CAUSES OF LANDSCAPE EVENTS AND PREVENTIVE MEASURES

ABSTRACT

The article describes the phenomenon of landslides, which are natural emergencies, and provides information on the causes of their occurrence, elements, signs of landslide danger and methods of moving the population when they occur. It is indicated that the nature of this emergency depends on the geological and geomorphological structure of the slope and that it consists of elements called a landslide surface, a landslide chamber, a landslide base, a landslide terrace, a landslide-wave belt and a landslide body. In addition, residents living in areas where there is a high probability of this process are given recommendations on what signs indicate a landslide and what to do if such a situation occurs. The article also emphasizes that in 1958, in order to study these phenomena, promptly notify the population and evacuate it to safe places, a special Engineering and Geological State Observation Service was created in Uzbekistan, which currently has 7 regional observation stations and 21 posts throughout our country.

АННОТАЦИЯ

В статье описывается явление оползней, являющихся чрезвычайными ситуациями природного характера, а также дается информация о причинах их возникновения, элементах, признаках оползневой опасности и способах перемещения населения при их возникновении. Указывается, что характер данной чрезвычайной ситуации зависит от геолого-геоморфологического строения склона и что он состоит из элементов, называемых оползневой поверхностью, оползневой камерой, оползневым основанием, оползневой террасой, оползнево-волновым поясом и телом оползня. Кроме того, жителям, проживающим в районах, где велика вероятность возникновения этого процесса, даны рекомендации о том, какие признаки указывают на оползень и что делать, если такая ситуация произошла. В статье также подчеркивается, что в 1958 году в целях изучения этих явлений, своевременного оповещения населения и эвакуации его в безопасные места в Узбекистане была создана специальная Инженерно-геологическая государственная служба наблюдений, которая в настоящее время имеет 7 региональных станций наблюдений и 21 пост по всей территории нашей страны.

Keywords: Landslide, rock, sliding mass, sliding trajectory, landslide surface (slip line), landslide body, landslide base, landslide terraces, landslide or break wall, landslide body, landslide tongue.

Ключевые слова: Лавина, скальный массив, оползневая масса, траектория оползня, поверхность лавины (линия скольжения), лавинный дом, основание лавины, лавинные террасы, лавинная или обрывная стенка, тело лавины, язык лавины

Introduction. An avalanche is a large mass of soil or rock with high moisture content that moves down the slopes of mountains, hills and ridges under the influence of its own gravity. The slope of the impermeable rock layer underlying the soil on the slopes plays an important role in the occurrence of an avalanche. The more the slope of the impermeable rock layer matches the relief, the higher the probability of the mass lying on it forming an avalanche. For an avalanche to occur, as a result of precipitation in areas with a risk of landslides, the soil mass on the slope becomes saturated with moisture, becomes fluid and moves rapidly downhill along the surface of the impermeable rock layer underlying the soil.

Figure 1. Scheme of landslide formation

The volume of a landslide can range from several tens of thousands of m³ to several hundred thousand m³ and more. Large-scale landslides move at high speed in their direction, destroying all living things, destroying crops, disabling settlements, civil and industrial facilities, and highways. Therefore, landslides, like earthquakes, are considered one of the most dangerous natural disasters. To date, a large number of landslides have been observed in the territories of the Central Asian Republics.

Methods. The external and internal structure of landslide-prone slopes varies, depending on the geological and geomorphological structure of the slope. Any landslide has elements called the avalanche surface, avalanche chamber, avalanche base, avalanche terrace, avalanche and breakwall, and avalanche body[1,2].

The trajectory of the sliding mass along a certain surface is called the landslide surface (slip line). The shape of the landslide surface is wavy, arcuate, and straight.

Large depressions formed on slopes as a result of a landslide are called landslide troughs[3,4].

The stepped slopes formed by the landslide are called landslide terraces.

Figure 2. The layout of the landslide base

a - the situation where the landslide base coincides with the slope line, b - the situation where the landslide base does not coincide with the slope line (photo by G.O. Mavlonov and others)

A landslide or rupture wall is the part of the landslide surface that is uncovered after the landslide has occurred. The height of the landslide walls can range from a few meters to several tens of meters, and the length can range from several tens of meters to hundreds of meters or more[5,6,7].

The landslide body is a mass that has been pushed. The size of the mass that has been pushed is determined by the boundary of the landslide wall. The size of the landslide body varies and depends on the width of the area where the landslide occurred and the thickness of the mass that has been pushed.

Results. Chaulisoy landslide - April 30, 1960, 30 people died, total mass 200 thousand m³, Khojikent landslide - 1961, 12 people died, total mass 1000 m³, Dzhigaristan landslide - May 4, 1991, 56 people died, total mass 176 thousand m³.

For example, on February 11, 1911, a 9-magnitude earthquake occurred in the Muzkol mountain range of the Pamirs, which resulted in the Ugoy landslide. The landslide carried 2.5 km³ of rock over a distance of 2.5 km, blocking the Murghab River. As a result of the disaster, the village of Ugoy was buried under the landslide, and 54 people died. Today, the world-famous Lake Sorez has formed here in front of a natural dam with a depth of 703-788 m and a width of 4.3-5.3 km.

Figure 3. Landslide occurrence

As a result of a landslide that occurred in the village of Sharora, Tajikistan on December 7, 1987, a rock fragment 900 meters wide and about 70 meters thick moved, crushing more than 450 people. The cause of this landslide was the saturation of porous rocks distributed underground, the rise in the groundwater level, and a 7-point earthquake.

