DISPLACEMENT MONITORING IN CABRIL DAM USING GNSS


The HSCT data analyses from the two plumblines top coordinometer bases (Figure 7 and Figure 8) point to an approximate symmetric structural behaviour, whether one considers the HP, the temperature or the time effects. Considering these analyses time span, they also show that the most relevant time effect occurs towards upstream, which should be associated with the swelling reactions. Figure 9 and Figure 10 present the triangulation HSCT data analyses, and although these geodetic marks are located in a different position (over the dam centre axis, near the crest) it is also verifiable, even considering a smaller time span, that the same effects are the most prominent ones with a similar evolution over time. Contrarily, in the GNSS separation of effects (Figure 11) it is not possible to clearly discern a time effects component. Nevertheless, the limited time span (almost three years of monitoring) is not enough to draw any conclusions about the evolution of this effect. Figure 12 displays the separation of effects results for a HSCT model applied to the


triangulation data considering the GNSS operation period. In this equivalent model, where once more only the HP and temperature effects are separated, there are a lot less observations from the triangulation method than those provided from the GNSS for the same analyzed period. It is relevant to note the similarity between the HSCT solutions for both the triangulation and GNSS data (Figure 11), which once more is indicative of the reliability of the GNSS method.


Figure 12. Separation of effects results for the radial displacements measured by triangulation at the geodetic mark positioned in block KL at elevation 295m


Vol XXXI Issue 3


DAM ENGINEERING


163


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