摘要
It is important to be able to measure stresses in tunnel linings to verify design assumptions and validate numerical models.For sprayed concrete-lined tunnels,continuous monitoring of stresses from the time of spraying onwards is desirable,and this can only be achieved using pressure cells installed on and in the sprayed concrete lining.Although there has been some success in using radial pressure cells between the ground and the lining,a method for obtaining reliable absolute values of stress from tangential pressure cells embedded in the sprayed concrete has not been available.This paper describes numerical and experimental studies of the behavior of pressure cells for monitoring stresses in a sprayed concrete lining and describes an original methodology to achieve reliable results.In particular,data from tangential pressure cells require careful interpretation,as they are sensitive to temperature,and this temperature sensitivity is found in parametric numerical analyses to vary as the stiffness of the concrete and its coefficient of thermal expansion evolve at early age.Tangential pressure cells are also sensitive to shrinkage strains in the concrete,and a methodology for removing this effect is described.Using the approach described in this paper,it is now possible to use pressure cells to measure absolute values of stresses in and on sprayed concrete tunnel linings from early age into the long-term.An example of radial and tangential pressure cells installed in the Heathrow Terminal 4 concourse tunnel is used to illustrate the methodology.
