LAUSR

For secure construction and operation of a coastal waste disposal facility on a sandy seafloor, the proper bottom sealing material is one of the controlling factors. The conventional sealing material cannot mobilize enough strength against the load by covering soil and landfilling, and the ordinary cement-treated clay also has a drawback of crack generation due to shear deformation. To overcome these disadvantages of the conventional materials, the clay with the addition of a small amount of cement (CASC) was proposed as a new sealing geomaterial. Since the cement content of CASC is about 2-4%, which is lower than the minimum cement content required for strength mobilization of general cement-treated clay, it is expected to keep ductile property after the long-term consolidation. To examine the performance of CASC, a series of experimental studies (vane shear test, consolidation test, and hollow cylinder torsional permeability test (HCTPT)) was conducted for Tokuyama Port clay. The vane shear tests proved that CASC exhibits the strength development up to 3 kPa under unconsolidated condition after curing. The consolidation tests showed that the cement addition reduces the compressibility of the clay, and consequently, relatively large void ratio induces the increase in hydraulic conductivity, but CASC still could satisfy the sealing requirement. The HCTPTs revealed that hydraulic conductivity of CASC does not increase even if large shear deformation is applied while the lean-mix cement-treated clay shows permeability increase due to the crack. Considering above results, CASC was concluded to be a feasible option for the artificial sealing.