Ice roads

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Contents

Introduction

Ice roads have connected remote Canadian communities for generations. In the province of Manitoba alone, the network of ice roads that are constructed annually service 30 communities, numbering approximately 29,000 people [1]. Ice roads have contributed to the continued survival of northern communities and have made remote, large-scale arctic mining projects a possibility. Diavik Diamond Mine, in the Northwest Territories, for example, received 2,757 shipments over ice roads, amounting to over 100,000 tonnes of supplies in 2015 alone[2].

Activities involving road infrastructure on floating ice surfaces carry inherent risk. The variability of ice as a natural material and the unpredictable nature of climatic conditions create for unique design challenges. It is imperative that at all stages of ice road development, planning, construction, operation, and maintenance, the implications of design choices are understood and risks are identified and mitigated. Ice roads have been a blessing to the mining industry, but lapses in design carry the potential for grave consequences.

Route Planning

There are many factors involved in planning the ice roads route. From the perspective of safety and reliability, it is critical that winter roads minimize over-ice spans, and constrain ice-crossings to areas most likely to yield competent ice, such as deep lakes. Acting in opposition, from a financial perspective, limiting the length of the road by creating the most direct path to the objective is favourable, while environmental considerations further complicate the matter. Ice road planning typically begins with the consultation of aerial satellite images of the region, for both winter and summer months. The use of summer-month photos allows for the identification of small bodies of water and rivers that may be impossible to see in winter photography, furthermore, the nature of the region can be determined. Changes in land elevation for over-land crossings, for example, should be avoided as they may require gravel-infilling and leveling, while understanding the network of waterways is essential to the planning of over-ice roadways. Contrasting these images with winter photographs will allow the general route to be planned, involving the balancing of road length with over-ice duration.

During the process of route planning, it is critical to avoid shorelines, shallow rivers, and other shallow bodies of water. Shallow bodies accommodate ice of of smaller effective thickness, which is less likely to provide a stable, safe road surface. The use of 1:50,000 topographic maps is recommended in the planning of ice road right-of-ways [3].

In order to minimize the amount of damage done to the environment it is necessary to plan a route that avoids environmental conflict. The ice road should plan to minimize the amount of creek and river crossings as this is the number one cause of environmental damage [1]. Heavily wooded areas should also be avoided to minimize the amount of damage from construction. For assistance in environmental planning it is required that the following stakeholders be engaged:

  • Department of Fisheries and Oceans
  • Department of Transportation
  • Local communities/ communities of interest
  • Land Use Officers
  • Heritage resource officials
  • Wildlife Section of Department of Renewable Resources
  • Environment Canada

In addition to previously mentioned environmental considerations, ice-rich soils should be planned around as they are prone to extensive terrain damage. If equipment operates on top of these areas, the damage can be irreversible due to the soft properties of ice-rich soils. The issue with identifying ground ice is the fact that it cannot be recognized through routine surface checks; the use of geotechnical drilling is required [3].

Ice Type

The design characteristics of ice vary considerably according to the conditions during formation. The primary properties of ice, strength, variability, and quality, can vary greatly between disparate ice surfaces, as well as at the local level. There are four primary types of ice that may be encountered in the field. Differentiation between lake and river formation is noted for blue ice, as the differences in the formation environmental effect the properties of the ice.

Blue Ice (Lake)

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Blue Ice (River) [1]

Layer of ice that forms underneath the surface layer of ice. Blue ice located in a lake setting has grown under calm conditions, resulting in long column-like crystals containing few ice bubbles. The relative lack of air bubbles in the ice structure results in an ice layer that is optically clear, through which the water below can be seen giving the ice it's blue appearance [1].

Freshwater lake blue ice possesses the lowest spatial variability in ice thickness and greatest uniformity due to the calm conditions of formation. Consequently, it is characterized by excellent ice quality and superior strength [1].

Blue Ice (River)

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Blue Ice (River) [1]

Due to water currents in river settings, river blue ice is characterized by medium to high variability in ice thickness. Furthermore, the action of currents against the underside of the ice surface contributes to a tendency for ice thickness to be lost. This results in strength variability across the body of ice [1].

