Deformation behaviour of railway embankment ... - Liikennevirasto

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126 was then argued that the variation in plastic strains for different aggregate types at the same density is related to the surface characteristics of the aggregate. The crushed stone particles are rougher and more angular and therefore exhibit a higher angle of shearing resistance due to a better particle interlock. Consequently, angular materials undergo smaller plastic deformations compared to the materials, such as gravel, with rounded particles. The type of aggregate is also said to play an important role in the material behaviour. Barksadale (1972, 1991) concluded in his studies that the accumulation of permanent axial strain is strongly dependent on the aggregate type. 6.9.3 Particle Surface Roughness Many investigations have addressed the effect of macro and micro roughness of the particles on the deformation behaviour (Cheung 1994, Kolisoja 1997, Thom and Brown 1989). The ability of the material to resist permanent deformations has been found to correlate better with the macro level surface roughness, i.e. the visible roughness of the individual particles based on the number of protrusions in the surface (Thom and Brown 1989, Brown and Selig 1991). 6.9.4 Electro-chemical properties Among the factors depending on the electro-chemical properties, in turn, the interactions between aggregate particles and the pore water located in the pore spaces are of great significance. The finer the particles the material is composed of, the greater is the significance. Electro-chemical properties of aggregate are assumed to have an especially wide effect on the moisture content sensitivity of the material. Thus, a material that adsorbs plenty of water may retain relatively high degree of saturation in even fairly coarse-grained aggregate if water has been available even temporarily. Therefore, that kind of material is liable to the development of excess pore water pressure in rapid loading conditions, such as traffic loading. Excess pore water pressure causes stiffness to decrease, which in turn lays the basis for the development of permanent deformations. A method for recognising this type of problem-aggregates is to measure the dielectricity of the material. This method has been applied, for example, in Finland and in the USA (Saarenketo and Scullion 1996). 6.10 Temperature Temperature changes above 0 °C apparently do not affect much the deformation behaviour of unbound coarse-grained aggregates. However, if the pore water located between the soil particles freezes, the stiffness of the material increases considerably. This has been experimentally proven even with very low moisture content both with laboratory and in-situ measurements (Huhtala and Pihlajamäki 1986). At the particle level, the reason for the strengthening caused by freezing are the very strong bonds between the soil particles produced by ice. The bonds efficiently prevent the movement of the particles. Because water in partly saturated materials is
127 concentrated at the contact points between the particles, relatively low moisture content is sufficient to markedly increase the stiffness. Due to the viscose properties of ice, the strengthening effect is apparently stronger the shorter the loading time and the lower the material temperature. On the regions of seasonal frost, the annual temperature changes have many unfavourable effects on the mechanical behaviour of the unbound coarse-grained materials (see Section 6.6). However, it should be noted that the effects are not caused by the temperature or temperature changes as such but changes in the state of the material as well as environmental circumstances produced by the freezing and frost action. If granular materials are fully saturated when they freeze, they can at least in principle loosen due to the freezing expansion of water. As the freeze melts in the spring, permanent deformations may be developed in the loosened layer as the material is recompacted by the traffic loading (Kolisoja 1997). If uneven frost heave occurs, large local shear strains that loosen the materials can result. Moreover, when the heave recovers unevenly during the thawing period, shear strains are also produced.
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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
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10 TABLE OF CONTENTS ABSTRACT .....
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12 8.9 Trondheim NTNU/SINTEF’s re
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14 combination of resilient strains
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16 Modelling is an important necess
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18 Figure 2.1:2 Two-dimensional sta
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20 σ xx − σ 3 2 det τ yx σ yy
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22 stresses. As it can be seen from
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24 grains. The resistance to partic
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26 The reason was argued to be that
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28 term matric suction implies the
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30 Figure 3.2.1:1 Idealisation of t
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32 ε ε 2 ν = , (Eq. 3.2.2:4) whe
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34 where sij = σ −σ , (Eq. 3.2.
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36 addition, when both the complexi
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38 supplement continuum mechanics m
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40 Figure 4.2:1 A typical variation
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42 Figure 4.2:3 Modulus of resilien
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44 provided that the applied stress
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46 material (Uzan 1985). Dilation i
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48 Figure 4.5:1 Resilient modulus o
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50 The grain size distribution of g
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52 The grain sizes that determine t
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54 4.6.3 Fines content A simple cha
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56 grained than for fine-grained ag
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58 and the shape of the particles a
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60 Figure 4.7:1 Effect of the wetti
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62 Figure 4.7:3 Modulus of resilien
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64 Figure 4.7:6 Dry -density as a f
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66 Figure 4.7:7 Resilient response
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68 The form index can be measured u
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70 Hovinmoen are gravel materials.
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72 5 MODELLING OF RESILIENT DEFORMA
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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
Page 112 and 113: 110 ample fine-grained fractions th
Page 114 and 115: 112 of a dolomitic limestone with a
Page 116 and 117: 114 Fuller curve (Equation 4.6.2:3)
Page 118 and 119: 116 Figure 6.6:7 Elastic and plasti
Page 120 and 121: 118 Figure 6.7:1 Dependence of the
Page 122 and 123: 120 0,7 0,6 Elastic limit Failure s
Page 124 and 125: 122 Figure 6.8.1:1 Influence of fin
Page 126 and 127: 124 explain why the differences in
Page 130 and 131: 128 7 MODELLING OF PERMANENT DEFORM
Page 132 and 133: 130 Figure 7.2:1 Mohr-Coulomb repre
Page 134 and 135: 132 where K p (N) = bulk modulus wi
Page 136 and 137: 134 1993)) have reported that at le
Page 138 and 139: 136 ε 1,p = accumulated permanent
Page 140 and 141: 138 Barksdale (1972) conducted repe
Page 142 and 143: 140 Figure 7.6:2 Relationship betwe
Page 144 and 145: 142 also be employed for pavement d
Page 146 and 147: 144 repeated loads, although adapta
Page 148 and 149: 146 series of specimens (or in a mu
Page 150 and 151: 148 Figure 7.7:5 S-N design models
Page 152 and 153: 150 In conclusion, both Huurman (19
Page 154 and 155: 152 aim to simulate as closely as p
Page 156 and 157: 154 by the American Association of
Page 158 and 159: 156 Confining pressure is applied t
Page 160 and 161: 158 particles. During the test, the
Page 162 and 163: 160 method takes the average value
Page 164 and 165: 162 Figure 8.7.2:2 Schematic illust
Page 166 and 167: 164 through each platen is provided
Page 168 and 169: 166 measured for the 600 mm central
Page 170 and 171: 168 displayed on the monitor in gra
Page 172 and 173: 170 unbound granular materials. The
Page 174 and 175: 172 Figure 8.8.2:2 Permanent axial
Page 176 and 177: 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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RATAHALLINTOKESKUKSEN JULKAISUJA A-
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