In 1991, another powerful «Dzhigaristan» landslide occurred in the Akhangaron Valley. Here, 30 million m3 of porous soil slid down for 7 seconds, killing more than 50 people living there. The cause of the landslide is explained by the fact that the village is located below the slope, the rocks on the slope are composed of porous rocks of great thickness, blasting operations were carried out on these rocks for many years, and there was a lot of precipitation that year. Many more such examples can be cited.

The population living in areas where landslides are likely to occur should have information about the signs, characteristics and dangers of landslides and know what to do in case of such a situation.

Signs of landslide danger include:

- changes in the surface and relief of mountains and hills, sudden disappearance of spring waters or changes in their direction of movement;

- the appearance of various forms of piles of soil and rocks and cracks on the surface of the earth, the appearance of breaks in roads and crooked growth of trees;

- the formation of mounds of soil in areas with landslide risk or at the bottom of hills;

- the appearance of cracks in the walls of buildings and private houses located

Figure 4. Typical signs of landslides in areas with landslide risk

around the area where landslides are likely to occur. Usually, these signs appear as a result of rains and melting snow in the spring and autumn months.

Land development and irrigation procedures without a good study of the soil layer of hills and hills also lead to an increase in soil moisture and the development of landslides. Especially in areas prone to landslides, man-made changes such as mining, construction of railways and highways, laying of water and gas pipelines, and cutting down forests and shrubs also accelerate the process of landslides.

Movement of the population in case of a landslide

First of all, people living in areas with a risk of landslides must know in advance whether their homes are at risk of being covered by a landslide. Usually, it is not possible to live or build buildings for other purposes on land with a risk of landslides. If there is a risk of landslides in a populated area, the population is warned by local authorities and evacuated to safe places according to a pre-established plan.

After a landslide, it is necessary to check the electricity, water and gas supply systems in the area and make sure that they are in good condition.

To date, state avalanche monitoring services have been established in all mountainous and foothill regions of our Republic and they conduct scientific

research on the examination of dangerous geological areas, including areas

Figure 5. Scheme of evacuation of residents from an area where a landslide may occur

with a risk of landslides. Employees of the state monitoring service identify all dangerous processes in the area and determine measures to eliminate them. If such a risk exists, they inform local authorities about this through warning letters and help determine measures to warn the population.

The obligations of citizens living in areas with a risk of landslides are as follows:

- strictly follow the instructions of responsible persons and warning procedures issued by local authorities about the possibility of a landslide;

- actively participate in eliminating it in the event of a landslide;

- immediately report to the citizens' assembly upon receiving information about the possibility of a landslide;

- participate in the rapid evacuation of residents in landslide areas to safe areas;

- assist surveillance service personnel in marking dangerous areas and in other tasks.

There are indirect and direct methods of landslide prevention: Indirect methods of landslide prevention include:

-not carrying out construction and related excavation work on slopes;

-not allowing the accumulation of eroded rocks under slopes;

-increasing the number of deciduous trees on slopes;

-not allowing irrigation and plowing on slopes.

Direct methods of eliminating landslide movement and its impact include:

-constructing devices that regulate and control water flow;

-lowering the groundwater level;

-construction of retaining walls to prevent rock from sliding;

Discussions. Given the destructive nature of landslides, in 1958 the State Geological Engineering Observation Service was established in Uzbekistan to specifically monitor them. Currently, the State Observation Service has 7 regional observation stations and 21 posts throughout the territory of our country. Their observation areas include more than 8 thousand economic facilities, 144 health complexes, 170 highway areas, and more than 20 mining and hydraulic structures. The State Observation Service is on duty around the clock with the employees of the Ministry of Emergency Situations. The first problem in studying landslides is the uncertainty of their occurrence time.

Conclusion. In conclusion, it can be said that if indirect and direct methods of preventing landslides are followed, the death of all living things, the destruction of crops, and the failure of settlements, civil and industrial facilities, and highways will be prevented.

References:

1. R. Yeshboyev. Educational methodical manual on the subject of “Engineering Geology” // Tashkent. 2013. P. 96-102
2. SH. Shermatov. Fundamentals of hydrogeology and engineering geology.//T. “Turon-Iqbol” publishing house, 2005. P. 107-113
3. Nigmatov  I.,  Tojiyev  M.  Favqulodda  vaziyatlar  va  fuqaro  muhofazasi. Darslik–T.:Iqtisod-Moliya, 2011, 260 b.
4. Nigmatov I., Azimov A., Tojiev M. Favqulodda vaziyatlar va fuqaro muhofazasi fanidan amaliy mashg’ulotlar. Uslubiy qo’llanma. TDTU, 2015 y
5. Tukhtamirzaevich M. A. Flooding in the territory of the republic of Uzbekistan and the movement of the population therein //Scientific Impulse. – 2022. – Т. 1. – №. 5. – С. 2285-2291.
6. A.T.Mamadaliyev., Z.N.Mamadjanov., M.M. Sobirov. «Favqulodda vaziyatlar va fuqaro  muhofazasi». Darslik.-T.: “DIMAL”, 2024, 416 b
7. A.T.Mamadaliyev. «Injenerlik geologiyasi».Darslik.-T.: “DIMAL”,2024,275 b