Steel-lined pressure shafts – appropriate design for external pressure

During inspection work, when the pipe is empty, a thin-walled
steel pipe is susceptible to shell buckling due to external pressure.
Comprehensive research activities, including tests, began
in the 1960s, and analytical and empirical formulae were developed
for design.
Some of these different analytical design concepts are presented
in the first part of the paper, and their results are compared
for the whole range of pipe slenderness in practice.
Afterwards, the results of extensive numerical calculations are
shown. These deal with different imperfections in practice and
are not considered in the current design solutions. In addition,
the effect of the radial flexibility of the surrounding rock mass
has been studied – an issue ignored up to now. All these
results
are compared with the design formulae in practice.
It is therefore possible to conclude the paper with an appraisal
of the individual solutions in practice and sum up appropriate
design rules for external pressure.