Frost Heave

What is frost heave?

Frost heave is a common issue in northern climates where the ambient temperatures consistently falls below freezing during winter. Frost heave is characterized by ‘swelling soil’, which occurs when the soil surface lifts due to the expansion of water due to freezing.

The challenge of frost heave is intensified in areas where the soil quality is poor, and a high-water table exists. Soils capable of retaining and conducting water, usually rich in fine-grained particles are considered “frost-susceptible”. These soils can draw subsurface water from below by capillary action into the freezing zone above (similar to wicking). Additionally, fine and/or dirty sands, dirty gravel, clay-gravel, and quarry waste are also classified as highly or moderately frost-susceptible soils.

Once the freezing zone has been established, the water-bearing soil becomes ‘perched’ between layers of soil below and above. This can promote the formation of ice lenses. These are lens-shaped areas of ice within the soil that expand horizontally, further aggravating the frost heave severity. Its size depends upon the quantity of free water available and the length of time it is allowed to collect and freeze. Once formed, ice lenses will continue to grow by consuming the rising water at the freezing front. The pressure of one or more growing ice lenses is sufficient to significantly lift a layer of soil above it.

The problem of frost heave

The issue of frost heave poses a detrimental threat in northern climates where freeze-thaw cycles can repeat several times during winter. When the soil heaves, it creates abrupt bumps on road surfaces. This is especially troublesome if beneath a roadway as it can lead to rough driving conditions and eventually pavement cracking and failure. In addition, uneven ice lenses can grow larger in some areas. This causes differential heaving and further surface cracking. As the frozen ground thaws, the affected area can further soften and degrade under repeated traffic loading.

While eliminating the supply of water and the resulting phenomena of frost heave is not possible, its impact can be minimized if the moisture intrusion into the subsoil is controlled.

Frost heave boil on the ground.

Frost and ground heave solutions

Stratum uses geocell technology in structural foundations to reinforce and protect against frost and ground heave that is caused by expanding ice.

Foundation Heave Protection and Solutions

At a temperature of 4 degrees Celsius, water begins to expand by approximately 10% as it turns to ice. The force of expansion can create frost heave in overlying structures, causing damage to foundations for buildings, homes, and other load-bearing supports (such as column bases and pylons). It is known to weaken pavement structures, crack road surfaces, and contribute to pothole formation. Additionally, silty clay soils found in our northern climate (considered among the most frost-susceptible) are prone to frost heave. Due to the extremely small size of its particles or gradation, silty soils, and certain clays (depending on plasticity) permit and encourage the flow of water by capillary action.

Frost heave is most often found at the following locations:

  • Transitions from cut to fill
  • Where ditches are inadequate or non-existent
  • Over culvert pipes
  • Adjacent to driveways that dam roadside ditches and/or collect water
  • Wherever there is an abrupt change in subgrade material
Frost heave boil on the ground.

Stratum’s geotechnical engineers use their extensive cold climate experience to design structures reinforced with NPA Geocells that provides foundation heave protection and virtually eliminates pavement deformation due to frost heave action.

 

Design with Geosynthetics for Frost Heave 

An NPA geocell-reinforced granular base course acts as a beam/slab that transfers a load from a weak spot to an adjacent competent area. The increased rigidity of geocell reinforcement in a base layer resists and protects the softer area from failure. Vertical loads from both below and above the road surface are distributed horizontally, relieving the pressure of expanding ice in a concentrated area that results in frost heave and boil spots.

Using geocell reinforcement in structures beneath a building or other foundation will have the same benefit. It provides foundation heave protection in the same way it protects and strengthens pavement structures and prolongs the foundation’s lifespan while reducing maintenance needs.

Industries that benefit from Ground Heave Protection and Solutions

Rail

Canada has one of the largest rail systems in the world, running over rugged terrain and through some of the world’s most challenging weather. With 50-plus passenger and freight railways operating on more than 44,000 km of track, the supporting base and sub-base layers can be severely affected. These rails are interrupted not only by heaving soil but are subject to the fluctuations of deteriorating permafrost. NPA geocells offer increased dimensional stability and superior creep resistance under extreme environmental conditions. Our sustainable construction techniques minimize environmental impact and can be installed during winter to keep Canada’s railways operational 365 days a year.

 

Air

Effective ground heave solutions are also crucial for airports, airfields and intermodal ports that require heavy-duty pavement to support aircraft and shipping loads. Globally, as new airport and runway construction expands, structures are often built on marginal or swamp land that is subject to soil heave and ground movement. NPA geocells offer the highest durability and lifespan expectations under such heavy dynamic loads. Additionally, they provide effective expansive soil treatment that eliminates the risk of frost heave, frost boils or ground heave damage.

Alternative Energies

Typically access roads and work areas for wind, solar and hydroelectric facilities are in exposed, remote terrain with expansive soft clays or peat soils. As they require special dimensions and load bearing capacities, when coupled with extreme cold conditions, these projects present a unique need for ground heave solutions. Expansive soil stabilization can be achieved by utilizing geocell components in the design. This can extend the foundation’s structural lifespan by a factor of 6. This ensures uninterrupted and worry-free operations, safeguarding against damage from soil heave and frost boils throughout the service life.

 

Infrastructure

Natural disasters don’t wait for fair weather. Structures, including building foundations, are more resilient to ground heave damage when designed with geocell components. In instances of natural disaster, NPA geocell solutions can be deployed quickly regardless of weather conditions, to create or restore critical/temporary infrastructure. This allows for efficient delivery of aid and supplies. Moreover, the characteristics of geocell structures not only provide an effective solution for rapid reconstruction efforts but also enhance protection against potential future disasters.

 

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