Slope Floor Research Articles

Hydraulic characterization of a wastewater treatment clarifier by an acoustic doppler current profiler

Optimization of the solids removal performance of a clarifier requires, in part, a complete understanding of the tank hydraulics. This paper presents velocity measurements obtained by utilizing an acoustic doppler current profiler (ADCP). The latter provides the necessary temporal and spatial scale to understand and analyze in a detailed way density-driven flows in wastewater clarifiers. Velocity profiles and Reynolds shear stresses of a full-scale installation were investigated. Two different clarifiers were investigated that differ in floor slopes and solids removal mechanisms. The ADCP revealed that sloped clarifiers provide significant solids transport towards the central removal sump. Implications in the design of clarifiers are discussed and new insight is provided into the transport of solids and purpose of the solids removal system. The velocity measurements suggest that the analysis of the removal mechanism should be considered from a fluid mechanical perspective. It was also seen that a scraper-equipped, central solids removal design creates non-ideal flow fields compared with a suction, radial removal design. Shear stress corresponded well with simulation results from literature. The paper has to be seen as a first attempt to apply this proven measurement technology in wastewater treatment.

Numerical simulations of the internal tide in a submarine canyon

Three-dimensional numerical simulations of the generation and propagation of the semidiurnal internal tide in a submarine canyon with dimensions similar to those of the Monterey Canyon are carried out using a primitive equation model. Forcing with just sea level at the offshore boundary in an initially horizontally homogeneous ocean with realistic vertical stratification, internal tides are generated at the canyon foot and rim, and along portions of the canyon floor. The results compare favorably with observations, both indicating enhancement of energy along the canyon floor propagating at an angle consistent with linear internal wave theory. Due to the earth's rotation, internal tide energy is distributed asymmetrically in the cross-canyon direction, favoring the southern side. The effect of canyon floor slope is explored, with the finding that small changes in the slope result in large changes in the amount and distribution of the internal tide energy. Canyons whose floors are subcritical with respect to the semidiurnal frequency along their entire length have very little baroclinic energy, whereas canyons that are near-critical along much of their length, such as the Monterey Canyon, develop strong internal tides that propagate shoreward. Canyons that are near-critical at their mouths but supercritical further inshore generate the most internal tidal energy overall, although little of it makes it onto the continental shelf shoreward of the canyon head. The effects of internal tides within the canyons can be seen outside the canyons as well. Water is transported from depth onto the adjacent continental shelf along the canyon rims. This tidal pumping can be responsible for alongshore internal tide propagation and tidal-period surface currents with relatively small horizontal scales of variability.

Spatial arrangement of branches in relation to slope and neighbourhood competition.

To gain a better understanding of the effects of spatial structure on patterns of neighbourhood competition among hardwood trees, the three-dimensional extension of primary branches was surveyed for ten community-grown Castanea crenata (Fagaceae) trees with respect to the positioning of neighbouring branches and the slope of the forest floor. There were significantly more branches extending towards the lower side of the slope than towards the upper side, but structural properties such as branch length and vertical angle were not affected by slope. When horizontal extension of a branch towards its neighbour was compared for a C. crenata branch and a neighbouring heterospecific, the former was significantly narrower than the latter when the inter-branch distance (horizontal distance between the base positions of two neighbouring branches) was short (< approx. 5 m). Castanea crenata branches tended to extend in a direction avoiding neighbouring branches of heterospecifics when the inter-branch distance was short. Furthermore, for an inter-branch distance <3 m, the horizontal extension of a C. crenata branch was less when it was neighbouring a heterospecific branch than when neighbouring a conspecific branch. These results suggest that horizontal extension of C. crenata branches is more prone to spatial invasion by nearby neighbouring branches of heterospecifics, and that the invasion can be lessened when C. crenata trees are spatially aggregated. The reason why such an arrangement occurs is discussed in relation to the later leaf-flush of C. crenata compared with that of other species in the forest.