White Ice (Snow Ice)

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White Ice [1]

Forms via the natural or deliberate flooding of snow on the top surface of the ice. The white colour of the ice is due to the entrapment of air bubbles in the ice as it freezes. White ice formed by the natural flooding of the ice surface possesses poor strength characteristics due to the high concentration of air bubbles in the structure of the ice. Consequently, it is advised that naturally-formed white ice is not considered in the measurement of the effective ice thickness. Man-made white ice, constructed according to best practices, is considered to possess similar strength attributes to freshwater lake ice [1]. Uniform white ice of high quality can be achieved through the following process:

  • Clear snow and natural white ice from the ice surface
  • Pump freshwater in thin layers over the exposed ice surface
  • Allow for the layer to freeze completely
  • Inspect the ice surface prior to flooding of second layer

Frazil Ice (Slush Ice)

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Frazil Ice [1]

Non-structurally competent ice formed through the amalgamation of disk-shaped ice particles. Typically formed in rivers other other turbulent waters [1].

Jam Ice

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Jam Ice [1]

Characterized by its jagged surface profile that is the result of the accumulation of pieces of ice that freeze together, forming a single rough ice covering. Typically forms on moving water, such as rivers and streams. Jam ice possesses low strength characteristics due to the heterogeneity of the body of ice and unpredictable and non-uniform ice thickness [1].

Ice Crack Mechanisms

There are a number of mechanisms by which cracks may form in an ice covering. Certain fracture types indicate severe loss of structural competency, while others do not necessarily indicate a loss of load bearing capacity. Consequently, it is imperative that the fracture mechanisms of ice coverings are understood and can be identified in the field.

Load-Induced Cracks

Occur when the load bearing capacity of the ice covering is exceeded by a stationary or moving load. When the strength of ice is exceeded by a load, cracks begin to form in through the ice. Crack formation occurs in three stages [4]:

  • Radial cracks: Extend linearly outward from the point of loading. Radial cracks typically indicate that the applied load is approximately half of the failure load of the ice and that immediate action should be taken to remove the load from the ice surface.
  • Circumferential cracks: Cracks that form in a circular shape around the applied load, between radial cracks. Circumferential cracking is a serious indicator that the load may break through the ice. All personnel should evacuate the area.
  • Combination: When the circumferential cracks connect two radial cracks, triangular ice wedges are formed that may plunge into the water without notice. At this point the structural integrity of the ice has been overcome and the surface of the covering has failed. The rate of failure is primarily a product of ice thickness. Radial and circumferential cracking may occur slowly enough in thick ice coverings to facilitate action on the part of the operator to evacuate the loaded area, while thin ice may fail near-instantaneously.

Arising from Differences in Ice Thickness and Buoyancy

The ice of the lane is thicker than the surrounding ice, due to the insulative properties of the snow cover. The buoyancy of the ice along the cleared increases as the ice mass becomes thicker, causing it to rise above the surrounding ice, buried beneath the weight of the snowbanks. The bending action of the ice surface results in longitudinal tensions cracks that form parallel with the direction of traffic. Cracks along the cleared lane are not typically of concern as they rarely extend through the thickness of the and they can be managed with repairs. When several longitudinal cracks coalesce at the surface, shallow pieces of ice may be ejected, forming pot-holes. Pot-holes present a hazard to vehicles traveling on the ice road [4].

Thermal Contraction Cracks

Weather conditions have the potential to significantly increase the risk factor associated with an ice road. A significant drop in temperature causes the ice to shrink which may cause thermal contraction cracks. The exposure of the ice surface to changing temperatures, such as snow removal, is what promotes the occurrence of thermal contraction cracks. These cracks occur as dry cracks but may become wet cracks under certain conditions, such as heavy loads or may even extend under continuing temperature fluctuations. If the dry cracks are filled with water and refreeze, there is the possibility of a pressure ridge forming. These are ice sheets that have moved together to form ridges and are capable of rising up to three meters above the ice road surface and extend along the entire length of the crack [4].

