evaluation of the ADDAMS computer program modules relevant
evaluation of the ADDAMS computer program modules relevant evaluation of the ADDAMS computer program modules relevant
dumped at Townsville and Mackay were supplied, in a variety of forms, by the respective Port Authorities. For all four of the disposal sites modelled, representative median particle sizes and percentages of sand, silt, and clay for the capital and maintenance dredge spoil and the seabed sediments were taken from or estimated using data from consultants’ reports and other published data (Morris, 2001a-d). The median particle sizes of the Weipa, Townsville, Hay Point, and Mackay maintenance dredging spoils were about 0.05 mm, 0.05 mm, 0.1 mm, and 0.0024 mm, respectively. Those of the Townsville, Hay Point, and Mackay capital dredging spoils were about 0.1 mm, 0.6 mm, and 0.14 mm, respectively. Because the cohesive sediment option is currently unavailable in MDFATE, the minimum median particle size permitted is 0.006 mm. This is smaller than the representative median particle sizes used for the Weipa, Townsville, and Hay Point analyses, but significantly larger than that of the Mackay maintenance dredging sediments. The results of the Mackay analyses suggested that the losses of spoil from that disposal site were consequently underestimated significantly. It was also necessary, because of the unavailability of the cohesive sediment option, to use higher than appropriate sand and silt fractions for the Weipa, Townsville, and Hay Point sediments. The effect of this on the results of the analyses is uncertain. However, increasing the sand fraction had little effect on the results of the Hay Point analyses. The specific gravity of the Hay Point and Mackay dredged sediments were obtained from consultants’ reports. In the absence of relevant data, the specific gravity of both the Weipa and Townsville dredged sediments was assumed to be 2.65. It was assumed that the Weipa, Townsville, and Hay Point seabed sediments were moveable in all cases. The relatively coarse Mackay seabed sediments were assumed to be fixed in most analyses, but the assumption that they were moveable gave similar overall results. The volume fraction of solids in the dredge hopper for the sediments for all four disposal sites modelled were estimated from data taken 28
from consultants’ reports or supplied by the respective Port Authorities, or estimated from correlations of void ratio with particle size (Morris and Williams, 2000). MDFATE tended to terminate prematurely in the Weipa and Townsville analyses when the volume fraction of solids in the dredge hopper was about 0.5 or less. This instability appeared to be linked to the unavailability of the cohesive soil option. It was circumvented by inputting a higher volume fraction of solids in the hopper, and reducing the in-hopper volume of spoil to compensate. This was considered to have had little effect on overall results of the analyses, but may have had a significant but unquantifiable effect on the (calculated) detailed topography of the disposal sites (Morris, 2001a,b). The bulk void ratios and in-hopper densities of the dredge spoils for the four sites modelled were estimated using data from consultants’ reports or supplied by the various Port Authorities. Varying the seabed void ratio of the spoil had comparatively large effects on the estimated changes in the bathymetry, but little effect on the estimated losses from the Townsville, Hay Point, and Mackay disposal sites In the absence of data for any of the sediments modelled, the critical shear stresses for avalanching were taken from a table of representative geotechnical sediment parameters incorporated in MDFATE. The overall results of the Townsville, Hay Point, and Mackay analyses were insensitive to moderate changes in the critical shear stress. It was assumed that the Weipa, Townsville, and Hay Point dredged sediments were stripped during descent, but that the Mackay sediments were not. Sensitivity analyses showed that the overall effects of these assumptions on the results of the Townsville, Hay Point, and Mackay analyses were small. Because the cohesive sediment option was unavailable, it was assumed that the sediments at all of the disposal sites modelled were non-cohesive. It was difficult to gauge the effect of this assumption on the analyses, but the results obtained suggest that overall, it was small. However, it may have had a significant effect on the detailed topography of the Weipa, Townsville, and Mackay disposal sites. 29
- Page 1 and 2: EVALUATION OF THE ADDAMS COMPUTER P
- Page 3 and 4: ACKNOWLEDGEMENTS The author wishes
- Page 5 and 6: For Townsville, the period from Jun
- Page 7 and 8: This had little effect on the resul
- Page 9 and 10: CONTENTS ABSTRACT .................