Seismic stratigraphy of the deep Ulleung Basin in the East Sea (Japan Sea) back-arc basin

Analysis of multi-channel seismic reflection profiles has revealed that the Ulleung Basin in the East Sea (Sea of Japan) back-arc basin comprises the southern and northern depocenters containing thick (over 11 and 5km, respectively) Neogene–Quaternary sediments. Back-arc closure that began in the middle Miocene caused regional uplift along the southern and southeastern basin margins, bringing large volumes of sediment into the basin. Much of this sediment supply was deposited directly onto the base of the slope and basin floor, resulting in widespread mass-transport deposits especially in the southern basin. Since the latest late Miocene, mass-transport deposits have retreated rapidly in an updip direction as the tectonic activity along the basin margins waned significantly. The apparent dominance of mass-transport deposits in the Ulleung Basin suggests that the sedimentation pattern in this basin is quite different from those in the other basins (Japan and Yamato Basins) in the East Sea where basinal turbidite and hemipelagic sedimentation has prevailed throughout the Neogene and Quaternary. The maximum two-way travel-time sediment thickness in the Ulleung Basin, about twice that of the Japan and Yamato Basins, further suggests more massive sedimentation in the Ulleung Basin.

Geomorphology, facies architecture, and high-resolution, non-marine sequence stratigraphy in avulsion deposits, Cumberland Marshes, Saskatchewan

Abstract This paper demonstrates field relationships between landforms, facies, and high-resolution sequences in avulsion deposits. It defines the building blocks of a prograding avulsion sequence from a high-resolution sequence stratigraphy perspective, proposes concepts in non-marine sequence stratigraphy and flood basin evolution, and defines the continental equivalent to a parasequence. The geomorphic features investigated include a distributary channel and its levee, the Stage I crevasse splay of Smith et al. (Sedimentology, vol. 36 (1989) 1), and the local backswamp. Levees and splays have been poorly studied in the past, and three-dimensional (3D) studies are rare. In this study, stratigraphy is defined from the finest scale upward and facies are mapped in 3D. Genetically related successions are identified by defining a hierarchy of bounding surfaces. The genesis, architecture, geometry, and connectivity of facies are explored in 3D. The approach used here reveals that avulsion deposits are comparable in process, landform, facies, bounding surfaces, and scale to interdistributary bayfill, i.e. delta lobe deposits. Even a simple Stage I splay is a complex landform, composed of several geomorphic components, several facies and many depositional events. As in bayfill, an alluvial ridge forms as the feeder crevasse and its levees advance basinward through their own distributary mouth bar deposits to form a Stage I splay. This produces a shoestring-shaped concentration of disconnected sandbodies that is flanked by wings of heterolithic strata, that join beneath the terminal mouth bar. The proposed results challenge current paradigms. Defining a crevasse splay as a discrete sandbody potentially ignores 70% of the landform's volume. An individual sandbody is likely only a small part of a crevasse splay complex. The thickest sandbody is a terminal, channel associated feature, not a sheet that thins in the direction of propagation. The three stage model of splay evolution proposed by Smith et al. (Sedimentology, vol. 36 (1989) 1) is revised to include facies and geometries consistent with a bayfill model. By analogy with delta lobes, the avulsion sequence is a parasequence, provided that its definition is modified to be independent from sea level. In non-marine settings, facies contacts at the tops of regional peats, coals, and paleosols are analogous to marine flooding surfaces. A parasequence is redefined here as a relatively conformable succession of genetically related strata or landforms that is bounded by regional flooding surfaces or their correlative surfaces. This broader definition incorporates the concept of landscape evolution between regional flooding surfaces in a variety of depositional settings. With respect to landscape evolution, accommodation space has three spatial dimensions — vertical (x), lateral (y), and down-the-basin (z). A flood basin fills in as landforms vertically (x) and laterally accrete (y), and prograde down-the-basin (z). Vertical aggradation is limited by the elevation of maximum flood stage (local base level). Differential tectonism and geomorphology control the slope of the flood basin floor and the direction of landscape evolution. These processes produce parasequences that include inclined stratal surfaces and oriented, stacked macroforms (clinoforms) that show the magnitude and direction of landscape evolution.

