Tunnelling and Underground Space Technology 17 (2002) 341–353
0886-7798/02/$ - see front matter ᮊ 2002 Elsevier Science Ltd. All rights reserved.
Thermal and mechanical behaviour of refrigerated cavernsin hard rock
R. Glamheden *, U. Lindblom
Department of Civil Engineering, Sycon Teknikkonsult AB, SE-205 09 Malmo, Sweden
Gecon AB, Viktor Rydbergsgatan 1A, SE-411 34 Goteborg, Sweden
Received 1 December 2001; received in revised form 15 April 2002; accepted 20 April 2002
One key issue in the design of unlined caverns for low temperature products is understanding the disturbance of the rock
fracture network. Increasing aperture and extension of fractures inevitably affect the rock mass stability, the heat loss from stored
products, and the risk of ice growth in cases when water invades the cavern. Consequently, it is essential that the designer of a
refrigerated cavern has appropriate knowledge of the coupled thermal and mechanical behaviour of the fractured rock mass.
Chalmers University of Technology in Gothenburg, Sweden has for several years, carried out research in the field of mechanical
and physical phenomena of rock masses subjected to low temperatures. The main investigation was performed in a pilot scale
cavern in hard rock, constructed as a vertical cylinder with a diameter of 7 m and a height of 15 m. The facility was equipped
with comprehensive instrumentation, including approximately 200 temperature gauges and 140 deformation gauges. In the test,
the temperature in the cavern was reduced in a stepwise manner to y40 8C, with comprehensive monitoring of relevant parameters
such as relative humidity, air and rock temperature, rock strain, rock fracture aperture, cavern convergence and rock mass
deformation. Prior to the field test, major efforts were made to predict the field results by analytical and numerical methods. The
essential results of the theoretical analyses and the actual measurements of thermal and mechanical behaviour of the cavern are
given in thispaper.
ᮊ 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Igneous rock; Rock cavern; Underground storage; Refrigeration; Thermal strain; Thermal deformation; Thermal properties
*Corresponding author. Tel.: q46-25-56-88; fax: q46-30-46-96.
E-mail address: email@example.com (R. Glamheden).
Cooling down of a rock material makesitsmineral
matrix shrink, and this phenomenon has some distinct
effectson the rock mechanical situation around a refrig-
erated storage cavern:
● changesin rock parameters
● relaxation of compressive rock stresses near the
● opening of existing fractures at total relaxation of the
development of new fractures
Unlike rock mechanical tunnel design in general, one
of the key issues in designing unlined caverns for low
temperature productsisan understanding of the distur-
bance in the rock fracture network in the surrounding
rock mass caused by the refrigeration. Increasing aper-
ture and extension of the fractures, which will follow,
inevitably affect the rock mass stability, as does the
development of new fractures. The problem is a coupled
Expansion and development of fractures also increases
the risk for thermal erosion effects and ice growth from
water invading the cavern (Bromset al., 2001).To
prevent such effects, large provisions of energy to the
cavern could be required.
Particularly when storing liquefied gas products such
as LPG and LNG, an increase of the fracture porosity
around the cavern augmentsthe risk for boil-off and gas
escape through the fracture system. Such phenomenona
at an extended scale may make it difficult and costly to
maintain an appropriate storage temperature (Jacobsson,
1977; Lasseter and Witherspoon, 1974).
In order to understand the physics that influences the
fracture aperture, the rock mass must be considered as
an assembly of discrete blocks. The magnitude of any
individual fracture aperture isdependent on the defor-