Collapse - what is it? Causes and consequences of collapses. The most catastrophic collapses of the earth's surface over the past thirty years Collapses over the past 10 years

Landslides, mudflows and landslides are dangerous geological phenomena.

In 1911 In the Pamirs, an earthquake caused a giant landslide. About 2.5 billion m 3 of soil slid. The village of Usoy and its inhabitants were overwhelmed. The landslide blocked the valley of the Murgab River, and the resulting dam lake flooded the village of Saraz. The height of this formed dam reached 300 m, the maximum depth of the lake was 284 m, and the length was 53 km. Such large-scale disasters happen rarely, but the troubles they bring are incalculable.

Landslides are mass displacements rocks down the slope under the influence of gravity.

Landslides form in various breeds as a result of disruption of their balance, weakening of strength. They are caused by both natural and artificial (anthropogenic) reasons. Natural causes include an increase in the steepness of slopes, eroding their bases with sea and river waters, seismic tremors, etc. Artificial causes include destruction of slopes by road excavations, excessive removal of soil, deforestation, improper agricultural practices of agricultural land on slopes, etc. According to international statistics up to 80% of modern landslides are associated with anthropogenic factors. They can also arise from earthquakes.

Landslides occur when the slope is steeper than 10°. On clay soils with excessive moisture, they can also occur at a steepness of 5-7°.

Landslides are classified according to the scale of the phenomenon, activity, mechanism and power of the landslide process, and place of formation.

Based on their scale, landslides are divided into large, medium and small-scale.

Large Landslides are usually caused by natural causes and form along slopes for hundreds of meters. Their thickness reaches 10-20 m or more. The landslide body often retains its solidity.

Medium and small scale landslides are smaller in size and are characteristic of anthropogenic processes.

The scale of landslides is characterized by the area involved in the process. In this case, they are divided into grandiose - 400 hectares or more, very large - 200-400 hectares, large - 100-200 hectares, medium - 50-100 hectares, small - 5-50 hectares and very small - up to 5 hectares.

Based on their activity, landslides can be active or inactive. Their activity is determined by the degree of capture of bedrock of slopes and the speed of movement, which can range from 0.06 m/year to 3 m/s.

The activity is influenced by the slope rocks that form the basis of the landslide, as well as the presence of moisture. Depending on the quantitative indicators of the presence of water, landslides are divided into dry, slightly wet, wet and very wet.

According to the mechanism of the landslide process, landslides are divided into shear landslides, extrusion landslides, viscoplastic landslides, hydrodynamic landslides, and sudden liquefaction landslides. Landslides often show signs of a combined mechanism.

According to the place of formation, landslides are divided into mountain, underwater, snow and artificial earthen structures (pits, canals, rock dumps).

In terms of power, landslides can be small, medium, large and very large. They are characterized by the volume of displaced rocks, which can range from hundreds to 1 million m3. A type of landslides are snow avalanches. They are a mixture of snow crystals and air. Large avalanches occur on slopes of 25-60°. They cause great damage and cause loss of life. Thus, on July 13, 1990, on Lenin Peak in the Pamirs, as a result of an earthquake, a large derailment snow avalanche demolished the climbers' camp, located at an altitude of 5300 m. 48 people died. It was the biggest tragedy in domestic mountaineering.

Mudflows (mudflows). On June 8, 1921, at 24:00, a mass of earth, silt, stones, snow, sand, driven by a mighty stream of water, collapsed on the city of Alma-Ata from the mountains. This stream demolished the dacha buildings located at the foot of the city along with people, animals, orchards. A terrible flood burst into the city, turning its streets into raging rivers with steep banks of destroyed houses. Houses along with their foundations were torn down and carried away by a stormy stream. The result was great loss of life and enormous material damage. The cause of the mudflow is heavy rainfall in the upper part of the Malaya Almaatinka River basin. The total volume of mud-stone mass of 2 million m 3 cut the city with a 200-meter lifeless strip. It's just Selis a stormy mud or mud-stone flow that suddenly appears in the beds of mountain rivers.

The immediate causes of mudflows are heavy rainfalls, washing out of reservoirs, intensive melting of snow and ice, as well as earthquakes and volcanic eruptions. Anthropogenic factors also contribute to the occurrence of mudflows, which include deforestation and degradation of soil cover on mountain slopes, rock explosions during road construction, stripping operations in quarries, improper organization of dumps and increased air pollution, which has a detrimental effect on soil and vegetation cover.

one example of the disaster that a mudflow can bring.

When moving, a mudflow is a continuous stream of mud, stones and water. Mudflows can transport individual rock fragments weighing 100-200 tons or more. The leading front of the mudflow wave forms the “head” of the mudflow, the height of which can reach 25 m.

