Norio Katakura

Improvement of soft ground using solidified coal ash and its effects on the marine environment.

This paper presents some research results pertaining to the application of solidified coal ash (SCA) for improving the stability of soft ground. The results pertain to the physical properties of SCA required for use as an alternative to sand in sand compaction piles (SCPs), and the assessment of possible environmental impacts resulting from construction of SCA piles in marine environments. The results of field tests indicate that the physical properties of SCA (permeability, internal friction angle, and grain-size distribution) are favorable for use in soil improvement applications. Also, the results show that SCA is sufficiently suitable as an alternative to sand in SCPs, although SCA piles cannot be compacted to the same extent as sand piles. Finally, test results showed no adverse environmental impacts on natural benthos resulting from placement of SCA piles in marine environments. Thus, the results of this study confirm that SCA is a viable alternative material to sand in SCPs that are used for ground improvement in marine environments, and that large quantities of SCA may be required for such applications resulting in an alternative use for an otherwise waste material.

An Experimental Study on the Applicability of Transplanting Sheet Method for Zostera japonica

In the previous study, a new method for transplanting zostera japonica which doesn’t require much diving work was developed. This method is to put a biodegradability sheet close to living areas of zostera japonica and to move the sheet to the destination after zoster japonica grows enough on the sheet. Although the applicability of the sheet was already confirmed through a field survey, it was also observed that some zostera japonica are removed from the sheet after transplanting the sheet. In this study, laboratory experiments were conducted to clarify the requirements for zostera japonica to remain certainly on the sheet. The results of the laboratory experiments show that when the sheet is moved, more than 5cm of shoot roots need to remain and the moved sheet should be attached firmly to the destination ground.

DEVELOPMENT OF A HIGH EFFICIENCY DEHYDRATION METHOD OF DREDGING SLUDGE FOR USE OF TIDAL FLAT CONSTRUCTION

A new method for the dehydration of dredging sludge with high efficiency was developed. This new hydration method produces hydrated sludge with relatively high water content and low strength, which is enough for tidal flat construction, and achieve the increase of the efficiency of treatment and the reduction of the cost and the working space for the treatment. Using paper sludge as main content of flocculation material, a large scale of flock of dredging sludge can be produced. This results in the high efficiency of dehydration processes which consists of the first flocculation process in a tank and the second dehydration process by belt press. A small scale laboratory test and a large scale field test were carried out and verified the efficiency of this hydration method.