Natural causes of landslides. Landslides, avalanches and mudflows
Snowy avalanches, stormy sat down treacherous landslides... All these natural phenomena are associated with mountainous terrain and can pose a significant danger to both people and their homes, roads, bridges and other objects. What is it?
snow avalanche is a mass of snow sliding down steep mountain slopes and moving at speeds of up to 30 meters per second. It is almost impossible to escape from her. The greatest destruction is caused not even by the avalanche itself, but by the air wave that “runs” ahead of it. Avalanches can be caused by intense melting of snow accumulated over the winter, an earthquake and a nearby explosion, causing shaking of the slopes. In Russia, avalanches most often occur in the North Caucasus, the Urals, and in the mountains Eastern Siberia and the Far East. Avalanche areas are under constant control of special services, which from time to time provoke artificial avalanches (warning the population about this), build protective structures and carry out rescue operations.
Curious what it is a formidable phenomenon, like an avalanche, often becomes a source of inspiration for poets. “...Avalanches are coming one after another, and behind the rockfall the rockfall is roaring...” sang Vladimir Vysotsky. And how many lines where avalanches are mentioned are there in Yuri Vizbor’s poems! Artists can wax poetic about danger, but ordinary life it's best to avoid it.
To avoid getting caught in an avalanche, You must not go to the mountains in snowfall and bad weather, be aware of avalanche-prone slopes (steeper than 30 degrees), and not cross narrow ravines surrounded by steep “sides.” The most avalanche-dangerous period is spring and summer (from 10 am to sunset). If you notice an avalanche that has occurred high in the mountains, quickly move out of its path safe place or take cover behind a high rock. If it is impossible to leave, free yourself from all things, take a horizontal position (with your head towards the avalanche), tuck your knees to your stomach, cover your nose and mouth with a mitten, scarf or collar. If you get into an avalanche, try to “swim” with it, staying as close to its edge as possible. Try to create space around your chest and face to breathe. Don't scream - it's useless: the snow completely absorbs sounds, and screams and meaningless movements weaken you and deprive you of oxygen. If you are buried in an avalanche, do not despair: save your energy and do not let yourself fall asleep - there have been cases when people were dug out from under an avalanche even 5-10 days after the incident.
What is a mudflow? This is a temporary flow of water carrying large amounts of clay and debris rocks of different sizes. Such a flow sometimes suddenly appears in river beds and mountain valleys of the North Caucasus, some regions of Eastern Siberia and the Far East. Mudslides occur after heavy rains, intense melting of snow and glacier, as well as after an earthquake or volcanic eruption. The height of a mudslide wave can reach 15-20 meters, and the roar turbulent stream can be heard for tens of kilometers. Places where mudflows may occur And possible time their formations are usually known. About this danger of tourists and local population mountain rescuers warn. In dangerous areas, anti-mudflow dams and dams are built, the level of mountain lakes is lowered, and slopes are strengthened by planting shrubs and trees on them. You can escape from a mudflow only if you manage to avoid it. Having heard the sound of an approaching stream, you need to immediately climb the slope to a height of at least 80-100 meters from the bottom of the ravine. If you were hit by a stone thrown from a mudflow, give yourself first aid as with any bruise: apply a bandage, ice, and when you return to the village, consult a doctor.
Let's landslide is called the displacement (sliding) of soil along the slope of a mountain or the side of a ravine, a steep shore of the sea, lake or river. Landslides happen when water washes away a slope or rocks become too wet. The cause of a landslide can be ground shaking caused by an earthquake, explosion or human activity. A landslide is not always instantaneous: sometimes the earth moves down the slope at a speed of several meters per year, gradually destroying the area. Landslides are a threat to houses, pipelines, roads; they can also become the cause of death, as happened in the summer of 2005 on one of the “wild” beaches of Crimea. Scientists and workers at special stations study landslides and predict their occurrence. If you are in a dangerous zone, you can find out about the threat of a landslide by jamming the doors and windows of the building and seepage of water from the slope. If you feel something is wrong, inform the Ministry of Emergency Situations employees about it, and act according to the situation. After a landslide has occurred, do not enter a damaged house without making sure that there is no threat of collapse. Do not turn on the lights and gas, check that the gas pipeline and electrical wiring are not damaged.
Landslide - sliding and separation of rock masses down a slope under the influence of gravity.
According to the power of the landslide process, that is, the involvement of rock masses in the movement, landslides are divided into
· small - up to 10 thousand cubic meters,
medium - 10-100 thousand cubic meters,
· large - 100-1000 thousand cubic meters,
· very large - over 1000 thousand cubic meters.
The surface along which a landslide lifts off and moves downward is called a sliding or displacement surface; By its steepness they distinguish:
B) flat (5°-15°);
B) steep (15°-45°).
Landslides are classified according to the depth of the sliding surface:
Surface - no deeper than 1 m - slivers, alloys;
Small - up to 5 m; deep - up to 20 m;
Very deep - deeper than 20 m.
Called:
1. increasing slope steepness as a result of erosion by water;
2. weakening of the strength of rocks due to weathering or waterlogging by precipitation and groundwater;
3. exposure to seismic shocks;
4. construction and economic activity.
Collapse- separation and fall of masses of rocks down from the slopes of mountains under the influence of gravity.
Landslides occur on the slopes of river banks and valleys, in the mountains, and on the shores of the seas.
The reason for the formation of landslides is an imbalance between the shearing force of gravity and the holding forces. It is caused by the same reasons as landslides.