Debris flows are characterized by linear dimensions, volume, speed of movement, structural composition, density, duration and recurrence.

The length of mudflow channels can range from several tens of meters to several tens of kilometers. The width of the mudflow is determined by the width of the channel and ranges from 3 to 100 m. The depth of the mudflow can be from 1.5 to 15 m.

The volume of mudflow mass can be equal to tens, hundreds of thousands and millions of cubic meters.

The speed of movement of mudflows in individual sections of the channel varies. On average, it ranges from 2 to 10 m/s or more.

The duration of movement of mudflows is most often 1-3 hours, less often - 8 hours or more.

The frequency of mudflows varies depending on different mudflow-prone areas. In areas fed by rain and snow, mudflows can occur several times during the year, but more often once every 2-4 years. Powerful mudflows are observed once every 10-12 years or more.

Mudflows are classified according to the composition of the transported material, the nature of the movement and power.

Based on the composition of the transferred material, they are distinguished:

mud flows - a mixture of water, fine earth and small stones;

mud-stone flows - a mixture of water, fine earth, gravel, pebbles and small stones;

water-stone streams - a mixture of water with large stones.

Based on the nature of their movement, mudflows are divided into connected and disconnected flows. Cohesive flows consist of a mixture of water, clay, sand and represent a single plastic substance. Such a mudflow, as a rule, does not follow the bends of the channel, but straightens them. Disjointed streams consist of water, gravel, pebbles and stones. The stream follows a bend in the channel with high speed, exposing it to destruction. According to their power, mudflows are divided into catastrophic, powerful, medium and low power.

Catastrophic mudflows are characterized by the removal of more than 1 million m3 of material. They happen on globe once every 30-50 years.

Powerful mudflows are characterized by the removal of material in a volume of 100 thousand m3. Such mudflows rarely occur.

In mudflows of weak power, the removal of material is insignificant and amounts to less than 10 thousand m 3. They occur every year.

Landslides (mountain collapse)- separation and catastrophic fall of large masses of rocks, their overturning, crushing and rolling down steep and steep slopes.

Landslides of natural origin are observed in the mountains, on sea ​​shores and cliffs river valleys. They occur as a result of a weakening of the cohesion of rocks under the influence of weathering, erosion, dissolution and the action of gravity. The formation of landslides is facilitated by: geological structure terrain, the presence of cracks and rock crushing zones on the slopes.

Most often (up to 80%) modern collapses are associated with the anthropogenic factor. They are formed mainly during improper work, during construction and mining.

Landslides are characterized by the power of the landslide process (the volume of falling rock masses) and the scale of manifestation (involvement of the area in the process).

According to the power of the landslide process, landslides are divided into large (rock detachment with a volume of 10 million m3), medium (up to 10 million m3) and small (less than 10 million m3).

According to the scale of manifestation, landslides are divided into huge (100-200 ha), medium (50-100 ha), small (5-50 ha) and small (less than 5 ha).

Consequences of landslides, mudflows, landslides. Landslides, mudflows, and avalanches cause great damage to the national economy, the natural environment, and lead to casualties.

The main damaging factors of landslides, mudflows and landslides are impacts from moving masses of rocks, as well as the flooding and obstruction of previously free space by these masses. As a result, buildings and other structures are destroyed, settlements, national economic facilities, and forests are hidden by rock layers, river beds and overpasses are blocked, people and animals die, and the landscape changes.

In particular, these dangerous geological phenomena threaten the safety of railway trains and other ground transport in mountainous areas, destroy and damage bridge supports, rails, and coatings highways, power lines, communications, oil pipelines, hydroelectric power stations, mines and other industrial enterprises, mountain villages, vacation sites.

Significant damage is caused to agriculture. Mudflows lead to flooding and littering of agricultural crops with debris over areas of hundreds and thousands of hectares. Arable lands located below landslide areas often become swampy. At the same time, crop losses and an intensive process of land withdrawal from agricultural use occur.

These phenomena can cause significant damage to the cultural and historical heritage of the peoples inhabiting mountainous areas.

The scale of the consequences is determined by:

the size of the population caught in the landslide zone;

the number of dead, wounded and homeless;

number of settlements included in the zone natural disaster;

the number of national economic facilities, health-improving and socio-cultural institutions that were destroyed and damaged;

area of ​​flooding and obstruction of agricultural land;

number of dead farm animals.

The secondary consequences of these natural disasters are emergencies associated with the destruction of technologically hazardous objects, as well as the interruption of economic and vacation activities.

Landslides, mudflows and landslides on the territory of the Russian Federation occur in mountainous regions North Caucasus, Ural, Eastern Siberia, Primorye, Sakhalin Islands, Kuril Islands, Kola Peninsula, as well as along the banks of large rivers.

