Civil Engineering Reference
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On every second tendon the anchor loads were measured by means of a so-called “lift-
ing test”, in which the required force for lifting of the anchor head was determined. The
results of these lifting tests showed that the service load of the tendons in a large area
had been exceeded (green contour line in Fig. 25.19). The areas in which the measured
anchor forces exceeded the force that may lead to stress cracking corrosion and in which
the measured anchor forces exceeded the service load by more than 50% are surrounded
by the red and the blue contour lines in Fig. 25.19, respectively.
25.3
Back Analysis of Monitoring Results
Since the failure mechanism of the slope obviously could not be modeled by sliding
using limit equilibrium analyses, the monitoring results were back analyzed using the
FEM. For this purpose, a parametric study was carried out with the pseudo-three-di-
mensional computation section and FE-mesh represented in Fig. 25.20. In these anal-
yses the tendons were simulated by truss elements (Section 10.3.2). In addition to the
alternating sequence of clay slate and sandstone, the encountered fault zone and anti-
cline were modeled by finite elements. With the parameters specified in Fig. 25.20 (right)
the best agreement between monitored and calculated displacements and anchor forces
was achieved.
Figure 25.20
Back analysis of monitoring results, FE-mesh, boundary conditions and parameters
Figure 25.21 shows the calculated displacements of the southern slope resulting from
the excavation of the cut down to the lower berm before the stabilizing fill was placed.
Accordingly, layers of clay slate and sandstone suffer a rotational movement towards
the cut, triggered by exceeding the shear strength along the steeply dipping bedding-par-
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