Deformation behaviour of railway embankment ... - Liikennevirasto

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60 Figure 4.7:1 Effect of the wetting - drying cycles on the resilient behaviour of a crushed limestone (Thom 1988). A physical explanation for the above-mentioned results is probably provided by the suction mechanism working very efficiently in the most fine-grained fractions of the aggregates. When the material dries, the available water concentrates at the particle contacts. The finest grained material gathered close to the contact points of the coarse grained particles can then be assumed to work as some sort of bond between the large particles. However, if dry material is directly wetted to a certain relatively low moisture content the suction mechanism does not necessarily work in the above described way, especially if the amount of water is insufficient to thoroughly moisturise all particle surfaces. Wu et al. (1984) have presented an excellent example of a test series whose results illustrate clearly the effect of the degree of saturation on the stiffness of granular material under very low level of strains. Wu et al. performed resonant column tests for five different materials whose grading varied from silt to sand. The results show that in partly saturated conditions the values of the shear modulus can even double in comparison with dry and fully saturated conditions (Figure 4.7:2). They concluded that for the materials investigated in the research the optimum degree of saturation corresponding to the maximum value of the shear modulus varies from 5.0 to 17.0 % depending on the effective grain size d 10 .
61 Figure 4.7:2 Variation in the shear modulus as a function of the degree of saturation and confining pressure σ' 0 for a silt material (Glacier Way Silt) (Wu et al. 1984). Figure 4.7:3 shows the resilient modulus as function of the sum of the principal stresses for five different levels of saturation tested by Kolisoja (1996b). The single curve that differs most from the other curves is the one for dry material that shows significant lower stiffness than curves for material with water. It should be noted that during the tests Kolisoja found a certain degree of internal instability, which resulted in the finer materials not settling to the bottom of the sample during the test.
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A 5/2006 Deformation behaviour of r
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Finnish Rail Administration Publica
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4 Past investigations have shown cl
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6 Brecciaroli, Fabrizio - Kolisoja,
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8 kuvataan jakamalla jännitykset j
Page 12 and 13: 10 TABLE OF CONTENTS ABSTRACT .....
Page 14 and 15: 12 8.9 Trondheim NTNU/SINTEF’s re
Page 16 and 17: 14 combination of resilient strains
Page 18 and 19: 16 Modelling is an important necess
Page 20 and 21: 18 Figure 2.1:2 Two-dimensional sta
Page 22 and 23: 20 σ xx − σ 3 2 det τ yx σ yy
Page 24 and 25: 22 stresses. As it can be seen from
Page 26 and 27: 24 grains. The resistance to partic
Page 28 and 29: 26 The reason was argued to be that
Page 30 and 31: 28 term matric suction implies the
Page 32 and 33: 30 Figure 3.2.1:1 Idealisation of t
Page 34 and 35: 32 ε ε 2 ν = , (Eq. 3.2.2:4) whe
Page 36 and 37: 34 where sij = σ −σ , (Eq. 3.2.
Page 38 and 39: 36 addition, when both the complexi
Page 40 and 41: 38 supplement continuum mechanics m
Page 42 and 43: 40 Figure 4.2:1 A typical variation
Page 44 and 45: 42 Figure 4.2:3 Modulus of resilien
Page 46 and 47: 44 provided that the applied stress
Page 48 and 49: 46 material (Uzan 1985). Dilation i
Page 50 and 51: 48 Figure 4.5:1 Resilient modulus o
Page 52 and 53: 50 The grain size distribution of g
Page 54 and 55: 52 The grain sizes that determine t
Page 56 and 57: 54 4.6.3 Fines content A simple cha
Page 58 and 59: 56 grained than for fine-grained ag
Page 60 and 61: 58 and the shape of the particles a
Page 64 and 65: 62 Figure 4.7:3 Modulus of resilien
Page 66 and 67: 64 Figure 4.7:6 Dry -density as a f
Page 68 and 69: 66 Figure 4.7:7 Resilient response
Page 70 and 71: 68 The form index can be measured u
Page 72 and 73: 70 Hovinmoen are gravel materials.
