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34-612: The Tana Valley is the core area for "the River-Sami Culture" in Finnmark; salmon fishing is central in regard to that culture. History: According to written sources since the last half of the 16th century , fishing has been a major livelihood for the Sami people in the river valley . Another source says since the 17th century . Environmental concerns: erosion at the mouth of the river, in addition to extreme weather ,

68-491: A blizzard. If the ice road is part of a winter road, then closure can also be due to an over-land segment that has become unserviceable. Ice crossings can be made to support higher loads if they are reinforced, and there are a number of ways this has been done in the past. Also, because these structures are vulnerable to a warming climate, which reduces their operational lifespan, they may benefit from reinforcement along problematic segments, such as creek crossings and where

102-401: A conventional optical fiber is the part of the fiber that guides the light. It is a cylinder of glass or plastic that runs along the fiber's length. The core is surrounded by a medium with a lower index of refraction , typically a cladding of a different glass, or plastic. Light travelling in the core reflects from the core-cladding boundary due to total internal reflection , as long as

136-475: A number of guidelines have been published with information in these regards. An ice road may be constructed year after year, for instance to service community needs during the winter. It could also be for a single year or two, so as to supply particular operations, such as a hydroelectric project or offshore drill sites. The ability of an ice road to safely support the weight of a vehicle (or any other loads applied onto it), referred to as bearing capacity ,

170-405: A public road, which is relatively uncontrolled, such an approach introduces a high safety factor against breakthroughs and is therefore desirable. For industrial roads, the design may be less conservative so as to handle their functional requirements, i.e. higher A values can be used, but under the close supervision of a professional engineer. When using Gold's formula, a purely elastic response

204-400: A pump or a spraying system. The aim is to bring the thickness up to what is required for the heaviest vehicles that are anticipated when the ice road opens. Vehicles traveling on an ice road include ordinary automobiles and trucks of various sizes and weights. Standard winter tires are sufficient, i.e. cleats and tire chains can damage the road surface. However, tire chains may be stored in

238-435: A short duration; b) a load that remains stationary during an extensive time period; and c) dynamic loading of the ice cover, from a traveling vehicle. For standard traffic activities, guidelines typically use a simple empirical formula to determine the maximum vehicle weight that should be allowed on an ice road. This formula, which was initially proposed in 1971, is often referred to as Gold's formula : where P

272-486: A thin layer, thereby increasing its density and reducing its insulating properties. The other is to remove it altogether, typically with vehicles fitted with a snowplow . Once the ice has reached the target thickness (via accelerated growth after removing the insulating effects of the snow), road construction per se may commence. At that point, the ice is able to safely support the heavier equipment required for that phase, which mostly consists of artificial thickening using

306-426: A vehicle travels on the road, a dynamic loading regime is exerted onto the ice cover. Below a specific speed, referred to as critical , the ice cover beneath the vehicle will assume the shape of a bowl moving with the vehicle, pushing away the water around it, as the keel of a boat does. At (and above) the critical speed, a series of waves will form behind and in front of the vehicle. "If the celerity of these waves

340-434: Is a stub . You can help Misplaced Pages by expanding it . Ice road An ice road or ice bridge is a human-made structure that runs on a frozen water surface (a river, a lake or a sea water expanse). Ice roads are typically part of a winter road , but they can also be simple stand-alone structures, connecting two shorelines. Ice roads may be planned, built and maintained so as to remain safe and effective, and

374-410: Is assumed, which is, by definition, instantaneous and independent of loading time. Ice, however, naturally exists at a high homologous temperature , i.e. near its melting point. As is the case for any other material under these conditions, response to loading is not only elastic, but incorporates other components, namely: Thus, an ice cover may be able to safely support a vehicle, but if it remains on

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408-415: Is in the vicinity of Seidaholmen - and downstream of it. In August that year, media said that disassembly of the barrier had started. The Tana Bridge (or Nybrua) was constructed in 2020, replacing the function of a neighboring bridge from 1948; its main span is 234 metres (768 ft). The Sami Bridge at Utsjoki was constructed in 1993. The European route E6 highway follows the western shoreline of