Landslides often lead to large-scale catastrophic consequences. Thus, the 1963 landslide in Italy with a volume of 240 million m3 covered 5 cities, killing 3 thousand people.

In 1989, landslides in Checheno-Ingushetia caused damage to 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural and public service facilities in 82 settlements.

In 1985 in Colombia, as a result of the eruption of the Ruiz volcano, a gigantic mudflow occurred, which overwhelmed the city of Armero, resulting in the death of 22 thousand people and the destruction of 4.5 thousand residential and administrative buildings.

In 1982, a mudflow 6 km long and up to 200 m wide hit the villages of Shiveya and Arenda in the Chita region. Houses, bridges, 28 estates were destroyed, 500 hectares of cropland were washed away and covered, people died.

When huge masses of rocks fall from the slopes under the influence of gravity, not everyone is able to escape. Especially if we are talking about a landslide or village that originated high in the mountains, when a huge amount of sedimentary rocks, diluted with river waters, rainfall or melted snow, rushes down at great speed.

A landslide is a mass of loose rocks separated from the slopes, which slides down an inclined plane without losing its coherence and solidity. They can be either dry or moistened to create a fluid flow.

Each landslide has its own speed, and therefore it often happens that the process of movement is completely invisible to the human eye, since it is only 0.06 meters per year. True, this is not always the case: landslides are quite capable of rushing at a stunning speed of 3 m/s.

In this case, if the relevant services do not have time to warn the population about landslides, the collapse often has catastrophic consequences. For example, one of the largest landslides that occurred as a result of an earthquake in Tajikistan was four hundred meters wide and more than four kilometers long. After huge masses of rushing rocks covered the village of Sharora that day, the consequences were terrible: landslides buried 50 houses, resulting in the death of more than two hundred people.

Landslides can move over different distances, up to four hundred hectares, and according to the amount of moving mass, landslides are:

• small – collapse of loose mass up to 10 thousand m3;
• medium – ground collapse 100 thousand m3;
• large – collapse of loose masses of 1000 m3;
• the largest - a collapse of more than 1 thousand m.3.

Occurrence of landslides

Most often, landslides form on the coasts of rivers, reservoirs and on mountain slopes: 90% of displacements are recorded at an altitude of one to two kilometers. In this case, landslides form on slopes whose angle is nineteen degrees, and on clay soil with strong moisture in the rocks, landslides occur even at a slope of five degrees.

Despite the fact that the reasons for the occurrence of such displacement of the earth are different, landslides are formed mainly due to the erosion of rocks by water in combination with weathering and waterlogging. A landslide can also occur as a result of an earthquake or erosion of the slopes by sea or river waters.

Land collapse caused by natural causes occurs mainly after rainstorms, which wet the soil so much that it becomes mobile. At this moment, the frictional force that adheres it to the slopes turns out to be weaker than the force of gravity, which causes the rocks to move.

One of the most dangerous and unstudied is an underwater landslide, which is formed during the movement of sedimentary rocks at the edge of the shelf (the consequences are dangerous because they raise a tsunami). According to statistics, about 80% of landslides occur due to human activity - building roads on slopes, deforestation, unreasonable management Agriculture.

Mudflow

Despite the fact that a mudflow is also a downward flow of loose masses, it differs from landslides in that it is a downward flowing mountain river into which a huge amount of loose rock has fallen.

The reasons for their appearance are heavy rains, increased melting of snow, the collapse of a large amount of loose soil into the river or the breakthrough of rubble, which causes a sharp rise in water.

After which the river is transformed into big flow destructive force, and in such a village there is a mixture of water, stones, loose soil (about 60%). The height of the front line of the mudflow ranges from 5 to 15 meters, and the wave can rise up to 25 meters.

The higher the mudflows originate, the more destructive the collapse. High-mountain mudflows begin at an altitude exceeding 2.5 thousand km. Such a mudflow can carry about 26 thousand m3 of rock from one square kilometer. While mid-mountain mudflows (from 1 to 2.5 thousand km) carry out from 5 to 15 thousand m3 from an area of ​​similar size, low-mountain mudflows - no more than 5 thousand m3.

Mudflows are formed in different ways:

• If the collapse was caused by erosion processes, due to the washout and erosion of nearby soil, debris material first enters the stream, after which a mudslide wave is directly formed.
• A mudflow can also occur due to a blockage, when waves begin to accumulate in one place, eroding rocks. Since this cannot continue for long, the mass in the village breaks through the blockade and rushes down.
• Another method of formation, when the village is at maximum saturation with loose masses, occurs due to the collapse of a landslide into river waters.

