SEALING GEOMATERIAL FOR COASTAL DISPOSAL FACILITY USING MARINE CLAY WITH THE ADDITION OF A SMALL AMOUNT OF CEMENT

Abstract

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.