Cone-penetrometer exploration of Sinkholes: Stratigraphy and soil properties     

D. Bloomberg  S. B. Upchurch  M. L. Hayden  R. C. Williams 《Environmental Geology》1988,12(2):99-105

Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine, transgressions. The resulting deposits include five stratigraphic units. I and II represent Plio-Pleistocene marine sediments with Unit II being the zone of soil clay accumulation. III and IV are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units I and II. Conduit fill is a mixture of materials with low cohesion. The fill materials indicate centripetal and downward movement of insoluble sediments derived from the surrounding strata. Loss of cohesion results in near-zero friction ratios. Very low friction ratios, coupled with materials with little cohesion, indicate potentially-liquefiable soils in the immediate vicinity of zones where piping failure may be imminent. SPT does not provide sufficient data to predict these zones of potential, failure. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast, SPT data fail to produce consistent indicators of sinkhole stratigraphy or properties. With laboratory soil data, SPT indicates general, inconclusive trends.  相似文献   

Cation disorder in garnets along the Mg3Al2Si3O12-Mg4Si4O12 join: an infrared,Raman and NMR study     

Paul McMillan  Masaki Akaogi  Eiji Ohtani  Quentin Williams  Ronald Nieman  Robert Sato 《Physics and Chemistry of Minerals》1989,16(5):428-435

We have obtained infrared and Raman spectra for garnets synthesized at high (static) pressures and temperatures along the join Mg₃Al₂Si₃O₁₂ (pyrope) — Mg₄Si₄O₁₂ (magnesium majorite). The vibrational spectra of Mg-majorite show a large number of additional weak peaks compared with the spectra of cubic pyrope garnet, consistent with tetragonal symmetry for the MgSiO₃ garnet phase. The Raman bands for this phase show no evidence for line broadening, suggesting that Mg and Si are ordered on octahedral sites in the garnet. The bands for the intermediate garnet compositions are significantly broadened compared with the end-members pyrope and Mg-majorite, indicating cation disorder in the intermediate phases. Solid state ²⁷Al NMR spectroscopy for pyrope and two intermediate compositions show that Al is present only on octahedral sites, so the cation disorder is most likely confined to Mg-Al-Si mixing on the octahedral sites. We have also obtained a Raman spectrum for a natural, shock-produced (Fe,Mg) majorite garnet. The sharp Raman peaks suggest little or no cation disorder in this sample.  相似文献   

Cyclicity in the late Precambrian Elatina Formation,South Australia: Solar or tidal signature?     

G. E. Williams 《Climatic change》1988,13(2):117-128

New observations from two late Precambrian (~800-650 Ma) sedimentary rhythmites in South Australia (Reynella Siltstone and Chambers Bluff Tillite) reveal cycles structurally similar to the ~12-laminae cycles of the ~650-Ma Elatina Formation but which comprise from 15 to 26 or more laminae. The new data are difficult to accomodate in depositional models for the Elatina Formation whereby its laminae are regarded as annual and the cyclicity ascribed to solar variability (Williams and Sonett, 1985) or to the combined influences of the sunspot cycle and the lunar nodal tide (Zahnle and Walker, 1987). If, however, the long-term Elatina Cycle and not the individual lamina is taken as a yearly climatic signal, the Elatina and other rhythmites studied may be interpreted as the deposits of marine ebb-tidal deltas that record variability in the velocity and range of paleo-ebb tides. The basic laminae-cycles would represent lunar fortnightly cycles of diurnal and/or semidiurnal laminae, commonly truncated through non-deposition at neap tides. Despite numerous empirical similarities between the Elatina and sunspot series, the ebb-tidal model for deposition is preferred because it accounts plausibly for observations from all three rhythmites studied.  相似文献   

DISCUSSION OF PAPERS     

Michael Price  Ann Williams 《Ground water》1988,26(6):798-798

  相似文献   

全球地学断面图数字化指南     

H.-J.Gotze  R.T.Williams  周琦  刘心铸 《地球学报》1993,14(2):185-195

  相似文献   

The common agricultural policy and the general environmental policies concerned with agriculture in the European Community and their implications for fertilizer consumption     