Thermal Expansion Cracks

Thermal expansion cracks in conjunction with thermal contraction cracks may also lead to pressure ridges. Once a contraction crack has filled with water and refrozen, a sudden rise in temperature will cause the ice sheet to expand and move upwards in locations with thinner ice. These pressure ridges may extend over several kilometres and must be avoided as they significantly decrease the strength of the ice. Effectively monitoring thermal expansion cracks must be done in order to identify and mitigate the formation of pressure ridges. Once a ridge has formed, the ice road path must be redirected a safe distance away from the ridge [4].

Wind Cracks

Wind velocity is another component of weather fluctuations that has a significant effect on the creation of pressure ridges. If wet cracks are exposed to a minimum wind velocity of 55 km/h, they can begin to form ridges. These ridges usually extend in a parallel or perpendicular direction to the shoreline. In order to mitigate the occurrence of wind cracks, ice roads must be continuously monitored for the formation of wet cracks [4].

Water Level Fluctuation Cracks

A change in the water level of a lake or river will cause ice sheet movement and a significant amount of wet cracks. This primarily occurs in rivers where the ice sheet has been grounded, usually along a shoreline. It is usually recommended to avoid crossing these areas and direct an ice road’s path a safe distance away to reduce risk of failure [4].

Dynamic Wave Cracks

As snow is removed from the surface of an ice sheet there will be induced thickening of the ice. However, on the sides of the road where snow banks are built there will be the opposite effect and ice cover will decrease. It is in these areas of thinner ice where waves may crack and rupture the ice. Waves are primarily caused by vehicles traveling too fast over areas where the ice is thin [4].

Construction

Allowable Load Determination

The design and construction of ice roads is complex and dangerous process that must be planned strategically. For some mining operations in Northern remote areas, ice roads represent the lifeline of the project, without which the feasibility of ongoing production may be threatened. Due to the inherent risks of performing activities on top of floating ice, planning must be safety oriented. Any decision regarding ice road construction must involve the consideration of many variables, such as ice thickness and quality, road use, temperature change, wind velocity, number and types of cracks, amount of snow cover and presence of water currents. As ice road construction is a seasonal activity, fluctuations in weather conditions must be considered and constantly monitored [5].

In Ontario, the regulations and standards of ice road construction are regulated under the Occupational Health and Safety Act (OHSA) to assist in protecting the health and safety of all employees and contractors. The industry best practice requires a risk-based approach consisting of hazard identification, assessment, elimination and control. Risk Management and Analysis of ice roads are of paramount importance for ensuring the safety of workers. The risk analysis will output a risk factor that will be used in the following formula, known as Gold’s Formula, to compute the allowable load on the road surface [4].

Gold's Formula forms the basis for all ice infrastructure guidelines written and used in Canada. The formula calculates the allowable load on an ice surface, given the effective thickness of competent ice and a constant that relates the strength of ice and the level of risk tolerance. Gold's Formula is not appropriate for loads less than 5,000kg. For information regarding light loads on ice surfaces, consult Ice Testing.

Gold's Formula

P=Ah²

Where P is the allowable load in kilograms, A is a risk factor determining the likelihood of failure and h is the effective thickness of competent ice in centimeters. For information regarding effective ice thickness determination, please consult Ice Testing. [4]

A Value Selection

The range of allowable loads, for a given effective ice thickness, is determined by the selection of the A value. The value of A corresponds to the level of risk, inherent in the ice infrastructure, and effects the hazard controls that must be implemented to reduce the risk of breakthrough.

Increasing the value of A, for a given effective ice thickness, increases the maximum allowable load. Consequently, the risk level associated with the ice road increases and the hazard controls become more intensive. The affect of varying the value of A is illustrated[4]:


A Value Determination [1]


The corresponding increase in hazard controls, associated with varying the value of A, is provided[4]:


Hazard Controls [1]


The relationship between the effective ice thickness and A value is illustrated[4]:


Ice Bearing Capacity Plot [4]

Lane Width

Once the allowable load has been found to support construction equipment, the design of the driving lanes may begin. The width of driving lanes is dependent on the allowable load that has been determined using Gold’s formula. Example recommended lane widths are provided.