Landfalls happen:
1. large - weight 10 million m3 or more;
2. medium - weight from several hundred to 10 million m3;
3. small - several tens of cubic meters.
Anti-landslide measures in which the population should take part are the drainage of surface water, tree planting, installation of various supporting engineering structures, excavation of trenches in order to drain the soil of the landslide massif, unloading and leveling of the landslide slope.
In addition, the population living in landslide-prone areas should not allow excessive water leakage from taps, damaged water pipes or standpipes; It is necessary to temporarily arrange drainage drains when surface water accumulates (with the formation of puddles).
To protect against landslides and collapses, tunnels and dams are built.
Mudflows: types, causes, characteristics, protection against mudflows.
The main types of mudflows: water-stone; mud; mud-stone.
Debris flows are characterized by linear dimensions (length and width), speed of movement, duration and power (volume).
By power (volume), mudflows are divided into catastrophic, powerful, medium and low power.
Catastrophic mudflows are characterized by the removal of more than 1 million cubic meters of material. m, most often formed as a result of earthquakes and volcanic eruptions.
Powerful mudflows are characterized by the removal of material in a volume of 100 thousand to 1 million cubic meters. m and occur rarely.
During mudflows of average power, material removal from 10 to 100 thousand cubic meters is observed. m and occur once every 2-3 years.
In mudflows of low power, the removal of material does not exceed 10 thousand cubic meters. m and occur annually, sometimes several times a year.
Classification of mudflows.
Classification of mudflows according to the height of their sources. Classification of mudflows by composition.
Anti-mudflow measures can be divided into two main groups: agromeliorative and hydraulic (engineering).
The first group includes activities carried out in the watershed: improvement of forestry, including afforestation; correct plowing of slopes (across) and their grassing; terracing the slope and organizing surface runoff.
Hydrotechnical measures are the most rational, and they are carried out by influencing the formed mudflow, since anti-erosion measures carried out on slopes are not always effective and cannot retain the entire surface flow. Therefore, part of it ends up in the riverbed, it is capable of carrying large amounts of solid material and can cause significant damage to cities and localities found.
Mudflow control structures (ponds, spurs) are installed to protect the bottom and banks of river channels from erosion or to protect any structures located along the river.
Mudflow retention structures are dams and sediment traps. In the fight against mudflows, mudflow retention dams are widely used, which are capable of retaining large volumes of mudflow.
Snow avalanches: types, characteristics, protection against avalanches.
Based on the nature of the movement and depending on the structure of the avalanche source, the following three types are distinguished: flume, wasp, and jumping.
The flume moves along a specific drainage channel or avalanche flume.
Osovaya is a snow landslide, does not have a specific drainage channel and slides across the entire width of the area.
Jumping occurs from flumes where there are steep walls or areas of sharply increasing steepness in the drainage channel. Having encountered a steep ledge, the avalanche lifts off the ground and continues to move through the air in the form of a huge jet. Their speed is especially high.
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If you are caught in an avalanche
The main thing is not to panic. Remember: your life is in your hands. Many people caught in an avalanche remained alive and well because they fought.
Try to stay on the surface, and to do this, throw away your skis, poles, and backpack; try, making swimming movements, to escape from the main channel to the edge of the avalanche.
Cover your nose and mouth from the snow (for example, with a scarf or hood), and do not take deep breaths.
If possible, try to cling to stationary objects.
When stopping an avalanche, create around the head and chest air space- First of all, squeeze the snow off your face.
If you have seen an avalanche
Remember the place where you saw people. Inspect the surface for signs of a person (pieces of equipment, scraps of clothing). Often the victim is close to the discovered items.
If you have enough people in your group, begin search and rescue immediately.
Large piles of snow, places of turns, turbulences are the most likely places for people to be found in an avalanche.
Having found a person, free his mouth and nose from the snow, warm him up.
When carrying out rescue operations, do not forget about your own safety.
The damaging effect of snow avalanches on engineering structures, equipment, and people is determined by their main characteristics: size, speed, impact force, ejection range, recurrence of avalanches and density of avalanche snow.
The dimensions of an avalanche are characterized by volume (m3) or mass (t). Depending on the amount of snow involved in the movement, the volume (mass) of an avalanche can vary from several tens of cubic meters (tons) to several million cubic meters (tons) of snow /77/. The destructive power of such avalanches varies. An avalanche with a volume of 10 m3 poses a danger to humans and light equipment. Large avalanches are capable of destroying capital engineering structures and forming difficult or insurmountable blockages on transport routes. The volume of an avalanche is estimated by direct measurements on the ground or from aerospace and aerovisual data using snow and meteorological observations. The simplest calculations can be made based on data taken from a topographic map.
Speed is one of the main characteristics of a moving avalanche; here the speed of movement of the avalanche front and the speed of the flow behind the front are taken into account. For conducting snow avalanche calculations, the most important speed is in the frontal section (avalanche speed), the value of which can reach 50-100 m/s.
The force of the impact directly determines the magnitude of the impact of the avalanche on objects located in its zone of action; it can be 40 t/m3, and if there are foreign inclusions in the avalanche body - up to 200 t/m2. The frontal impact of avalanche snow on an obstacle is replaced by flow pressure if the avalanche does not stop in front of the obstacle. Many dry avalanches are accompanied by a snow-dust cloud, sometimes avalanches are preceded by air shock waves; hit air wave and snow-dust cloud is similar to the impact of an air wave during explosions. The impact of water-saturated avalanche flows is similar to the hydraulic impact, which is calculated in the same way as the impact saturated with air liquid or mudflow.
Determining the ejection range is one of the main tasks of assessing the possibility of hitting objects located in avalanche zones. There is a distinction between the maximum ejection range and the most probable one. Maximum range The release of an avalanche (the distance that an avalanche can cover under all conditions conducive to a given source) is determined taking into account the height of its fall. The most probable range of the release is determined based on actual data directly on the ground. This is necessary when placing structures in the avalanche zone (Fig. 2.1).
There are average long-term and intra-annual (seasonal) frequency of avalanches. The first is defined as the frequency of avalanches in a given avalanche source on average over a long-term period. Intra-annual is the frequency of avalanches in an avalanche source during the winter and autumn periods. In some areas, avalanches can occur 15-20 times during winter and spring.
The density of avalanche snow is one of the most important physical parameters avalanches; the impact force of the avalanche, the labor costs for clearing and the ability to move along the surface of the avalanche depend on it. For avalanches from dry snow, the density is -200-400 kg/m3, from wet snow - 300-800 kg/m3. When planning the regime of human activity in an avalanche-prone area, the potential period of avalanche formation is taken into account - the time interval between the first and last avalanches in a given area during the year (season).
Protection against snow avalanches.
Permanent protective measures include effective and durable structures, support barriers in areas where an avalanche may begin, dividing or braking barriers along the avalanche route, and blocking barriers at the lowest point of the avalanche.
Purpose of temporary protective measures consists of creating conditions of safety and stability in areas where an avalanche may occur by deliberately causing small avalanches to remove dangerous amounts of snow piece by piece.
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"MURMANSK ACADEMY OF ECONOMICS AND MANAGEMENT"
Faculty: Economic
Speciality : 080502.65 "Economics and enterprise management"
Essay
by discipline : Life safety
“Landslides, landslides and mudflows. Characteristics, causes, countermeasures, security measures"
Introduction
1. Landslides
4. Ways to combat landslides, mudflows and landslides
5. Rules of behavior for people in the event of mudflows, landslides and collapses
Introduction
Natural disasters have threatened the inhabitants of our planet since the beginning of civilization. Somewhere more, somewhere less. One hundred percent security does not exist anywhere. Natural disasters can cause colossal damage, the amount of which depends not only on the intensity of the disasters themselves, but also on the level of development of society and its political structure.
Natural disasters typically include earthquakes, floods, mudslides, landslides, snow drifts, volcanic eruptions, landslides, droughts, hurricanes and storms. In some cases, such disasters can also include fires, especially massive forest and peat fires.
Are we really so defenseless against earthquakes, tropical cyclones, and volcanic eruptions? What advanced technology cannot prevent these disasters, and if not prevent them, then at least predict and warn about them? After all, this would significantly limit the number of victims and the extent of damage! We are not nearly so helpless. We can predict some disasters, and we can successfully resist some. However, any action against natural processes require good knowledge of them. It is necessary to know how they arise, the mechanism, conditions of propagation and all other phenomena associated with these disasters. It is necessary to know how displacements of the earth's surface occur, why rapid rotational movement of air occurs in a cyclone, how quickly masses of rocks can collapse down a slope. Many phenomena still remain a mystery, but, it seems, only over the next few years or decades.
IN in a broad sense words, an emergency situation (ES) refers to the situation in certain territory resulting from an accident, dangerous natural phenomenon, catastrophe, natural or other disaster that may result or have resulted in human casualties, caused damage to human health or the environment natural environment, significant material losses and disruption of people's living conditions. Each emergency situation has its own physical essence, causes of occurrence and nature of development, as well as its own characteristics of impact on humans and their environment.
1. Landslides
mud flow collapse landslide
Landslides are the movement of rock masses down a slope under the influence of gravity. They are formed in various breeds as a result of disruption of their balance and weakening of their strength and are caused by both natural and artificial reasons. Natural causes include an increase in slope steepness, erosion of their bases by sea and river waters, seismic tremors, etc. Artificial, or anthropogenic, i.e. caused by human activity, the causes of landslides are the destruction of slopes by road excavations, excessive removal of soil, deforestation, etc.
Landslides can be classified according to the type and condition of the material. Some are composed entirely of rock material, others are composed only of soil layer material, and others are a mixture of ice, rock and clay. Snow landslides are called avalanches. For example, a landslide mass consists of rock material; stone material is granite, sandstone; it can be strong or fractured, fresh or weathered, etc. On the other hand, if the landslide mass is formed by fragments of rocks and minerals, that is, as they say, the material of the soil layer, then we can call it a landslide of the soil layer. It may consist of a very fine granular mass, that is, clay, or a coarser material: sand, gravel, etc.; this entire mass can be dry or water-saturated, homogeneous or layered. Landslides can be classified according to other criteria: the speed of movement of the landslide mass, the scale of the phenomenon, activity, power of the landslide process, place of formation, etc.
From the point of view of the impact on people and on construction work, the speed of development and movement of a landslide is its only important feature. It is difficult to find ways to protect against the rapid and usually unexpected movement of large masses of rock, and this often causes harm to people and their property. If a landslide moves very slowly over months or years, it rarely causes accidents and preventive measures can be taken. In addition, the speed of development of a phenomenon usually determines the ability to predict this development; for example, it is possible to detect harbingers of a future landslide in the form of cracks that appear and expand over time. But on particularly unstable slopes, these first cracks can form so quickly or in such inaccessible places that they are not noticed, and a sharp displacement of a large mass of rock occurs suddenly. In the case of slowly developing movements of the earth's surface, it is possible to notice a change in the features of the relief and the distortion of buildings and engineering structures even before a major movement. In this case, it is possible to evacuate the population without waiting for destruction. However, even when the speed of the landslide does not increase, this phenomenon on a large scale can create a difficult and sometimes insoluble problem
Another process that also sometimes causes rapid movement of surface rocks is the erosion of the base of the slope sea waves or a river. It is convenient to classify landslides according to the speed of movement. In its most general form, rapid landslides or collapses occur within seconds or minutes; landslides from average speed develop over a period of time measured in minutes or hours; Slow landslides form and move over a period of days to years.
