Cranfield University

More documents

Recommendations

Info

Soil Compaction Models 6 SOIL COMPACTION MODELS The availability of a reliable and user friendly soil compaction model would enable re- searchers, machinery designers, manufacturers, farm advisers and farmers to evaluate the impact of machinery on soil density at the respective design selection and use stages. An important requirement is the option to quickly assess soil parameters, ideally in the field, to account for different soil conditions and enable accurate predictions for different soil conditions. With such a tool it would be possible to determine the impact of vehicles on the increase in soil density ahead of the treatment. The chosen approach to assess soil parameters will be compared to traditional methods and verified in field. This chapter contains a literature review (Section 6.1), followed by a comparison of the pressure prediction of different soil compaction models and a sensitivity analysis (Section 6.2). After this a novel “in-situ” method to derive VCL parameters will be introduced and validated both in the soil bin and in the field (Section 6.3). In the following Section 6.4 the approach to derive VCL parameters in-situ is validated for tracks. Then, the method developed in the soil bin laboratory with tyres and track is utilized by small scale plate sinkage tests (Section 6.5), further validating the entire approach. In the following Section 6.6 the VCL parameters gained in the soil bin are compared to parameters determined using the classical triaxial cell test apparatus. In a subsequent step (Section 6.7) traditional plate sinkage predictions using the Bekker approach are compared to the measured rut depths. A mathematically drawn similarity found in literature between triaxial and plate sinkage tests will be subsequently discussed (Section 6.8). Finally (Section 6.9) the possible influence of peak vs. average contact pressures on the developed methodology will be considered and the chapter closes with an overall discussion and conclusion (Section 6.10). Appendix 1 contains additional detailed information concerning Sections 6.2 throughout to 6.8. Consequently, some of the figures given in the thesis sections will be repeated in the Appendix allowing the reader to easily follow the argumentation. 6.1 Literature Review The material in the literature review was selected to provide 1) an overview of model types, 2) an update on published material since the more recent reviews, 3) review the pos- Ph.D. Thesis Dirk Ansorge (2007) 90
Soil Compaction Models sibilities to obtain the mechanical parameters of the soil, and 4) derive a conclusion from literature. 6.1.1 Theoretical Background of Soil Compaction Models Preliminary soil compaction models can be divided into empirical models and soil mechanics models. The available soil mechanics models describe qualitatively the true impact of different treatments on soil compaction. However, quantitatively they fit best the data they were originally generated for. Reasons for this are the influence of organic matter, soil moisture content, soil type, and physical soil structure on both pressure transmission within the soil and on soil compactability. At a first glance these facts increase the attractiveness of empirical models. However, to generate an empirical model one has to use large amounts of input data in order to make it reliable and applicable in a range of situations. The second drawback is the fact that it con- tributes little to the fundamental understanding of soil physical behavior and soil physical laws. Soil mechanics models are usually a combination of soil mechanical principles and nu- merical techniques. Most models use either a finite element analysis or some approach which can be categorized into elastic theory and minor extensions of it. The advantage of taking the elastic theory approach is that it is a simple route for improvement and cannot only predict stress, but predict both stress and strain using Young’s Modulus and Poisson’s Ratio. A slightly different approach based on the elastic theory is the critical state soil mechanics which aims on describing volumetric soil response in regard to