Winter is a magical time that is known for its wonders in the form of snow and ice underfoot. Many children's winter Games associated with them: sledding and skating, snowball fights, making a snowman. However, when entering the ice, there is a danger that it is not strong enough. How can you measure its strength? Color! If you know what color the solid ice is, then by sight you can determine whether the danger lies in wait for a person in this area or it is safe here.

The color of ice in the ocean

Despite the common misconception that different shades appear due to impurities in the water of any substances, ice has its own color, like snow. So, crusts of ice in the ocean, which have not endured a single summer, are white. Why? Because the water there is restless and when it freezes, thousands of air bubbles turn out to be inside. They provide white young ice and serve as an identification mark.

And what color is the ice that survived the winter? After the winter has passed, the crust begins to thaw and freezes again by the next winter. The upper layer no longer has bubbles, and every year there is more and more dense ice. It acquires a blue hue, and quite old - blue and azure.

What color is ice?

The color changes in contrast to the density. For example, the first ice is like a gossamer - thin and transparent. It has no color and it is immediately noticeable that it is dangerous, but beautiful. Melted or not dense enough - yellow. This is not a bright color, but only a straw shade, but it is noticeable.

Ice turns green when the water has been frozen for a long time. Often this depends on the color of the water itself, but it can be due to the refraction of light or the composition of the ice. In addition, another answer to the question of what color is ice is white. It is not uncommon to see white patches on frozen puddles in winter. This is a thin crust, entirely consisting of voids in the form of air bubbles. Well, and also - blue, a deeper shade, so beloved by artists. It is inherent in ice floes at a depth.

What color is the strongest ice?

Two colors are considered the most reliable: green and blue. When thinking about what color ice is, one cannot take into account only the bright shades of these colors. This is important to consider. If the ice is unnaturally bright, there is every reason to believe that this is not its color. Or something was in the water and could affect the quality of the ice when freezing, or it was spilled after freezing, which could also affect its density.

Thinking about what color the ice is, you need to show not only research curiosity, but also apply knowledge in practice: having noticed a person in an unsafe area in time, you need to get him out of there. Even more useful is to know how to act when a person, without calculating the thickness of the ice, fell under a thin crust of frozen water.

Thus, ice can be called an amazing state of water. It gives not only amazing sensations when riding it, but also pleases the eye, allows you to develop caution and makes you treat it as a dangerous element. Therefore, knowledge about the color of strong and weak ice helps to save the life of oneself and those who find themselves in a dangerous situation.

As soon as the reservoirs are covered with a crust of ice, a whole army of connoisseurs of winter extreme sports immediately appears - fishermen, tourists, lovers of sledding off the mountainous bank of the river or those who want to turn part of the river or pond into a skating rink. Motorists are also on the alert: finally, they do not need to get to the nearest bridge or crossing, because there is an ice road! Residents of lake and river regions arrange pedestrian and automobile crossings to shorten the path to their destination. How can you tell if it's safe to walk, drive, or skate on the ice? It is not worth risking endangering yourself and your comrades: there are special rules for each of these cases. If you have children, be sure to teach them how much first ice is safe. It is easier to prevent an accident than to save someone who has fallen on fragile ice!

For a person

Experienced hunters and fishermen are able to recognize the approximate thickness of ice by its color. Blueish or "green" ice is considered strong, and the more transparent the ice cover, the stronger it is. Matte white or yellowish color indicates unreliability. If you see a section of the river under the ice, on which there are no traces of animals and humans, think about why. Most likely this is the place where the springs hit, the ice crust there is very thin, and because of the snow it is not visible.

You need to know:

1. Ice at least 10 cm thick in fresh water and 15 cm thick in salt water is considered safe for humans.
2. In the mouths of rivers and channels, the strength of ice is weakened.
3. The ice is unstable in places of fast currents, gushing springs and runoff waters, as well as in areas where aquatic vegetation grows, near trees, bushes, and reeds.
4. If the air temperature is above 0 degrees for more than three days, then the strength of the ice is reduced by 25%.

Video about the rules of being on the ice

Fix the material ice strength:

• blue ice - strong,
• white - its strength is 2 times less,
• dull white or with a yellowish tint - unreliable.

Should not be treated winter walks thoughtlessly and not to prepare in advance. It is very difficult for a person who has fallen through the ice to get out, since the edges of the polynya will break off under its weight. An adult or a child can drown from hypothermia, which occurs after a quarter of an hour. Some people get cold shock.

You can download a memo about safety and rules of conduct on ice after the article

For winter crossing

We present the data in the table below.