Neogene-Quaternary contourite and related deposition on the West Shetland Slope and Faeroe-Shetland Channel revealed by high-resolution seismic studies

The Neogene and Quaternary sediments of the Faeroe-Shetland Channel and West Shetland shelf and slope rest upon a major regional unconformity, the Latest Oligocene Unconformity (LOU), and have been deposited through the interaction of downslope and parallel-to-slope depositional processes. The upper to middle continental slope is dominated by mass-transport deposits (debris flows), which progressively diminish downslope, and were largely generated and deposited during glacial cycles when ice sheets supplied large quantities of terrigeneous sediment to the upper slope and icebergs scoured sea-floor sediments on the outer shelf and uppermost slope. Large-scale sediment failures have also occurred on the upper slope and resulted in deposition of thick, regionally extensive mass-transport deposits on portions of the lower slope and channel floor. In contrast, large fields of migrating sediment waves and drift deposits dominate most of the middle to lower slope below 700 m water depth and represent deposition by strong contour currents of the various water masses moving northeastward and southwestward through the channel. These migrating sediment waves indicate strong northeastward current flow at water depths shallower than ∼700 m and strong southwestward current flow at water depths from ∼700 to >1,400 m. These flow directions are consistent with present-day water-mass flow through the Faeroe-Shetland Channel. The Faeroe-Shetland Channel floor is underlain by thin conformable sediments that appear to be predominantly glacial marine and hemipelagic with less common turbidites and debris flows. No evidence is observed in seismic or core data that indicates strong contour-current erosion or redistribution of sediments along the channel floor.

ABSTRACT: Turbidite and Deepwater Depositional Systems of Borneo: Foredeep Slope and Basin Floor Fan Systems

ABSTRACT: Turbidite and Deepwater Depositional Systems of Borneo: Foredeep Slope and Basin Floor Fan Systems

ABSTRACT: Improved Sequence Stratigraphic and Reservoir Characterization Models: Mesaverde Group, Southwestern, Wyoming

Abstract The combination of excellent outcrops and subsurface data sets makes the Rocky Mountain region a great place to do predictive stratigraphy and reservoir characterization. Several years ago, five behind outcrop core wells were drilled and logged in the Cretaceous Mesaverde Group, Rock Springs Uplift, Wyoming. The Mesaverde is a 2nd order regressive-transgressive clastic wedge that is estimated to contain 52,000 TCF and 776 MMBNGL in a variety of alluvial to open marine reservoirs. Data from these wells and surrounding outcrops, combined with regional studies, have resulted in significant updating of the depositional and reservoir-geological models for this succession. Our studies document numerous 3rd and 4th-order sequence bounding unconformities and transgressive erosion surfaces that occur in both overall progradational and overall retrogradational successions. Synsedimentary faulting and lateral variations in subsidence, in conjunction with the presence of high-frequency unconformities, have resulted in a complex stratigraphy on basin to reservoir scales. Incised valleys have been identified in three of the four Mesaverde formations, including the overall transgressive Almond Formation. Reservoir architecture of the fluvio-estuarine Ericson Sandstone is strongly tied to changes in accommodation / sediment supply that can be linked to repeated transits of shoreline transgression and regression. Because of the ramp setting, shoreline dislocations associated with unconformities can be significant. The Blair Formation, previously interpreted as a slope and basin floor fan deposit, is re-interpreted as a lowstand delta. The sequence stratigraphic and reservoir models developed, have application not just to developing gas resources in the Mesaverde, but to improving our understanding of analogous reservoirs worldwide.

