1,143 research outputs found
Modelling the equalizing process of rockfill dumps with a plough: Subsea cut and transport processes
No full textA way to equalize granular rockfill dumps at a sea or river bed is the use of a plough. A plough can be modeled as a set of straight blades in sequence. Several cutting models for dry and saturated sand are present in the literature. In cutting coarse material, the increase in pore water pressures caused by dilatancy of the grain structure play a minor role. This results in a different shape of the layer cut than for traditional cutting methods in fine soils. The layer cut has a limited surface slope resulting in grains rolling down under the angle of repose ?. Failure of the grain structure in coarse material depends mainly on the gravitational, shear and inertial forces between grains. This master thesis gives an analytical model for cutting rockfill larger than medium coarse sand with straight cutting blades (Chapter 4.2). A description is given of the important processes involved in equalizing with a plough and the different stages of filling. The analytical model is realized by use of models made by S.Miedema for cutting saturated sand and models for cutting dry sand by Hettiaratchi, and Reece (1966). The analytical model is verified by performing a physical scale model. The scale model is used to attempt to simulate the process in a discrete element computer model EDEM.Coastal Engineering and Dregdging EngineeringHydraulic EngineeringCivil Engineering and Geoscience
The International Linear Collider beam dumps
No full textThe ILC beam dumps are a key part of the accelerator design. At Snowmass 2005, the current status of the beam dump designs were reviewed, and the options for the overall dump layout considered. This paper describes the available dump options for the baseline and the alternatives and considers issues for the dumps that require resolution
The vegetation of mining dumps in SW-Sardinia
No full textThe vegetation of mining dumps of SW-Sardinia includes several endemic or rare species, that have been confined to such artificial habitats by a millennial mining activity. The extreme edaphic specialisation of these species reflects with unusual fidelity the heterogeneity of substrata, therefore creating a system of plant communities that largely contributes to the environmental diversity of this part of the island. The phytosociological study presented in this paper recognized eight associations, distinguished by the cluster analysis in two main groups, the first including hemicrypto-chamaephytic vegetation, the second including nanophanerophytic garigues.
Six associations are belonging to the first group, five of which newly described: Helichryso tyrrhenici-Dianthetum sardoi ass. nov., occurring on gross-grained, hard-sloping dumps deriving from the geologic unit of Gonnesa; Coincyo recurvatae-Helichrysetum tyrrhenici ass. nov., colonizing dumps made of metamorphitic flakes and finer particles; Resedo luteolae-Limonietum merxmuelleri ass. nov., colonizing small-grained mining dumps with high concentrations in sulphides and heavy metals; Ptilostemono casabonae-Iberidetum integerrimae ass. nov., replacing the previous one on older and more consolidated dumps, where the concentration of phytotoxic elements was reduced by the meteoric agents; Epipactidetum tremolsii ass. nov., colonizing muddy deposits originating from ferrous clay; Euphorbio cupanii-Santolinetum insularis Angiolini & Bacchetta 2003, occurring on very old, stabilized dumps. All these associations can be ascribed to the class Scrophulario-Helichrysetea Brullo, Scelsi & Spampinato, 1998. Within this class, a new Sardo-Corsican alliance, Ptilostemono casabonae-Euphorbion cupanii is here proposed, differentiated by a pool of rare or endemic species. In addition to the above- mentioned associations, it is proposed, as well, to include into the new alliance the Polygono scoparii-Helichrysetum tyrrhenici Biondi, Vagge, Fogu & Mossa 1996 corr., that was described for the gravelly riverbeds of Central-Southern Sardinia.
