it was discovered that water-swelling urethanes mixed with various soil materials showed a tendency to have a constant swelling rate for both fresh water and artificial sea-water. Also it was discovered that the water-swelling urethanes with larger water contents and smaller particle sizes tended to have a quicker increase of viscosity, and that the strength of hardening materials was related to the particle diameters of soil materials. In this way, the basic characteristics of water-swelling urethanes can be understood in relation with soil materials. These characteristics need to be known before the injection of such filling materials. Therefore, there is a possibility that the water-swelling urethanes are highly applicable to ground improvements. Key Words:Chemical injection method, Ground improvement, Swelling ratio, Swelling urethane filling material