Lane Dimensions [4]
Operating Vehicles Cleared Width - Bank to Bank (m) Driving Lane - Width (m)
Light Vehicle Traffic (5,000kg) 20 10
Construction (22,000kg) 25 15
Super B Train (Double Trailer Length) (63,500kg) 30+ 20

Road Embankments

When clearing snow on ice roads and building snow banks there are consequences that must be identified and managed. Clearing snow results in an increase of ice thickness in that area due to the absence of insulating snow. Therefore, as snow is cleared, the rise in volume of the uncovered ice will increase its buoyancy and rise slightly above the thinner ice beneath the snow bank.

Winter Ice Road Diagram [3]

Creating snow banks has an opposite effect than clearing snow, the increase of snow coverage results in the thinner of the ice. This inconsistency in ice thickness and buoyancy between the snow banks and the cleared road may cause longitudinal cracks along the surface of the ice. Through regular monitoring, cracks extending up to the cleared surface may be identified and repaired. However, it is more difficult to identify cracks underneath the snow banks and as the ice is thinner in these areas, this could be quite hazardous to operating vehicles if the cracks extend upward to the surface [4].

Development Equipment

Activities involving the development, construction, and maintenance of ice road infrastructure require a broad range of machinery and equipment.

Amphibious Cross Terrain Vehicle

Cross terrain vehicles, such as the ArgoXTV, may be used to facilitate ice surveys.[6]. Workers driving an Argo while also wearing a winter water survival suits are very safe when far out on the ice checking it’s thickness. A good substitute for the Argo that has a higher carrying capacity is the Hagglund amphibious vehicle, pictured here conducting an ice profile survey. Although larger, it can still operate in open water.

Snowcat

Snowcat style vehicles are relatively light weight, fully cabbed, tracked vehicles for transportation over snow or ice. This vehicle is sent in next, when ice is suitable for pick up sized equipment, but not industrial loads. They are fitted with blow blades to remove snow from the to-be road until the ice is thick enough to start real development [6]. Snow insulates the ice, so removing it in these early stages is a key part of creating a good base.

Industrial Equipment

Once the ice is thick enough, an array of standard road construction vehicles begin work. These include graders, plows, excavators, and water trucks [7]. Although the road is not ready for regular traffic, the ice is strong enough to support development as long as the equipment is not carrying extra load, or moving too quickly. One type of industrial equipment not suggested for use on ice roads are crawler style tractors and excavators [5]. The heavy vibration, and concentrated center of weight have led to many incidents over time.

Commercial Loads

After construction, full sized transport trucks, and even trains of trucks, are allowed onto the road. Even double length “Super B” style tankers are allowed, as long as ice thickness permits. These types of vehicles dominate most of the traffic, however light pick-ups, all-terrain vehicles, and snow mobiles are still commonplace.

Equipment Modification

There are things that can be added to various types of equipment to make then more suitable for use on the ice road. These devices are not yet enforced by law, but are however strongly recommended [5].

Escape Hatches

A means of escape is essential for the equipment operator in the event of falling through ice with the door jammed. This can be accomplished by installing pop-out windows, or roof hatches in the cabs of equipment. This is not always an option, for example if the structural design of the canopy is impacted by modification [5].

Outriggers

Outriggers are a long steel or wooden beams attached to a piece of equipment, usually pointing off the back of it. The purpose of such outriggers is to slow the rate at which the equipment falls through the ice. This can give the operator a few extra very critical seconds to escape unharmed. It is recommended that during development and maintenance, outriggers should be utilized whenever total water depth is deeper than the seat height of the equipment [5].

Tires

Although one may initially believe studded tires or tire chain modifications would be good on ice roads, this is not the case. These types of tire modification, while increasing traction, destroy the road [5]. Conversely, standard winter deep lug tread tires are recommended [8].

Costing

Costing information for ice road infrastructure construction is inherently variable, given the unique set of challenges faced in different regions. Costing figures have been gathered from completed projects and reflect costs that were specific to the particular project. Costing information reflects an order to magnitude assessment, as each project varies considerably.

Summary

The overall cost of ice road construction is approximately $80,000 to $100,000 per mile, based on average costing from the construction of the ice road infrastructure in Alaska’s Prudhoe Bay and North Slope projects [9].

