Pneumatic Flow Mixing Method for Beneficial Use of Dredged Soil

A huge amount of soft soil is dredged by grab dredger or pump dredger at many ports every year to maintain enough sea route and sea berth. These soft soils used to be transported and dumped out to a disposal site or land reclamation site. It is becoming more difficult to construct any disposal area for dredged soil and subsoil. In order to prolong the service life of the sites, beneficial use and volume reduction of the dredged soil are desirable. The pneumatic flow mixing method was developed in Japan for beneficial use of dredged soil, land reclamation and land development, in which dredged soil is mixed with relatively small amount of cement in a transporting pipeline. The soil mixture forms several separated mud plugs in the pipeline, and is thoroughly mixed during the transporting. The mixture transported and deposited at reclamation site gains relatively large strength rapidly so that no additional soil improvement is required. This method is expected to promote the beneficial use of dredged soil and to provide an economical and rapid construction for land reclamation, and was applied to the Central Japan International Airport and Tokyo/Haneda International Airport. In this article is described briefly the development of pneumatic flow mixing method and its two large scale applications as well as the mechanical properties of the stabilized soil.