Safe thickness, m		Taking into account the weight, t
where there is fresh water	where the sea water
0,10	0,15	up to 0.1	5
0,20	0,25	up to 0.8	10
0,25	0,30	up to 3.0	20
0,35	0,45	up to 6.5	25
0,40	0,50	to 10	26

For technology

Safe thickness, m		Taking into account the weight, t	Taking into account the distance to the ice edge, m
where there is fresh water	where the sea water
0,70	0,55	up to 20	30
100	0,95	up to 40	40

When organizing a crossing for equipment, the following factors are taken into account:

• the depth of the reservoir;
• flow rate;
• the distance between the banks of the river;
• traffic intensity;
• when a hydroelectric power plant is located nearby, the route calculation data is compared with the operating mode of the hydroelectric power plant.

Theory and practice

The ice track is cleared of snow on both sides of the axis (not less than 10 m) and marked with milestones (every 15-20 m). Since the traffic on the track is one-way, the road with reverse traffic should be laid at least 100 m. see. The holes are arranged according to the principle of chess cells at a distance of 5 m from the axis in the direction in both directions. For safety, they are fenced with a snow embankment around the circumference and covered with wooden shields. The emerging "hanging" of ice is brought down mechanically. Measurements are made by the local hydrometeorological service every 5 days, and more often in case of thaws.

In addition to the weight of the equipment, adjustments are made for traffic intensity according to the formula:

H tr \u003d n a P

It takes into account:

• H is the ice thickness;
• n is the coefficient of traffic intensity (with a throughput of 500 cars per day, the indicator n is equal to 1, if 1 is 500, then 400 is 0.8, etc.);
• a is an indicator of the load characteristics (wheeled, caterpillar);
• P is the mass of the load, t.

The formula can be supplemented, depending on the characteristics of local conditions.

As you can see, it is much easier to secure the movement of one person, but only if this person follows the rules. Ultimately, the table of permissible ice thickness (and load on it) when organizing the crossing of equipment will look like this:

Required ice cover thickness (cm) taking into account the average daily t for the past 3 days			Distance between cars, m
– 10 ° and below	- 5 °С	With a short-term thaw to 0 °
Tracked vehicles
4	18	20	28	10
6	22	24	31	15
10	28	31	39	20
16	36	40	50	25
20	40	44	56	30
30	49	54	68	35
40	57	63	80	40
50	63	70	88	55
60	70	77	98	70
Wheeled vehicles
3,5	22	24	31	18
6	29	32	40	20
8	34	37	48	22
10	38	42	53	25
15	46	50	64	30

Amendments and clarifications

When using the table, it should be taken into account that the average daily temperature and “ideal” conditions for the formation of the “freshwater shelly” ice variety are taken. The porous ice thickness will have to be doubled. In the presence of salt water in the reservoir, the correction factor is reduced to 1.2. With frequent thaws, the carrying capacity of each piece of equipment is determined in a practical way.

If necessary, the ice cover is artificially thickened, clearing the space for this, pouring water on it and waiting for the layers to freeze. If it is required to transport equipment to the place of diving operations in places where ice covers sea water bodies, the conditions change as described in the first table of the article.

But let us return once again to the requirements of behavior in winter on a river or a pond, which are valid for a person, and especially for children, who are more often than adults are unreasonable. It is believed that the ice for the safe presence of a person on it must be at least 10-15 cm (depending on the water, fresh or salty). When mass events on ice, the norm increases to 25 cm. You should also know how to behave if someone (or yourself) fell through the ice, because panic can lead to a sad outcome.

When the seemingly strong ice for safe movement has been replaced by porous and brittle, you can suddenly find yourself in the water, pull yourself together and follow the recommendations:

1. Spread your arms to the sides so that you can lean on without breaking the edges of the “font” and not choking.
2. You will have to crawl out of the hole, avoiding jerky movements. If you have "ice awls" and a rope with you, use them for pulling up.
3. The main rule: do not rely on individual sections of a small area, but try to position yourself so that the largest area serves as a support.
4. Roll away from the edges of the dip, and when standing on your feet, do not run, move slowly and without raising your legs above the ice surface.
5. When assisting a fallen one, find something that will help expand the area of ​​\u200b\u200bsupport ( Sports Equipment, plywood, plastic).
6. Do not stand on the edge of the hole, act at the optimal distance.
7. Throw the rope to the one who is in the hole and pull with uniform movements, helping to get out.
8. When you get home, change the victim's clothes, give him some tea (no alcohol added!) and call an ambulance.

