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Soil Compaction Models value. A further increase in preconsolidation stress did not produce a consecutive decrease in soil failure as expected. Full details can be found in Appendix 1/1.1.2.1. COMPSOIL The model SOILFLEX (Keller et al., 2006) provides the possibility to change critical soil mechanics parameters embedded in COMPSOIL directly while keeping both initial DBD and soil moisture content as given in the experiment. From theory an increasing magnitude of the slope of the virgin compression line means that increases in DBD result from smaller pressure changes. A decreased intercept means less pressure for the same DBD. With a reduction in the intercept soil compaction increased significantly. With a slope of ~ 0.15 the results came into the range measured in the soil bin by Ansorge (2005, a). The recompression lines were not changed because their influence can be ignored for single passes. Changing VCL parameters it was possible to improve predictions significantly. 6.2.3 Discussion and Conclusions on Comparison of Soil Compaction Models The comparison of measured and calculated pressure showed some deviation, yet the magnitude is too small to explain the differences in soil compaction seen especially with COMPSOIL. Changing critical state soil parameters to fit the data seems a promising way to adapt a soil mechanics models for a particular soil. Following the proposal for an in-situ access to VCL parameters in Section 6.1.5, this will be the aim of the following Section. 6.3 Derivation of VCL Parameters from Soil Bin and Validation/Evaluation The compression behaviour of soil is shown in Figure 68 as a function of soil volume depending on the exerted pressure. The soil indicates a semi-logarithmic relationship of volume with pressure. If the pressure is plotted on logarithmic scale and the volume is re- placed by the relative density of the soil, the virgin compression line (VCL) is derived. The VCL as defined by Schofield and Wroth (1968) is a unique function relating the relative density of a soil at a given moisture content to the natural logarithm of the spherical pressure it is subjected to. According to their definition spherical pressure is the arithmetical Ph.D. Thesis Dirk Ansorge (2007) 102
Soil Compaction Models average of major, intermediate, and minor principal stresses: � 1, � 2 , and � 3 , respectively. As mathematically this is also the definition of the mean normal pressure p, this thesis will use the term mean normal pressure after O’Sullivan et al. (1998). Therefore the virgin compression line basically describes soil density in dependence of exerted stress. Volume Figure 68: Compression behaviour of soil Pressure An approach to gain information about the VCL is to investigate the slope of the soil displacement curves from this work and the work by Ansorge (2005, a) in the soil bin laboratory. Soil density can be gained from initial density and the slope of the soil displacement curves which were assumed to be linear over the upper 0.5 m for each treatment as first assumed by Ansorge (2005, a) and in detailed reconsidered in Section 2.2.1.1. The contact pressure can be calculated below a tyre from the known area and known load, assuming uniform stress distribution over the contact area. The exerted stress for the VCL model is in some relation to this contact pressure. Knowing the initial soil stress exerted by the roller during soil bin preparation and knowing the resulting initial soil density gives the first point on the virgin compression line. Knowing the increase in density for different contact pressures the virgin compression line can be created and the recompression line could be gained from multi passes. If in a future step it was further possible to determine the virgin compression line just from tyre sinkage at two different inflation pressures, a very important characteristic of soil compaction could easily be determined in the field. Ph.D. Thesis Dirk Ansorge (2007) 103
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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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Page 67 and 68: Laboratory Studies Into Undercarria
Page 77 and 78: Field Study With Full Size Combine
Page 99 and 100: Alleviation of Soil Compaction Howe
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Page 103 and 104: Alleviation of Soil Compaction in a
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Page 107 and 108: Soil Compaction Models sibilities t
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Page 111 and 112: Soil Compaction Models Wroth (1968)
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Page 117: Soil Compaction Models Utilizing Ke
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
Page 127 and 128: Soil Compaction Models Predicted In
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 and 142: Soil Compaction Models This result
Page 143 and 144: Soil Compaction Models 6.6.1.3 Wate
Page 145 and 146: Soil Compaction Models σσ 1 (kPA)
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Page 149 and 150: Soil Compaction Models The response
Page 151 and 152: Soil Compaction Models On medium so
Page 153 and 154: Soil Compaction Models SOILFLEX tak
Page 155 and 156: Ancillary Experiments 7 ANCILLARY E
Page 157 and 158: Ancillary Experiments Average conta
Page 159 and 160: Ancillary Experiments In order to c
Page 161 and 162: Ancillary Experiments contrary, the
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Ancillary Experiments 7.3.2 Influen
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Ancillary Experiments The results f
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Ancillary Experiments Figure 117: S
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Ancillary Experiments Contact Press
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Ancillary Experiments Figure 123: F
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Ancillary Experiments Sinkage (mm)
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Ancillary Experiments model which o
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Ancillary Experiments 7.3.5 The Inf
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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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