In addition to financial costs, ice road road construction places a heavy strain on water sources. One mile of ice road, 40 feet wide by 6 inches in depth requires approximately 1 to 1.5 million gallons of water [9].

Example Costing

There are five primary cost categories that must be considered when performing ice road costing: initial route clearing, administrative, ice profiling, construction, and maintenance costs.

A breakdown of cost information has been derived from the Yellowknife Joint Venture Ice Road.

Costing [10]
Initial Route Clearing Cost ($) Unit of Measure
Plowing, Drilling and Flooding 18,000 Per mile
Fixed Costs Machinery (average) 40,000 Per machine
Team Costs
Ice Profiling 6,00 Per mile
Snow Cats 6,000 Per mile
Plows 6,000 Per mile
Helicopter Support 650 Per mile
Administrative
General Manager 150,000 Per year
Cost Controller 80,000 Per year
Machine Operator 70,000 Per year
Maintenance Crews 70,000 Per year
Camp Catering 10 Per meal

Ice Testing

Due to the inherent risk of working with natural materials, ice thickness checking is critical in determining the safety and strength of any ice road. Thorough testing must be conducted and recorded in order to ensure that the ice roads are safe for workers and will support the loads that will be applied by equipment and vehicles.

Testing Procedure

Safety Requirements: Until the thickness of an ice sheet has been proven to be more than 18cm for the entirety of the work area, all members of the testing crew must wear an approved flotation suit [11]. Regardless of ice thickness the individual performing thickness tests must wear a CSA approved safety harness, and may never work alone. The tester must have a life line secured to the safety harness. The life line must be a polypropylene rope with minimum length of 30m and diameter of 1cm. While on the ice each worker must carry with them a set of ice rescue picks until the end of the initial construction phase. Workers may not progress onto the ice for any reason if the thickness is less than 10 cm [11][5].

Initial Testing: Ice thickness testing must first be conducted at the point of ingress to the ice. Once the minimum thickness of 10 cm has been confirmed at the point of ingress, workers may move onto the ice surface in the confirmed area. Test holes may then be created at regular intervals in addition to spot checks starting from the ingress point as described in ‘Creating A Working Area’. Ice Chisels and/or needle bars may be used to create test holes in ice less than 30 cm thick [11]. For ice thicker than 30 cm an auger must be used. Workers must vacate the area surrounding a test hole that finds the ice thicknesses to be less than 10cm.

Creating a Working Area: Each measurement must be taken with an ice thickness measuring stick. Each test hole must pass the required thickness before testers may progress onto unknown ice. With each confirmed thickness test the workable area grows. The confirmed area must be clearly marked, commonly with flags, cones, or poles[5]. The interval of thickness checks may be regulated regionally. Common intervals are determined based on relevant activity and water conditions. Regulations commonly state that areas within 250m of shore should be tested every 30m. Beyond 250m of shore test holes may be separated by as much as 250m for lakes and slow moving rivers. Rivers with significant current must be tested at a minimum of every 30m. If a test finds an area of thin but safe ice, additional tests should be conducted in the surrounding area to establish the extent of the thin ice [11]

Relevant Ice Thickness

Minimum ice thicknesses, relevant to ice thickness measuring programs, are provided:

Minimum Ice Dimensions [11]
Load (Slow Moving) Minimum Effective Thickness (cm)
Person Walking (<120kg) 10
Snowmobiles (Machine + rider <500kg) 18
3/4 Ton 4x4 Vehicle (Total weight <5,000kg) 38

Effective Ice Thickness

Accurately determining the effective ice thickness of an ice cover is critical in the determination of the maximum allowable load. In the measurement of effective ice thickness, only well-bonded white and blue ice is measured. Ice of poor quality, or is not bonded, should not be included. A list of ice conditions that should not be included in the measurement of effective ice thickness is provided [1]:

  • Ice layer with water lens, greater than 5 mm in diameter, comprising greater than 10% of ice volume
  • Ice layer consisting of frazil ice
  • Ice layer comprising poorly bonded and separating layers
  • Ice containing wet cracks

Ice Strength Factors

The loads that ice can support depends on a several factors including, ice thickness, cracks, traveling speed, water pressure, ice formation process, snow cover, and ice type among others factors.

