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Soil Compaction Models “Full Pressure” approach is practically not sound as it sets intermediate and minor principal stresses equal to the major principal stress. As a result a soil is predicted too strong when its parameters are used as input variables in COMPSOIL. 6.6.1.2 Influence of Moisture and Initial Soil Density The influence of moisture content and initial soil density was investigated in fast loading tests. In the range of 8.2 – 12.5 % moisture content the samples appear independent of moisture content as they merge between 100 – 200 kPa depending on their initial densities ranging from 1.31 g/cm 3 to 1.54 g/cm 3 . No influence of initial density is expected, however, the independency of moisture content in this range was not expected. Probably the range of only 4 % was too small. Again, these curves are close to “Full Pressure” from the soil bin experiment as shown in Figure 89. Overall the repeatability of results was within +/- 15 % when applying confining pressure. The necessity to actually adjust a VCL for different sandy loam soils can be seen when comparing the VCLs of different authors in Figure 89. The VCL obtained from this experiment and which represents a typical VCL result applying confining pressure is intermediate between those from O’Sullivan et al. (1998) and Leeson and Campbell (1983). Relative Density 2 1,9 1,8 1,7 1,6 1,5 1,4 1,3 Common VCL O'Sullivan et al. (1999) in-situ VCL Full Pressure in-situ VCL 0.38 Pressure Leeson&Campbell (1983) 1 10 100 1000 Mean Normal Pressure (kPa) Figure 89: VCLs from O’Sullivan (1998), Leeson and Campbell (1983), and the one gained by confining pressure. Ph.D. Thesis Dirk Ansorge (2007) 126
Soil Compaction Models 6.6.1.3 Water and System Compressibility The previous relationships do not take the water compressibility and the elasticity of the triaxial system into account. Therefore the elastic response of the system including the water was evaluated by pressurizing the cell without a sample three times up to 350 kPa and relieving the pressure again to determine the effect on the apparent volume change which in turn would influence the relative density. Considering the compressibility of the system, which has been disregarded in the previous figures, shifts the VCL further away from the origin on the horizontal axis making the soil to appear stronger as shown in Figure 90. Rel. Density 2 1,9 1,8 1,7 1,6 1,5 1,4 1 10 100 1000 Mean normal Pressure Pressure (kPa) (kPa) System Compressibility not accounted System Compressibility accounted for Figure 90: VCL with and without compensation for water compressibility Water compressibility was not taken into account in the previous discussion as it is identi- cal for all curves and would only shift them in total and not have an influence on their rela- tions amongst each other. 6.6.2 Axial and Radial Pressure As there was poor agreement for the VCL from the soil bin gained by the tyre passes and the VCLs created with radial pressure in the triaxial test apparatus the idea arose to apply radial and axial pressure simultaneously replicating stress conditions during a tyre pass as implied by Eq. 6 in Section 6.3.2. Radial pressure was set to 25 kPa and axial load was applied replicating the instant loading time and magnitude of a tyre pass in the soil bin. Ph.D. Thesis Dirk Ansorge (2007) 127
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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 91 and 92: Field Study With Full Size Combine
Page 99 and 100: Alleviation of Soil Compaction Howe
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Page 107 and 108: Soil Compaction Models sibilities t
Page 109 and 110: Soil Compaction Models depends on t
Page 111 and 112: Soil Compaction Models Wroth (1968)
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Page 119 and 120: Soil Compaction Models average of m
Page 121 and 122: Soil Compaction Models Depth (mm) -
Page 123 and 124: Soil Compaction Models ture content
Page 125 and 126: Soil Compaction Models with four ot
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Page 129 and 130: Soil Compaction Models Depth (mm) -
Page 131 and 132: Soil Compaction Models and 13.7 % b
Page 133 and 134: Soil Compaction Models Rel. Density
Page 135 and 136: Soil Compaction Models VCL paramete
Page 137 and 138: Soil Compaction Models The approach
Page 139 and 140: Soil Compaction Models surface stay
Page 141: Soil Compaction Models This result
Page 145 and 146: Soil Compaction Models σσ 1 (kPA)
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Page 149 and 150: Soil Compaction Models The response
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Page 153 and 154: Soil Compaction Models SOILFLEX tak
Page 155 and 156: Ancillary Experiments 7 ANCILLARY E
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Page 159 and 160: Ancillary Experiments In order to c
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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 183 and 184: Ancillary Experiments 7.3.5 The Inf
Page 185 and 186: Ancillary Experiments 7.3.7 Discuss
Page 187 and 188: Ancillary Experiments Terzaghi (194
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Page 191 and 192: 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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