Rescuers operating in conditions where movement on ice is required should remember:

1. When choosing a route, you need to remember about drifting ice (on the sea, lake), find out the speed and direction of the current, wind.
2. It is worth stocking up on anti-slip devices.
3. On water with currents, the thickness of the ice can be different everywhere.
4. In swamps, unlike rivers, the ice is stronger in the center and weaker at the edges.

Rules of conduct on a frozen pond

1. Do not experiment with checking the strength of the cover with your feet, take a pole with you.
2. Find existing trodden paths.
3. If you are one of the first to build such a hiking trail, test the strength of the ice in front of you with a stick, avoid places that do not inspire confidence.
4. Remember the signs of a fragile coating: crackling, mobility, the appearance of water above the surface. If this happens, move from this place with your legs apart, slowly or even crawling.
5. You can not move in a company (between travelers or skiers you need gaps of at least 5 meters), with skis fastened to your legs, with ski poles attached to your hands.
6. Anglers need to count the number of holes in a certain area and drill them at a considerable distance from each other.
7. If you have a load (satchel, backpack), it is better to secure it with a rope and drag it at a distance.
8. If it becomes necessary to overcome an area of ​​unstable ice, go there with a belayer. Even moving at a distance of 5 meters, he will help in case of an accident.
9. If you have the opportunity, it is best to drill a hole and measure the thickness of the ice before your winter hike.
10. It is not recommended to fish near melted or damaged areas of ice.
11. Stock up on a twelve meter (or longer) rope, at one end of it there should be a load.

Failure to comply with safety rules at water bodies in the autumn-winter period often causes death and injury to people. Only last year during this time two people died on the reservoirs of the Spassky district.

To avoid accidents, it is necessary to follow the rules of safe behavior on the water. What are they?

Sergey SHALASHOV,

state inspector of the Kamsko-Ustyinsky inspection site.

Autumn ice from November to December, before the onset of stable frosts, is fragile. Bonded in the evening or night cold, it is initially able to withstand a small load, but during the day, quickly heating up from the melt water seeping into it, it becomes porous and very weak, although it retains sufficient thickness. And this year, besides, constant temperature drops do not allow to gain a foothold on the reservoirs of a solid ice surface.

In order to avoid tragedies, it must be taken into account that water bodies, as a rule, freeze unevenly: first near the coast, in shallow water, in bays protected from winds, and then in the middle. On the same body of water, one can find alternation of ice, which, with the same thickness, has different strength and carrying capacity.

The main condition for the safe stay of a person on the ice is that the thickness of the ice corresponds to the load. For one person, it should be at least 10 centimeters, for a pedestrian crossing - 15, for the passage of cars - at least 30.

Ice strength can be determined visually. For example, blue ice is considered the strongest, white ice is half as strong, and gray, matte white and with a yellowish tinge is generally unreliable. Particular care must be taken when the ice is covered with a thick layer of snow, blocking the access of cold to the surface. The use of skating rinks located on water bodies is allowed only after a thorough check of the strength of the ice. Its thickness must be at least 12 centimeters, and for mass skating - at least 25.

In no case should you go out on the ice at night and in poor visibility (fog, snowfall, rain). It is safest to go ashore and go down to the ice in places where it is visible, that is, not covered with snow. In case of a forced crossing of a reservoir, it is safest to stick to beaten paths or go along an already laid ski track, or use ice crossings. But if they are not there, before descending onto the ice, you need to look around very carefully and outline the upcoming route. The frozen pond is best crossed on skis. At the same time, they must be unzipped so that they can be thrown off if necessary. ski poles should be held in hands, not throwing loops on the brush. If you have a backpack, it is better to hang it on one shoulder - this will also make it easy to free yourself from the load, if necessary.

No need to go on the ice alone, in unfamiliar places, especially at night. And, of course, special control during this dangerous period should be established for children who are very fond of skating on ice. But they, like adults, should know and remember that this is far from safe. Be careful!

