Rehabilitation of Urft Dam - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 797

per part of the dam exhibits a higher permeability coeffi cient of , which is
as already mentioned probably due to cyclic temperature changes and the corresponding
strains.

Below the left abutment, the permeability coeffi cients of the unweathered rock mass
parallel to the schistosity Sch and the joints of J1 resulted in and

, respectively. For the weathered rock mass, were

derived (Fig. 24.32).
In the remaining areas a permeability coeffi cient of parallel to
the schistosity Sch and the joints of J1 resulted for the unweathered rock mass.
The corresponding values for the weathered rock mass are and

, respectively (Fig. 24.32).
Accordingly, permeability tensors [K Sch ] and [K J1 ] of both discontinuity sets could be
evaluated and then, assuming impermeable intact rock, superimposed to describe the
permeability of both the unweathered and the weathered rock mass in these areas (Sec-
tion 6.4.2).
The parameters describing the deformability of the masonry and the rock mass listed in
Fig. 24.19 could be verifi ed by means of the back analyses. This indicates that the mod-
uli resulting from the LFJ tests are obviously in agreement with the large-scale deform-
ability of both the masonry and the rock mass. Furthermore, it could be confi rmed that
the shear parameters of the discontinuities were selected on the safe side.
In Fig. 24.25 the equipotentials derived from monitoring results are opposed to the
analysis results. A good agreement is achieved. Over a relatively short distance at the
upstream side of the foundation rock, a large reduction of hydraulic heads occurs as
would be the case if a grout curtain had been carried out in this area. This is a result of
the anisotropic permeability of the foundation rock.
The comparison of measured and calculated quantities of seepage water also shows
good concurrences (Figs. 24.26 and 24.27). The considerable differences between the
left abutment and the remaining areas can be attributed to the inhomogeneity of the
permeability of the foundation rock (Fig. 24.32).
In Figs. 24.29 and 24.30, the measured horizontal displacements due to a rise of the
storage level of 20 m are opposed to the results of two analyses carried out using the
mesh represented in Fig. 24.31 (realistic mesh) and using a mesh in which the dam and
the rock foundation were modeled in a more idealized way (idealized mesh). With both
analyses, a reasonable agreement with the monitoring results could be achieved.

24.8 Stability Proof

The load cases self-weight, impounding, temperature changes and earthquake were in-
vestigated for the stability proof. For permanent and temporary design situations ac-
cording to the requirements of DIN 19700-11 (2004), no vertical tensile stresses at the
upstream side of the dam were calculated.