Page 74 and 75: 72 5 MODELLING OF RESILIENT DEFORMA
Page 76 and 77: 74 5.2.2 Resilient modulus as a fun
Page 78 and 79: 76 M r k2 k3 ⎛ θ ⎞ ⎛ q ⎞ =
Page 80 and 81: 78 the model showed good representa
Page 82 and 83: 80 discussed. However it can be exp
Page 84 and 85: 82 et al. (2003) calculated the res
Page 86 and 87: 84 p u = unit pressure (1 kPa), δp
Page 88 and 89: 86 Figure 5.2.5:2 Vertical resilien
Page 90 and 91: 88 2 1 ⎛ ⎞ = A q ε ν p ⎜1
Page 92 and 93: 90 Figure 5.3:2 An example of the c
Page 94 and 95: 92 by incorporating a coefficient o
Page 96 and 97: 94 6 FACTORS AFFECTING PERMANENT DE
Page 98 and 99: 96 cycles. He drew the general conc
Page 100 and 101: 98 accumulated strain, ε p , is co
Page 102 and 103: 100 Figure 6.3:1 Effect of loading
Page 104 and 105: 102 load” is not equal to the fai
Page 106 and 107: 104 Chan (1990) noticed, in his stu
Page 108 and 109: 106 Youd (1972) studied the behavio
Page 110 and 111: 108 Figure 6.5:2 Comparison of plas
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110 ample fine-grained fractions th
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112 of a dolomitic limestone with a
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114 Fuller curve (Equation 4.6.2:3)
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116 Figure 6.6:7 Elastic and plasti
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118 Figure 6.7:1 Dependence of the
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120 0,7 0,6 Elastic limit Failure s
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122 Figure 6.8.1:1 Influence of fin
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124 explain why the differences in
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126 was then argued that the variat
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128 7 MODELLING OF PERMANENT DEFORM
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130 Figure 7.2:1 Mohr-Coulomb repre
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132 where K p (N) = bulk modulus wi
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134 1993)) have reported that at le
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136 ε 1,p = accumulated permanent
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138 Barksdale (1972) conducted repe
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140 Figure 7.6:2 Relationship betwe
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142 also be employed for pavement d
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144 repeated loads, although adapta
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146 series of specimens (or in a mu
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148 Figure 7.7:5 S-N design models
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150 In conclusion, both Huurman (19
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152 aim to simulate as closely as p
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154 by the American Association of
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156 Confining pressure is applied t
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158 particles. During the test, the
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160 method takes the average value
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162 Figure 8.7.2:2 Schematic illust
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164 through each platen is provided
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166 measured for the 600 mm central
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168 displayed on the monitor in gra
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170 unbound granular materials. The
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172 Figure 8.8.2:2 Permanent axial
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174 performance-related (functional
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176 the six supports of the vertica
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178 under the same isotropic stress
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180 9 CONCLUSIONS 9.1 Resilient def
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182 − Permanent deformation resis
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184 Balay J., Gomes Correia A., Jou
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186 Cheung, L.W. (1994). Laboratory
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188 El abd, A., Hornych, P., Breyss
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190 Hoff, I., Nordal, S., and Norda
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192 Kolisoja, P. (1996b) Large Scal
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194 Mitry, F.G. (1964). Determinati
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196 Plaistow, N.C. (1994). Non-Line
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198 Tam, W.A. and Brown, S.F. (1988
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200 Wellner, F. (1996). Influence o
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Liite RHK:n julkaisuun A 5/2006 1 L
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Liite RHK:n julkaisuun A 5/2006 3 2
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Liite RHK:n julkaisuun A 5/2006 5 R
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RATAHALLINTOKESKUKSEN JULKAISUJA A-
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