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Soil Compaction Models Depth (mm) 0 100 200 300 400 500 600 700 Displacement (mm) 0 20 40 60 80 100 120 Conc Factor 5 Conc Factor 4 Soil Bin VCL Depth (mm) Ph.D. Thesis Dirk Ansorge (2007) 100 200 300 400 500 600 700 Dispalcement (mm) 118 0 20 40 60 80 100 120 0 Conc Factor 5 Conc Factor 4 Soil Bin VCL Figure 83: Measured (points) and predicted (lines) soil displacement for the normal (2.5 bar) (left hand side) and high inflation pressure (3.5 bar) (right hand side) treatment on subsoiled sandy loam Overall it seems as if a � of 5 is appropriate to describe the pressure propagation for a sandy loam soil and a � of 4 to describe a clay soil. This can be explained by their different particle size distribution which overall gives the sandy loam a coarser network compared to the clay. 6.3.5 Discussion and Conclusions on in-situ VCL The approach from Etienne and Steinemann (2002) utilizing a screw driver test to describe soil strength at the surface triggered the idea of developing an easy accessible way to measure soil specific parameters. With the in-situ VCL approach presented here, such a possibility has been found. A new approach to gain the slope and intercept of a soil and water content specific in-situ VCL was derived from easily accessible tyre and soil data. The approach was successfully validated both in the soil bin laboratory and in the field. Necessary parameters are tyre load, inflation pressure, tyre width and diameter, rut depth, uniform soil density depth or working depth, and density of this soil. From this, it was possible to provide a relatively simple critical state soil mechanics soil compaction prediction model (COMPSOIL; O’Sullivan et al., 1998) with soil specific
Soil Compaction Models VCL parameters. The predicted soil displacement was highly accurate. The models of Gupta and Larson (1982) and Bailey and Johnson (1989) which require more input parameters can hardly be more accurate, however, the larger amount of input parameters these need make them unsuitable for such an in-situ approach. Chi et al. (1993) point out that the derivation of critical state soil mechanics parameters is the largest source of error when comparing soil compaction model predictions to real data. This source was reduced here due to the small number of necessary parameters and the large sample size. It was possible to use a soil mechanics model based on critical state soil mechanics theory (Schofield and Wroth, 1968) and gain its soil specific soil physical parameters from simple empirical measurements. This allowed qualitative but more importantly quantitative cor- rect predictions. The output from COMPSOIL is more distinct than for models such as TASC (Diserens and Spiess, 2004) or SOCOMO (van den Akker, 2004) which only predict soil stresses. Although the screw driver test for TASC is easier to perform than gaining an in-situ VCL, the additional information gained from COMPSOIL due to the accurate soil displacement and soil density increase prediction with depth make the additional effort worthwhile. Thus the in-situ VCL approach improves considerably the user-friendliness of COMPSOIL due to the ability to adapt easily to different soil types. Considering the different approaches taken to derive VCL parameters, the approach de- scribed here to gain an in-situ VCL has the advantage of easily accessible information and very large sample size compared to any laboratory based approach. The large sample size and in-field test avoids the major issue of variations with small sample testing for critical state soil mechanics models as pointed out by Chi et al. (1993) when investigating the ac- curacy of soil compaction models. The sample size is of concern for the approach taken by Gurtug and Sridgaran (2002) who obtained compaction characteristics from plastic limit tests for fine grained soils as these are usually carried out with only a few grams of soil. Compared to the improvement of Kirby et al. (1998) who derive all critical state soil mechanics parameters from one constant cell volume triaxial cell test, the field test only pro- vides the information for soil compaction, but without any laboratory equipement. No pedo - transfer functions as for example included by Keller et al. (2007) in SOILFLEX are necessary as the approach can be repeated on any soil type and the resulting in-situ VCL will Ph.D. Thesis Dirk Ansorge (2007) 119
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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 83 and 84: 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 115 and 116: Soil Compaction Models level. Criti
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Page 123 and 124: Soil Compaction Models ture content
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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: Soil Compaction Models Rel. Density
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
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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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Page 169 and 170: Ancillary Experiments 7.3.2 Influen
Page 171 and 172: Ancillary Experiments The results f
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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
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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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