soil hydrostatic and shear stress. This was implemented by both Schofield and Wroth (1968) and Kurtay and Reece (1970). A detailed description of elastic soil modeling is given by Wulfsohn and Adams (2002). The authors describe the basics beginning with a purely elastic behavior following Hooke’s law (which was utilized by Soehne, 1953 and all approaches based on his work) and finishing with a detailed explanation of Critical State Soil Mechanics. On the contrary FEA models are difficult because they require many empirically determined input parameters. Critical state soil mechanics theory was initially developed for saturated clay soils, and later used to explain behavior of agricultural soils for example by Spoor and Godwin (1979). Towner (1983) describes the stress state in partially saturated soils with Ph.D. Thesis Dirk Ansorge (2007) 91
Page 1 and 2:
Cranfield University School of Appl
Page 3 and 4:
Abstract Ancillary experiments show
Page 5 and 6:
Table of Contents TABLE OF CONTENTS
Page 7 and 8:
Table of Contents 4.1.3 Analysis of
Page 9 and 10:
Table of Contents 11.1.1.1 Comparis
Page 11 and 12:
List of Figures and Tables Figure 3
Page 13 and 14:
List of Figures and Tables Figure 1
Page 15 and 16:
Nomenclature NOMENCLATURE Abbreviat
Page 17 and 18:
Introduction 1 INTRODUCTION 1.1 Bac
Page 19 and 20:
Introduction � Ansorge, D. and Go
Page 21 and 22:
Introduction 1.2 Aim To elucidate t
Page 23 and 24:
Introduction a) the soil compaction
Page 25 and 26:
Experimental Methods 2.1.1.1 Test F
Page 27 and 28:
Experimental Methods had been mount
Page 29 and 30:
Experimental Methods track; the loa
Page 31 and 32:
Experimental Methods 800/10.5/2.5 t
Page 33 and 34:
Experimental Methods term. In the m
Page 35 and 36:
Experimental Methods Soil Surface F
Page 37 and 38:
Experimental Methods Depth (cm) 0 1
Page 39 and 40:
Experimental Methods ence surface c
Page 41 and 42:
Experimental Methods chine derives
Page 43 and 44:
Experimental Methods depth. The dat
Page 45 and 46:
Experimental Methods with water and
Page 47 and 48:
Experimental Methods 2.4 Statistica
Page 49 and 50:
Laboratory Studies Into Undercarria
Page 51 and 52:
Page 53 and 54:
Page 55 and 56: Laboratory Studies Into Undercarria
Page 77 and 78: Field Study With Full Size Combine
Page 99 and 100: Alleviation of Soil Compaction Howe
Page 101 and 102: Alleviation of Soil Compaction not
Page 103 and 104: Alleviation of Soil Compaction in a
Page 105: Alleviation of Soil Compaction diff
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 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
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
Page 207 and 208:
Appendix Figure 32: VCL sample at t
Page 209 and 210:
Appendix comparison at the deepest
Page 211 and 212:
Appendix Estimated Pressure (kPa) 2
Page 213 and 214:
Appendix 11.1.1.2.1 SOCOMO One of t
Page 215 and 216:
Appendix by Seig (1985) who showed
Page 217 and 218:
Appendix Soil water content 15 % an
Page 219 and 220:
Appendix Adapting critical state so
Page 221 and 222:
Appendix density is obtained by add
Page 223 and 224:
Appendix Table 5: Values of constan
Page 225 and 226:
Appendix choice of a concentration
Page 227 and 228:
Appendix 11.1.3.1 Dense/Hard and Lo
Page 229 and 230:
Appendix 11.1.3.2 Stratified Soil C
Page 231 and 232:
Appendix To summarize the ability t
Page 233 and 234:
Appendix In the following the predi
Page 235 and 236:
Appendix concentration factor of 4,
Page 237 and 238:
Appendix 11.1.5.1 Confining Pressur
Page 239 and 240:
Appendix Figure 24. The VCL created
Page 241 and 242:
Appendix Rel. Density 2 1,9 1,8 1,7
Page 243 and 244:
Appendix relation of � 1 to � 2
Page 245 and 246:
Appendix Rel. Density 2 1,9 1,8 1,7
Page 247 and 248:
Appendix Rel. Density 1,7 1,68 1,66
Page 249 and 250:
Appendix Depth (mm) 0,0 100,0 200,0
Page 251 and 252:
Appendix Figure 42: Plate in cookin
Page 253 and 254:
Appendix � z � � �� k c p
Page 255 and 256:
Appendix Table 8: n and k depending
Page 257 and 258:
Appendix to the plate sinkage equat
Page 259 and 260:
Appendix with a slight deviation fr
Page 261:
Appendix Table 12: DBD values for a
show all

Cranfield University

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?