Face Support

As was described in the general category of pipe jacking/microtunneling, a variety of face support methods are used according to the type of ground being excavated, the elevation of the installation with respect to the groundwater table and the geometric configuration of the installation. 

For larger diameter projects (say 2 m and above), most of the face support methods available in conventional tunnelling can be used - including earth-pressure-balance (EPB) support. For microtunneling projects in which it is not permitted for a person to enter the small diameter tunnels, face support in difficult ground typically relies on a slurry excavation and face-support system. When boring above the water table and in moderate diameters, another option known as auger boring can be employed (see separate description under spoil handling).