ISSN:1064-119X    

DOI:10.1080/10641199609388298

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Geotechnical properties and distribution characteristics of the Pacific seamount sediments, which coexist with cobalt‐rich manganese deposits (crusts and nodules), are essential data for the design of a seafloor mining system for the deposits. Samples were cored by a large‐diameter gravity corer during the research vessel Hakurei‐maru No. 2 survey cruises on the Pacific seamounts in 1991 and 1992. Various distribution characteristics of the sediments were studied. Analysis of the core samples showed that the geotechnical properties of the sediments become very important, in view of the new findings of debris‐flow‐like resedimentation of the cobalt‐rich manganese deposits and large shallow‐buried deposits beneath the sediments. These new findings are also very significant in terms of reserve reassessment Fundamental geotechnical properties of the sediments, such as size distribution, solid density, bulk density, water content, coefficient of internal friction, and cohesion are presented. Based on these data, their effects on the mining system design are also presented.

ISSN:1064-119X    

DOI:10.1080/10641199609388299

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This article describes the history and development of ports and harbors in Japan, and new technologies of dredging and reclamation, particularly two methods recently developed with consideration of environmental concerns: (1) a high‐density pneumatic transport system to minimize the effect on the environment, and (2) a high‐density dredging system based on the same pneumatic transport system and capable of dredging a very thin soil layer, together with construction records of these systems.

ISSN:1064-119X    

DOI:10.1080/10641199609388300

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This study shows that calcium carbonate plays an important role as a cementing agent of various marine sediments. The measured vane shear strength of marine soil samples is shown to vary with depth and is strongly correlated with the calcium carbonate content. The results show that an increase in calcium carbonate of 1% causes an increase in shear strength of about 10 kPa. Moreover, under accumulating self‐weight, consolidation is found to be enhanced by calcium carbonate. It was also found that both the cementation and condensation due to calcium carbonate are the major factors accounting for the strength development of marine sediments, beside consolidation. These effects are often greater than those due to grain size effects.

ISSN:1064-119X    

DOI:10.1080/10641199609388301

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The Trans‐Tokyo Bay Highway comprises the Ukishima access, two artificial islands, at Kisarazu and Kawasaki, a shield tunnel, and a bridge. The ground along the route is soft clay or loose seabed mud, so various ground improvement works had to be carried out before the construction of large‐scale structures could be commenced. In this report is described how the sand compaction pile method (SCP), the slurry mixture cement treatment method, the dry mixture cement treatment method, and the deep mixing method (DMM) were used for ground stability and improvement.

ISSN:1064-119X    

DOI:10.1080/10641199609388302

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The present status of geothermal experiments using the Japanese submersible Shinkai in hydrothermal areas is briefly reported. Although extensive diving investigations have revealed metal‐rich deposits in hydrothermal fields, they are valuable only from a purely scientific standpoint and are obviously not economically cost‐effective, mainly because of the deep water depth of the sites. The long‐term measurement of heat flow using submersibles can be a powerful tool to uncover the thermal regimes in a hydrothermal system. Usage of submersibles is inevitable to deploy such instruments, because of the need to have sufficient accuracy in positioning and flexibility in the placement of instruments or sensors. In 1994, three long‐term heat flow monitoring systems were successfully deployed at the TAG active mound of the Mid‐Atlantic Ridge at 26°N and on the ridge crest of the East Pacific Rise at ∼ 18°S, using the submersible Shinkai 6500 and its support vessel Yokosuka. The systems are presently working, waiting for recovery in 1995.

ISSN:1064-119X    

DOI:10.1080/10641199609388303

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:1064-119X    

DOI:10.1080/10641199609388297

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor