Mixed Face Conditions
Mixed face conditions for a hard rock tunnel boring machine (TBM) can be alleviated by creating a frozen mass that encompasses the runner face, presenting a homogenous, strengthened zone to allow tunneling to proceed safely.
Mass ground freezing of a designated area along the tunnel alignment allows for a ‘safe haven’ for the tunnel boring machine to undergo inspection and cutter head changes. The freeze pipes within the alignment may be constructed with aluminum, or heated and pulled as the TMB enters the frozen mass to avoid damage to the TBM.
Launch and Retrieval Blocks
When ground freezing is the method used for groundwater control and support of excavation for deep shafts, the freeze can be extended via additional freeze pipes to create a targeted stabilized mass for cutting of the eye for TBM launch or retrieval.