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Unstable soil and loose sediment are serious challenges during tunnelling operations. The ground must be safely stabilised so it will not collapse during excavation and subsequent construction work. One way of achieving this is by freezing critical ground areas with liquid nitrogen (LIN).
Lances are inserted into the ground and flushed with liquid nitrogen. The frozen areas around the lances increase the static load-bearing capacity and the impermeability of the ground. This allows tunnelling and boring work to continue safely.
We innovate for you
Here at Linde, we understand the challenges involved in underground construction work. We have developed a wide portfolio of lances with different freezing zone profiles to support all ground freezing and excavation challenges.
Highlights include our AGF Eco lance with its distinctive fade-out zone towards the top of the lance. With AGF Eco, the frost body develops along the full length of the freeze lance inserted into the ground. This extended chill zone reduces the amount of heat that can permeate from the surface down to the area of interest. It also warms up the exhaust gas that is vented at the point of use so there is less build-up of cryogenic fog. By utilising the liquid nitrogen more efficiently and extending the frost body, AGF Eco reduces the volume of liquid nitrogen needed.
AGF Trim lance
Our innovative lance portfolio also includes a removable freezing lance for tunnelling and pipe jacking applications. This was designed to overcome the problems that can arise as tunnel boring machines (TBMs) approach lances. Accidental collisions can result in emergency stops, costly and time-consuming repair work and subsequent project delays. Our removable lances overcome this challenge. They are simply disconnected from the LIN supply and quickly defrosted before the TBM arrives. Only a very small area around the lances is defrosted so they can be easily pulled out from the ground by crane. The frozen ground is not affected and remains completely frozen, allowing tunneling work to progress safely.
Benefits of our freezing lance portfolio at a glance
- Innovative lance portfolio offering perfect fit for different freezing challenges
- Easy handling and optimum freezing performance
- Rapid withdrawal in the case of removable lances
- Access to our in-depth knowledge and experience in ground-freezing applications
- Assistance in positioning the lances for most effective freezing performance
- Support during project set-up, installation and gas supply
- Customisation of lance installations to the individual ground-freezing requirements
- Support with LIN handling and safety instructions