Ice Thickness: In Canada initial strength estimates are often made from the ice thickness using a modified version of Gold's Formula which can then be subjected to the influence of factors such as cracks.

P=6x(h+0.5W)²

Where: P = load limit (kg) h = blue ice thickness (cm) W = white ice thickness (cm)

Presence of Cracks: Any ice sheet will contain cracks, these cracks are caused by thermal expansion and movement. Natural cracking occurs throughout the year but is most frequent during the spring and early winter. Not all cracks will affect the strength of the ice, however others decrease the ice strength by varying degrees.

Crack Influence on Ice Strength [11]
Crack Type Effective Ice Strength (%)
Dry Crack, Intersecting 90
Dry Crack, Non-Intersecting 90
Wet Crack, Intersecting 50
Wet Crack, Non-Intersecting 75
Hairline Cracks 100
Refrozen Cracks 100

Both dry and wet cracks can be refrozen given time, water and sufficiently low temperatures. Refrozen cracks do not affect the load bearing capacity of the ice. This recovery process can be accelerated by reducing stress on the roads though the reduction of transport loads, travel frequency, and by flooding the road with sufficient time to allow for complete refreezing.

Rapid Temperature Drops: If the temperature changes by more than 18 degrees Celsius in a 24 hour period, the ice must be thoroughly inspected in order to determine if thermal stresses resulted in significant cracking, as cracks reduce the load bearing capacity of the ice[1][11].

Moving Loads:As a load or vehicle moves over the ice the ice deflects under the load and causing a wave under the ice. A slow moving vehicle deflects the ice slowly, allowing waves to pass the vehicle and providing time for the ice’s crystal lattice to adjust and maintain almost all of its initial strength[5]. If the vehicle is fast moving, this deformation occurs too rapidly, the ice does not have time to adjust and the deflection will be subjected to the wave pressure at its weakest point, results in more severe cracking. While this cracking may not result in immediate failure the ice will be permanently weakened, and upon repeated rapid loading the ice may fail under a load that the road had supported for numerous trips. The Saskatchewan Ministry of Highways and Infrastructure, has reported that an empty vehicle traveling between 25-35 km/h often results in more audible cracking in the ice than a fully loaded vehicle traveling at 8-10 km/h. The greatest damage has been found to be when vehicles and the waves they generate are traveling at the same speed. similar speeds results in the the greatest pressure on the ice at its weakest point. For this reason many companies limit their vehicle speeds to 15 km/h while on ice roads. Please consult Safety Design for more information regarding the speed of vehicles on ice roads[1][5].

The risk of damage is greater when dealing with shallow bodies of water consisting of a depth less than 50 times the ice thickness and the shore. Due to the waves interactions with the shoreline, ice road should begin and end at a 45 degree angle to the shoreline to prevent wave superposition and increased stresses on the ice[5].

Repeating Loads:Each passing load will cause cracking of some level. Each crack slightly degrades the strength of the ice. Frequent loading may result in ruts, dry cracks, wet cracks and even holes in the ice. Before an ice road becomes dangerous it should be closed, loads lightened or area detoured while the ice recoveries. Flooding the ice and allowing it to freeze will accelerate the recovery process.

Maximum Loading:Maximum allowable weights are regionally regulated and often are ice thickness dependent. Maximum loads are the maximum load permitted on a given sheet of ice, however the particular ice sheet may not be able to support this load depending on its strength.

Typical Loading Limits in Canada[11]
Minimum Blue Ice Thickness (cm) Maximum Load (kg) Load Type
46 14,800 Light Traffic Only
74 34,500 Commercial Traffic

Variable Ice Testing

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Ice Radar System [12]

In order to test ice conditions with higher efficiency than drilling, the “Ice Road Radar” ground penetrating radar technology was created by EBA Engineering in 2007. This system utilizes a bathymetry radar system that transmits signals from the surface and receives the reflection from the ice to determine properties including the ice type and thickness[12]. The schematic is displayed below with Tr being the transmission and R1,2,3 being the receiving antennas. These systems are attached to the rear of vehicle and are towed across the area of interest, travelling up to 80 km/h with accurate results [12]. By implementing the Ice Road Radar system, testing can occur more frequently and more reliable ice data can be obtained for safety assessment. The continuous sampling also allows more properties to be obtained including cracks, ice mapping and air content in ice roads; which are unattainable through simply drilling.

