Seite - 1355 - in Book of Full Papers - Symposium Hydro Engineering

The largest rates of differential settlements were observed upstream in a distance of about 20 m to 25 m from the core. The section between this shear zone and the AC core showed only translatoric movements and no essential differential settlements were observed, which precludes additional saturation settlements. The results indicate that the shear zone was mobilized together with a sliding wedge deformation, closing the gap between the core and the adjacent upstream zone. After 12 years of reservoir operation the differential settlements between the upstream and downstream side of the core continuously increased up to approx. 36 cm and the maximum horizontal core displacements increased up to 13.5 cm. The Finstertal Dam is a rockfill dam with an inclined asphalt concrete core and an asymmetric dam body. The plinth for the core is situated on a rock cusp and the foundation of the dam shoulders is inclined on both sides. Figure 6 depicts a typical cross section and the zoning of the dam. The asphalt concrete core with a total height of 96 m is inclined with 1H:4V. The width of the core is 70 cm at the bottom and 50 cm at the top. The core is located at a distance from the dam axis which means it is outside the area with the highest level of strain [7]. A filter and transition zone was designed on the upstream side of the core. Downstream, the core is supported by a drainage zone as well as a stiff zone with moraine (zone 3b) and rockfill (zone 3 and 3a) material. The dam has a very extensive monitoring equipment with horizontal deformation gauges, vertical inclinometers, earth and pore water pressure cells, piezometers, extensometer, geodetic monitoring devices, perpendiculars, strong motion instruments, seepage collecting systems and three devices to measure a widening of the asphalt core on different elevations (5 m, 21 m and 40 m below storage level) [3]. (1) Core (2a) Upstream filter layer (2b,c) Drainage zone (3,3a) Rockfill (3b) Moraine (4) Protective lining (5) Moraine material Fig. 6: Cross-section of Finstertal Dam [3]. In 1981 the AC core thickness devices indicated a widening of the core during the impounding. Figure 7 shows the differential displacements between the upstream filter zone and the downstream core surface at two different elevations (40 m and 5 m below the maximum reservoir level). At the beginning of the first impounding, the dam first behaves as anticipated but when the reservoir level almost reached its maximum, the core was shifted downstream for 1355