Geochemical studies of the amazonian basin using transition elements and ree

SUMMARY OF COMMUNICATIONS THEMES ON EARTH SCIENCESOrganizer: A.C. Rocha-Campos SEQUENCE STRATIGRAPHY OF THE PASSA DOISGROUP IN THE SERRA DO ESPIGAO, PARANA BASIN,BRAZIL ∗ Jose Roberto Canuto Instituto de Geociencias, USP, Sao Paulo, SP.Presented by Antonio C. Rocha-Campos ThePassaDoisGroupisdividedintoformationsandmembers, representing variations of lithofacies separatedby unconformities or correlative conformities.The contact between the Passa Dois and TubaraoGroups is represented by a paraconformity, and the con-tact between the Passa Dois and Sao Bento Groups corre-sponds to a regional unconformity or correlative confor-mity.Intracratonic basins differ physiographically frompassivemarginbasins,forwhichtheconceptsofSequenceStratigraphy were originally developed; so some adjust-ment has to be done for the application of the theory.The3rdorderchronostratigraphicframeworkforthePassa Dois Group begins by offshore marine sedimenta-tion of the Taquaral Member upon the coastal marine re-gressivesedimentsoftheupperpartofthePalermoForma-tion, through a conformable contact representing a trans-gressive surface. After this, a highstand phase prevails,bounded at its top by the maximum flooding surface, thatis coincident with the lower conformable contact of theAssistencia Member, which represents a new lowstandphase. Sea level rises again, through transgression, de-positing the offshore sediments of the Serra Alta Forma-tion. Deposition of the sediments of the Teresina Forma-tion follows, suggesting a new lowstand phase with waveand tidal structures, than passes to the Serrinha Memberof deeper waters with hummocky structures indicating anew highstand phase. A new lowstand phase occurs withwell-sorted sandstones showing cross-stratification withmedium to high angles, with clay drapes, suggesting therecurrence of tidal conditions, corresponding to the baseof the Morro Pelado Member, that passes, by transition,to continental deposits, bounded at their top by a regionalunconformity or a correlative conformity considered be-tween the Passa Dois and the Sao Bento Groups, corre-sponding to a 2nd order sequence.The thicknesses of each pair of units, deposited inshallowerwatersatitsbaseandbydeeperwatersatitstop,do not exceed 500 m. Considering a rate of deposition ofthe order of 1 m per each 10,000 years, they correspond to3rd order sequences. The bounding surfaces that separatethe sequences are of conformable type 2. Depositionalsystems characteristic of steeper slopes, or of floor basinfans or slope fans, that are common in sequences of type 1arenotobserved. Thedurationofdepositionoftherelatedpairsvariedfrom1to10M.a.,wellwithintheknowndura-tion of stages, which strengthens the hypothesis that theyrepresent 3rd order sequences. — ( December 10, 1999 ).

