TBMs operate like moving underground factories. At the front is a large circular rotating plate called a cutterhead that breaks up the ground while internal systems remove soil and install concrete segments to form the tunnel walls. To construct the tunnels between Glen Waverley and Box Hill, we will use TBMs which are designed for soft ground. To construct the tunnels between Glen Waverley and Cheltenham, we will use convertible TBMs. They will be slurry machines from Clarinda to the stabling facility in Heatherton, then will be converted to earth pressure balance (EPB) machines to work in the softer ground to Cheltenham.