Study of the physical and mechanical characteristics of road icing

Troshin D.I. - postgraduate student. Scientific adviser: Ph.D., associate professor Chabutkin E.K. Yaroslavl State Technical University snow cover cannot be regarded as a substance with a definite structure. Depending on the state and properties of the snow-ice cover can be divided into five categories: freshly fallen snow, retaining the original crystalline form of snowflakes; stale snow that has changed its structure by precipitation; snow crust formed by mechanical action or variable temperature conditions; snow-ice crust, formed during further compaction and freezing of the snow crust; ice, when all the snow crystals turned into ice. Group 1 - ice formation as a result of sublimation of water vapor, i.e. its transition directly into ice, bypassing the stage of water (hoarfrost and crystalline hoarfrost); group 2 - the formation of ice mainly due to the precipitation and freezing of supercooled water drops (granular frost and ice); Group 3 - ice formation due to precipitation and freezing of non-supercooled water (icy ice) and freezing of wet snow. Consideration of the classification of icing groups is possible in winter, when, after a thaw, a sharp cold snap occurs or when light rain falls or steam is deposited on the cooled surface of the road surface. Assuming that the icing process is characterized by an air temperature close to 0°C at an air humidity of 90-95%. Snow-ice run-ups in the border strip do not have a definite structure. A feature of such icings is pollution. Studies conducted at the Department of SDM YaGTU showed that the percentage of impurities, on average, is 7 ... 12% of the total volume, but there are also heavily polluted icings, reaching fifty percent of impurities. Snow-ice run-ups in the border strip can be classified according to the types of inclusions, of which three main ones can be distinguished: with sand impurities; with the inclusion of water-oil emulsions (places for washing cars and service stations); with the inclusion of various fine materials (entrances from adjacent dirt roads). For urban roads, the most typical type of icing with sandy impurities and their volume is 90% of the total number of surveys. Therefore, further we will consider only this type of icing. When choosing a method for dealing with icing on roads, the following basic physical and mechanical properties of ice can be distinguished: ice adhesion to other materials, hardness, strength, heat capacity, thermal conductivity, latent heat of melting, density, porosity. However, in the process of developing icing on roads, not all physical and mechanical properties of ice equally affect the working body of ice-cutting machines. Let us single out those properties of ice that significantly affect the process of its destruction.

Study of the physical and mechanical characteristics of road icing. Page 2
Density pure ice at 0°C and at a pressure of 0.1 MPa it is 916.8 kg/m³, but depending on the conditions of ice formation, temperature, structure, presence of various impurities, ice can have a density of 760 to 950 kg/m³. The compressibility factor is 2·10B -5 . The melting point of pure ice at a pressure of 0.1 MPa is 0°C. In turn, an increase in pressure by 0.1 MPa leads to a decrease in the melting point by 0.0075°C. The coefficient of linear expansion is equal to 5.07·10 -5 in the temperature range from -5 to -10°C. The heat capacity of ice at constant pressure is: 2.1172647 + 2.7000084 t, (J/kg °C), where t is the temperature (taking into account the sign). Thermal conductivity coefficient: C = 2.219004 (1 + 0.62802 t), (W / m ° C) The difference in thermal conductivity coefficients for -20 and 0 ° C is only 3%, therefore, the thermal conductivity coefficient is assumed to be constant C = 2.219 (W/m·°С) or Cl=0.0053 (cal/cm·s·°С). Ice strength. Various literature sources provide data on the strength of ice, a wide spread of these data is explained by the fact that the strength of ice depends not only on temperature, but also on a number of other factors: the presence of impurities, structure, load application rate, etc. In addition, ice constantly the process of recrystallization occurs by moving the boundary between the crystals, changing the shape and size of the crystals. Ice porosity as hardness and strength depend on the density of ice, the greater the density of ice, the less porosity. Table 1 presents ice porosity data. Table 1 - Dependence of ice porosity on density Based on observations, it was determined that the density and porosity of ice are related by the dependence where q - porosity; ρ 0 - density of monolithic ice; ρ is the density of the investigated ice. The main feature of ice is that under normal conditions it is at temperatures close to the melting point, therefore it contains a certain amount of a liquid phase, which acts as a lubricant when the crystals slide relative to each other. In addition, ice does not enter into chemical reactions with other substances, and does not form solid, indestructible materials.