The mudflow does not flow continuously, but in waves, carrying out hundreds, and in some cases millions, of cubic meters of viscous substance in the village at a time (some blocks in the village can often weigh about 100 tons). The phenomenon can have different powers:

• Small flow is a frequent phenomenon, it occurs annually, in this village there is no more than 10 thousand m3 of rock;
• A flow of average power is formed every two to three years; the village contains from 10 to 100 thousand m3 of soil.
• A strong flow occurs once every five to ten years and such a village contains at least 100 thousand m3 of loose rock.

Since mudflows are part of a mountain river, they are capable of moving at a speed of about 10 m/s, so they go down very quickly, in 20-30 minutes, and the phenomenon itself lasts from one to three hours (if a mudflow hits an obstacle, then, growing , the flow passes over it, increasing its energy).

Moreover, only the consequences of a low flow do not lead to catastrophic results. A medium-power mudflow, having picked up speed, is capable of demolishing foundationless buildings, while a powerful mudflow, carrying with it a huge amount of loose soil, boulders and other obstacles captured along the road, destroys buildings, roads, destroys trees, floods fields and kills all living things that appear on a way.

What to do during collapses

People living or staying in areas where landslides and mudflows are a common occurrence should be well aware of the signs and characteristics of these dangerous landslides. For example, one of the first signs of impending disaster is water seepage on the slopes.

Therefore, as soon as the first signs of danger appear (despite the rapid nature of the disaster, modern equipment makes it possible to detect their appearance in time), the inhabitants of the region are usually evacuated. Before leaving your home, you must tightly close all ventilation ducts, window and door openings, turn off electricity and gas, and turn off the water.

If it so happens that landslides or mudflows appeared suddenly and moved so quickly that they did not have time to warn the population in time and people received information a few minutes before the appearance of the mud flow or even noticed it themselves, you need to immediately run away to a safe place. Usually these are hills or mountains that are located away from the stream (it is advisable to rise to a height of no less than 100 meters). During the ascent, you should not go through valleys or gorges, as mudflow lateral flows may appear there.

If it so happens that people and structures find themselves in a moving area of ​​a landslide, you need to leave the room, go up, and while stopping the moving mass, beware of rolling blocks, stones and other objects. It is necessary to keep in mind that when a landslide stops, a very strong shock may well occur, and be prepared for this.

When a landslide or mudflow stops, you need to return not immediately, but after a few hours, since there is a danger that a new landslide will occur. If there are no signs that a landslide or mudflow may recur, you can return home, after which you can immediately begin searching for and extracting victims who are in the village, freeing cars and other vehicles blocked by mud.

Employees of the American aerospace agency NASA have made the DRIP-SLIP software package freely available, which makes it possible to monitor landslides around the world. The system scans satellite images and determines where a disaster could occur in the near future. /website/

The system is a collection of location maps updated every 24, 48 or 72 hours. This allows you to monitor the situation in real time. The capabilities of the complex are demonstrated using the example of a map of landslides that were recorded from 2007 to 2013.

“We are interested in quickly and accurately identifying unreported landslides to better understand the nature of their occurrence. This information will make it possible to clarify maps that depict the regions most prone to landslides and take measures to prevent them,” NASA experts noted.

Landslides often go unnoticed and unreported, resulting in a large number of casualties. "We know that a large number of Landslides occur during this time period in Nepal. Documenting them is very important to better understand why these events occur and what impact they have,” experts say.

Risk area - Nepal

Scientists pay special attention to Nepal, since landslides in this country are very current problem. Landslides occur here during the monsoon season and lead to the death of dozens and sometimes hundreds of people. One of the most destructive landslides occurred in this country last year after a strong earthquake.

Due to hesitation earth's crust the mountain slopes collapsed and avalanches of mud rushed down the mountainsides and hills. The largest landslide occurred in the Miagdi region, about 140 kilometers from Nepal's capital Kathmandu. Landslides also occurred in other regions. People who survived the devastating earthquake died under layers of sliding earth.

Landslide record holder

Landslides occur quite frequently around the world. The largest landslide in modern history occurred on February 18, 1911 in the Pamirs in Tajikistan. After a strong earthquake, 2.2 billion cubic meters of loose material slid from the Muzkol ridge from a height of 5 thousand meters. The force of the impact of the collapsed mass caused a seismic wave that circled the entire globe several times.

The landslide covered the village of Usoy with all its residents, property and livestock, resulting in the death of 54 people. In addition, the descending mass blocked the Mugrab River, which is why Lake Sarez, 4–5 kilometers wide, was formed. Over time, the lake grew, flooding the villages of Sarez, Nisor-Dasht and Irkht. Currently, the lake still exists, its length and width are already 75 kilometers.

The lake still poses a danger to nearby settlements. This area is located in a seismically active zone, and weak tremors can trigger a breakthrough of Lake Sarez. In the event of a tragedy, a huge mass of water mudflow will pass almost until Aral Sea. About 6 million people live in the potentially dangerous zone.

