The MIIS Eprints Archive: No conditions. Results ordered -Date Deposited. 2021-08-05T15:43:16ZEPrintshttp://miis.maths.ox.ac.uk/images/sitelogo.gifhttp://miis.maths.ox.ac.uk/miis/2006-04-04Z2015-05-29T19:46:21Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/57This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/572006-04-04ZMaturity effects in concrete damsModel equations for determining the coupled heat, moisture and maturity changes within a concrete block are introduced and briefly examined. Preliminary results are obtained for the heat exchange between concrete slabs in contact driven by maturity differences.ND Fowkesfowkes@maths.uwa.edu.auH Mambili Mamboundoumambili@cam.wits.ac.zaOD Makindemakindeo@unorth.ac.zaY Ballimballim@cicil.wits.ac.zaA Patinianthony@civil.wits.ac.za2006-04-04Z2015-05-29T19:46:23Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/58This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/582006-04-04ZFracturing rock with ultra high pressure waterModelling issues are considered for the process of cracking rock in mines using ultra high pressure water. The elevated pressures are caused by the ignition of a propellant and may be as large as 1000MPa. We first consider time, length and pressure scales and then derive a model for the propagation of a two-dimensional crack. A number of aspects of this model are considered and similarity solutions and behaviour near the crack tip are investigated. Consideration is given to a simplified model where the elastic component of the interaction between the rock and the fluid is handled using an elementary closure law: in this case much progress may be made and closed-form solutions may be determined. Conditions are also identified where a model based on “impulsive” lubrication theory is appropriate. However, this leads to a very challenging problem. Finally, some other ways of extending the model to include (for example) fluid leak-off into the rock are discussed.A.D. Fittadf@maths.soton.ac.ukN.D. Fowkesfowkes@maths.uwa.edu.auD.P. Masondpmason@cam.wits.ac.zaT.G. Myersmyers@maths.uct.ac.zaE.A. Mossemoss@mech.wits.ac.zaJ. Cheng2006-04-04Z2015-05-29T19:46:24Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/59This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/592006-04-04ZOptimal order quantities with volume discounts before and after price increaseAn inventory problem in which annual demand is normally distributed with known means and standard deviations is considered. A purchase price increase is imminent before the next order is placed. Volume discounts are also given in accordance to the size of the order. A model to compute an optimal order quantity and an optimal delivery point is presented. This model can also account for any price change that may occur from time to time.M.M. Alimali@cam.wits.ac.zaL.C. Masingalondiwe@cam.wits.ac.zaT. Jekottomasz.jekot@supergroup.com2006-04-04Z2015-05-29T19:46:26Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/60This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/602006-04-04ZFault slip in a mining contextRecent articles on the broad range of computational and analytic techniques currently used to investigate excavation collapse are reported. Advances in physical models are also described. Simple models for determining fault slip due to underground and surface excavations and structures are investigated.N.D. Fowkesfowkes@maths.uwa.edu.auD.P. Masondpmason@cam.wits.ac.zaJ.A.L. Napierjnapier@cam.wits.ac.za2006-04-04Z2015-05-29T19:46:28Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/61This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/612006-04-04ZScheduling of material through a steel plantThis paper addresses the optimal scheduling of material in a steel plant. The genetic algorithm is adapted to handle various constraints in the processing mills.M.M. Alimali@cam.wits.ac.zaP. Kaeloplaelo@cam.wits.ac.zaJ. Ackermanackerman.johan@columbus.co.za2006-04-04Z2015-05-29T19:46:30Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/62This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/622006-04-04ZPiped water cooling of concrete damsPiped water is used to remove hydration heat from concrete dams during construction. By examining simple models we obtain an estimate for the temperature rise along the pipe network and within the concrete. To leading order, for practically useful networks, the temperature distribution is quasi-steady, so that exact analytic solutions are obtained. The temperature in the water increases linearly with distance along the pipe and varies logarithmically with radial distance from the pipe in the concrete. Using these results we obtained estimates for the optimal spacing of pipes and pipe length. Some preliminary work on optimal network design has been done. This is work in progress.J. Charpinjcharpin@maths.uct.ac.zaT. Myersmyera@maths.uct.ac.zaA.D. Fittadf@maths.soton.ac.ukN. Fowkesfowkes@maths.uwa.edu.auY. Ballimballim@civil.wits.ac.zaA.P. Patinianthony@civil.wits.ac.za2006-04-04Z2015-05-29T19:46:32Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/63This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/632006-04-04ZDiscrimination and identification of unexploded ordinances (UXO) using airborne magnetic gradientsThe problem of discriminating the magnetic dipoles of objects on the surface of the earth, possible unexploded ordinances (UXO), from the effect of the earth’s magnetic field in airborne magnetic field gradient data was proposed. A model of simultaneous equations was developed which hoped to discriminate between the effect of the earth’s magnetic field and the possible UXO by solving for multiple dipoles using multiple data points. The simplifying assumption, that the location of each dipole is known, proved to produce unfavorable results when the flight path has a varying altitude making the model impractical. Current work suggests that a more practical solution to the problem can be achieved with subspace tracking.M.C. Jeoffreysmjeoffreys@cam.wits.ac.za2006-04-04Z2015-05-29T19:46:34Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/64This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/642006-04-04ZTransportation of water-based slurry in an open furrow, launder or streamThe transport of large boulders in a furrow from a mining area to a nearby pond was considered. The furrow is filled with a mixture of water and soil particles flowing down to the pond at a very high velocity. Due to operating constraints, the slope of the furrow is reduced progressively. A formula is derived, relating the slope of the furrow and the composition of the fluid to the maximum size and shape of the transported boulders. The characteristics of the boulders carried all
the way down to the pond may then be determined.J.P.F. Charpinjcharpin@maths.uct.ac.zaT.G. Myersmyers@maths.uct.ac.zaM. Lombemlombe@maths.uct.ac.zaP. de Hillpierredh@lynxgeo.com2006-04-04Z2015-05-29T19:46:35Zhttp://miis.maths.ox.ac.uk/miis/id/eprint/65This item is in the repository with the URL: http://miis.maths.ox.ac.uk/miis/id/eprint/652006-04-04ZModelling surface heat exchanges from a concrete block to the environmentThe presented problem was to determine an appropriate heat transfer boundary condition at the surface of a concrete slab exposed to the environment. The condition obtained involves solar radiation and convective heat transfer, other terms were shown to be small compared to these. It is shown that this boundary condition leads to a temperature variation that has qualitative agreement with experiments carried out by the Cement and Concrete Institute.J.P.D. Charpinjcharpin@maths.uct.ac.zaT.G. Myersmyers@maths.uct.ac.zaA.D. Fittadf@maths.soton.ac.ukY. Ballimballim@civil.wits.ac.zaA. Patinianthony@civil.wits.ac.za