Ice crush resistance. Numerous experiments by various scientists have shown that the resistance of ice varies over a wide range depending on its structure, porosity, temperature, the presence of impurities, the direction of compression relative to the location of the crystals, etc. In the process of compression, ice samples begin to break down before the stresses in it reach the tensile strength . The conducted studies have shown that the presence of inclusions in the snow-ice massif significantly affects the strength characteristics of ice. The load leading to destruction can be 2-3 times lower compared to pure ice. The tensile strength of ice also strongly depends on temperature and increases with its decrease. This dependence can be expressed by Korzhavin's empirical formula σ = А + В·θ, where θ is the negative ice temperature, °С without a minus sign; A and B are empirical coefficients in the temperature range from 0 to -10°C, A ≈ 15 and B ≈ 3.4. However, the presence of impurities in the structure of ice formations also greatly changes the pattern of changes in strength characteristics depending on the temperature factor. If the differences in the strength characteristics of pure ice and samples with impurities at a temperature of -5°C can reach up to 40 ... 50%, then at higher temperatures this difference can be already 60 ... 70%. Ice tear resistance in tension depends mainly on the same factors as the crushing resistance, only the tensile strength is less. The amount of tensile strength is affected by the presence of impurities. If ice samples under compression after the appearance of cracks can allow a further increase in the load, then at break, the destruction occurs simultaneously. Ice fracture resistance determined by bending ice samples. The magnitude of the ultimate strength in this case depends on the sample size. According to I.P. Butyagin, the tensile strength of large specimens is, on average, three times less than that of small specimens. According to the data of K.P. Korzhavin, the tensile strength at fracture resistance depends on the loading rate. With an increase in the bending speed from 0.00033 m/s to 0.003 m/s, the ultimate strength decreased from 0.92 to 0.36 MPa. Ice shear resistance. The tensile strength of ice in shear is less than in tension, according to B.P. Weinberg, on average, almost twice σ growth = 1.11 MPa, σ av = 0.58 MPa. Shear strength increases with decreasing temperature and can vary depending on the structure of the ice and the direction of the cut relative to the direction of the axes of the crystals. Thus, according to its physical and mechanical properties, ice can be attributed to quasi-isotropic solids with elastic-plastic properties, but under shock loads it behaves like a brittle body due to the presence of impurities, cracks and pores. The values ​​of the ultimate strength of ice under various deformations are ambiguous, since the resistance to acting loads depends on the conditions for the formation of the ice cover.

In ice there are always cavities with brine and cavities filled with air or gases. The ratio of the volume of bubbles with gas or air to the total volume of the ice sample, expressed as a percentage, is called ice porosity . Sea ice porosity can range from 5 to 13%.

Density fresh ice , devoid of air bubbles, at a temperature of 0 0 C is 0.918 g cm 3, and the specific volume is 1.090 cm 3 g -1. Consequently, during ice formation, the specific volume increases (density decreases) by about 9%.

Density sea ​​ice depends on temperature, salinity and porosity. The density of ice determines the draft (immersion) of floating ice, which for fresh ice is about 9/10, and for sea ice - up to 5/6 of their thickness.

Formation (crystallization) of sea ice does not occur at some fixed temperature, as with fresh ice, but continuously from the freezing point of sea water to the temperature at which all the brine will freeze. The melting (melting) of ice also occurs continuously as the temperature rises.

The color of ice, like water, is explained by the selective absorption and scattering of light rays and depends on the size and amount of impurities in it. Completely clean, fresh, devoid of air bubbles, ice, when viewed in a large piece, appears pale blue.

Ice found in the sea, according to the color or hues seen in large masses of ice, can be roughly classified into brown, white, green, and light blue or blue.

The initial types of ice - ice fat, sludge, thin moistened young ice - have a dark gray color with a steel tint. As the thickness increases, the color of the ice changes to light gray and then to white. When melting, thin ice floes moistened with water again take on a dark gray color.

There is ice of green, red, pink, yellow and even black colors, which are explained by the presence in the ice in large quantities of various mineral and organic suspensions (bacteria, plankton, eolian particles, etc.).

§ 7. Ice strength

Ice strength is understood as the property of hull structures to maintain local strength (i.e., not receive damage) under the action of ice loads that occur when an icebreaker moves in ice and during ice compression. The ice strength of a ship is determined by its size, the shape of the lines, the material and design of the hull, the speed, as well as the thickness and physical and mechanical characteristics of the ice cover.

Ice loads acting on the hull of an icebreaker when operating in ice are significantly higher than the local loads of other types of ships. The nature of ice loads: impacts on the ice during the operation of the icebreaker incursions or during continuous movement in ice, static pressure during ice compression. The greatest dynamic loads in the nose end occur when hitting the ice. The aft end is subjected to significant dynamic loads during reverses and when working in reverse. Impact ice loads are local in nature and are applied mainly in the area of ​​the active waterline. During ice compression, the pressure of ice on the hull is distributed over a significant section along the length of the hull.

Determining the magnitude of the design ice loads acting on the outer skin and framing is the first step in the design and calculation of icebreaker hull structures.

Canadian shipbuilders proceed from the assumption that the ice load is distributed along a 0.9 m high belt, and it is applied in the most unfavorable way - in the area between the load waterline and the waterline corresponding to half the draft. For ships with shell thickness less than 25.4 mm and spacing over 508 mm, the ice load is considered to be applied directly at the waterline. Ya. E. Yansson considers this assumption acceptable for icebreakers operating in middle latitudes.