The most destructive landslide

The most tragic in terms of the number of victims was a landslide that occurred in the Chinese province of Gansu in 1920. Most of the territory of this province is occupied by a loess plateau, which is a homogeneous soil mixed with lime, clay and sand. The soil here is fertile, so the area was densely populated. After the earthquake, the cohesion of the loess was disrupted, and the earthen mass rolled down in entire hills. She destroyed everything within a radius of 50 thousand square kilometers.

The situation was aggravated by the fact that everything happened winter night when all the people were in their houses. “The shocks followed one after another with an interval of several seconds and merged with the deafening roar of collapsing houses, the screams of people and the roar of animals that came from under the rubble of buildings,” recalled the miraculously surviving missionary.

One of the houses, moved by a mass of rocks, was moved almost a kilometer. However, the house remained undamaged. The man and child who were there were also not injured. Because of the darkness and noise, they did not even understand what had happened. Along with the house, the section of the road also moved. Now this place is called “Death Valley”. More than 200 thousand people are buried there.

Landslides in Russia

Scientists consider landslides to be the most dangerous natural disaster. The danger is that they can occur absolutely anywhere where there is a slope. Landslides are not associated with geographical location and can get off in any country, including Russia. Most often with this natural phenomenon Residents of the North Caucasus, Volga region, Primorye, Eastern Siberia and the Urals have to deal with.

For example, in 2006, heavy snowfalls and continuous rains in the mountains caused severe landslides in Chechnya. The upper layers of rocks up to two meters thick rolled down the slopes, burying residential buildings in the villages of Shuani, Benoy, Zandak and others. In the village of Shuani alone, a landslide destroyed about 60 houses in one day. Residents left their homes, taking only documents with them.

The Russian Black Sea coast is also a risk zone. Mountain slopes built up with many infrastructure facilities create favorable conditions for landslides. The danger increases especially in autumn-winter period when the mountain slopes are washed away by rain. Active human activity, including construction and landscape impacts, are also additional risk factors.

Landslides are sliding movements of rock masses down a slope under the influence of gravity. They occur on the slopes of mountains, ravines, hills, and on river banks.

Landslides occur when the stability of a slope is disrupted by natural processes or people. At some point, the coherence forces of soils or rocks turn out to be less than the force of gravity, the entire mass begins to move and a catastrophe can occur.

Earth masses can slide down slopes with barely noticeable speed (such displacements are called slow). In other cases, the rate of displacement of weathering products turns out to be higher (for example, meters per day), sometimes large volumes of rocks collapse at a speed exceeding the speed of an express train. All these are slope displacements - landslides. They differ not only in the speed of displacement, but also in the scale of the phenomenon.

Consequences of landslides.

Landslides can destroy homes and endanger entire communities. They threaten agricultural land, destroy it and make it difficult to process, and create a danger during the operation of quarries and mining. Landslides damage communications, tunnels, pipelines, telephone and Electricity of the net; threaten water management structures, mainly dams. In addition, they can block a valley, form temporary lakes and contribute to floods, as well as generate destructive waves in lakes and bays, underwater landslides tear telephone cables. As a result of landslides, riverbeds and roads may be blocked, and the landscape may change. Landslides threaten the safety of road and rail transport. They destroy and damage bridge supports, rails, road surfaces, oil pipelines, hydroelectric power stations, mines and other industrial enterprises, and mountain villages. Arable lands located below landslide areas often become swampy. In this case, there is a loss of crops and an intensive process of land withdrawal from agricultural use.

These phenomena can cause significant damage to the cultural and historical heritage of peoples and to the mental state of people inhabiting mountainous areas.

Landslides predominantly occur in areas of living tectonics, where processes of slow sliding of crustal blocks along faults and rapid movements in earthquake foci interact and alternate.

Landslides on the territory of the Russian Federation occur in the mountainous regions of the North Caucasus, the Urals, Eastern Siberia, Primorye, and about. Sakhalin, Kuril Islands, Kola Peninsula, as well as on the banks of large rivers.

Landslides often lead to large-scale disasters. Thus, the 1963 landslide in Italy with a volume of 240 million cubic meters. meters covered 5 cities, killing 3 thousand people. In 1989, landslides in Checheno-Ingushetia caused damage to 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural and public service facilities in 82 settlements.

Occurrence and classification of landslides.

