摘要:

The synthesis of anchor equilibrium equations with recently derived chain equilibrium expressions enables calculations for anchor system capacity which account for the anchor‐chain interaction. This forms the basis for a study into the effects of relative chain size on anchor performance, and extrapolation of scale‐model tests to prototype events. Applications of these expressions are particularly suited to clay soils, where the failure mechanism of the soil is local and hence the anchor capacity is essentially independent of anchor orientation. Expressions are derived for the ultimate holding capacity of anchors in terms of two fundamental anchor parameters. Analytical relationships for the development of embedment and capacity with drag distance are shown to compare favorably with numerical solutions and also with field test data.

ISSN:1064-119X    

DOI:10.1080/10641199609388305

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Mine tailings from an open‐pit molybdenum mine were discharged at 50 m depth to Alice Arm, B.C., Canada, during 1981–1982 We report here the results of a sediment‐trap survey to determine the scale of transport of suspended tailings within the fiord. Tailings clearly affect the particle fluxes in the deeper water of Alice Arm out to a distance of about 12–14 km, as demonstrated by increased particle fluxes and enrichment of these particles in heavy metals (Cd, Zn, Pb). However, the disposal strategy appears to have been effective in trapping suspended tailings within Alice Arm; there was no evidence of tailings entering surface water or escaping the inlet Three months after the mine closed, particle fluxes in Alice Arm dropped to natural or near‐natural levels. Natural inorganic particle delivery is abo recorded in the traps as seasonal pulses from rivers draining into the head and sides of the arm.

ISSN:1064-119X    

DOI:10.1080/10641199609388306

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The physical and chemical properties of the substrates of marine brine ponds are described in relation to the quantity and quality of the salt produced. It is revealed that the production of good quality salt is achieved in those ponds with coarse sediments; it is better sorted and negatively skewed. Low salt production is observed in those ponds with fine sediments and rich in organic carbon. In ponds with fine sediments, a thick, dark‐colored rich organic layer is formed below the salt that causes problems during the harvest High amounts of colloidal Fe hydroxides rich in Cu, Zn, Cr, Cd, Pb, Ni, and V are observed in the brine of evaporation ponds with fine substrate. The high contents of organic carbon encountered in ponds with moderate salt quality is because of high biological activity, including intense vegetation, in the surrounding region. The knowledge resulting from this research can be used for the improvement of the quality and the increase of the quantity of salt produced in crystallization ponds and in the construction of saltworks.

ISSN:1064-119X    

DOI:10.1080/10641199609388307

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The formation of economic‐grade noble metal and heavy mineral placers at high latitudes is facilitated by the interaction of high‐energy waves and currents with the multimodal size and density fractions of glacial material (Emory‐Moore & Solomon, 1989). Placers which form under such conditions tend to exhibit very irregular distribution patterns, such that these deposits are typically not distinguished by traditional sediment dispersal modeling techniques. In an effort to model sediment dispersal patterns in high‐latitude repons more effectively, multivariate geostatistical analyses, which have proven successful in modeling complex sediment dispersal patterns in a number of marine and lacustrine areas, were carried out on sediment geochemical data for 184 samples from a typical high‐latitude coastal site (North Cardigan Bay). A Q‐mode factor analysis of North Cardigan Bay sediments revealed that > 99% of the total variance in the data can be explained by four end members, representing (1) mixed quartz and orthoclase, (2) mixed aluminosilicates, (3) carbonates, and (4) heavy minerals. Linear programming was used to estimate the relative amount of these end members in each sample; the data from this analysis were used to model sediment dispersal. By comparison with the results of a comprehensive study of North Cardigan sediments by Moore (1968), this modeling approach accurately predicts the sediment distribution pattern for North Cardigan Bay. This sediment dispersal modeling procedure represents a significant improvement over traditional techniques, in that sediment dispersal is not constrained to occur along concentration gradients and it requires only the type of sediment geochemical information that would be obtained in a standard reconnaissance‐level exploration survey.

ISSN:1064-119X    

DOI:10.1080/10641199609388308

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

As a result of favorable environmental conditions, ferromanganese concretions in the eastern part of the Gulf of Finland achieve the highest levels of abundance and variability found in shallow‐water environments. The abundance of the Mn‐rich spheroidal concretions concentrated in the most prospective fields in the Russian sector of the Gulf of Finland reaches 50 kg/m2, and the total weight of these concretions is calculated to be about 6 million tonnes. This weight is considered to be relatively constant with time because of the cyclic processes of growth and dissolution of the concretions. The spheroidal concretions contain on average 33.8% MnO2, 20.2% Fe2O3, and 2.7% P2OS. The concentrations of Cu, Ni, Zn, Mo, etc., in the concretions are near the regional background levels. The contents of these elements have increased during the last few decades as a result of the anthropogenic input of the metals into the Baltic. The growth rate of the spheroidal concretions is calculated to be about 0.03–0.08 mm/yr. The technology of extraction of Mn from the Mn‐rich spheroidal concretions has been developed by the Hypronikel Institute in St Petersburg. This will permit the commercial recovery of these concretions in the future.

ISSN:1064-119X    

DOI:10.1080/10641199609388309

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This is the first article to describe mineralization of midplate submarine rift zones and hydrothermal manganese oxide mineralization of midplate volcanic edifices. Hydrothermal Mn oxides were recovered from submarine extensions of two Hawaiian rift zones, along Haleakala and Puna Ridges. These Mn oxides form two types of deposits, metallic stratiform layers in volcaniclastic rocks and cement for clastic rocks; both deposit types are composed of todorokite and bimessite. Thin Fe‐Mn crusts that coat some rocks formed by a combination of hydrogenetic and hydrothermal processes and are composed of δ‐MnO2. The stratiform layers have high Mn contents (mean 40%) and a large fractionation between Mn and Fe (Fe/Mn = 0.04). Unlike most other hydrothermal Mn oxide deposits, those from Hawaiian rift zones are enriched in the trace metals Zn, Co, Ba, Mo, Sr, V, and especially Ni (mean 0.16%). Metals are derived from three sources: mafic and ultramafic rocks leached by circulating hydrothermal fluids, clastic material (in Mn‐cemented sandstone), and seawater that mixed with the hydrothermal fluids. Mineralization on Haleakala Ridge occurred sometime during the past 200 to 400 ka, when the summit was at a water depth of more than 1,000 m. Hydrothermal circulation was probably driven by heat produced by intrusion of dikces, magma reservoirs, and flow of magma through axial and lateral conduits. The supply of seawater to ridge interiors must be extensive because of their high porosity and permeability. Precipitation of Mn oxide below the seafloor is indicated by its occurrence as cement, growth textures that show mineralizing fluids were introduced from below, and pervasive replacement of original matrix of clastic rocks.

ISSN:1064-119X    

DOI:10.1080/10641199609388310

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:1064-119X    

DOI:10.1080/10641199609388304

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor