Civil Engineering Reference
In-Depth Information
22.11 Conclusions
Experience gained during this project indicates that, despite comprehensive site inves-
tigation and testing prior to construction, certain aspects influencing the stability of
an underground opening may only be found out during construction. In this project,
these were the level of high horizontal in-situ stresses normal to the cavern axis and the
occurrence of steeply dipping discontinuities striking parallel to the cavern axis which
could not be verified and detected by means of investigations before construction. Only
continuous mapping and monitoring during construction and a contemporary inter-
pretation of monitoring results by means of back analyses have allowed these features
to be assessed with sufficient reliability. As a result, the required support for the cavern
walls turned out to be greater than expected but nevertheless quite economic in compar-
ison with other caverns of this size.
This demonstrates that the most reliable source of information is the excavation itself.
The results of mapping, monitoring and back analyses carried out during excavation
enable the design assumptions to be checked and provide a sound basis for design
amendments, if necessary, and a safe and economic construction.
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