Based on their scale, landslides are divided into large, medium and small-scale. Large landslides are usually caused by natural causes. Large landslides are usually caused by natural causes and occur 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 characteristic of anthropogenic processes.
Landslides can be active or inactive, which is determined by the degree of capture of slope bedrock and the speed of movement.
The activity of landslides is influenced by the rocks of the slopes, as well as the presence of moisture in them. Depending on the quantitative indicators of the presence of water, landslides are divided into dry, slightly wet, wet and very wet.
According to the place of formation, landslides are divided into mountain, underwater, snow and landslides that occur in connection with the construction of artificial earthen structures (pits, canals, rock dumps, etc.).
In terms of power, landslides can be small, medium, large and very large and are characterized by the volume of displaced rocks, which can range from several hundred cubic meters to 1 million m3 or more.
Landslides can destroy populated areas, destroy agricultural land, create danger during the operation of quarries and mining, damage communications, tunnels, pipelines, telephone and electrical networks, and water management structures, mainly dams. In addition, they can block the valley, form dam lake and contribute to flooding. Thus, the economic damage they cause can be significant.
2. Sat down
In hydrology, a mudflow is understood as a flood with a very high concentration of mineral particles, stones and rock fragments, occurring in the basins of small mountain rivers and dry ravines and usually caused by rainfall or rapid snow melting. Selel is something between a liquid and a solid mass. This phenomenon is short-term (usually it lasts 1-3 hours), typical for small watercourses up to 25-30 km long and with a catchment area of up to 50-100 km2.
The mudflow is a formidable force. The stream, consisting of a mixture of water, mud and stones, rapidly rushes down the river, uprooting trees, tearing down bridges, destroying dams, stripping the slopes of the valley, and destroying crops. Being close to a mudflow, you can feel the shaking of the earth under the impact of stones and blocks, the smell of sulfur dioxide from the friction of stones against each other, and hear a strong noise similar to the roar of a rock crusher.
The danger of mudflows lies not only in their destructive force, but also in the suddenness of their appearance. After all, rainfall in the mountains often does not cover the foothills, and mudflows appear unexpectedly in inhabited areas. Because of high speed flow, the time from the moment a mudflow occurs in the mountains to the moment it emerges in the foothills is sometimes calculated in 20-30 minutes.
The main reason for the destruction of rocks is sharp intraday fluctuations in air temperature. This leads to the formation of numerous cracks in the rock and its fragmentation. The described process is facilitated by periodic freezing and thawing of water filling the cracks. Frozen water, expanding in volume, presses on the walls of the crack with enormous force. In addition, rocks are destroyed due to chemical weathering (dissolution and oxidation of mineral particles by subsoil and groundwater), as well as due to organic weathering under the influence of micro- and macroorganisms. In most cases, the cause of mudflows is rainfall, less often intensive snow melting, as well as breakthroughs of moraine and dam lakes, landslides, landslides, earthquakes.
IN general outline The process of formation of a mudflow of storm origin proceeds as follows. Initially, water fills the pores and cracks, simultaneously rushing down the slope. In this case, the adhesion forces between particles sharply weaken, and the loose rock comes into a state of unstable equilibrium. Then the water begins to flow over the surface. Small particles of soil are the first to move, then pebbles and crushed stone, and finally stones and boulders. The process is growing like an avalanche. All this mass enters the ravine or channel and draws new masses of loose rock into movement. If the water flow is insufficient, then the mudflow seems to fizzle out. Small particles and small stones are carried down by the water, while large stones create a blind area in the riverbed. The stopping of a mudflow can also occur as a result of attenuation of the flow velocity as the river slope decreases. There is no specific recurrence of mudflows observed. It has been noted that the formation of mud and mud-stone flows is facilitated by the previous long-dry weather. At the same time, masses of fine clay and sand particles accumulate on mountain slopes. They are washed away by the rain. On the contrary, the formation of water-stone flows is favored by the previous rainy weather. After all, the solid material for these flows is mainly found at the base of steep slopes and in the beds of rivers and streams. In the case of good previous moisture, the bond of stones with each other and with the bedrock weakens.
Shower mudflows are sporadic. Over the course of a number of years, dozens of significant floods can occur, and only then in a very rainy year a mudflow occurs. It happens that mudflows are observed quite often on the river. After all, in any relatively large mudflow basin there are many mudflow centers, and downpours cover first one or another center.
Many mountainous regions are characterized by the predominance of one or another type of mudflow in terms of the composition of the transported solid mass. Thus, in the Carpathians, water-rock mudflows of relatively small thickness are most often encountered. In the North Caucasus there are mainly mud-stone streams. From the mountain ranges surrounding the Fergana Valley in Central Asia, as a rule, mud flows descend.
