Cranfield University

More documents

Recommendations

Info

Soil Compaction Models cles varies even more. The organic matter content of real field soil adds to the difficulty of the system as it changes across a field. Not to mention the implication of water content on the behavior of soil, particularly cohesion and friction (Spoor and Godwin, 1979). In the following examples are chosen to show the effect of certain parameters on grain behavior and the complexity of the physics involved. Delie and Bouvard (1997) show that spherical inclusions are easier to compact than angu- lar inclusions. The effect of particle size and bond strength on the breakage of lactose ag- glomerates was shown by Ning et al. (1997). The effect of humidity in monodisperse glass beads on quasi - static behavior of granular media was shown by Fraysse (1997). Even the rotation of particles changes mechanical behavior of granular media, i.e. the failure and dilatancy of the media (Oda et al., (1997)). The characteristics of force distributions in granular media is shown by Radjai et al. (1997). The authors show that the contact network consists of two complementary sub- networks. Firstly a strong sub-network ranging through the whole media and carrying a force larger than the average force. Secondly, the weak sub-network carrying less than the average pressure. The weak sub-network is responsible for the dissipation of the stress whereby the forces decay in a power law function. In the strong sub-network forces have a decreasing exponential distribution. As the contacts in the strong sub-network are non- sliding contacts, these contacts carry the whole deviatoric stress. These results are based on a numerical simulation of a few thousands of particles in two dimensions and are expected to theoretically agree with the real soil conditions. 6.1.5 Discussion and Conclusions on Literature All the results from above show the important decision every scientist has to make when trying to model the behavior of granular material. It is a decision between the trial to come to a mere physical approach including all variations and differences between different media in one equation or a more general approach just accounting for the behavior of the material observed while being robust against inherent variations at the grain level. The approach taken by Etienne and Steinmann (2002) with their screwdriver test is a good example of a general approach accounting for large variations and being robust on the grain Ph.D. Thesis Dirk Ansorge (2007) 98
Soil Compaction Models level. Critical state soil analysis might be an appropriate way if it was possible to define critical state soil parameters either directly or at least indirectly with a test as easy as for example the screwdriver test. The advantage of the critical state soil analysis is the possi- bility to predict real changes in soil density, rather than “just” defining a threshold value above which soil compaction is expected to happen. 6.2 Comparison of Soil Compaction Models The variety of approaches used to model and estimate soil compaction rose the question how their performances compare and whether it is possible to tune variables such that the predictions agree with the measured data. This is only a digest of the entire comparison. The detailed version can be found in the Appendix 11.1.1. Most soil compaction models give different final outputs ranging from final DBD (O’Sullivan et al., 1998/COMPSOIL) through the prediction of an area of excess of soil stability (van den Akker, 2004/SOCOMO) to just a danger of soil compaction (Etienne and Steinmann, 2002/TASC). Their common basis is the calculated stress propagation in the soil leading to the final prediction of soil compaction. Thus comparing their performance in stress prediction to measured stresses in the soil bin can determine the accuracy of these models. There- fore this section contains a comparison of soil compaction models with respect to pressure prediction followed by a sensitivity analysis of COMPSOIL and SOCOMO. 6.2.1 Comparison of Pressure Prediction The vertical stress propagation predicted by SOCOMO, COMPSOIL, and TASC was compared to measured stresses from the soil bin during the project conducted by Ansorge (2005, a). COMPSOIL overpredicted the stresses compared to the measured stresses in all cases con- sidered; hence showed poor agreement between measured and predicted values. SOCOMO showed the closest prediction to the measured parameters at the soil surface, although the predicted soil stresses were too high except for one data point. At depth the TASC model gave good estimations and predicted soil pressures closer to the measured ones than SOCOMO. It is not clear why or how, yet interestingly stress decrease with depth seems too small for SOCOMO compared to reality. Ph.D. Thesis Dirk Ansorge (2007) 99
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:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64: 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 and 106: Alleviation of Soil Compaction diff
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: Soil Compaction Models however, the
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?