1. Natural causes occurrence of landslides.

Landslides can be caused by various factors. The earth's surface consists mainly of slopes. Some of them are stable, others, due to various conditions, become unstable. This occurs when the angle of repose of a slope changes or if the slope becomes burdened with loose materials. Thus, the force of gravity turns out to be more power soil connectivity. The slope becomes unstable even with shaking. Therefore, every earthquake in conditions mountainous terrain accompanied by displacements along the slope. Slope instability is also facilitated by an increase in water content in soils, loose sediments or rocks. Water fills the pores and disrupts the adhesion between soil particles. Interformational waters can act like a lubricant and facilitate sliding. The cohesion of rocks can be disrupted by freezing and by the processes of weathering, leaching, and leaching. Slope instability may also be associated with a change in the type of plantings or destruction of vegetation cover.

The situation is also serious when the rocks on the slope are covered with loose materials or soil. Loose sediments are easily separated from underlying rocks,

especially if the sliding plane is “lubricated with water.”
Unfavorable (from the point of view of the possibility of occurrence
landslides) and those cases where rocks are represented
layers of strong limestone or sandstone with

underlying softer shales. As a result of weathering, an interface plane is formed, and the layers slide down the slope. In this case, everything depends mainly on the orientation of the layers. When the direction of their fall and slope are parallel to the slope, it is always dangerous. It is impossible to accurately determine the value of the slope angle, more than which the slope is unstable, and less than which it is stable. Sometimes this critical angle is determined to be 25 degrees. Steeper slopes appear to be no longer stable. Rainfall and shaking have the greatest influence on the occurrence of landslides. At strong earthquakes Landslides always occur. The occurrence of landslides is also influenced by: the intersection of rocks with cracks, the location of soil layers with a slope towards the slope, the alternation of water-resistant and aquiferous rocks, the presence of softened clays and floating sands in the soil, an increase in the steepness of the slope as a result of erosion (on river banks).

2. Anthropogenic causes of landslides.

Landslides can be caused by cutting down forests and shrubs on slopes, plowing slopes, excessive watering of slopes, clogging and blocking of exit points groundwater.

The occurrence of landslides is influenced by blasting operations, which result in the formation of cracks, and this is also an artificial earthquake.

Landslides can form when slopes are destroyed by pits, trenches and road cuts. Such landslides can occur during the construction of housing and other objects on slopes.

Classification of landslides.

1. By material

A) rocks
B) soil layer

B) mixed landslides

2. According to the displacement rate, all slope processes
are divided into:

A) exceptionally fast (3m/s)
B) very fast (Zdm/m)

B) fast (1.5 m per day)
D) moderate (1.5 m per month)

D) very slow (1.5 m per year) E) extremely slow (6 cm per year) Slow offsets(very slow).

They are not catastrophic. They are called dragging, creeping displacement of loose sediments, and sliding and sliding. This is really a movement—sliding, since its speed does not exceed several tens of centimeters per year. Such displacement can be recognized by the twisted trunks of trees growing on a slope, the bending of strata and surfaces, the so-called stripping of strata, and with the help of sensitive instruments.

Solifluction and helifluction are types of such slow displacements. Previously, solifluction meant displacements in soils and loose sediments saturated with water. The term was later extended to glacial conditions, where soils shift due to alternating freezing and thawing. The term helifluction is now recommended to refer to displacements caused by alternating freezing and thawing. The danger of these slow shifts is that they can gradually turn into a fast shift and then a catastrophic one. Many large landslides began with the sliding of loose material or the slow sliding of blocks of rock. Bias average speed(fast).

Displacements that occur at a speed of meters per hour or meters per day. These include most typical landslides. The landslide area consists of a detachment, sliding and frontal zone. In the detachment zone, the main separation crack and the sliding plane along which the landslide body separated from the underlying rock can be distinguished.

Fast displacements.

Only rapid landslides can cause real disasters with hundreds of casualties. Such displacements include those whose speed is several tens of kilometers per hour (or much more), when escape is impossible (there is no time left for real evacuation).

There are different types of such disasters: “Rock collapse.” Landslides - flows occur when solid material

mixes with water and flows at high speed. Landslides - flows can be mud (they also include volcanic mud flows), stone or transitional. Rapid displacements also include avalanches, both snow and snow-stone.

3. Landslides are classified according to their scale:

A) large

B) average

B) small-scale.

Large landslides are usually caused by natural causes and occur along slopes for hundreds of meters. Their thickness reaches meters or more. The landslide body often retains its solidity.

Medium and small-scale landslides are smaller in size and are characteristic of anthropogenic processes.

