Practices of reused dredgings by cement treatment

Dredged soils treated with cement are used popularly as fillings in many reclamation projects. But the basic property of the strength uniformity has not been clarified for this artificial geomaterial, due to the fact that the strength is easy to obtain by increasing cement content. It is considered important to assess the strength variance properly when we intend to provide a recycled geomaterial with high quality at low cost. An empirical and simple correlation is proposed concerning compressive strength, cement content and water content. Based on the empirical relation, the variance property of compressive strength is interpreted, and some data actually obtained during construction are presented. Aiming to overcome the deficiencies of the conventional method by means of unconfined compression tests, a quality assessment is experimentally performed using the cone penetration test. In order to reduce the construction cost, special working ships have been introduced in practical engineering. The working ships are equipped with a cement treatment system, handling the soft dredging in a large quantity. Improved dredgings have already found applications in various marine construction projects. In particular, clayey dredgings usually show very small permeability, offering the possibility of reusing the dredgings in different seep-proof structures. Finally, difficulties are mentioned concerning the reuse of dredging from a practical viewpoint.