In the design and construction of Wind-type icebreakers, American specialists were guided by an ice load with an intensity of 210 kgf / cm ^, distributed along the waterline along a narrow belt. The width of this belt was taken such that the total force created by the ice pressure was sufficient to squeeze out the icebreaker's hull during compression. Such a calculation scheme leads to an overestimation of the area of ​​application of the ice load by several times and, thereby, to an underestimation of the acting loads and stresses. In addition, it is not taken into account that the loads in the extremities arising from impacts with ice can significantly exceed the loads from compression of the hull by ice. The main factors on which the magnitude of the ice load depends are insufficiently taken into account: the shape of the hull contours, the speed of the ship in ice, the thickness and strength of the ice.

Table 4

Ice load intensity when calculating the onboard set of a powerful icebreaker

Load intensity, kgcm""

Hull area----_._

on frames on stringers

Fore end 80 47

Middle part 40 24

Aft end - 60 35

When building Moskva-type icebreakers in Finland, Finnish shipbuilders used the recommendations of Soviet specialists. The side plating of these icebreakers was calculated for an ice pressure of 100 kgf/cm^ in the bow, 50 kgf/cm^ in the middle part, and 75 kgf/cm^ in the aft end. The intensity of the ice load on the frames and side stringers, adopted in the calculation of hull structures, is indicated in Table. 4 . The experience of designing the hull structures of icebreakers of the Moscow type turned out to be successful: during many years of operation, their hull structures (with the exception of the bottom ones) did not have significant ice damage.

in the USSR, d. E. Kheisin and Yu. When substantiating this method, the ice cover was considered as an isotropic plate lying on an elastic foundation (water). Ice was considered to be a completely elastic material, and its elastic constants and tensile strength values ​​were taken from the data of natural experiments. When determining impact loads, a given configuration of the ice floe edges was conditionally accepted. In order to clarify the obtained solutions, the calculated ice loads were compared with the actual strength of floating vessels. At the same time, information about ice damage and data from the experience of operating icebreakers in the Arctic and in the freezing non-Arctic seas were taken into account.

The calculation method developed on this basis is suitable for icebreakers of all classes. It allows, when determining the ice loads, which are assigned at the extremities based on the conditions of impact on the ice, and in the middle part of the hull - from the conditions of static compression by ice fields, to take into account the dimensions of the icebreaker, the shape of its hull and speed, as well as the ice conditions in which it floats. Following are the main dependencies of the specified method.

Loads on board set. The magnitude of the ice load depends on the configuration of the ice floe edge in the area of ​​contact with the side. As the analysis shows, the edge outlined along the arc of a circle (assuming a radius value in the range from 10 to 40 m) leads to the distribution and values ​​of ice loads that are in good agreement with the data of full-scale tests and the experience of operating ships in ice. Ice load in tf/m acting on the bow of the icebreaker,

* For salty arctic ice upon impact is 350-600 tf/.n^ .

The coefficients k^, k^, ku and k^ are determined from the graphs of Fig. 44-47. The values ​​of the angles a and P are taken at the level of the design waterline^.

Ice loads for the side framing in the middle part of the hull are determined based on the conditions of static compression of the icebreaker by ice. As the design loads acting on the ship's hull in compression, the ultimate loads are accepted that destroy ice of a given thickness. Observations show that near the side of the icebreaker, the destruction of the ice cover during compression occurs mainly from bending, which is explained by the significant inclination of the side to the vertical. Taking into account what has been said, cases of compression of icebreakers having in the middle part "inclined" f > 8°) or "vertical" (Р<8°) борт, рассматриваются отдельно.

^ To check the accuracy of measuring angles a "and B, you need to stand,

1T.^p^^T.\"Tc "" """"""" short?atGnoGpGv„"o?;iRk;;!

smooth them out and enter the corrected angles into the calculation.

k^=y 1oN ~~ ultimate strength of ice in bending;

/r^, - ice thickness (Fig. 50).

The design load in tf/l in the middle part of the hull of icebreakers with a "vertical" side is determined by the formula

where k^ is a coefficient equal to 62 for salt ice and 73 for fresh; k is the calculated thickness of ice during compression, m. Ice loads acting on the aft end are determined from the condition of the icebreaker hitting the ice when reversing or when the stern piles up on the ice edge when yawing. The stern is in lighter conditions than the bow. In addition, the shape of the stern of icebreakers is very favorable for the perception of ice forces due to the greater inclination of the side in the stern. Because of this, the value of ice loads in the aft end is assigned in fractions of the maximum load acting on the fore end:

(14)

The value of the coefficient k = 0.7 was assigned based on the condition of the stern hitting the ice at a speed of 4-5 knots. The load in this case must be at least 30% higher than the load in the middle part of the icebreaker. The extent of the aft end reinforcement area should be about 20% of the ship's length, counting from the aft perpendicular.