Worked Scenarios

Example 1

Conditions: Surveying crews have reported 8cm of white ice and 32cm of blue ice. Inspections report the ice road surface contains hairline cracks, dry intersecting cracks, and refrozen intersecting cracks.

To determine the load bearing capacity of the ice road, Gold's Formula is utilized:

Equ1.jpg

Accounting for cracking and ice conditions:

Equ2.jpg

The road will hold a vehicle and load totaling approximately 7,000kg, as long as the vehicle is the only load on the road and the vehicle is traveling at a maximum of 15km/h.

Example 2

Conditions: Surveying crews have reported 12cm of white ice and 51cm of blue ice. Inspections report that the last flooding and refreezing have refrozen all the previous cracks. The inspection discovered a small number of new dry, non-intersecting cracks in the ice surface.

Gold's formula:

Equ3.jpg

Accounting for cracking and ice conditions:

Equ4.jpg

The load limit for the above ice road will be 14,800kg. While the Gold Formula predicts that the ice can support a larger load, good practice states that until the blue ice thickness reaches a thickness of 74cm loads must not surpass the 14,800kg limit.

Safety Design

In Ontario, ice roads are primarily governed by the Occupational Health and Safety Act (OHSA), specifically Regulations for Construction Projects (O. Reg. 213/91)[3]. Therefore, the best practice of “Recognize, Assess and Eliminate/Control” must be used for all instances on ice covers including; traversing ice covers by foot, operating snowmobiles, trucks or tracked vehicles, driving over lake or river ice crossings, and monitoring ice conditions during ice road construction. Under the OHSA section 25(2)(h), employers must include these best practices in contracts on ice road construction projects. The best practices, were developed through careful consideration of operating procedures.

Approved Use of Ice Covers

From the bearing capacity established during the process of strength characterization, only vehicles with a gross vehicle weight under the load limit can be approved for transport on the ice road. Vehicles travelling on the ice road must have approved documents, with the weight breakdown of the vehicle, fuel, tools and equipment that they carry. It is necessary that a scaling station is present at the entry point of any ice road to verify the gross vehicle weight.

Minimum Distances between Vehicles and Equipment

Vehicles weight classifications include: light (less than 5,000kg) and heavy (between 5,000-63,500kg). Spacing between light vehicles should be at least 200 times the thickness of the ice and 500 times the thickness of the ice for heavy vehicles [3]. If these distances are larger than the ice road, only one vehicle is permitted on the ice road at a time. If the vehicles plans to be stationary, based on the vehicle weight classification, there is a max time limit. Parked vehicles and equipment should be spaced no closer than two vehicle and equipment lengths for time periods of less than two hours; any longer than two hours is prohibited [3].

Maximum Speed when Travelling on Ice Cover

Speed limits are a function of weather, gross vehicle weight, ice quality and position on the ice road. It is mandatory that all speed limits are posted, typically with lower speed limits around the shore. The suggested maximum speed limits are outlined:

Suggested Maximum Speed Limits [13]
Vehicle/Ice Conditions Suggested Maximum Speed Limit (km/h)
Vehicle profiling during construction 10
Vehicle approaching shore line 10
Vehicle passing flood crews 10
Load vehicles travelling in opposite directions 10
Meeting oncoming vehicles 10
Vehicle operating at the minimum ice thickness for its weight 25
Vehicle operating at ice conditions that are two times the minimum ice thickness for its weight 35

Ice Cover Closure

There are two types of road closures: temporary and suspended. Temporary closures occur if poor weather, surface or ice conditions are present; this includes poor visibility due to blizzards, water overflow, drifting snow, and cracking from excessive wear. Suspended closures are the result of ice thaw and typically cover an extended period of time. It is required that the closed ice road is identified with closure signs, cones, and fencing.

