http://bura.brunel.ac.uk/handle/2438/180 2013-05-24T12:32:43Z 2013-05-24T12:32:43Z Salih, Nihad Bahaaldeen http://bura.brunel.ac.uk/handle/2438/7363 2013-04-22T11:24:26Z 2013-01-01T00:00:00Z

Title: Stability of dams constructed on problematic substrates Authors: Salih, Nihad Bahaaldeen Abstract: Dissolution of soluble substrates such as gypsum presents a major hazard to dams in many parts of the world. This research simulates hypothesised conditions beneath the Mosul Dam, northwest Iraq, where collapse of a karstic system associated with continuous fresh water supply from its massive reservoir water is a recognised problem. The gypsum substrates at Mosul Dam vary in purity and thickness. Experimental work used gypsum rocks and gypseous soils. Gypsum rocks from northern Iraq and similar rocks from Bantycock gypsum mine, UK, were analysed for short-term mechanical response following immersion (5 to 50 weeks) and long-term loading during immersion (maximum 50 weeks). New experimental devices were developed from a conventional oedometer. Cylinder samples (NX, standard diamond drill core size = 54mm diameter, length/diameter ratio equal to 2.5) provided a proxy for massive gypsum strata, while thin samples (NX = 54mm in diameter, 20mm thickness) represented thin layers and lenses. Rectangular bar samples (240 x 40 x 20 mm and 140 x 40 x 20 mm) were tested for short-and long-term mechanical four-point bending behaviour. Samples were permanently submerged at a variety of water pressures, with the influence of groundwater recharge and flow on dissolution simulated by regular changes of water. Stress on each sample was progressively increased to a maximum of 2688 kPa. Small increases in strain were recorded by the end of each test but no failures occurred within 60 days of tests. However, notable failure due to water pressure and axial stress over long time periods of 166 and 238 days occurred. Visible physical changes were observed, notably a decrease in sample mass and volume. Similar change was recorded in ultrasonic velocities. These indicate that gypsum collapse risk beneath dams requires prolonged exposure to dissolution. Gypseous soils from Iraq and similar artificially-prepared soils were also tested. Gypseous soil samples (diameter = 50mm and length = 20mm) and box model strata results showed that gypseous soils are significantly weakened by dissolution over 15 weeks and 50 weeks respectively. Dams built on gypsum substrates are likely to experience ongoing weakening of their foundations, with a progressively increasing risk of failure. This is expected to be enhanced for dams with a large and deep reservoir that induces high ground water pressure. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

2013-01-01T00:00:00Z Paul, P http://bura.brunel.ac.uk/handle/2438/7215 2013-02-27T10:32:29Z 2013-01-01T00:00:00Z

Title: Comparing and contrasting traditional membrane bioreactor models with novel ones based on time series analysis Authors: Paul, P Abstract: The computer modelling and simulation of wastewater treatment plant and their specific technologies, such as membrane bioreactors (MBRs), are becoming increasingly useful to consultant engineers when designing, upgrading, retrofitting, operating and controlling these plant. This research uses traditional phenomenological mechanistic models based on MBR filtration and biochemical processes to measure the effectiveness of alternative and novel time series models based upon input–output system identification methods. Both model types are calibrated and validated using similar plant layouts and data sets derived for this purpose. Results prove that although both approaches have their advantages, they also have specific disadvantages as well. In conclusion, the MBR plant designer and/or operator who wishes to use good quality, calibrated models to gain a better understanding of their process, should carefully consider which model type is selected based upon on what their initial modelling objectives are. Each situation usually proves unique. Description: Copyright @ 2013 MDPI AG

2013-01-01T00:00:00Z Fan, M Dinwoodie, JM Bonfield, PW Breese, MC http://bura.brunel.ac.uk/handle/2438/4757 2012-01-13T12:10:55Z 1999-01-01T00:00:00Z

Title: Dimensional instability of cement bonded particleboard: Behaviour of wood chips from various stages of manufacture of CBPB Authors: Fan, M; Dinwoodie, JM; Bonfield, PW; Breese, MC Abstract: A technique for the dissection and measurement of wood chips used in cement bonded particleboard (CBPB) removed from the unpressed mat and the pressed board has been developed. The prepared chips were subjected to changing relative humidity (RH) conditions. The results illustrated the contribution of wood chips to the performance of CBPB. The trend in change of dissected chips was similar to that of CBPB but to a different degree under both a single and cyclic change in RH. However, the compression, contortion and chemical degradation of, and the inclusion of cement in, wood chips within CBPB resulted in an increase in mass change but decrease in dimensional change of dissected chips which were about 0.7, 3.0 and 1.3 times the change of raw wood chips respectively in mass, length and thickness over period tested. The combined effects of anisotropic characteristic, distribution and orientation of wood chips within CBPB brought about a significantly different ratio between length and thickness change of dissected chips to CBPB, having a ratio of about 2.5 for length and 15 for thickness. The nature of hysteresis loop for dissected chips was also very close to that of CBPB but dissimilar to that of raw wood chips. Chips from the various stages of the production process showed very different responses to RH due to the effect of the processing parameters (pressure, curing temperature and time) on the nature of wood chips. The chips coated without any curing treatment were the most resistant to changing RH while raw wood chips had the greatest change in mass and the chips dissected from final product had the greatest change in dimensions. With the exception of raw wood chips, all types of chips showed a consistent increase in mass and a slight decrease in dimension with increasing number of cycles. Description: The published version of this article can be viewed at the link below.

1999-01-01T00:00:00Z Fan, M Bonfield, PW Dinwoodie, JM Breese, MC http://bura.brunel.ac.uk/handle/2438/4756 2012-01-20T15:58:53Z 2000-01-01T00:00:00Z

Title: Dimensional instability of cement bonded particleboard: SEM and image analysis Authors: Fan, M; Bonfield, PW; Dinwoodie, JM; Breese, MC Abstract: Scanning electron microscope (SEM) and image analysis were applied to quantify the structure of commercial cement bonded particleboard (CBPB) to obtain a more fundamental understanding of the instability of CBPB and to provide a basis of information for modelling the stress–strain behaviour of CBPB. Surfaces through the thickness of the board and vertically within the board were analysed mainly with respect to the distribution, size, shape and percent area occupied by individual components (void, cement paste and wood chips). Results showed that the area occupied by wood chips 1) increased from the surface to the core layer (from 34 to 49%), 2) was 5% higher for vertical surfaces than for horizontal surfaces, 3) but was in total only about 40%; this is much lower than the volume fraction (about 75%) of raw materials used in the manufacture of CBPB. This confirms the mechanism/organisation of mat formation, showing the more significant effect of wood chips on thickness than on length changes with changing moisture content and indicating that the wood chips are compressed in CBPB. The wood chips nearly all lie flat in the horizontal planes throughout the board thickness and were randomly distributed on the horizontal plane. The mean angle was about 10.7° between wood chips and the horizontal surface and about 44.7° between wood chips and the longitudinal direction within a horizontal plane, verifying that the change in thickness should be much higher than that in length or width, and the change in length and width should be similar. The size and shape of the wood chips were very different among six horizontal layers and between the horizontal and the vertical layers. Description: The published version of this article can be viewed at the link below.

2000-01-01T00:00:00Z