442-492: Is making the mouth of the river wider but more shallow (as of the 2020s); there is a risk that salmon [or more salmon] during low tide will turn away (from the river) during approach to the river for spawning, according to a committee leader in Tana's municipal council. The ocean has a (considerable) effect on the river, for c. 10 km from the mouth of the river. In its upper course, it runs for 256 km (159 mi) along

476-544: Is protected and is an important home to wetland birds. There are large deposits of sand in the delta that are exposed sandbars at low tide. During the summer of 2024, salmon fishing will be banned, as ordered by Finnish authorities and Norwegian authorities; however, fishing for species other than salmon will be facilitated; There will be some opportunities for fishing humpback salmon ; The summer season (for fishing) started in May. In July 2024, media said that on Finland's side of

510-438: Is the mode field diameter . This is the diameter at which the intensity of light in the fiber falls to some specified fraction of maximum (usually 1/e ≈ 13.5%) . For single-mode fiber, the mode field diameter is larger than the physical diameter of the core, because the light penetrates slightly into the cladding as an evanescent wave . The three most common core sizes are: This article related to telecommunications

544-402: Is the load, h is the thickness and A is a constant with a unit of pressure. It may be linked with an idealized elastic response of the ice cover: where σ max is the maximum tensile strength at the bottom of an infinite ice plate resting on an elastic foundation. The parameter C is based on the theory of thick plates . Hence, with this idealized formulation, A is representative of

578-485: Is the primary concern when designing, building and using that structure. Generally speaking, a vertically loaded ice cover will react in two ways: 1) it will sink, and 2) it will bend in flexure. In order to meet the ice bearing criteria, the top surface should not sink below the water line and the applied flexural stress should not exceed the ice's flexural strength . Three loading regimes have to be considered: a) maximum weight for standard usage or for parking during

612-406: Is the same as the vehicle speed, the deflection and the stresses in the ice sheet are amplified, similar to resonance in an oscillating system" (pp. 8–10). The critical speed depends on ice thickness and water depth. Another issue that arises is the reflection of these waves from the shoreline back toward the vehicle. This can induce additional stresses on the ice – one way to mitigate this issue

646-486: Is to avoid approaching shorelines at 90 degrees. The critical speed is what determines the speed limit for vehicles traveling on ice roads. That limit can be as low as 10 km/h (6.2 mph) to 35 km/h (22 mph). Dynamic loading of the ice cover may also dictate a minimum distance between vehicles. The effects of dynamic loading on a floating ice sheet has been investigated via field testing. The most compelling evidence of such wave patterns, however,

680-731: The Finnish–Norwegian border , between Utsjoki Municipality (in Finland) and Karasjok Municipality and Tana Municipality (in Norway). The river is the fifth longest in Norway. The last 105 kilometres (65 mi) of the river run through the municipality of Tana in Norway. The river discharges into the Tanafjorden , one of the largest and most unspoiled river deltas in Europe. The delta

714-427: The angle between the light and the boundary is greater than the critical angle . As a result, the fiber transmits all rays that enter the fiber with a sufficiently small angle to the fiber's axis. The limiting angle is called the acceptance angle , and the rays that are confined by the core/cladding boundary are called guided rays . The core is characterized by its diameter or cross-sectional area. In most cases

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748-409: The core's cross-section should be circular, but the diameter is more rigorously defined as the average of the diameters of the smallest circle that can be circumscribed about the core-cladding boundary, and the largest circle that can be inscribed within the core-cladding boundary. This allows for deviations from circularity due to manufacturing variation. Another commonly quoted statistic for core size

782-449: The distance between the water in the hole and the ice surface. The vehicle should be removed before the water reaches the surface in that hole. Another reason why the amount of freeboard matters is that if the water makes its way onto the ice surface (through cracks and fissures), the ice cover's bearing capacity diminishes rapidly, which can accelerate breakthrough. For long-term loads, a professional engineer may have to be consulted. As