It is significant that the mudflow, unlike a water flow, does not move continuously, but in separate shafts, sometimes almost stopping, then again accelerating its movement. This occurs due to the delay of the mudflow mass in the narrowing of the channel, at sharp turns, and in places where the slope sharply decreases. The tendency of a mudflow to move in successive shafts is associated not only with congestion, but also with the non-simultaneous supply of water and loose material from various sources, with the collapse of rock from slopes and, finally, with the jamming of large boulders and rock fragments in constrictions. It is when jams break through that the most significant deformations of the riverbed occur. Sometimes the main channel becomes unrecognizable or is completely submerged, and a new channel is developed.
3. Landfalls
Landslide is the rapid movement of masses of rocks forming predominantly steep slopes of valleys. When falling, the mass of rocks detached from the slope is broken into separate blocks, which, in turn, breaking up into smaller parts, cover the bottom of the valley. If a river flowed through the valley, then the collapsed masses, forming a dam, give rise to a valley lake. Collapses of the slopes of river valleys are caused by river erosion, especially during floods. IN high mountain areas The cause of collapses is usually the appearance of cracks, which, saturated with water (and especially when water freezes), increase in width and depth until the mass separated by the crack from some shock (earthquake) or after heavy rain or some other reason, sometimes artificial (for example, a railway excavation or quarry at the foot of a slope), will not overcome the resistance of the rocks holding it and will not collapse into the valley. The magnitude of the collapse varies within the widest range, ranging from the collapse of small rock fragments from the slopes, which, accumulating on flatter sections of the slopes, form the so-called. scree, and until the collapse of huge masses, measured in millions of m3, representing enormous disasters in cultural countries. At the foot of all the steep slopes of the mountains you can always see stones that have fallen from above, and in areas that are especially favorable for their accumulation, these stones sometimes completely cover significant areas.
When designing a railway route in the mountains, it is necessary to especially carefully identify areas that are vulnerable to landslides, and, if possible, bypass them. When laying quarries in the slopes and carrying out excavations, you should always inspect the entire slope, studying the nature and bedding of rocks, the direction of cracks, and sections, so that quarry development does not violate the stability of the overlying rocks. When constructing roads, especially steep slopes are laid with pieced stones dry or on cement.
In high mountain areas, above the snow line, snow avalanches often have to be reckoned with. They occur on steep slopes, from where accumulated and often compacted snow periodically rolls down. In the areas snow avalanches settlements should not be built, roads should be protected with covered galleries, and on slopes forest plantations, which best keep snow from sliding. Landslides are characterized by the power of the landslide and the scale of manifestation. According to the power of the landslide process, landslides are divided into large and small. According to the scale of manifestation, landslides are divided into huge, medium, small and small.
A completely different type of collapse occurs in areas of rocks that are easily leached by water (limestones, dolomites, gypsum, rock salt). Water seeping from the surface very often leaches large voids (caves) in these rocks, and if such a cave is formed near the earth's surface, then upon reaching a large volume, the ceiling of the cave collapses, and a depression (funnel, failure) is formed on the surface of the earth; sometimes these depressions are filled with water, and the so-called. "failed lakes" Similar phenomena are typical for many areas where the corresponding breeds are common. In these areas, when constructing permanent structures (buildings and railways), it is necessary to conduct a soil study at the site of each building in order to avoid destruction of the constructed buildings. Ignoring such phenomena subsequently causes the need for constant repair of the track, which entails high costs. In these areas, it is more difficult to resolve issues of water supply, search and calculation of water reserves, as well as the production of hydraulic structures. Direction groundwater flows are extremely whimsical; the construction of dams and the excavation of ditches in such places can cause the occurrence of leaching processes in rocks previously protected by artificially removed rocks. Sinkholes are also observed within quarries and mines, due to the collapse of the roof of rocks above mined-out spaces. To prevent the destruction of buildings, it is necessary to fill the mined-out space under them, or leave the pillars of the mined rocks untouched.
4. Ways to combat landslides, mudflows and landslides
Active measures to prevent landslides, mudflows, and landslides include the construction of engineering and hydraulic structures. To prevent landslide processes, retaining walls, counter-banquets, pile rows and other structures are constructed. The most effective anti-landslide structures are counter-banquets. They are located at the base of a potential landslide and, by creating a stop, prevent the soil from moving.
Active measures also include fairly simple ones that do not require significant resources or consumption of building materials for their implementation, namely:
To reduce the stressed state of slopes, soil masses are often cut off in the upper part and laid at the foot;
Groundwater above a possible landslide is removed by installing a drainage system;
Protection of the banks of rivers and seas is achieved by importing sand and pebbles, and the slopes by sowing herbs, planting trees and shrubs.
Hydraulic structures are also used to protect against mudflows. Based on the nature of their impact on mudflows, these structures are divided into mudflow control, mudflow dividing, mudflow retention and mudflow transforming structures. The mudflow control hydraulic structures include mudflow passages (chutes, mudflow diversions, mudflow diversions), mudflow control devices (dams, retaining walls, rims), mudflow release devices (dams, thresholds, drops) and mudflow control devices (half-dams, spurs, booms) constructed in front of dams, rims and retaining structures. walls.
