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Ancillary Experiments An argument supporting the hypothesis of a shear force effect was the similar vertical soil displacement caused by the rear/implement tyres to that of the rubber track (Ansorge and Godwin, 2007). However, the penetrometer resistance results for the smaller implement tyres did not show a peak close to the surface and as shown in Figure 98, merging of the data for the track and rear tyres occurred at a depth of less than 300 mm. Depth, mm 0 50 100 150 200 250 300 Displacement, mm 0 10 20 30 40 50 60 70 80 90 100 110 y = -6.31x + 362 y = -6.01x + 382 y = -8.73x + 587 y = -5.36x + 488 y = -5.97x + 602 y = -5.91x + 591 Figure 97: Displacement vs. Depth, top 300 mm with regression lines. □ track 10.5t; Dep th (mm) ■ track 12t; � 680/10.5/2.2; × 900/10.5/1.9; + 800/10.5/2.5; ♦ 800/10.5/1.25 0 100 200 300 400 500 600 700 800 Pem etrome ter Resistance (M pa) 0 0,5 1 1,5 2 2,5 3 Figure 98: Penetrometer resistances for rear tyres and track at 12 t. Δ control; • 600/4.5/1.4; + 500/85/4.5/1.4b; ■ track12t ; � LSD at 95% confidence level Ph.D. Thesis Dirk Ansorge (2007) 140
Ancillary Experiments Average contact pressure for the track was virtually identical to that of the 500-85/4.5/1.4 tyre at 83 kPa and 85 kPa, respectively (Ansorge and Godwin, 2007). For the 600/4.5/1.4 tyre a larger contact pressure of 110 kPa was measured. Nevertheless all three treatments caused similar soil displacement. Thus their increases in soil density agree well with their average contact pressures. As the true pressure distribution underneath a track was not uni- form, one could argue that the dense layer was caused by the pressure peaks underneath the track; this was not visible from the study of the vertical soil displacement. Hence, neither both the absolute contact pressure or its distribution could be the cause of the higher penetrometer resistance. The different slip behaviour of a tyre and a track could be responsible for this increase in soil strength indicated by the peak in penetrometer resistance. Calculating shear displacement resulted in twice the displacement underneath a track compared to that for a tyre ac- cording to Wong (2001). This seems rather strange as the track operated generally at a lower slip (5 %) compared to tyres (10 %) in this investigation (Ansorge, 2005, b). The shear displacement, however, is gained by the integration of slip velocity underneath the implement over the distance traveled. Hence the long contact area of the track (2.4 m) cou- pled with constant slip velocity led to a greater total shear displacement. The resulting constant shear strain application over the entire contact length additionally increased plastic shear displacement. Total length of the contact area for the tyre was about half (1.2 m) of that of the track, whereby the slip velocity depended on the position of the soil with respect to the tyre. The highest slip velocity occurs at the beginning of the contact patch when the tyre surface velocity is greater than that of the deformed section of the tyre under its centre line due to differences between the actual and the rolling radius (Wong, 2001). Thus shear strain decreases from the soil surface to the centre line. The longer the soil was subjected to a force, the larger became the plastic deformation due to the spring-damper behavior of the soil during compaction as shown by Aboaba (1969) who changed the contact time of a roller by altering forward velocities. The varying slip velocity of a tyre and consequently longitudinal force cause more of an impact loading which may recover elastically. The longitudinal soil displacement by a track and a tyre resulting from the different contact times under these given conditions will be discussed in the next Section. Ph.D. Thesis Dirk Ansorge (2007) 141
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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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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)
Page 113 and 114: Soil Compaction Models however, the
Page 115 and 116: Soil Compaction Models level. Criti
Page 117 and 118: Soil Compaction Models Utilizing Ke
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
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)
Page 147 and 148: Soil Compaction Models pressure to
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: Ancillary Experiments 7 ANCILLARY E
Page 159 and 160: Ancillary Experiments In order to c
Page 161 and 162: Ancillary Experiments contrary, the
Page 163 and 164: Ancillary Experiments Figure 102: S
Page 165 and 166: Ancillary Experiments track and the
Page 167 and 168: Ancillary Experiments even when hav
Page 169 and 170: Ancillary Experiments 7.3.2 Influen
Page 171 and 172: Ancillary Experiments The results f
Page 173 and 174: Ancillary Experiments Figure 117: S
Page 175 and 176: Ancillary Experiments Contact Press
Page 177 and 178: Ancillary Experiments Figure 123: F
Page 179 and 180: Ancillary Experiments Sinkage (mm)
Page 181 and 182: Ancillary Experiments model which o
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
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
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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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