4. The scale of landslides is characterized by the amount of land involved in the process.
area:

A) grandiose -400 hectares or more
B) very large - 200-400 ha

B) large - 100-200 ha
D) medium - 50-100 hectares
D) small 5-50 ha

E) very small up to 5 ha

5. By volume ( power)

A) small (10 thousand cubic meters)

B) medium (from 10 to 100 thousand cubic meters)

B) large (from 100 thousand to 1 million cubic meters)
D) very large (more than 1 million cubic meters)

6. According to activity, landslides can be:

A) active
B) not active

Their activity is determined by the degree of capture of bedrock slopes and the speed of movement, which can range from 0.06 m/year to 3 m/s

7. Depending on the availability of water: A) dry

B) very wet

8. According to the mechanism of the landslide process: A) shear landslides

B) extrusion

B) viscoplastic

D) hydrodynamic

D) sudden liquefaction

Landslides often show signs of a combined mechanism.

9. Landslides are divided according to the place of formation:

B) coastal

C) underwater, (B, C) can cause a tsunami

D) snowy

D) landslides of artificial earthen structures (canals,

foundation pits...)

The scale of the consequences is determined by:

1) the size of the population caught in the landslide zone

2) the number of dead, wounded, left homeless

3) the number of settlements that fell into the disaster zone
disasters

4) the number of national economic facilities, medical-
health and socio-cultural institutions,
found to be destroyed and damaged

5) area of ​​flooding and obstruction of agricultural
lands

6) the number of dead farm animals.

Protection measures for landslides.

The population living in landslide-prone areas should know the sources, possible directions and characteristics of this dangerous phenomenon. Based on the forecast data, residents are informed in advance about the danger and measures regarding the identified landslide sources and possible zones of their action, as well as the procedure for submitting signals about the threat of this dangerous phenomenon. Also, informing people earlier reduces the stress and panic that can subsequently arise when emergency information about an immediate landslide threat is communicated.

The population of dangerous areas is also obliged to take measures to strengthen houses and the territories on which they are built, as well as participate in the construction of protective hydraulic and other engineering structures. The population is notified using sirens, radio, television, and local warning systems.

If there is a threat of a landslide and if there is time, advance evacuation of the population, farm animals and property to safe areas is organized. Valuable property that cannot be taken with you should be protected from moisture and dirt. Doors and windows, ventilation and other openings are tightly closed. Electricity, gas, and water supply are turned off. Flammable, toxic, etc. hazardous substances removed from the house and buried at the first opportunity in pits or cellars. In all other respects, citizens act in accordance with the procedure established for organized evacuation.

If there is a threat of a natural disaster, residents, taking care of their property, make an emergency independent exit to a safe place. At the same time, neighbors and all people encountered along the way should be warned about the danger. For an emergency exit, you need to know the routes to the nearest safe places (mountain slopes, hills not prone to landslides).

In the event that people, buildings and other structures find themselves on the surface of a moving landslide area, they should, after leaving the room, move upward if possible, acting according to the situation, and beware of blocks, stones, debris, structures, and earthen ramparts rolling down from the back of the landslide when braking the landslide. , scree.

After the end of the landslide, people who hastily left the disaster zone and waited out it in a nearby safe place should, after making sure that there is no repeat threat, return to this area in order to search for and provide assistance to the victims.

Observation and prediction of landslides.

1. Monitor unusual incidents and behavior
animals, behind sediments.

2. Analysis and forecasting of possible landslides.

For more accurate forecast necessary:

A) rock mass analysis

B) analysis of the conditions of already known and existing landslides.

B) presence of experience and special knowledge.

3. Carrying out complex protective engineering work.
They are active landslide protection measures.

1) Planning slopes, leveling hillocks, sealing cracks

2) Carrying out planned and strictly dosed explosions

3) Construction of tunnels and covered fences, as well as protective walls

4) Reducing the steepness of a slope using technology or targeted explosions

5) Construction of roads, overpasses, viaducts

6) Construction of retaining walls, construction of rows of piles

7) Arrangement of guide walls

8) Interception of groundwater by a drainage system (a system of special pipes), regulation of surface flows by patches and ditches

9) Protection of slopes by sowing grass, trees and shrubs

10) Relocation of power lines, oil and gas pipelines and
other objects in safe areas

11) Protection of slopes, road, automobile and railway embankments by concreting and landscaping.

4. Training for people living, working and vacationing in dangerous areas

5. Compliance safe mode, building codes and regulations, as well as instructions and standards.

Glacier collapses.

Tongues of mountain glaciers descend into valleys, where they sometimes even approach populated areas. In many alpine valleys you can, as they say, touch a glacier with your hand. Typically, the forward movement of glacial tongues occurs at a speed of several meters per year, while they melt and feed with water. mountain rivers. However, it happens that for some reason a glacier loses stability and suddenly moves tens or even hundreds of meters in a few days. This phenomenon in itself does not yet represent a catastrophe; however, the situation is worse when, having lost stability, the glacier breaks off and collapses into the valley.