Cable mudflow cutters, mudflow barriers and mudflow dams are used as mudflow dividers. They are installed to retain large fragments of material and allow small parts of the debris flow to pass through. Mudflow-retaining hydraulic structures include dams and pits. Dams can be blind or with holes. Blind-type structures are used to retain all types of mountain runoff, and with holes - to retain the solid mass of mudflows and allow water to pass through. Mudflow-transforming hydraulic structures (reservoirs) are used to transform a mudflow into a flood by replenishing it with water from reservoirs. It is more effective not to delay a mudflow, but to direct it past it settlements, structures using mudflow diversion channels, mudflow diversion bridges and mudflow drains. In landslide-prone areas, measures can be taken to move individual sections of roads, power lines and objects to a safe place, as well as active measures to install engineering structures - guide walls designed to change the direction of movement of collapsed rocks. Along with preventive and protective measures, an important role in preventing the occurrence of these natural disasters and in reducing damage from them is played by monitoring landslide, mudflow and landslide-prone areas, harbingers of these phenomena and predicting the occurrence of landslides, mudflows and landslides. Observation and forecasting systems are organized on the basis of hydrometeorological service institutions and are based on thorough engineering-geological and engineering-hydrological studies. Observations are carried out by specialized landslide and mudflow stations, mudflow batches and posts. The objects of observation are soil movements and landslide movements, changes in water levels in wells, drainage structures, boreholes, rivers and reservoirs, groundwater regimes. The obtained data characterizing the preconditions for landslide movements, mudflows and landslide phenomena are processed and presented in the form of long-term (years), short-term (months, weeks) and emergency (hours, minutes) forecasts.
5. Rules of behavior for people in the event of mudflows and mudflowshher and landslides
The population living in hazardous areas must know the outbreaks, possible directions and characteristics of these hazardous phenomena. Based on forecasts, residents are informed in advance about the danger of landslides, mudflows, landslides and possible zones of their action, as well as the procedure for submitting danger signals. This reduces the stress and panic that can arise when communicating emergency information about an immediate threat.
The population of dangerous mountainous areas is obliged to take care of strengthening houses and the territory on which they are built, and to participate in the construction of protective hydraulic and other engineering structures.
Primary information about the threat of landslides, mudflows and avalanches comes from landslide and mudflow stations, parties and hydrometeorological service posts. It is important that this information is communicated to its destination in a timely manner. Warning of the population about natural disasters is carried out in the established order by means of sirens, radio, television, as well as local warning systems that directly connect the units of the hydrometeorological service, the Ministry of Emergency Situations with settlements located in dangerous zones. If there is a threat of a landslide, mudflow or landslide, early evacuation of the population, farm animals and property to safe places is organized. Houses or apartments abandoned by residents are brought into a state that helps reduce the consequences of a natural disaster "and the possible impact of secondary factors, facilitating their subsequent excavation and restoration. Therefore, the transferred property from the yard or balcony must be removed into the house; the most valuable things that cannot be taken with you must be covered from exposure to moisture and dirt. Close doors, windows, ventilation and other openings tightly. Turn off flammable and toxic substances from the house and place them in remote pits or separate cellars. Otherwise, proceed in accordance with the procedure. , established for organized evacuation.
If there was no advance warning of the danger and residents were warned about the threat immediately before the onset of a natural disaster or noticed its approach themselves, everyone, without worrying about property, makes an emergency exit to a safe place on their own. At the same time, relatives, 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. These paths are determined and communicated to the population based on the forecast of the most likely directions of arrival of a landslide (mudflow) to a given settlement (object). Natural safe ways for emergency exit danger zone are the slopes of mountains and hills that are not prone to landslide processes.
When climbing to safe slopes, valleys, gorges and recesses should not be used, as side channels of the main mudflow may form in them. On the way, assistance should be provided to the sick, elderly, disabled, children and the weak. For transportation, whenever possible, personal transport, mobile agricultural machinery, riding and pack animals are used.
In the event that people and structures find themselves on the surface of a moving landslide area, they should move upward if possible and beware of rolling blocks, stones, debris, structures, earthen ramparts, and screes. When the speed of a landslide is high, a strong shock is possible when it stops, and this poses a great danger to people in the landslide. After the end of a landslide, mudflow or collapse, people who had previously hastily left the disaster zone and waited out the danger in the nearest safe place, making sure that there is no repeated threat, should return to this area to search for and provide assistance to the victims.
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Landslides, landslides and mudflows are dangerous geological phenomena and, although the reasons for their occurrence are different, they all have a similar impact on nature, humans, and objects of their economic activity. The measures to prevent them, eliminate their consequences, and the basic actions of the population in the event of emergencies caused by them are also similar. General condition the occurrence of these dangerous natural phenomena - the beginning of displacement of soil or rocks. In the territory Russian Federation There are areas where landslides, mudflows and landslides often occur. This North Caucasus, Ural, Sayan Mountains, Primorye, Kamchatka, Sakhalin.
A landslide is the separation and catastrophic fall of large masses of rocks, their overturning, crushing and rolling down on steep and steep slopes.
Causes of landslides
Landslides of natural origin are observed in the mountains, on sea shores and cliffs of river valleys. They occur as a result of a weakening of the cohesion of rocks under the influence of weathering, erosion, dissolution, as well as gravity and tectonic phenomena. Any ingress of water or snow into the weaker bonding layers leads to their gradual weakening. This is why landslides most often occur during periods of rain and melting snow. In winter, frozen water plays the role of fastening cement, preventing separated blocks of rock from coming apart. When the ice in the cracks melts, individual blocks in some rock mass can barely hold on, and even the slightest impact on them is enough for them to fall down the slope or cliff.
IN Lately The largest number of collapses (80%) is associated with human activity. Mainly due to improper work during construction and mining, as well as during blasting and plowing of slopes. Large landslides are also caused by earthquakes. Grandiose landslides occur in the mountains, where they often dam rivers.