Discovering information through virtual reality

SUMMARY OF COMMUNICATIONS THEMES ON EARTH SCIENCESOrganizer: A.C. Rocha-Campos SEQUENCE STRATIGRAPHY OF THE PASSA DOISGROUP IN THE SERRA DO ESPIGAO, PARANA BASIN,BRAZIL ∗ Jose Roberto Canuto Instituto de Geociencias, USP, Sao Paulo, SP.Presented by Antonio C. Rocha-Campos ThePassaDoisGroupisdividedintoformationsandmembers, representing variations of lithofacies separatedby unconformities or correlative conformities.The contact between the Passa Dois and TubaraoGroups is represented by a paraconformity, and the con-tact between the Passa Dois and Sao Bento Groups corre-sponds to a regional unconformity or correlative confor-mity.Intracratonic basins differ physiographically frompassivemarginbasins,forwhichtheconceptsofSequenceStratigraphy were originally developed; so some adjust-ment has to be done for the application of the theory.The3rdorderchronostratigraphicframeworkforthePassa Dois Group begins by offshore marine sedimenta-tion of the Taquaral Member upon the coastal marine re-gressivesedimentsoftheupperpartofthePalermoForma-tion, through a conformable contact representing a trans-gressive surface. After this, a highstand phase prevails,bounded at its top by the maximum flooding surface, thatis coincident with the lower conformable contact of theAssistencia Member, which represents a new lowstandphase. Sea level rises again, through transgression, de-positing the offshore sediments of the Serra Alta Forma-tion. Deposition of the sediments of the Teresina Forma-tion follows, suggesting a new lowstand phase with waveand tidal structures, than passes to the Serrinha Memberof deeper waters with hummocky structures indicating anew highstand phase. A new lowstand phase occurs withwell-sorted sandstones showing cross-stratification withmedium to high angles, with clay drapes, suggesting therecurrence of tidal conditions, corresponding to the baseof the Morro Pelado Member, that passes, by transition,to continental deposits, bounded at their top by a regionalunconformity or a correlative conformity considered be-tween the Passa Dois and the Sao Bento Groups, corre-sponding to a 2nd order sequence.The thicknesses of each pair of units, deposited inshallowerwatersatitsbaseandbydeeperwatersatitstop,do not exceed 500 m. Considering a rate of deposition ofthe order of 1 m per each 10,000 years, they correspond to3rd order sequences. The bounding surfaces that separatethe sequences are of conformable type 2. Depositionalsystems characteristic of steeper slopes, or of floor basinfans or slope fans, that are common in sequences of type 1arenotobserved. Thedurationofdepositionoftherelatedpairsvariedfrom1to10M.a.,wellwithintheknowndura-tion of stages, which strengthens the hypothesis that theyrepresent 3rd order sequences. — ( December 10, 1999 ).

The thermal regime of a retrogressive thaw slump near Mayo, Yukon Territory

The development of a retrogressive thaw slump near Mayo, Yukon Territory, has been traced from initiation by bank erosion (~1949) of the Stewart River to stabilization in 1993-1994. The stabilized headwall of the slump is 450 m from the river, and the slope of the slump floor is 3°. A transect of the slump from the river to the stabilized headwall was drilled in July 1995, to determine the extent and rate of permafrost degradation in the slump floor. Thermistors were placed in access tubes to 12 m depth at five sites, four near the transect and one in undisturbed terrain, to determine the magnitude of thermal disturbance due to slump development. Data loggers at the sites recorded the ground temperature at 1 m depth for two years from August 1995. The annual mean ground temperatures measured by the data loggers varied between 1.2° and 1.8°C in the slump, compared with -2.4°C in undisturbed ground, indicating a disturbance of about 4°C due to slumping. The depth of thaw in the slump floor is consistent with the Stefan solution for thawing of permafrost. Conduction is the dominant mode of heat transfer in the slump, where the soil is fine grained and there is almost no organic horizon. Winter ground temperatures at 1 m depth were nearly 6°C warmer in the slump than in the surrounding forest, even though snow depths were similar, due to the release of latent heat during prolonged frost penetration. These data demonstrate the importance of subsurface conditions on near-surface ground temperatures in winter.

Geoelectrical investigation of old/abandoned, covered landfill sites in urban areas: model development with a genetic diagnosis approach

Geoelectrical methods have an important, albeit difficult role to play in landfill investigations. In the present economic conditions, with the environmentally sensitive regime, adequate desk-study and model development are essential ingredients for a successful site investigation of landfills. This paper attempts to develop a genetic investigative model for old/abandoned landfill sites where the records of operations are not available. The main elements of the model are the site boundaries, age and nature of anthropogenic deposits, depth and dip of the layers of refuse and sealing materials, the integrity and shape of the capping zones or separating walls and basal floor slopes, the position of concealed access roads in the site, the water table (or perched water bodies within the refuse) and the presence of leachate. The attendant geotechnical, hydrogeological, and bio-geochemical constraints at such sites are also incorporated in the model for consistency of practical solutions to landfill problems. The nature of anthropogenic deposits and the spatial–temporal characteristics of leachates are reviewed in a geoelectrical context. The analogy between waste degradation and leaching, and the well-known weathering processes of supergene mineral enrichment and saprolite formation in crystalline rocks is explored, and used to develop a conceptual resistivity-vs.-depth model for landfill sites. The main tenet of the model is that vertical conductivity profiles will attain maximum values in the zone of mineral enrichment near the water table and tail-off away from it. This conceptual resistivity model is shown to be consistent with non-invasive observations in landfill sites in different geographical environments. Power–law relationships are found to exist between some geoelectrically important hydrochemical parameters (fluid conductivity, chloride content and total dissolved solids) in leachates and leachate-contaminated groundwater from some landfill sites. Since some chemical parameters of fill are known to vary consistently with time, a plausible hydrochemical and age-deductive scheme for saturated fill is proposed for geoelectrical models of landfills without significant amounts of metal. Practical suggestions are made for a consistent approach in geoelectrical investigation and diagnosis of old landfill sites. A few field examples are used to illustrate the diagnosis approach.

