Technical Review of the Lined Rock Cavern Concept and Design ...

Room 3 bas a 0.5 mm thick lining of stainless steel.
The concrete lining is 0.3 m thick and conventionally
reinforced. The room has been subjected to a great
number of loads, 28 NfPa at most, including 91
cyclic loads, see Figure 4. In principle the design of
the room corresponds with that of Room 2.
3.4 Monitoring system
The radial expansion in the rooms and the deformations
in the rock and concrete are continuously
registered during pressure testing. Extra measuring
devices are installed in the rock in Room 3 for the
purpose of studying the movements in the nearby
weakness zone. Strains in the steel lining in Room 2
have also been measured continually. The radial rock
mass deformations are measured by multiple
extensometers, labelled "E" in Figure 5. Miniextenso
meters "M" are installed in the concrete to
measure tangential strains in the concrete. The
expansion of the whole system, i.e. the total radial
deformation, is measured by convergence lines, I'C",
inside the test rooms. The measuring installations are
somewhat different in the three rooms, due to
geological variations and different lining material
'.'
A-I?
All sensors are continuously monitored by dataloggers
during the test periods.
Figure 5. Measuring installations in the test rooms,
schematic horizontal section.
4 RESULTS
4.1 Rock mass behaviour
The deformations in the rock mass in all three rooms
have been recorded by a total of 64 sensors divided
between 24 extenso meters. Table 2 shows measured
deformations for 20 extenso meters at five different
pressure levels. The total defonnation for all
horizontal extenso meters is shown in Figure 6. The
largest deformation measured in Room 2 is 5.65 mm
at 52 l\I1Pa. At pressures higher than 40 l\I1Pa there
were distinct sound phenomena in the form of bangs
and popping noises in the rock mass. The sounds
were heard att irregular intervals and continued to
be audI"ble during depressurizing right down to low
pressure levels.