Cranfield University

More documents

Recommendations

Info

Ancillary Experiments mm which was significantly different from zero. This compared to a mean position of 2.05 mm for the wheel which was not significantly different from zero with an LSD equal to 2.18 mm. Looking at the assigned tilt variables B, F, and I for both treatments, tilts B and I were negative and tilt F was significantly different from both indicating a positive, i.e. a forward soil movement. In further support of the previous arguments it is interesting to note that the longitudinal movement which ceases at approximately 150 mm is equivalent to the point where the magnitude of penetrometer resistance drops back to that of the rear tyres (Figure 98) and even below front tyres (Figure 27). Hence it was shown that in this very situation overall the track caused a significant backward soil movement at the surface whereas the wheel tended to cause a forward soil movement which was not significantly different from zero. As available slip data could not be accurately assigned over the distance the units travelled across the sand columns, it could be argued that the track had positive slip and the tyre negative slip thus causing these differences. However, the sand columns enclose three replications of lug-void cycles over a distance of 0.5 m and the data in Figure 99 and Figure 100 did not indicate a change in behaviour. Therefore the slip conditions could be regarded as constant with respect to longitudinal soil movement over the distance traveled and as both units are driven, it must be positive slip. Moreover penetrometer resistance randomly taken over the length of the soil bin always showed a higher surface strength for the track. These findings may change un- der the application of greater thrusts/slips. According to Wong (2001) soil movement below a tyre is accompanied by a flow pattern including two opposing flow directions; except for two extreme conditions: At 100 % slip, soil will only flow backward. For a locked wheel, only a soil wedge will be formed push- ing the soil forward whereby the size of the wedge depends on sinkage and the correspond- ing rake angle of the tyre. Any slip condition between these two extremes will include both forward and backward flow of soil. The higher the slip, the larger the backward movement will become. Following the soil trajectories given by Wong (2001) for a towed wheel, one at 37 % slip, and one at 63 % slip on a clay soil, at a slip range of about 10 – 15 % total longitudinal soil movement below a tyre could be zero due to the equilibrium of backward and forward soil flow. This was observed in this condition for the tyre. For the track on the Ph.D. Thesis Dirk Ansorge (2007) 144
Ancillary Experiments contrary, the bow wave and therefore forward soil movement was smaller due to the smaller rake angle and reduced sinkage. However, the backward flow pattern was more pronounced due to the constant slip conditions leading to an overall backward soil movement. Figure 101 shows backward soil movement at the very beginning of a passage of a track/tyre and agreed with the results above. When a track started, soil was moved back- wards as shown by the left hand figure which shows a clear shear failure boundary compared to the edge of the footprint from the track. In contrast, after the start of the tyre, no shear displacement could be seen, see right hand figure, although the soil lug disturbance pattern indicate high slipage at the start. Shear Failure Track Unit Starting No Shear Failure Wheel Unit Starting Figure 101: Soil disturbance after the track (left) and tyre (right)at the onset of movement Therefore the following conclusions can be drawn: � The peak in penetrometer resistance is not caused by the increased bearing capacity created by the pass of the front sprocket whereby afterwards merely the surface compacts as the load can be carried by the deeper soil because it is spread. This pronounced vertical compaction should be detectable in soil displacement curves. � The peak in penetrometer resistance for the track is caused by the application of a constrained shear force for a long period of time (average slope in Figure 97 for tracks larger than for tyres, thus there is no additional vertical compaction close to the surface). Ph.D. Thesis Dirk Ansorge (2007) 145
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:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Field Study With Full Size Combine
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
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 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: Ancillary Experiments In order to c
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?