A. J. Williams 《Marine pollution bulletin》1994,29(6-12):500-507

This paper traces the major developments in the European Common Agricultural Policy (CAP) and related environmental policy and examines their impact on the use of crop nutrients. The objectives of the CAP were set out in the Treaty of Rome in 1957 and have not been explicitly revised. The Community has, however, progressed from being a significant importer to a major exporter of food. Various changes in the policy measures/reforms, have been implemented, each to control the continuing increase in farm output. The latest of these in May 1992 reduced commodity prices towards world market levels, introduced 15% set aise for arable land, as well as agreeing a number of agri-environmental measures. Further changes are anticipated following the Uruguay Round of the General Agreement on Tariffs and Trade (GATT) and as new trade agreements are reached with the countries of the former Eastern Bloc. Inevitably, existing farm systems will be subject to careful reappraisal. The Community's environmental objectives were added to the Treaty in 1987 with the passing of the European Single Act. The interaction between agriculture and the environment has been a prominent concern. The Directive 91/676, which seeks to protect water against pollution caused by nitrate from agricultural sources, is the first Directive to have a major direct impact on farm practive. The Fifth Environmental Action Plan for 1993–2000 ‘Towards Sustainability’ selects agriculture as one of five industries for specific attention. The plan seeks an extensification of agriculture and a reduction in the use of chemicals. Changes in the amount of plant nutrients from both farmyard manure and mineral fertilizers used in agriculture are quantified. Methods of determining the efficiency with which they are utilized are assessed. New advisory techniques which will improve the efficiency of nutrient use on the farm are considered, as are the implications for the future demand for nutrients from mineral fertilizers. This paper is the view of the European Fertilizer Manufacturers Association.  相似文献   

Reply to 'Can magnetic-force microscopy determine micromagnetic structures?' by Grütter and Allenspach     

W. Williams  V. Hoffmann  F. Heider  T. Göddenhenrich  C. Heiden 《Geophysical Journal International》1994,116(2):506-507

  相似文献   

Swimming behavior of Dungeness crab,Cancer magister Dana,megalopae in still and moving water     

Miriam Fernandez  Oscar O. Iribarne  David A. Armstrong 《Estuaries and Coasts》1994,17(1):271-275

In the Grays Harbor estuary, juvenile Dungeness crab (Cancer magister Dana) are found at higher densities in epibenthic shell deposits compared to open mud flat. Differences in predation rate between habitats have been suggested to be due to habitat preference and differential survival. Megalopae preferred shell over open space in still-water conditions. However, it is not known whether megalopae are able to select shell in flowing water since larval preference is known to differ between still and flowing water. Here we report the first experimental study of swimming behavior of Dungeness crab megalopae in a range of current velocities (0–40 cm s^?1) equivalent to natural flow in Grays Harbor estuary. Experiments were conducted in daylight using a recirculating flume. Megalopae swimming speeds ranged from 8.5 cm s^?1 (8 body lengths s^?1) in still water to 44.8 cm s^?1 (44 body lengths s^?1) at flow speeds of 40 cm s^?1, Neither swimming behavior nor sheltering behavior in shells showed any flow-related pattern. Megalopae spent a large proportion of time swimming against the current and made headway upstream against all current velocities tested. The results suggest that Dungeness crab megalopae are able to maneuver and actively search for settlement sites under current velocities found in natural habitats, including intertidal shell deposits, and support the hypothesis of active selection of shell by megalopae.  相似文献   

Desertification,drought and landcare: Australia's role in an international convention to combat desertification     

Martin Williams  Megan McCarthy  Geoff Pickup 《The Australian geographer》1995,26(1):23-32

  相似文献   

Factors Affecting Efficient Aquifer Restoration at In Situ Uranium Mine Sites     

James L. Osiensky  Roy E. Williams 《Ground Water Monitoring & Remediation》1990,10(2):107-112

In situ mining of uranium typically requires the injection of a reactive leaching solution (lixiviant) such as sodium carbonate/bicarbonate, ammonium carbonate/bicarbonate, or sulfuric acid, and an oxidant such as hydrogen peroxide or oxygen into an ore-bearing, confined aquifer. It also requires the environmental restoration of the source aquifer. The stratigraphy of sandstone uranium deposits typically consists of interbedded layers of poorly consolidated sands and clays and gravels deposited in fluvial or coastal environments. The parameters that influence the migration of lixiviant during mining and restoration in these environments include induced hydraulic gradients, hydrodynamic dispersion, heterogeneity, anisotropy, physicochemical reactions, leakage into and/or through confining layers, and convergence of flow lines due to partial well penetration.
The effectiveness of the various methods of aquifer restoration is sit -specific and is dependent upon the site hydrogeology and hydrogeochemistry, and the chemistry of the lixiviant. Each method of aquifer restoration has advantages and disadvantages. Selection of the most effective and economically feasible method requires detailed knowledge of the site-specific hydrogeologic conditions.  相似文献