ABSTRACT
This chapter discusses the techniques and highlights the applications and limitations of the different construction methods. With most tunnelling methods, the ground is mined in 'advances', that is, a tunnel section is created as part of the total tunnel void in a single cycle. One of the oldest methods of tunnel construction involves the use of timbering to provide the temporary support for the ground during tunnelling and is still used extensively in all underground works. In stiff clays, such as London Clay in the United Kingdom, where the ground has some stand-up time, open face tunnelling can be adopted in association with segmental linings, such as spheroidal graphite iron segmental linings. A partial cutting machine with an axial cutterhead has to be heavier for the same power of the head motor in order to absorb the reaction forces of the forward drive compared to one with a transverse cutterhead.