Emergency Response Plan

The safety plan for the ice road must also include a written emergency plan that complies with OHSA regulation 213/91 – Construction Projects [3]. This plan must include all possible emergency scenarios, procedures for rescue, identification of respondents, evacuation plans and PPE location, emergency radios, first aid equipment and emergency response training. Upon completion of all listed requirements, the plan must be approved by the constructor and joint health and safety committee and posted in a general location.

Safety Plan

Based on the safety design, an ice road safety plan can be implemented and communicated to all supervisors and workers. It must be a written document that identifies the ice road hazards and how they are controlled. Recognizing the hazard is stating that there is potential for the ice cover to fail/breakthrough under the load of a person or vehicle. Assessing the hazard involves conducting a risk analysis based on severity and likelihood of the consequences; with severity ranging from a fatality to ice road closure and likelihood scaling from high to once in the lifetime. To control the hazard the design should consider adequate lane widths, snowbank positions, control speeds, ice performance criteria and bearing capacity factors [3]. Maintenance, administrative, and monitoring controls can also be applied for higher levels of assessment.

Training

In order for an employee to be deemed fit for work on an ice road the following certification and training must be completed:

  • First Aid and CPR (St. John’s Ambulance or Red Cross)
  • Ice Rescue Training
  • Winter Survival for Remote Locations Equipment Certification
  • Transportation of Dangerous Goods - if required
  • Workplace Hazardous Material Identification System (WHMIS) – If deemed appropriate
  • Occupational Health Committee (OHC) Level 1 and 2

References

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 Work Safe Alberta. (2013). Best Practice for Building and Working Safely on Ice Covers in Alberta. Edmonton: Government of Alberta
  2. Rio Tinto. (n.d.). Ice roads. Retrieved from Rio Tinto: http://www.riotinto.com/diamondsandminerals/ice-road-12112.aspx
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Stanley Associates Engineering Limited. (1993). Environmental Guidelines for the Construction, Maintenance and Closure of Winter Roads in the Northwest Territories. Yellowknife: The Northest Territories Department of Transportation.
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 Infrastructure Health and Safety Association. (2014). Best Practices for Building and Working Safely on Ice Covers in Ontario. Retrieved from http://www.ihsa.ca/PDFs/Products/Id/IHSA029.pdf
  5. 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 Safe Operating Procedures for Winter Roads Committee. (2010). Winter Roads Handbook. Saskatoon: Saskatchewan Ministry of Highways and Infrastructure
  6. 6.0 6.1 Holland, E. (2015). How to Build an Ice Road. Pacific Standard. Retrieved from http://www.psmag.com/nature-and-technology/how-to-build-an-ice-road> This is the case because on top of being extremely light, and having good range, they also float and operate on water
  7. Wise, J. (2009). Building Canadas Epic Ice Road. Popular Mechanics. Retrieved from http://www.popularmechanics.com/technology/infrastructure/a1290/4212314/
  8. Urlich, B. (2011). To ice road truckers, tires are the difference between life and death. Modern Tire Dealer. Retrieved from http://www.moderntiredealer.com/blogpost/b-o-b/340316/to-ice-road-truckers-tires-are-the-difference-between-life-and-death
  9. 9.0 9.1 ASGC Incorporated. (2005). North Slope Borough Comprehensive Transportation Plan. North Slope Borough
  10. The Goldstein Group. (2010). Cost Breakdown and Construction Profile: Yellowknife Joint Venture Ice Road. Wellesley: Babson College.
  11. 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Northwest Territories Department of Transportation. (2007). A Field Guide to Ice Construction Safety. Yellowknife.
  12. 12.0 12.1 12.2 Mesher, D. E. (2008). Ice Road Assessment, Modeling and Management. Retrieved from EBA Engineering Consultants: http://conf.tac-atc.ca/english/resourcecentre/readingroom/conference/conf2008/docs/c1/mesher.pdf
  13. Infrastructure Health and Safety Association, "Best Practices for Building and Working Safely on Ice Covers in Ontario," IHSA, Toronto, 2014.
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