As concerns the second group, two new association have been recognized: Dorycnio suffruticosi-Genistetum corsicae ass. nov., found on abandoned, well consolidated mining dumps, with an upper layer altered by pedogenetic processes; Polygalo sardoae-Linetum muelleri ass. nov., occurring in the vicinities of the mines on steep rocky slopes made of Paleozoic metalliferous limestones. Both of them can be ascribed to the alliance Teucrion mari Gamisans & Muracciole 1985, grouping the Sardo-Corsican aspects of Cisto-Lavanduletea Br.-Bl. in Br.-Bl., Molinier & Wagner 1940
Monitoring the growth or decline of vegetation on mine dumps
No full textThe author has identified the following signficant results. It was established that particular mine dumps throughout the entire test area can be detected and identified. It was also established that patterns of vegetative growth on the mine dumps can be recognized from a simple visual analysis of photographic images. Because vegetation tends to occur in patches on many mine dumps, it is unsatisfactory to classify complete dumps into categories of percentage vegetative cover. A more desirable approach is to classify the patches of vegetation themselves. The coarse resolution of conventional densitometers restricts the accuracy of this procedure, and consequently a direct analysis of ERTS CCT's is preferred. A set of computer programs was written to perform the data reading and manipulating functions required for basic CCT analysis
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High power electron beam dumps at CEBAF
No full textThe CEBAF accelerator produces a very small emittance CW electron beam of up to 200 {mu}A average current. The resulting beam power, up to 1 MW at 5 GeV, and the very high beam power density, pose challenging problems for beam dump design. Two styles of high power dumps have been developed. The first, rated for 100+ kW, is used for beam tune-up and accelerator commissioning. The beam power is entirely contained in metal in this dump, minimizing the problems associated with radioactive water handling. Full power 1 MW dumps are used with the experimental halls. In these dumps, one-third of the beam power is directly absorbed in water. Both dump designs require the beam to be rastered when the smallest beam sizes are used. Design details for each of these dumps will be presented
The charged beam dumps for the International Linear Collider
No full textThe baseline configuration of the International Linear Collider requires 2 beam dumps per interaction region, each rated to 18MW of beam power, together with additional beam dumps for tuning purposes and machine protection. The baseline design uses high pressure moving water dumps, first developed for the SLC and used in the TESLA design, although a gas based dump is also being considered. In this paper we discuss the progress made by the international community on both physics and engineering studies for the beam dumps
Liquefaction flowslides in Rocky Mountain coal mine waste dumps
No full text Over the past 25 years there have been a large number of long runout flowslides from Rocky Mountain coal mine waste dumps. The waste dumps are constructed as end-dumped fills with an angle of repose of 38°. Dump heights range between 100 and 400 m. The dumps are normally founded on mountain slopes that are covered with a thin veneer of granular colluvial and dense stony till materials. Conventional stability analyses carried out for these dumps using friction angles equal to the angle of repose for the waste rock and typical values ranging from 30 to 32° for the foundation materials indicate that many should be stable. The flowslides occur rapidly and display surprisingly long runouts of up to 2 km in some cases. Detailed studies of three of these events indicate that static collapse of saturated or nearly saturated sandy gravel layers within the dumps may be responsible for the initial failure and the generation of high pore pressures which result in high runout mobility.Key words: mine waste dumps, flowslide, static liquefaction, collapse mechanics. </jats:p
The charged beam dumps for the international linear collider
No full textThe baseline configuration of the International Linear Collider requires 2 beam dumps per interaction region, each rated to 18MW of beam power, together with additional beam dumps for tuning purposes and machine protection. The baseline design uses high pressure moving water dumps, first developed for the SLC and used in the TESLA design, although a gas based dump is also being considered. In this paper we discuss the progress made by the international community on both physics and engineering studies for the beam dumps.The baseline configuration of the International Linear Collider requires 2 beam dumps per interaction region, each rated to 18MW of beam power, together with additional beam dumps for tuning purposes and machine protection. The baseline design uses high pressure moving water dumps, first developed for the SLC and used in the TESLA design, although a gas based dump is also being considered. In this paper we discuss the progress made by the international community on both physics and engineering studies for the beam dumps
Digging in Boston\u27s accounting dumps
No full textNew England accounting historians are, of course, lucky. We sit on a whole mess of accounting dumps-state, city, town, local historical societies, museums, and private collections-not to speak of the large college collections. Much of it isn\u27t even indexed. The author gives several brief examples taken from a History of Accounting in Massachusetts which the Massachusetts Society of CPAs will sponsor for publication late in 1976
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