Solutions
GEOFROST delivers safe and well proven solutions based on ground freezing technology, with focus on tunneling and construction in wet ground. The business areas are:

  • Tunnels for infrastructure and mining
  • Hydro power plant refurbishment
  • Municipal piping works
  • Civil works
  • Contaminated environment
  • Ground investigation

Wet ground excavation implies the risk of stability problems and loss of ground water control. GEOFROST delivers well proven and reliable ground freezing solutions, that are safe and characterized by working in all kinds of ground conditions. The solutions utilize the impermeability of the ground itself when it freezes, and the large increase in strength of frozen ground, which is similar to concrete. Projects range from large subsea tunnels to smaller short term auxilliary assignments.

Tunnels for infrastructure and mining
Tunnels and rock caverns are built in an increasing number of situations for various reasons, and the challenges are increasing.

Soil tunnels

The ground does not have enough strength to support tunnel excavation by itself. Ground strengthening/extensive support is necessary to secure the stability. Water ingress may contribute to the instability by eroding the excavated surface. Even the tunnel bottom may be unstable due to water pressure or squeezing.

GEOFROST provides temporary stabilization of soil enabling full face excavation in dry conditions. Frozen structure is maintained until loads may be transferred to permanent lining.

Tunnels lacking rock overburden

Geometrical restrictions for infrastructure tunnels can make it difficult to find tunnel alignments that have enough rock overburden all the way.

GEOFROST provides temporary stabilization of soil where rock is lacking, enabling drill and blast or TBM excavation as if it were rock.

Tunnels crossing leaking weakness zones

Tunneling well below the rock surface frequently crosses different fissures and weakness zones of varying width and characteristics. Some of these may imply stability and/or water leakage problems for excavation both with traditional drill and blast and with TBMs.

GEOFROST provides temporary stabilization and water proofing of complicated shear zone crossings.

Tunnel entrances

Rock tunnels usually need to pass through a soil layer in order to enter the rock. There may be unwanted consequences of the tunnel entrance excavations, which may imply:

  • slope stability problems
  • demolishing of houses in the alignment
  • infrastructure interruption
  • large volumes of ground to be deposited
  • negative impact on the landscape environment

GEOFROST enables soil tunneling from the surface until rock tunneling can continue and prevent one or more of the above listed disadvantages with open cut.

TBM start block

TBM excavation starting from a shaft directly into soft or wet ground may face challenges concerning the soft eye construction in the retaining wall, flooding of the shaft and settlements outside, when the soft eye is removed.

GEOFROST delivers temporary blocks providing good conditons for launching and retrieval of TBMs.

Ground improvement for TBM

TBM paths may cross zones of varying characteristics. In urban areas different kinds of obstacles may interfere with the alignment of the infrastructure project and thereby create difficulties.

GEOFROST delivers temporary frozen ground enabling TBM excavation without EPB shield through weak or water bearing ground. By freezing specific zones, a TBM can be designed to handle fewer different ground conditions.

GEOFROST does also deliver temporary support of access to obstacles in front of the TBM that needs to be removed.

Cross passages

Soft ground, sand below the water table and shallow overburden are challenging conditions for cross passage construction.

GEOFROST delivers temporary and water proof ground improvement for safe cross passage tunneling.

Hydro power plant refurbishment
Doing maintenance and refurbishment in water filled tunnels is challengeng when there is no working upstream gate or other easy way to cut off the water.

Tunnel plugging

Detwatering of waterways is required without a functioning gateway upstream.

GEOFROST delivers ice plugs for tunnel closing, so the tunnel can be emptied for water downstream and refurbishment can be carried out under safe conditions without diving.

Cofferdam sealing

Detwatering of waterways is required without a functioning gateway upstream.

GEOFROST delivers waterproof cofferdam core, so cofferdams can be made of permeable materials. The impermeable core can penetrate into impermeable underground.

Municipal piping works
In urban areas, new alignments for sewerage pipes are put deeper into the ground not only to secure the inclination of sewerage pipes, but also to avoid interference with existing pipes and cables. If branching off/connections that must interrupt the retaining wall is located below water table, it can cause stability problems and/or settlements to terrain and constructions outside the trench.

Deep trenches for water and sewerage

Safe excavation, not only avoiding failures but also avoiding soil entering the ditch where pipes are branching off the main pipe may be challenging.

GEOFROST delivers safe and water proof trench-protection, where pipes may enter the ditch through the protection.

