ABSTRACT
This chapter focuses on obtaining the additional information, especially in soft ground, as well as the preliminary analysis techniques that may be employed. It describes simple analytical methods, which can be used to estimate the stresses in the tunnel lining or the required lining thickness for a given deformation of the ground. Primary stresses are the stresses in the ground prior to the construction of the void. One of the key parameters that influences the choice of tunnelling technique is the stability of the ground as the tunnel is constructed. Centrifuge modelling has been used to investigate many aspects of soft ground tunnelling including stability, ground movements and the effects of tunnelling on adjacent piles and structures. The tunnel support is idealised as an elastically supported circular ring. The ground in which the tunnel is constructed is idealised as a continuum, that is, there are no discontinuities in the material.
