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Appendix Appendix 1 Further Details on Soil Compaction Models Appendix 1 contains additional detailed information concerning Sections 6.2 throughout to 6.8. Consequently, some of the figures given in the thesis sections will be repeated in the Appendix allowing the reader to easily follow the argumentation 11.1.1 Comparison of Soil Compaction Models The variety of approaches used to model and indicate soil compaction rose the question how it would be possible to compare them directly, ideally comparing the same parameters. Most soil compaction models give different final outputs ranging from final real DBD (O’Sullivan, 1998) over the prediction of an area of excess of soil stability (van den Akker, 2004/SOCOMO) to just a danger of soil compaction (Etienne and Steinmann, 2002/TASC). Their common basis is the calculated stress propagation in the soil leading to the final prediction of soil compaction. Thus comparing their performance in stress prediction to measured soil stresses in the soil bin can determine the accuracy of the stress prediction of the models. Therefore this section contains a comparison of soil compaction models with respect to pressure prediction and a sensitivity analysis of COMPSOIL and SOCOMO. 11.1.1.1 Comparison of Pressure Prediction The vertical stress propagation predicted by SOCOMO, COMPSOIL, and TASC will be compared in this section. During the project conducted by Ansorge (2005) in the soil bin soil stresses were also determined. The vehicle support mechanics were both the rubber track and the 800 mm section width tyre laden to different values and inflation pressures. The pressure in the soil below the treatments was measured using ceramic pressure transducers embedded on aluminum tubes as described in Ansorge (2005). The pressure was measured at depths of 250 mm, 400 mm, and 650 mm. As the ceramic pressure transducers were embedded into the soil parallel to the surface the pressure measured is the vertical normal stress component. All three models (TASC, SOCOMO and COMPSOIL) give vertical normal stress values at the measured depths. The model by O’Sullivan however, can not predict the stresses deeper than 475 mm. In consequence of this limit the O’Sullivan model was excluded from the Ph.D. Thesis Dirk Ansorge (2007) 191
Appendix comparison at the deepest reading. The second difficulty with the O’Sullivan model was that it could not account for tracks. Tracks were mimicked for this investigation with a conceptual load limitation to 10 t given by the spreadsheet. To get an average pressure the measured data was averaged over the time period it took to pass over the pressure transducer. Table 1 shows the measured and predicted vertical soil stress values for different implements and soil compaction models. Table 1: Measured and predicted vertical soil stress values for different implements Treatment and load and models Depth (mm) Measured vertical stress (bar) Predicted TASC soft/half firm(bar) Predicted O’Sullivan Ph.D. Thesis Dirk Ansorge (2007) (bar) Predicted SOCOMO (bar) Closest Model / Deviation pos/neg (not considering half firm of TASC) Track 12 t 250 0.80 1.10/0.97 0.95 0.85 SOCOMO (+6 %) Track 12 t 400 0.49 0.80/0.67 0.94 0.79 SOCOMO (+92 %) Track 12 t 650 0.38 0.49/0.43 - - - - - - 0.67 TASC (+26 %) Track 5 t 250 0.26 0.46/0.40 0.66 0.37 SOCOMO (+42 %) Track 5 t 400 0.10 0.33/0.28 0.58 0.36 TASC (+330 %) 800/10/2 250 1.18 1.86/1.73 1.70 1.34 SOCOMO (+14 %) 800/10/2 400 0.88 1.23/1.11 1.47 1.24 SOCOMO (+41 %) / TASC (+40 %) 800/10/2 650 0.50 0.64/0.62 - - - - - - 1.02 TASC (+28 %) 800/10/1 250 0.96 1.77/1.49 1.54 0.922 SOCOMO (-4 %) 800/10/1 400 0.53 1.20/1.07 1.35 0.90 SOCOMO (+70 %) 800/10/1 650 0.32 0.63/0.62 - - - - - - 0.81 TASC (+97 %) 800/10.5/2.5 250 1.6 1.98/1.77 1.85 1.42 O’Sullivan (- 11%) The resulting pattern of proximity between measured and calculated values is very interesting. The model COMPSOIL overpredicted the stresses compared to the measured stresses and it never showed the closest agreement between measured and predicted values. For the surface it seems as if SOCOMO shows the closest connection to the measured parameters. Apart from one case the predicted soil stresses were always too high. At depth the TASC model gave good estimations and predicted soil pressures closer to the measured ones than SOCOMO. It is not clear why or how, yet interestingly stress decrease with depth seems too small for SOCOMO compared to reality. For the pressure prediction in Table 1 a soft surface was assumed for the TASC model. The author had checked the appropriateness of this with a screw driver test (developed in that model to measure surface soil strength similar to a 192
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Cranfield University School of Appl
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Abstract Ancillary experiments show
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Table of Contents TABLE OF CONTENTS
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Table of Contents 4.1.3 Analysis of
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Table of Contents 11.1.1.1 Comparis
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List of Figures and Tables Figure 3
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List of Figures and Tables Figure 1
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Nomenclature NOMENCLATURE Abbreviat
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Introduction 1 INTRODUCTION 1.1 Bac
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Introduction � Ansorge, D. and Go
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Introduction 1.2 Aim To elucidate t
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Introduction a) the soil compaction
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Experimental Methods 2.1.1.1 Test F