- Page 11: 4.12 Cleveland Bay tidal velocity d
- Page 14 and 15: 1. INTRODUCTION Research is being u
- Page 16 and 17: 2. THE ADDAMS SUITE 2.1 ADDAMS Prog
- Page 18 and 19: The ADDAMS modules of primary inter
- Page 20 and 21: There are numerous minor discrepanc
- Page 22 and 23: Figure 3.1 Location of Albatross Ba
- Page 24 and 25: 3.3 Hay Point Ocean Disposal Site T
- Page 26 and 27: The analyses of the Mackay ocean di
- Page 28 and 29: 4. INPUT DATA USED IN ANALYSES 4.1
- Page 30 and 31: Figure 4.2 Cleveland Bay ocean disp
- Page 32 and 33: Because the Waterways Experiment St
- Page 34 and 35: data were all less than a month, an
- Page 36 and 37: Fig. 4.6 Cleveland Bay north-south
- Page 38 and 39: Fig. 4.10 Cleveland Bay north-south
- Page 42 and 43: To model the avalanching of spoil o
- Page 44 and 45: 5. RESULTS OF ANALYSES The analyses
- Page 46 and 47: Fig. 5.2 Estimated change in Albatr
- Page 48 and 49: Fig. 5.4 Estimated change in Clevel
- Page 50 and 51: Fig. 5.6 Estimated change in Dalrym
- Page 52 and 53: Fig. 5.8 Estimated change in Mackay
- Page 54 and 55: Consequently, all but one of the an
- Page 56 and 57: APPENDIX 1: INPUT DATA REQUIREMENTS
- Page 58 and 59: 46 (g/cc) or the water salinity (pp
- Page 60 and 61: 48 • HDPRE.OUT comprises the pre-
- Page 62 and 63: 50 • To create a topography file
- Page 64 and 65: 52 • In both cases, the data requ
- Page 66 and 67: 54 diameter, its maximum elevation
- Page 68 and 69: APPENDIX 5: TIDAL HARMONIC CONSTITU
- Page 70 and 71: APPENDIX 6: INPUT DATA REQUIREMENTS
- Page 72 and 73: REFERENCES Borgman, L. E. and Schef
- Page 74 and 75: Morris, P. H. (2001d). Land & ocean
- Page 76 and 77: AUTHOR Dr Peter H. Morris Peter H.
- Page 78: PERTH Western Australia Node Coordi
from consultants’ reports or supplied by <strong>the</strong> respective Port<br />
Authorities, or estimated from correlations <strong>of</strong> void ratio with particle<br />
size (Morris and Williams, 2000).<br />
MDFATE tended to terminate prematurely in <strong>the</strong> Weipa and Townsville<br />
analyses when <strong>the</strong> volume fraction <strong>of</strong> solids in <strong>the</strong> dredge hopper was<br />
about 0.5 or less. This instability appeared to be linked to <strong>the</strong><br />
unavailability <strong>of</strong> <strong>the</strong> cohesive soil option. It was circumvented by<br />
inputting a higher volume fraction <strong>of</strong> solids in <strong>the</strong> hopper, and<br />
reducing <strong>the</strong> in-hopper volume <strong>of</strong> spoil to compensate. This was<br />
considered to have had little effect on overall results <strong>of</strong> <strong>the</strong> analyses,<br />
but may have had a significant but unquantifiable effect on <strong>the</strong><br />
(calculated) detailed topography <strong>of</strong> <strong>the</strong> disposal sites (Morris,<br />
2001a,b).<br />
The bulk void ratios and in-hopper densities <strong>of</strong> <strong>the</strong> dredge spoils for<br />
<strong>the</strong> four sites modelled were estimated using data from consultants’<br />
reports or supplied by <strong>the</strong> various Port Authorities. Varying <strong>the</strong> seabed<br />
void ratio <strong>of</strong> <strong>the</strong> spoil had comparatively large effects on <strong>the</strong> estimated<br />
changes in <strong>the</strong> bathymetry, but little effect on <strong>the</strong> estimated losses<br />
from <strong>the</strong> Townsville, Hay Point, and Mackay disposal sites<br />
In <strong>the</strong> absence <strong>of</strong> data for any <strong>of</strong> <strong>the</strong> sediments modelled, <strong>the</strong> critical<br />
shear stresses for avalanching were taken from a table <strong>of</strong> representative<br />
geotechnical sediment parameters incorporated in MDFATE. The overall<br />
results <strong>of</strong> <strong>the</strong> Townsville, Hay Point, and Mackay analyses were<br />
insensitive to moderate changes in <strong>the</strong> critical shear stress.<br />
It was assumed that <strong>the</strong> Weipa, Townsville, and Hay Point dredged<br />
sediments were stripped during descent, but that <strong>the</strong> Mackay<br />
sediments were not. Sensitivity analyses showed that <strong>the</strong> overall<br />
effects <strong>of</strong> <strong>the</strong>se assumptions on <strong>the</strong> results <strong>of</strong> <strong>the</strong> Townsville, Hay<br />
Point, and Mackay analyses were small.<br />
Because <strong>the</strong> cohesive sediment option was unavailable, it was<br />
assumed that <strong>the</strong> sediments at all <strong>of</strong> <strong>the</strong> disposal sites modelled were<br />
non-cohesive. It was difficult to gauge <strong>the</strong> effect <strong>of</strong> this assumption<br />
on <strong>the</strong> analyses, but <strong>the</strong> results obtained suggest that overall, it was<br />
small. However, it may have had a significant effect on <strong>the</strong> detailed<br />
topography <strong>of</strong> <strong>the</strong> Weipa, Townsville, and Mackay disposal sites.<br />
29
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