Pumping station

New piping stations or connection to older deep laying pipes may be challenging in waterbearing ground.

GEOFROST delivers waterproof protection for excavation and installation of pumps and pipes.

Shafts

Shafts often being deep, usually faces some water cut off challenges that must be solved. Both due to efficient construction work inside the shaft, but maybe more crucial to avoid environmental impact on surroundings due to pore pressure reduction. This can cause settlements on structure and surfaces, damage to buildings, pipe breaking, sinkholes and change in the water balance/ground water regime.

GEOFROST delivers waterproof structures that prevent pore pressure drawdown outside the shaft.

Civil works
Lots of construction works takes place in the ground below ground water level, and different methods are available to secure the excavation and to control the ground water. Some ground conditions are more challenging than others and some surrondings more vulnerable than others, all depending on the works needed to be done.

Construction pits

A construction pit is a temporary excavation for placing basements and foundations into the ground. Area constraints often make it necessary to hold back the sides while making the permanent structure. In poor ground conditions, even the bottom may need support to enable the construction works. Water sealing might also be necessary to avoid impact on adjacent surrondings.

GEOFROST provides ground freezing services, alone or in combination with other methods, stabilizing the walls and bottom and making the pit water proof if necessary.

Retaining walls

  • Retaining walls may be difficult to install in ground with large boulders, talus material, obstacles found in fills or old city-remainings.
  • Water cut off also may be difficult against an uneven rock surface or other structures.
  • Cables, water and sewerage pipes often interrupt the planned continuity of a retaining wall and need to be relocated before construction.
  • Anchoring of a retaining wall may be difficult in soft soil.

GEOFROST delivers retaining walls and soil anchors. The walls can penetrate obstacles and seal against uneven surfaces, crossing cables and pipes.

Temporary underpinning

Structures at the edge of a construction pit may need temporary support until the balance is restored by improved foundation or backfilling of the excavated volume.

GEOFROST delivers temporary underpinnings without any need for structural works on the supported object itself. After having fulfilled its purpose, the temporary undepinning thaws away.

Ground improvement

Temporary ground improvement may be needed to get heavy machinery across soft and vulnerable ground.

GEOFROST delivers temporary ground improvement of the surface, providing access and at the same time protecting the underlying nature.

Contaminated environment
Focus on protecting the environment is increasing and the rules are getting stricter. Both insulating, removing without spreading and getting reliable samples are challenging.

Insulate contamination

Contamination found in the ground shall be cleaned up.

GEOFROST may:

  • insulate a polluted area from surroundings, to prevent contamination from spreading in the ground, whether it is caused by accident or discovered during exccavation. Frozen ground as an insulating material ads well to different construction materials and irregular shapes, can surround inclusions and make a complete cut off.
  • prevent clean water to enter an excavation pit with contamination, so the excavated volume needing cleaning or safe deposit can be minimized.

Removing contamination

Removing the “industrial” contaminated top layer of sediments in sea, lake or river by conventional methods often implies cleaning larger volumes than necessary.

GEOFROST provides a solution that makes it possible to:

  • only remove the thickness of the contaminated layer and
  • stabilize the contamination for safe transportation.

Sampling contaminated ground

It is difficult to preserve all contaminating contents in the ground and at right elevation when sampling, and thus to get correct analycis and the right mitigations.

GEOFROST delivers sampling method that preserves the contents.

Ground investigations
For investigation purposes, samples from the ground have always been valuable. Certain ground conditions are more challenging than others to get any samples from.

Sampling frictional soil

Undisturbed samples of frictional soils are difficult to get by ordinary geotechnical coring because the material may not follow to surface.

GEOFROST offers “undisturbed” sampling of frictional soils.

Sampling rock fissure filling

To investigate the content of rock fissures may be difficult because drilling fluid tend to wash away the filling.

GEOFROST offers “undisturbed” core drilling though fissures that will capture any filling present.

Sampling contamination

Undisturbed samples of contaminated ground may be difficult to get.

GEOFROST offers core drilling through contaminated ground that in addition to capturing the solid contamination, also will bring liquid and gaseous inclusions.

Sampling frozen ground

To validate the frozen ground parameters, samples of the ground freezing structure would be needed.

GEOFROST offers coring of frozen structures without thawing or disturbing the samples.

Testing frozen ground

There are few testing facilities for frozen ground.

GEOFROST is planning a mobile freezing laboratory for testing of frozen ground at subzero temperatures.