The machines are half way through the 10 mile tunnel and have excavated enough chalk and flint to fill more than 500 Olympic swimming pools.
The Chiltern Tunnel is the longest tunnel on the HS 2 project, designed to improve links between London, Birmingham and the north of England.
Campaigners are fighting against plans to build on woodland after the project was criticised for the impact it would have on the land it would take.
The two tunnels between the M 25 and South Heath have five shafts for emergency access and ventilation near Chalfont St Peter, Chalfont St Giles, Amersham, Little Missenden and Chesham Road.
The 1.3 million cubic meters of chalk and flint excavated will be used for a chalk grassland restoration project at the south portal of the tunnel.
The HS 2 Ltd said the project would create 127 hectares of new landscaping, wildlife habitat and biodiverse chalk grassland. Noak said this tunnel would take HS 2 beneath the Chiltern hills, safeguarding the woodlands and wildlife habits above ground and reducing disruption to communities during construction and operation.
Once complete, HS 2 will offer low carbon journey options connecting London with the major cities of the north and releasing capacity for more freight and local trains on our existing mainlines. She said that the project was based around saving a few minutes on train journeys, but it's also more environmentally friendly than not to travel. She said that much business can be done through video-conferencing and other technologies.