Load on the outer (side) skin. An analysis of the interaction of the hull with ice shows that the contact pressures that develop during the crushing of the ice edge depend on the mass of the icebreaker, the shape of its contours, speed, and also on the physical and mechanical characteristics of the ice. Due to the fact that some characteristics of the ice cover are not well understood, a rigorous determination of the calculated value of contact pressures seems difficult, and when assigning ice loads to the skin, the recalculation method from the prototype is used.

In this case, it is assumed that the ice load is distributed over the outer shell, and the distribution zone has the form of a spot stretched along the ship for several spacings. This gives reason to believe that in the considered section of the side, the intensity of the design load on the side plating p is proportional to the intensity of the design load on the side framing, i.e., p / ro \u003d CІTs, where the designations without an index refer to the icebreaker under consideration, and with the index O - to the ship -prototype.

For ships close to the prototype, we can assume that the conditions of their operation in ice are similar. Consequently, the parameters characterizing the physical and mechanical properties of ice, the configuration of the ice floe edge, as well as the speed of movement in ice, will be the same for both icebreakers:

It is also assumed that the intensity of the ice forces acting on the hull depends on the shape of the hull only to the extent that it affects the impact force, i.e., the reduced mass of the vessel and its reduced speed, and practically does not depend on the edge collapse geometry ice. The expression for the intensity of the ice load on the skin upon impact with a floating ice floe can be written as

where Рн is the intensity of the ice load on the skin in the fore end; - weight of the icebreaker; Ma is the mass of the ice floe.

In the case of a collision with a large ice field (M^M^ -> 0), formula (15) is simplified:

P" \u003d (P "o-" ° " ■ (16)

The ratio of the displacement of the icebreaker and the prototype close to it is approximately equal to the ratio of the cubes of their lengths. Considering this circumstance and the equality V = V0, formula (16) can be written as follows:

where L is the length of the icebreaker between perpendiculars, m;

ka \u003d (l.6cosß + 0,ll) "^ ° _ jn^ _ coefficient taking into account the influence of the angle of inclination ß of the frames to the vertical (t is the coefficient determined from the graph in Fig. 44);

Values ​​of coefficient k for icebreakers of different classes

I class .............. 30.5

II » ...............24

III » ...............18

The intensity of the ice load in the middle part of the hull, determined from the conditions of compression of the vessel in ice,

Pc = (Pc)o]/-57-^--|. (18)

where designations with a zero index refer to the prototype vessel. If we take as a prototype a powerful icebreaker with a structural strength of the side plating (pjo = 520 tf/m^), then the maximum thickness of ice, the pressure of which this icebreaker can withstand, can be taken equal to 4 g, and the limits of ice crushing strength (ojo = 250 tf/m m^ and for bending (Ор)о = 125 tf/m^ Taking into account what has been said, formula (18) is transformed:

p, = 0.52

If the strength characteristics of ice do not change during the transition from the prototype to the designed icebreaker, i.e. if

Oe/(Oe)o =^ öp/(Op)o = 1, then Pe = 82/1 i/h.

The intensity of the ice load on the plating in the aft end Pk is assigned according to the formula where k" - a numerical coefficient equal to 0.7.

The load Pk must be at least 30% higher than the load in the middle part. The length of the hull reinforcement area at the aft end should be taken equal to 20% of the ship's length.

When ships move in ice, in addition to "direct" impacts, "reflected" impacts are also observed, when the ship, having hit the side of the ice, sharply deviates in the opposite direction and hits the ice with the other side. The velocity projection on the normal to the side during the second impact is greater than during the first one. Accordingly, contact forces also increase, which sometimes leads to serious damage, as a result of which, in a number of cases, significant deformations of the side plating and framing were noted, for example, on the Ermak icebreaker during its first Arctic voyage, as well as on some transport ships of ice categories.

Ice loads in the bow, taking into account the reflected impact, will be greater than those given above [see Fig. formulas (10), (11), (17)], and are defined as follows:

X is the distance from the midsection of the section along which the reflected blow fell.

Other designations are the same as above. The graphs of the functions! q (P) and fp (P) are shown in fig. 51.

According to the found values ​​of the intensity of ice loads, their diagrams are built along the length of the icebreaker (Fig. 52, 53). Diagrams straight

they are laid in separate sections, based on design considerations (for example, taking into account the location of bulkheads). The theoretical load curves for the skin and fore end set are straightened in such a way that the number of sections does not exceed two or three. The values ​​of the intensity of the ice load of straightened diagrams are calculated for the side framing and the ice belt plating.

