文档介绍：: .
nel was excavated，the surrounding wall rock
materials often froze, the frost heaving caused damage to the liner layers and seeping
water froze into ice diamonds，which seriously interfered with the communication and
transportation. Similar problems of the freezing damage in the tunnels also appeared
in other countries like Russia, Norway and Japan .Hence it is urgent to predict the
freeze-thaw conditions in the surrounding rock materials and provide a basis for the
design，construction and maintenance of new tunnels in cold regions.
Many tunnels，constructed in cold regions or their neighbouring areas，pass
through the part beneath the permafrost base .After a tunnel is excavated，the original
thermodynamical conditions in the surroundings are and thaw destroyed and replaced
mainly by the air connections without the heat radiation, the conditions determined
principally by the temperature and velocity of air flow in the tunnel ，the coefficients
of convective heat transfer on the tunnel wall ，and the geothermal heat. In order to
analyze and predict the freeze and thaw conditions of the surrounding wall rock of a
tunnel，presuming the axial variations of air flow temperature and the coefficients of
convective heat transfer, Lunardini discussed the freeze and thaw conditions by the
approximate formulae obtained by Sham-sundar in study of freezing outside a circular
tube with axial variations of coolant temperature .We simulated the temperature
conditions on the surface of a tunnel wall varying similarly to the periodic changes of
the outside air temperature .In fact ，the temperatures of the air and the surrounding
wall rock material affect each other so we cannot find the temperature variations of
the air flow in advance; furthermore，it is difficult to quantify the coefficient of
convective heat exchange at the surface of the tunn