816-429: The ice cover tensile strength. Although recommended values for A range from 3.5 to 10 kg/cm (~ 50–150 lbs/in ), lower bound values are generally those that are used for safety purposes. This level of conservatism is justified because, unlike human-made materials such as steel or concrete, natural ice covers inherently contain a large amount of structural flaws (fractures, water and air pockets). Moreover, for

850-541: The ice cover, which would compromise its ability to support the weight it has been designed for. Maintenance comprises two main tasks: An ice road will typically be closed as a result of deterioration of the running or operating surface, before there is any risk of ice cover failure. Surface deterioration can happen when the ice surface becomes too soft, or because of an excessive amount of meltwater on its surface. Mid-season road closures can also happen for similar reasons, and also because of inclement weather, such as

884-415: The ice for too long, deformation will continue via microcracking, leading to the collapse of the ice cover below the vehicle. Recommendations vary as to how this can be avoided. Some sources prescribe a maximum of two hours for a stationary load, which is also what Gold recommended. Others advise to use the freeboard of the ice as an indicator, which can be done by drilling a hole in it and monitoring

918-415: The ice, the following factors need to be considered: Snow cover removal is the first major operation in an ice road construction scheme. It may only begin once the ice thickness is safe to support the machinery used for that operation. There are two ways of doing it, depending on available equipment and state of practice for that particular road. One is to pack the snow layer with tracked vehicles into

952-617: The parliament of Finland. The Tana is well known for its excellent salmon fishery and is the most productive salmon river in Finland and Norway. The world's record for Atlantic salmon is held by a salmon caught on the Tana; it was 36 kilograms (79 lb) and was taken in 1929 by the Nils Mathis Walle. In 2023, Norwegian authorities constructed a barrier with a trap that has sorted out hundreds of humpback salmon (on some days), while allowing other fish to pass. The installation

986-421: The river for most of the length of the river. In winter, there are usually two ice roads that are in use from December to April. These roads are located near Rustefjelbma and near Polmak and have a weight limit of 2 tonnes (2.0 long tons ; 2.2 short tons ), but few other limitations. [REDACTED] Media related to Tana River (Fennoscandia) at Wikimedia Commons Core area The core of

1020-407: The river was 4,426 kilograms (9,758 lb). Both Finland and Norway regulate the fishing on the river. During the years when the authorities permit fishing, one can purchase a fishing permit (for angling ). Some residents, can get a permit for fishing with barrier net ; ['salmon-letter owner' or] laksebreveier use net for fishing. New fishing rules, are being considered (as of March 2023) by

1054-490: The river). In 2023, on Finland's side of the river, some permits would allow fishing of humpback salmon - and the methods for that would be drift netting and seine fishing. In 2020, 18,600 kilograms (41,000 lb) was the annual total of salmon captured in the river. Previously, in 2002, fishermen on the river captured an annual total of 99,546 kilograms (219,461 lb) salmon, with an average size of 4.5 kilograms (9.9 lb). The annual sea trout catch for that year on

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1088-489: The river, applications were made to allow for young people to learn salmon fishing; however, individuals are not allowed to apply - applications must be made by an association or a "fishing area". In July 2024, there was salmon fishing for two days on the Finnish side of the river - and only in two places; only one fish 30–65 cm in length. Earlier (2022), authorities in Norway and in Finland [did] not permit salmon fishing (in

1122-421: The vehicle for emergency purposes; they can also come in handy when traveling on a winter road with grades steeper than 8% on over-land segments. Signage may indicate speed limits, for instance a maximum of 25 km/h (16 mph), and spacing between vehicles, for instance 500 m (1,600 ft) for loads more than 12,500 kg (27,600 lb). These restrictions are to decrease the risks of damage to

1156-431: Was captured by satellite imagery. When an ice road is part of a winter road , as is commonly the case, its design and construction is comprised within the overall road planning, i.e. in conjunction with the over-land segments. Either way, factors that need to be addressed before construction include the following: Factors that need to be considered in route selection include the following: Before first access to

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