Sand body geometry in a sand-rich, deep-water clastic system, Miocene Cingöz Formation of southern Turkey

Three types of sandstone bodies, canyon-fill, tongues and lobes are recognized, and their geometry and spatial organization described within an elongate, W–E trending deep-water clastic system. The canyon-fill comprises sheet-like, fining upward packages that pinch-out rapidly (over 20 m laterally) where they onlap against the basin margin slope to the north. To the south, bed packages pinch-out more gradually over 400–500 m where they are confined by basin floor topography that forms one margin to the canyon. Down-system from the canyon, tongues form narrow and elongate (0.5–1 km wide and 25 km long) sandstone bodies. They are non-erosive, and are thus not channels, but sedimentation is focused within palaeotopographic lows formed by basement structure and differential compaction. Lobes occur close to the mouth of the canyon, overlying the tongues. Packages of lobes (net sandstone ∼80%) and interlobe deposits (net sandstone ∼40%) are cut by distributary channels that allow sediment to bypass the lobes. The overall asymmetric geometry and elongate nature of this sand-rich deep-water clastic system, and consequently sandstone distribution and architecture, are controlled by the basin margin slope and basin floor palaeotopography.

Abstract: Towards prediction of deepwater sands on slope and basin floor

Abstract: Towards prediction of deepwater sands on slope and basin floor

Cenozoic depositional history of the Gulf of Mexico basin

A Geographic Information System (GIS) database incorporating information from 241 publications, theses, and dissertations; well logs and paleontologic reports; and interpreted University of Texas Institute for Geophysics (UTIG) deep-basin seismic lines was used to map and interpret 18 basinwide genetic stratigraphic sequences that form the Gulf of Mexico basin Cenozoic fill. Eight principal extrabasinal fluvial axes provided the bulk of the sediment infill in the basin. First-order temporal and spatial use of these axes reflects four continent-scale phases of crustal uplift. Abundant sediment supply has prograded the northern and northwestern basin margin 150 to 180 mi (240 to 290 km) from its inherited Cretaceous position. Margin outbuilding has been locally and briefly interrupted by hypersubsidence due to salt withdrawal and mass wasting. Three depositional systems tracts characterize Cenozoic genetic sequences: (1) fluvial --> delta --> delta-fed apron, (2) coastal plain --> shore zone --> shelf --> shelf-fed apron, and (3) delta flank --> submarine fan. One or more examples of the fluvial --> delta --> delta-fed apron systems tract occur in each of the major genetic sequences. Immense volumes of sand have bypassed the shelf margin to be deposited in slope and base-of-slope systems, primarily within fluvial --> delta --> delta-fed apron system tracts, during all major Paleogene and Neogene depositional episodes. Deposition and preservation of volumetrically significant coastal plain --> shore zone --> shelf --> shelf-fed apron tracts is typical of Paleogene through Miocene depositional episodes only. Fan system origin was commonly associated with major continental margin failures, but large submarine canyons occur mainly in Pleistocene sequences. Thick, potential reservoir sand bodies occur in offlapping delta-fed slope and subjacent basin floor aprons, in autochthonous slope aprons and related infills of slide scars and canyon cuts, and in submarine fans.

