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Soil Compaction Models be specific to that particular soil type. The same holds true for water content as the method simply can be repeated at any given moisture content and a water content specific in-situ VCL will be derived. This is a great simplification taking the work of Wheeler and Siva- kumar (1995), Toll and Ong (2003), Blatz and Graham (2003) and many others into account trying to link critical state soil mechanics parameters to soil moisture content. It was possible to account for water content not with soil stresses but as an influence on critical state soil mechanics i.e. soil physical parameters as found by Hettiarachi and O’Callaghan (1980), Hettiarachi (1987) and Kirby (1989). The robustness of the entire approach against the concentration factor introduced by Fröh- lich (1934) was surprising, but agrees with the findings of Etienne and Steinmann (2002) who are able to predict soil stresses independent of soil type with one concentration factor. Interestingly their concentration factor is 2 and the one most commonly used in this study is 5. However, for the work here, 5 is most appropriate. With respect to the physics of granular media, the framework of critical state soil mechanics theory embedded in COMPSOIL is regarded as an approach which is sensitive enough to describe soil density changes accurately by means of a physical concept (critical state soil mechanics theory, Schofield and Wroth, 1960), while at the same time it is stable against variations at the grain level. Much work has been conducted to describe factors influencing the physics of granular media at the grain level, yet it is virtually impossible to account for all of them in one model. The orientation of particles changes mechanical behavior according to Oda et al. (1997), particle size determines the strength of particle according to Ning et al. (1997), Delie and Bouvard (1997) found that spherical inclusions are easier to compact than angular inclusions. All these effects are averaged and thus do not affect the predicted soil displacement utilizing the in-situ VCL. At the onset of the in-situ approach it was mentioned that the error originating from disre- garding the elastic recovery of the soil when deteriming the in-situ VCLs would be ignored as the error is small. The entire section proved this assumption to be correct due to its high accuracy. The validation in the field even confirmed the validity of the whole approach on a different soil type. Now there is a method available which has been validated on the two of the most opposing soil types found in arable agriculture – a sandy loam and a clay soil. Ph.D. Thesis Dirk Ansorge (2007) 120
Soil Compaction Models The approach satisfies the requirements in the introduction of the Chapter. COMPSOIL embedded in SOILFLEX using the in-situ VCL approach enables researchers, machine designers, manufacturers, farm advisers, and farmers to evaluate the impact of their ma- chinery on soil density at the respective design selection and use stages. In future work consideration should be given to the behavior of tyre contact patches at different inflation pressures. When they deviate from the recommended inflation pressure either way, contact pressure predictions may be improved leading to a closer agreement of soil displacement prediction to measured data. The next section carries the in-situ VCL approach to tracks. Afterwards the whole in-situ VCL is repeated on a small scale plate sinkage experiment and finally compared to triaxi- ally derived VCLs. 6.4 Compaction Prediction using in-situ VCL for Rubber Tracks Figure 84 shows the VCLs for only tyres, only tracks, and including both. The resulting R 2 decreases from 0.87 to 0.63 if tracks are added to tyres. A VCL only including the tracks and the roller shows a greater R 2 of 0.82. The slope and intercept of the VCLs indicate that the tracks show a different soil compaction behavior compared to tyres. The contact pressure of tracks results in a smaller relative density than for the corresponding tyres. Rel. Density 1,95 y = -0,1876Ln(x) + 2,4409 R 2 y = -0,5337Ln(x) + 3,6157 R = 0,6321 2 y = -0,2432Ln(x) + 2,6726 R = 0,8216 2 1,9 1,85 = 0,8698 1,8 VCL from Tires 1,75 1,7 VCL from Tracks 1,65 y = -0,1876Ln(x) + 2,4409 1,6 R 1,55 VCL from Tires and Tracks 10 100 2 y = -0,5337Ln(x) + 3,6157 R = 0,6321 2 y = -0,2432Ln(x) + 2,6726 R = 0,8216 2 1,9 1,85 = 0,8698 1,8 VCL from Tires 1,75 1,7 VCL from Tracks 1,65 1,6 1,55 VCL from Tires and Tracks 10 100 Mean Normal Pressure (kPa) Figure 84: VCL gained from contact pressure and density increase measured from soil displacement including tracks The slope for the VCL without the tracks is steeper compared to the one including both tyres and tracks characterising the relative density change less prone to changes in mean Ph.D. Thesis Dirk Ansorge (2007) 121
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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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Page 85 and 86: Field Study With Full Size Combine
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Page 111 and 112: Soil Compaction Models Wroth (1968)
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Page 123 and 124: Soil Compaction Models ture content
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Page 131 and 132: Soil Compaction Models and 13.7 % b
Page 133 and 134: Soil Compaction Models Rel. Density
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Page 141 and 142: Soil Compaction Models This result
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Page 149 and 150: Soil Compaction Models The response
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Page 155 and 156: Ancillary Experiments 7 ANCILLARY E
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Page 169 and 170: Ancillary Experiments 7.3.2 Influen
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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
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Ancillary Experiments Terzaghi (194
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Ancillary Experiments contact area.
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Ancillary Experiments soil forward
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Conclusions � The longitudinal so
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Bibliography 10 BIBLIOGRAPHY Aboaba
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Bibliography Defossez, P., Richard,
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Bibliography Gregory, A.S.; Whalley
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Bibliography Lamande, M., Schjonnin
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Bibliography Seig, D., 1985. Soil C
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Appendix 11 APPENDIX Ph.D. Thesis D
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Appendix Figure 32: VCL sample at t
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Appendix comparison at the deepest
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Appendix Estimated Pressure (kPa) 2
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Appendix 11.1.1.2.1 SOCOMO One of t
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Appendix by Seig (1985) who showed
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Appendix Soil water content 15 % an
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Appendix Adapting critical state so
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Appendix density is obtained by add
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Appendix Table 5: Values of constan
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Appendix choice of a concentration
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Appendix 11.1.3.1 Dense/Hard and Lo
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Appendix 11.1.3.2 Stratified Soil C
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Appendix To summarize the ability t
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Appendix In the following the predi
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Appendix concentration factor of 4,
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Appendix 11.1.5.1 Confining Pressur
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Appendix Figure 24. The VCL created
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Appendix Rel. Density 2 1,9 1,8 1,7
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Appendix relation of � 1 to � 2
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Appendix Rel. Density 2 1,9 1,8 1,7
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Appendix Rel. Density 1,7 1,68 1,66
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Appendix Depth (mm) 0,0 100,0 200,0
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Appendix Figure 42: Plate in cookin
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Appendix � z � � �� k c p
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Appendix Table 8: n and k depending
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Appendix to the plate sinkage equat
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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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