Deformation behaviour of railway embankment ... - Liikennevirasto

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the model parameters, the repeated load triaxial apparatus at Nottingham University
was used.
To check the validity of the Dresden Model, Werkmeister et al. (2003) predicted the
surface deflection induced by plate bearing tests (Figure 5.2.5:1) using the FEprogram
FENLAP (Werkmeister et al. 2000). A comparison was carried out to assess
the accuracy of other material laws (e.g. Mayhew, Boyce and K-θ Model) by
comparing the results of calculated deflections from all the models against the
measured values. The best approximation is given by the Dresden-Model. The
maximum deflection under the load agrees with the measured value.
Figure 5.2.5:1 Comparison of measured and calculated resilient surface deflections
(Werkmeister et al. 2000).
In their study, Werkmeister et al. (2003) investigated the resilient deformation
behaviour of a Granodiorite with a maximum grain size of 32 mm at moisture contents
of 4, 5, 6, and 7 %. These seem to be small steps of moisture variation, but the
repeated load triaxial samples can be prepared with a very good accuracy (± 0.1%).
For repeated load triaxial test results with moisture content of 6 and 7 % it was not
possible to determine the material parameters. During repeated load triaxial tests at
7% (= optimum water content) water was draining out of the sample during the test,
which means there will be inhomogeneous conditions during testing. However, the
repeated load triaxial test results at moisture contents of 4 and 5% were taken into
account for modeling. Figure 5.2.5:2 clearly shows a high dependency of the resilient
deformation behaviour and, hence, the model parameters on the moisture content.
Increasing the water content resulted in a significant reduction in the stiffness, a result
also observed by others (Dawson et al. 1996, Barksdale and Itani 1989, Hicks and
Monismith 1971, Heydinger et al. 1996, Smith and Nair 1973, Raad et al. 1992,
Vuong 1992).