Loads on decks and transverse bulkheads. The design loads on decks and transverse bulkheads are assigned based on the design loads on the side framing. Formulas for determining these loads are given in § 21 and 22, where strength and construction of ice decks (platforms) and transverse bulkheads are considered.

Stud loads. A detailed theoretical analysis of the ship's stem impact on ice and the determination of the loads arising in this case were carried out in the work.

The ice strength of an icebreaker is ensured, however, not only by the assignment of ice loads and the choice of the appropriate material and design of its hull, but also by the fulfillment of a number of operational requirements. The most important of these requirements is the observance of a certain "permissible" speed in ice, the excess of which can lead to ice damage to the hull. The permissible speed of movement in specific ice conditions is determined by the power of the power plant and the strength of the icebreaker's hull, which perceives ice loads. For practical ■ determination of the safe possible speed of movement, it is necessary to have curves of ice and ultimate strength. The ice strength curve is calculated according to the method described above. It corresponds to the speed of movement at which the stresses arising in the hull structures during the interaction of the hull with ice are equal to the yield strength of the material. The ultimate strength curve is determined based on the calculation of structures in the elastic-plastic zone and corresponds to the speed of the icebreaker, at which the bearing capacity With the help of these curves, constructed in the coordinates V - k plotted on the graph of ice propulsion (see § 11), it is possible to determine the safe speed of the icebreaker in given specific and predicted ice conditions under various operating modes of the power plant.

Exit to a frozen body of water is always accompanied by the risk of falling through the ice. Therefore, when moving in winter along a lake or river, it is necessary to observe safety measures, be vigilant and careful.

It is believed that for the safe exit of one person on the ice, its thickness should be at least 10 cm, for a group of 4-5 people - at least 15 cm, with a mass exit on the ice - at least 25 cm.

First of all, anyone making even a short walk across a frozen body of water should have a stick with them. Never test the density of the ice with a kick. Tap on the ice with a stick: if a puddle of water has formed under it, then the ice is not strong enough. If moisture appears, immediately leave the place where you are standing, sliding, without lifting your feet from the surface.

There are several external signs by which the strength of ice can be determined. Clean and transparent ice, which has a bluish or greenish tint, is formed in frosty, calm and rainless weather. The ice crunches underfoot. Even in thin sections, it does not break through immediately, but, as it were, warns of the danger of radial cracks diverging underfoot.

Ice with shades grey, matt white or yellow almost twice as weak as transparent. Such ice is formed during frosty weather with snowfalls and is frozen snowflakes. It is especially insidious, as it collapses without a warning crackle.

Absolutely fragile porous ice, which is snow frozen during a snowstorm. Areas of such ice must be bypassed.

The thickness of the ice, even on the same body of water, is not the same everywhere. Thin ice located off the coast, in the area of ​​rapids and rifts, at the confluence of rivers, on bends and meanders, near frozen objects, trees and reeds, in the area of ​​underground sources, in places where warm water and sewage drain into reservoirs. The danger is polynyas, ice-holes, holes, cracks, which are covered with a thin layer of ice. Try to avoid such places as far as possible to avoid trouble.

Ice under snow and snowdrifts is unreliable. The snow covering the ice acts like a blanket. Therefore, under it, the ice grows much more slowly.

Basic rules of safe behavior on the ice:

Children must not be allowed on the ice without adult accompaniment;

You can not go out on the ice at night and in poor visibility;

It is safest to stick to beaten paths or go along an already laid track;

Once on thin, crackling ice, you should carefully turn back and with sliding steps return along the path to the shore;

When crossing a reservoir in a group, it is necessary to maintain a distance from each other (5–6 m).

IT IS FORBIDDEN: able to go out on the ice alcohol intoxication, jump and run on ice, gather big amount people in one place.

If you fall through the ice - keep calm and composure. Even a poorly swimming person can stay on the surface for some time due to the air cushion formed under the clothes. And only as the clothes get wet, a person loses additional buoyancy. This time is usually enough to get out of the hole. It should be remembered that the most productive first minutes of being in cold water, until the clothes got wet, the hands did not freeze, the weakness and indifference characteristic of hypothermia did not develop.

Try to breathe slowly and deeply. Spread your arms wide to the sides and try to cling to the edge of the ice so as not to sink headlong. Turn back in the direction you came from. The ice was strong enough in this direction up to the emergency section. So, he must withstand you on the way back. You don't have time to check other routes. Try carefully, without breaking off the edge, without sudden movements, crawling with your chest, lie down on the edge of the ice, throw one and then the other leg on it. If the ice holds, slowly roll away from the edge and crawl (or roll) towards the shore.

Press Service of the Main Directorate of the Ministry of Emergency Situations of Russia for the Republic of Mari El.