Landslide classification
Landslides are characterized by the power of the landslide process, which is determined by the volume of collapsed rocks and the scale of manifestation - the area of the landslide. (See Appendix 1)
- - according to the power of the landslide process, landslides are divided into very small, small, medium, large and gigantic;
- - according to the scale of manifestation - small, small, medium and huge.
Some of the types of landslides are rockfalls, ground collapses and glacier collapses. Another type of landslide is a collapse - the collapse of individual blocks and stones from the soil on steep slopes. Rockfalls are especially widespread. Their movement occurs in the form of a fall along a significant part of the path. The sizes of falling stones are usually not large, and the total volume of rockfall does not exceed tens of cubic meters. The stones move in the form of repeated jumps at speeds of up to approximately 40-60 m/s. The largest rockfalls occur as a result of heavy downpours. Rockfalls are most dangerous on highways, laid in steep gorges (for example, in Altai, the Caucasus).
Measures to protect against landslides
Mountain collapses are common occurrences in all countries of the world. Their scale can be grandiose and the consequences tragic. They can cause large blockages or collapses of roads and railways, destruction of populated areas and forests, and contribute to the formation of catastrophic flooding and loss of life.
In landslide-prone areas, measures can be taken to move individual sections of roads, power lines and objects to a safe place, as well as active measures to install engineering structures - guide walls designed to change the direction of movement of collapsed rocks.
Protection against landslides involves the use of the following special structures and measures:
- - vertical planning of territories to regulate wastewater surface water and installation of drainage systems;
- - changing slope topography to increase their stability;
- - soil fixation.
To protect against landslides and collapses, tunnels and dams are built. The main condition for preventing these dangerous natural phenomena today remains the preservation natural conditions balances that have developed in landslide- and landslide-prone areas over many years. Observation and forecasting systems play an important role in warning about these natural disasters.
Actions of the population in the event of a collapse
If you are caught in a landslide:
- - try to hide under a rock or behind the trunk of a large tree;
- - lie face down on the ground, clasp your head in your hands, breathe through your clothes;
- - do not make sudden movements so as not to cause a new collapse.
The consequences of landslides and collapses are the destruction of buildings and structures, the hiding of populated areas, agricultural and forest lands by masses of rocks, the blocking of overpasses and rivers, changes in the landscape, and the death of people and animals.
Let's look at several types of fairly common natural phenomena: landslides, landslides and mudflows. They belong to dangerous geological phenomena and, although the reasons for their occurrence are different, they all have a similar impact on nature, man, and the objects of his economic activity.
The measures to prevent them, eliminate their consequences and the main actions of the population in the event of emergencies caused by them are also similar.
A landslide is the 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 of river valleys. Collapses occur as a result of weakening of the bonding layers of rocks under the influence of weathering processes, erosion or dissolution of rock and the action of gravity.
The occurrence of landslides is facilitated by cracks, faults of rocks, their layered nature, when there is clay, looseness and voids between harder and heavier rocks.
Any ingress of water or snow into these weaker bonding layers leads to their gradual weakening. Therefore, landslides most often occur during periods of rain or melting snow.
September 27, 1995 in the Sunzhensky district of Ingushetia. 6 km from the village of Alkun, a mountain collapse 130-150 m long, 6-10 m wide and 40-50 m deep occurred. As a result, the mountain road was damaged, 15 people died, including 1 child.
Recently, the largest number of collapses is associated with human activity, due to violations of rules during construction, mining, blasting, and plowing slopes.
Landslides are characterized by the power of the landslide process, which is determined by the volume of collapsed rocks and the scale of manifestation by the area of the landslide.
According to the power of the landslide process, landslides are divided into very small, small, medium, large and giant; according to the scale of manifestation - small, small, medium and huge.
Landslide - displacement of rock masses along a slope under the influence of own weight and additional load due to erosion of the slope, waterlogging, seismic shocks and other processes.
The movement of a landslide begins as a result of an imbalance of the slope and continues until a new state of equilibrium is reached.
The largest landslide is considered to be a giant landslide that occurred on February 18, 1911 in the Pamir Mountains (Tajikistan). After strong earthquake An unimaginable amount of rocks slid down from the slope of the Muzkol ridge, from a height of 5 thousand m. The village of Usoy was overwhelmed. Rocks blocked the valley of the Murghab River, and its flow was stopped for 4 years. A dam with a height of more than 700 m was formed. A new lake in the Pamirs, Sarez, appeared, which has a length of 75 km and a depth of about 500 m.
Landslides occur on the slopes of mountains, hills, ravines, and on steep river banks. They can descend from slopes of varying steepness, starting from 19 degrees, and on clay soils even with a slope steepness of 5-7 degrees. Landslides are not catastrophic processes, but the damage they cause to the national economy is significant: homes are destroyed, communication tunnels, pipelines, telephone and electrical networks are damaged.
The triggers for landslide processes are tremors, earthquakes, volcanoes, construction work, soil watering, changes in the type of plantings, destruction of vegetation, and weathering.
Landslides caused by human economic activity are mainly associated with the overloading of landslide slopes with embankments and various engineering structures, the construction of housing and industrial facilities on them, the cutting down of forests and shrubs, excessive watering of gardens and vegetable gardens on the slopes, leakage of water from water supply lines, and the closure of underground outlets. water
An example of a landslide caused by human activity is the landslide that occurred on October 8, 1963 in Italy from the slope of Mount Toz. Here, in the upper reaches of the Piava River, north of Venice, the 265 m high Vajont Dam was built in 1960. Before construction, detailed geological studies were carried out, as a result of which it was recognized that there was no danger of landslides.