Stable isotopes and soil-geomorphology as indicators of Holocene climate change, northern Chihuahuan Desert

Coeval δ13C shifts recorded in buried soils at both piedmont slope and basin floor sites in the northern Chihuahuan Desert indicate a major shift from C4grasses to C3desert-scrub between 7 and 9 ka. The age assignments are based on stratigraphic correlations to charcoal dates and carbon-14 dates of carbonate. This shift is synchronous with a period of cooling in the North Atlantic that may have triggered a period of drought in the south-western United States. Coinciding with this vegetation change, geomorphic evidence in Rio Grande, piedmont, and basin floor eolian environments indicates a major period of erosion. Subsequent gradual enrichment of pedogenic carbonateδ13 C values in younger deposits suggests that C4grasses rebounded in the late Holocene (approximately 4 ka), which is consistent with other evidence of increased moisture regionally. A period of less severe aridity at approximately 2·2 ka is indicated by erosion and subsequent deposition along the alluvial fans and within the basin, and correlates with depleted pedogenic carbonate δ13C values suggesting a decrease in C4grasses. Isotope and packrat midden records should be used together to infer past environmental conditions at different elevations.

GEOTECHNICAL INVESTIGATION AT LIGNITE MINES

Mineral Resources EngineeringVol. 08, No. 04, pp. 405-418 (1999) No AccessGEOTECHNICAL INVESTIGATION AT LIGNITE MINESD. MONOPOLIS, E. STIAKAKIS, E. AGIOUTANTIS, and C. KAVOURIDISD. MONOPOLISDepartment of Mineral Resources Engineering, Technical University of Crete, 73100 Hania, Greece Search for more papers by this author , E. STIAKAKISDepartment of Mineral Resources Engineering, Technical University of Crete, 73100 Hania, Greece Search for more papers by this author , E. AGIOUTANTISDepartment of Mineral Resources Engineering, Technical University of Crete, 73100 Hania, Greece Search for more papers by this author , and C. KAVOURIDISDepartment of Mineral Resources Engineering, Technical University of Crete, 73100 Hania, Greece Search for more papers by this author https://doi.org/10.1142/S0950609899000372Cited by:6 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractOpen pit lignite mining provides the energy resources for about 80% of the electrical energy annually consumed in Greece. Optimum open pit slope stability design is related to the minable reserves as well as the cost of mining. This paper presents a geotechnical investigation for the "Tomeas 6" lignite mine at the Ptolemais-Amydeon basin (in northern Greece), including sample testing, interpretation of inclinometer and geodetic data, and slope stability analysis performed in order to determine the potential of mine slope failure. This investigation was initiated after slope cracks and floor heaving were observed following mining operations. Results indicate that cracking on the slope as well as floor heaving may be attributed to stress relief due to mining. FiguresReferencesRelatedDetailsCited By 6Analysis of Faults' Effect on the Stability of Surface Lignite Mining Areas Using the Distinct Element MethodMarwan Al Heib, Ioannis E. Zevgolis, Alexandros I. Theocharis, Nikolaos C. Koukouzas and Stella Coccia6 August 2021 | Geotechnical and Geological Engineering, Vol. 40, No. 3Α comprehensive geotechnical characterisation of overburden material from lignite mine excavationsAlexandros I. Theocharis, Ioannis E. Zevgolis and Nikolaos C. Koukouzas16 March 2021 | Geomechanics and Geophysics for Geo-Energy and Geo-Resources, Vol. 7, No. 2Investigating the elastoplasticity of an Australian soft rock based on laboratory test resultsMojtaba Karami and Ali Tolooiyan1 Oct 2020 | Engineering Geology, Vol. 276Slope failure incidents and other stability concerns in surface lignite mines in GreeceIoannis E. Zevgolis, Alexandros V. Deliveris and Nikolaos C. Koukouzas1 Nov 2019 | Journal of Sustainable Mining, Vol. 18, No. 4Probabilistic design optimization and simplified geotechnical risk analysis for large open pit excavationsIoannis E. Zevgolis, Alexandros V. Deliveris and Nikolaos C. Koukouzas1 Nov 2018 | Computers and Geotechnics, Vol. 103A kinetic behavior model at a surface lignite mine, based on geotechnical investigationE. Steiakakis and Z. Agioutantis1 May 2010 | Simulation Modelling Practice and Theory, Vol. 18, No. 5 Recommended Vol. 08, No. 04 Metrics History PDF download