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Experimental Methods had been mount
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Experimental Methods track; the loa
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Experimental Methods 800/10.5/2.5 t
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Experimental Methods term. In the m
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Experimental Methods Soil Surface F
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Experimental Methods Depth (cm) 0 1
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Experimental Methods ence surface c
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Experimental Methods chine derives
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Experimental Methods depth. The dat
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Experimental Methods with water and
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Experimental Methods 2.4 Statistica
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Laboratory Studies Into Undercarria
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Field Study With Full Size Combine
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Alleviation of Soil Compaction Howe
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Alleviation of Soil Compaction not
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Alleviation of Soil Compaction in a
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Alleviation of Soil Compaction diff
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Soil Compaction Models sibilities t
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Soil Compaction Models depends on t
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Soil Compaction Models Wroth (1968)
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Soil Compaction Models however, the
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Soil Compaction Models level. Criti
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Soil Compaction Models Utilizing Ke
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Soil Compaction Models average of m
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Soil Compaction Models Depth (mm) -
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Soil Compaction Models ture content
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Soil Compaction Models with four ot
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Soil Compaction Models Predicted In
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Soil Compaction Models Depth (mm) -
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Soil Compaction Models and 13.7 % b
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Soil Compaction Models Rel. Density
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Soil Compaction Models VCL paramete
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Soil Compaction Models The approach
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Soil Compaction Models surface stay
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Soil Compaction Models This result
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Soil Compaction Models 6.6.1.3 Wate
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Soil Compaction Models σσ 1 (kPA)
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Soil Compaction Models pressure to
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Soil Compaction Models The response
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Soil Compaction Models On medium so
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Soil Compaction Models SOILFLEX tak
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Ancillary Experiments 7 ANCILLARY E
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Page 175 and 176: Ancillary Experiments Contact Press
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Page 179 and 180: Ancillary Experiments Sinkage (mm)
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Page 185 and 186: Ancillary Experiments 7.3.7 Discuss
Page 187 and 188: Ancillary Experiments Terzaghi (194
Page 189 and 190: Ancillary Experiments contact area.
Page 191 and 192: Ancillary Experiments soil forward
Page 193 and 194: Conclusions � The longitudinal so
Page 195 and 196: Bibliography 10 BIBLIOGRAPHY Aboaba
Page 197 and 198: Bibliography Defossez, P., Richard,
Page 199 and 200: Bibliography Gregory, A.S.; Whalley
Page 201 and 202: Bibliography Lamande, M., Schjonnin
Page 203 and 204: Bibliography Seig, D., 1985. Soil C
Page 205 and 206: Appendix 11 APPENDIX Ph.D. Thesis D
Page 207: Appendix Figure 32: VCL sample at t
Page 211 and 212: Appendix Estimated Pressure (kPa) 2
Page 213 and 214: Appendix 11.1.1.2.1 SOCOMO One of t
Page 215 and 216: Appendix by Seig (1985) who showed
Page 217 and 218: Appendix Soil water content 15 % an
Page 219 and 220: Appendix Adapting critical state so
Page 221 and 222: Appendix density is obtained by add
Page 223 and 224: Appendix Table 5: Values of constan
Page 225 and 226: Appendix choice of a concentration
Page 227 and 228: Appendix 11.1.3.1 Dense/Hard and Lo
Page 229 and 230: Appendix 11.1.3.2 Stratified Soil C
Page 231 and 232: Appendix To summarize the ability t
Page 233 and 234: Appendix In the following the predi
Page 235 and 236: Appendix concentration factor of 4,
Page 237 and 238: Appendix 11.1.5.1 Confining Pressur
Page 239 and 240: Appendix Figure 24. The VCL created
Page 241 and 242: Appendix Rel. Density 2 1,9 1,8 1,7
Page 243 and 244: Appendix relation of � 1 to � 2
Page 245 and 246: Appendix Rel. Density 2 1,9 1,8 1,7
Page 247 and 248: Appendix Rel. Density 1,7 1,68 1,66
Page 249 and 250: Appendix Depth (mm) 0,0 100,0 200,0
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Appendix with a slight deviation fr
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Appendix Table 12: DBD values for a
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