In July 1963, when the reservoir was filled with water, the slope of Monte Toz began to slowly shift. On October 1, people noticed animals running away from the mountainside. Late in the evening of October 9, the slope suddenly collapsed, the rising wave overflowed the dam and fell from a height of 400 m. 40 million cubic meters of water poured into the valley. In 15 minutes, the town of Longarone and several other settlements were demolished. All houses were destroyed and all the inhabitants, every single person (about 2 thousand) died.
The main parameters of a landslide include its movement, power and scale. Depending on the steepness of the slope and the nature of the soil, a landslide can develop instantly. If its speed is more than 1 m per second, then it is almost a landslide, a collapse of rock, which is much more dangerous than a slowly sliding landslide.
A landslide speed of more than 1 m per minute is also considered catastrophic, since a short time It is almost impossible to organize the rescue of people, property and animals. The rate of landslide movement of more than 1 minute per day is considered fast, and less than 1 minute per month is considered slow.
Like landslides, landslides are characterized by the power of the landslide process - the volume of sliding rock mass, and scale - the area involved in the process. Based on the place of formation, they distinguish between mountain, underwater and snow landslides, as well as landslides of artificial earthen structures.
If there are signs of an approaching landslide (jamming of doors and windows of buildings, seepage of water on landslide-prone slopes), notify the nearest landslide station post. Turn off electrical and gas appliances, water supply network, prepare to evacuate. After the landslide has moved in the surviving structures, check the condition of the walls, ceilings, electricity, gas and water supply lines.
Mudflow (mudflow) is a temporary rapid mountain flow of water with high content stones, sand, clay and other materials. The volume of transported rock is millions of cubic meters. The duration of mudflows reaches 10 hours with a wave height of up to 15 m. The word mudslide comes from the Arabic “sayl”, which means “stormy stream”.
Mudflows in Tajikistan (May 1998) destroyed 130 schools and preschool institutions, 12 clinics and hospitals, 520 km of roads, 115 bridges, 60 km of power lines. Residential buildings and cotton crops on an area of 112 thousand hectares were damaged, gardens and vineyards were swept away, and a significant number of livestock died. The type of mudflow is determined by the composition of the mudflow-forming rocks. The main types of mudflows: water-stone, mud, mud-stone.
A water-rock mudflow is a flow in which coarse-grained material predominates. Formed mainly in the zone dense rocks. Mud mudflows form in areas where rocks of predominantly clayey composition occur. It is characterized by a significant content of clay and dust parts in the solid phase with their clear predominance over the rocky component of the flow. Mud-stone mudflow is characterized mainly by the content of coarse material compared to the mud component.
Unlike landslides and landslides that occur throughout our country, mudflows originate only in mountainous areas and move mainly along river beds or along gullies (ravines) that have significant slopes in their upper reaches. The entire area of origin and impact of a mudflow is called a mudflow basin.
For a mudflow to occur, three mandatory conditions must simultaneously coincide:
- 1. The presence on the slopes of the mudflow basin of a sufficient amount of easily transportable rock destruction products (sand, gravel, pebbles, small stones).
- 2. The presence of a significant volume of water to wash away stones and soil from the slopes and move them along the riverbed.
- 3. Sufficient steepness of the slopes (at least 10-15 degrees) of the mudflow basin and water flow (mudflow bed).
The immediate impetus for the occurrence of a mudflow can be: intense and prolonged rainfall; rapid melting of snow and glaciers; collapse into river beds large quantity soil, rocks; breakthrough of lakes, artificial reservoirs; earthquakes and volcanic activity.
Anthropogenic factors (results of human activity) often lead to the occurrence of mudflows. Examples of such activities include deforestation, blasting, quarrying, and mass construction carried out on slopes.
A mudflow can spread over long distances and cause massive obstruction and destruction along its path. In this case, the volume of a mudflow when moving down the channel can increase tens of times compared to the original due to the involvement of new rocks.
To prevent or reduce the effects of mudflows, the following work is carried out:
- - the surface of the earth is fixed by forest plantings;
- - the area of vegetation cover on the slopes is expanding;
- - Anti-mudflow dams and dams are constructed.
In addition, the construction of enterprises, residential buildings, and roads is prohibited on mudflow-prone slopes.
Actions in case of mudflow. If the noise increases, indicating an approaching mudflow, you must quickly turn off the electricity, gas, and water supply and leave the house.
When in the mountains, you need to climb up the slope from the bottom of the ravine as quickly as possible. Climb the rock, throwing away all heavy things that impede rapid movement.
Since heavy stones can be thrown out of the stream over long distances, threatening life. The chances of surviving in a mud-stone stream are slim: it is impossible to swim in it, and moving and colliding stones can injure a person. Therefore, help should be as quickly as possible. If a person finds himself in a mudflow, you need to give him a long pole, rope, ladder, etc. But you cannot pull him towards you, otherwise the load-bearing stones may crush him. You need to move with the flow, gradually bringing the victim to the shore.
You should be very careful when traveling on mountain roads. Careless, ill-considered actions in such places can cause collapses.
On the territory of Russia, landslides and landslides most often occur in the regions of the North Caucasus, the Urals, Eastern Siberia, Sakhalin, the Kuril Islands, the Kola Peninsula, as well as along the steep banks of large rivers and reservoirs. Mudflow-prone regions of Russia - the North Caucasus, the Urals, Southern Siberia, Kuril Islands, Kamchatka, Sakhalin, Chukotka.