PHYSICAL HABITAT OF CETACEANS ALONG THE CONTINENTAL SLOPE IN THE NORTHCENTRAL AND WESTERN GULF OF MEXICO

AbstractThe physical habitat of cetaceans found along the continental slope in the north‐central and western Gulf of Mexico was characterized from shipboard sighting data, simultaneous hydrographic measurements, and satellite remote sensing. The study area was encompassed by the longitude of the Florida‐Alabama border (87.5°W), the southernmost latitude of the Texas‐Mexico border (26.0°N), and the 100‐m and 2,000‐m isobaths. Shipboard surveys were conducted seasonally for two years from April 1992 to May 1994. A total of 21,350 km of transect was visually sampled in an area of 154,621 km2.Sighting localities of species in the study area were differentiated most clearly with bottom depth. Atlantic spotted dolphins (Stenella frontalis) were consistently found in the shallowest water on the continental shelf and along the shelf break. In addition, the bottom depth gradient (sea floor slope) was less for Atlantic spotted dolphins than for any other species. Bottlenose dolphins (Tursiops truncatus) were found most commonly along the upper slope in water significantly deeper than that for Atlantic spotted dolphins. All the other species and species categories were found over deeper bottom depths; these were Risso's dolphins (Grampus griseus), short‐finned pilot whales (Glob‐icephala macrorhynchus), pygmy/dwarf sperm whales (Kogia spp.), roughtoothed dolphins (Steno bredanensis), spinner dolphins (Stenella longirostris), sperm whales (Physeter macrocephalus), striped dolphins (Stenella coeruleoalba), Mesoplodon spp., pantropical spotted dolphins (Stenella attenuata), Clymene dolphins (Stenella clymene) and unidentified beaked whales (Ziphiidae). Risso's dolphins and short‐finned pilot whales occurred along the upper slope and, as a subgroup, were significantly different from striped dolphins, Mesoplodon spp., pantropical spotted dolphins, Clymene dolphins, and unidentified beaked whales, which occurred in the deepest water. Pygmy/dwarf sperm whales, rough‐toothed dolphins, spinner dolphins, and sperm whales occurred at intermediate depths between these two subgroups and overlapped them.

Original Article

Hydraulic flocculators, despite their superior plug-flow properties, negligible energy requirements and robust simplicity, are commonly perceived as being inflexible. Once built, it is argued, they do not provide the operational flexibility to compensate for flow fluctuations or changing raw water characteristics. The design procedure developed in this paper demonstrates the contrary, namely that hydraulic flocculators can be designed to satisfactorily cope with tapered velocity gradients, flow variations and water quality variations. The procedure is based on a two-step approach; the horizontal layout is first determined with average values for velocity gradient and water depth; then only the floor slope and exact water depths are determined to enable satisfactory flocculation for all design scenarios.

Design of around-the-end hydraulic flocculators

Hydraulic flocculators, despite their superior plug-flow properties, negligible energy requirements and robust simplicity, are commonly perceived as being inflexible. Once built, it is argued, they do not provide the operational flexibility to compensate for flow fluctuations or changing raw water characteristics. The design procedure developed in this paper demonstrates the contrary, namely that hydraulic flocculators can be designed to satisfactorily cope with tapered velocity gradients, flow variations and water quality variations. The procedure is based on a two-step approach; the horizontal layout is first determined with average values for velocity gradient and water depth; then only the floor slope and exact water depths are determined to enable satisfactory flocculation for all design scenarios.