These are turbulent streams with mud and stone blocks. The main component of this mixture is water, which determines the movement of the entire mass. The immediate causes of mudflows are heavy rainfalls, washing out of reservoirs, intensive melting of snow and ice, earthquakes and volcanic eruptions, deforestation, rock explosions during road construction, and improper organization of dumps.

Seli carry either fine particles solid material or coarse debris. In accordance with this, a distinction is made between stone streams, mud streams - stone and mud streams.

Snow avalanches.

Avalanches are also classified as landslides. Large avalanches are catastrophes that claim dozens of lives. Every year, several people die from avalanches in our mountains; on a European and global scale, the number of avalanche victims is much higher.

From a mechanical point of view, an avalanche occurs in the same way as other landslide displacements. The forces of snow displacement cross a certain limit, and gravity causes the snow masses to shift along the slope. A snow avalanche is a mixture of snow crystals and air. Snow quickly changes its properties after it falls, that is, it undergoes metamorphism. Snow crystals grow, the porosity of the snow mass decreases. At a certain depth below the surface, recrystallization can lead to the formation of a sliding surface along which a layer of snow slides. Gravity determines the occurrence of tensile forces in the upper part of the slope. Disturbances in the snow layer in these places usually lead to an avalanche.

The critical angle in this case is 22 degrees. However, this does not mean that an avalanche cannot occur on less steep slopes. Large avalanches occur on slopes of 25-60 degrees. Their occurrence depends not only on the absolute slope, but also on the profile of the slope. Concave slopes are less prone to avalanches than convex slopes. The convexity of the slope increases the tensile directions, although in winter it is not visible what is hidden under the snow, however, the so-called microrelief largely determines the possibility of avalanches. Smooth grassy slopes are prone to avalanches. Shrubs, large rocks and other obstacles of this kind inhibit the occurrence of avalanches. Avalanches occur very rarely in forests, but single trees on a slope do not prevent avalanches from occurring. The orientation of the slope is important: on the southern slopes at the beginning of winter there are fewer avalanches, but at the end of winter the southern slopes become avalanche dangerous, because as a result of melting the snow cover loses stability.

There are two main types of avalanches: dust avalanches andreservoir.

Dust avalanches are formed by a shapeless mixture of snow dust. There is no sliding plane between the shifting snow and the underlying snow. More and more snow is added from below, and the avalanche grows. Such avalanches often occur in one place or in a limited area. Layered avalanches are separated by a sliding plane from the base. They arise, like landslides, along the detachment zone and slide in the form of a layer, both along the underlying older layers of snow and along the bedrock slope. Formative avalanches are more dangerous than dust avalanches.

According to their shape, avalanches are also divided into two types: trough avalanches, rolling down hollows and gorges, and flat avalanches, moving along a flat surface.

The speed of a snow avalanche fluctuates over a wide range. Dust avalanches are faster. Those with a lot of air can reach speeds of up to 120-130 km/h. Heavy dust avalanches move at a speed of 50-70 km/h. Seam avalanches are slower, their speed is 25-36 km/h.

By size, avalanches are divided into large, medium, and small. The big ones destroy everything in their path. Medium ones are dangerous only for people, small ones are practically not dangerous.

There are several indirect causes of avalanches: instability of the slope, recrystallization of snow, formation of a sliding plane, snow deposits with a greater angle of repose than the slope. The direct cause is often a concussion. And a stone falling on a snow field can cause an avalanche. Avalanches also capture in their movement people who cross the snow massif prepared for avulsion. There is much debate about whether an avalanche can be caused by sound. The majority express doubts about this.

Avalanche protection.

As in the case of other landslide displacements, preventive measures play the most important role here. Avalanche-prone elephants are recognized quite easily. Studies of previous avalanches are important, since most of them descend on the same slopes, although exceptions are possible.

To forecast avalanches, both the wind direction and the amount of precipitation are important. With 25 mm of fresh snow, avalanches are possible, with 55 mm they are very likely, and with 100 mm the possibility of their occurrence must be assumed

In a few hours. The probability of avalanches is calculated by the rate of melting of a snow field.

Avalanche protection can be passive or active.

With passive protection, avalanche-prone slopes are avoided or barrier shields are installed.

Active protection consists of shelling avalanche-prone slopes. Thus, they cause small, harmless avalanches and prevent the accumulation of critical masses of snow.

Snow avalanches cause great damage and cause loss of life. So, on July 13, 1990, on Lenin Peak in the Pamirs, as a result of an earthquake, a large snow avalanche demolished a climbers’ camp located at an altitude of 5300 m. 48 people died.

Bibliography.

Zdenek Kukal " Natural disasters» Ed. 23knowledge" Moscow 1985

Encyclopedia of Security,

Ed. 2Stalker" 1997

“Basic patterns of landslide processes”

Ed. "Nedra" Moscow 1972