摘要:

Mass physical properties from two different sedimentary environments of the southern ocean were determined. The sediments of a silled basin within the Bransfield Strait are characterized by abundant biogenic opaline silica, whereas more terrigenous material due to ice‐rafting was deposited in the deeper part of the northern Weddell Sea. The high amount of biogenic opaline silica in the sediment of the Bransfield Strait causes a generally higher water content and porosity, whereas a lower shear strength, lower specific grain densities, and wet bulk densities were determined. With increasing burial depth, only small variations of the physical properties were recorded. In contrast to these generally smooth changes due to consolidation processes, more extreme variations of mass physical properties are caused by lithological changes like turbidites.

ISSN:0360-8867    

DOI:10.1080/10641198909379855

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

High‐resolution seismic‐reflection data acquired in the Pearl River mouth region of the South China Sea show the following seafloor instabilities: shallow faults, buried channels, gas‐charged sediments, mud diapirs and sand waves. This paper focuses on the interpretation of their depositional environments and models by means of an analysis of the seismic facies, a study of the dynamic characteristics of seismic facies parameters, and a determination of the velocity‐density properties of the geological units, depths, and stratification continuity. The causes of the instabilities are briefly discussed with examples in three aspects: (1) sea‐level change since Quaternary; (2) neotectonic movement mainly represented by earthquakes and fractures in this region; and (3) oceanographic‐hydrodynamic processes such as waves, tides, and currents. This paper shows that the high‐resolution seismic prospecting technique is a highly valuable means of discerning and studying the subbottom geohazards, and evaluating engineering/geological conditions.

ISSN:0360-8867    

DOI:10.1080/10641198909379856

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Many coastal fills constructed of dredged and dumped sand are loose and may be susceptible to liquefaction. This paper describes a methodology for liquefaction risk analysis for such fills and uses Harbor Island, a hydraulic fill in San Diego Bay, as an example. The characteristics of the fill were analyzed and the liquefaction susceptibility of the soils was evaluated. These were then coupled with the results of a seismic exposure analysis for the site so that the probability of liquefaction could be evaluated.

ISSN:0360-8867    

DOI:10.1080/10641198909379857

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper deals with the geotechnical considerations in selecting a pipeline route through a seabed subjected to iceberg scouring.

ISSN:0360-8867    

DOI:10.1080/10641198909379858

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A corer has been designed to sample and recover deep marine sediments without loss of hydrostatic pressure. The device consists of: the piston corer device of classical design; a pressure‐retaining core module (1.5 m long) with two high‐pressure (60–80MPa) self‐cleaning spherical valves at either end for pressure sealing the sample; and an acoustic control system for monitoring the performance of the corer during operation and commanding the closure of the valves. The core barrel is modular so that the pressure section can be placed in any position along the 6‐m core string. Sediment sampled in adjacent sections depressurizes, thus allowing a direct comparison between this and the sediment maintained under pressure. During sediment penetration, the corer control unit, housed in the tail section, detects the passage of the piston past two ultrasonic detectors activating the closure of the two spherical valves. Field tests of the control unit have verified its ability to perform successfully when subjected to the dynamic forces of a coring operation. Recovered sediment samples will be available for laboratory investigations; high pressure apparatus is already available for studying the migration of radionuclides and heavy metals in marine sediments. The interface needed between the corer and this equipment is under development.

ISSN:0360-8867    

DOI:10.1080/10641198909379859

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

When artificial islands are constructed, they are subject to surface subsidence, which is the resultant sum of the consolidation strata, many of which seem differ in character. When these strata are soft and thick, or heavily loaded, it becomes very difficult to estimate how much settlement will eventually take place, and over how long a period. For the estimate to be accurate, the settlement characteristics of each layer must first be determined.

ISSN:0360-8867    

DOI:10.1080/10641198909379860

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0360-8867    

DOI:10.1080/10641198909379854

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor