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Soil Compaction Models entire depth was assumed as no sideways movement of the soil could be detected. The re- sulting in-situ VCLs are shown in Figure 87. Relative Density 2,5 2 1,5 1 0,5 0 y = -0,2455Ln(x) + 2,6383 R 2 R = 0,8323 2 = 0,8323 10 Mean Normal Pressure (kPa) 100 Rel. Density y = -0,3144Ln(x) + 2,9358 R 2 R = 0,9798 2 = 0,9798 Ph.D. Thesis Dirk Ansorge (2007) 2,5 2 1,5 1 0,5 0 124 10 100 Mean Normal Pressure (kPa) Figure 87: Virgin compression line for plate sinkage tests with different plate sizes (left) and different pressures on same plate (right) The function for the different plates (left hand side of Figure 87) indicates a slightly weaker soil as the one for the same plate with different loads on the right hand side. Feed- ing the slope and the intercept of these VCLs into COMPSOIL gave a close agreement to the measured data as shown in Figure 88. Depth (mm) 0,0 100,0 200,0 300,0 400,0 500,0 600,0 700,0 800,0 Displacement (mm) 0 20 40 60 80 100 120 Plate Sinkage Diff. Plates Real Data In-Situ VCL Plate Sinkage Same Plate Triaxial VCL Figure 88: Measured and differently predicted soil displacement for the 900/10.5/1.9 on uniform soil conditions The VCL parameters created with the plate sinkage tests predict the 900/10.5/1.9 tyre closer to its real data than the appropriate parameters from triaxial cell test data; whereby axial and radial load is applied at the same time as described later in Section 6.6.2. Still, the best estimation is gained with the in-situ method using tyres.
Soil Compaction Models This result justifies the approach taken with the estimation of the VCL parameters only from contact pressure and rut depth when knowing the DBD profile with depth of the soil. It furthermore describes an alternative approach on a smaller scale to derive VCL parameters with the same procedure in-situ. This may have the advantage that field conditions can be assessed empirically before machines are used. However, for most farmers it is easier to take machines into the field and measure the rut depths than to conduct these sinkage tests. If in future work it was possible to link these small scale plate sinkage experiments to drop cone results (Godwin et al., 1991) a neat approach for a farmer friendly method not using whole machines might be created. 6.6 Triaxial Cell Test Apparatus VCL Compared to in-situ VCL In this section the in-situ VCL will be compared to a VCL gained with triaxial test equip- ment. The entire methodology for the triaxial cell test apparatus can be found in Section 2.3.1. Initially confining pressure will be applied followed by an investigation of the sys- tem and water compressibility. Subsequently axial and radial pressure will be applied try- ing to mimic real soil loading conditions occurring during the passage of a wheel. At the end all the different prediction results of the varying VCLs will be compared. The full de- tails of the entire section are given in Appendix 11.1.5. 6.6.1 Confining Pressure Applied In the first sequence only confining pressure was applied as this is the commonly referred way in literature to obtain a VCL according to Leeson and Campbell (1983). In the second sequence an axial stress higher than confining pressure was applied. 6.6.1.1 Influence of Time of Loading Samples at one density and one moisture content (10%) were loaded to 100 kPa, unloaded and then reloaded up to 250 kPa. Loading times ranged from 30 – 360 min because the short loading time from the soil bin experiment could not be repeated due to the impossi- bility to change cell pressure instantaneously. The different loading times did not influence the VCLs significantly and agreed well with a VCL gained from the tyre passes in the soil bin if the mean normal pressure was set equal to � 1; (“Full Pressure” in Figure 89). This Ph.D. Thesis Dirk Ansorge (2007) 125
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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 89 and 90: 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
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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 137 and 138: Soil Compaction Models The approach
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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 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 185 and 186: Ancillary Experiments 7.3.7 Discuss
Page 187 and 188: Ancillary Experiments Terzaghi (194
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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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