Landslide is a geological phenomenon of slope rock and soil sliding along the through shear failure surface. The occurrence of landslide caused disaster to people. The following is what I brought about the causes of the landslide. Welcome to read it!
To explore the formation conditions of landslide, we must consider the factors affecting slope stability. The factors affecting slope stability include internal factors and external factors The internal factors include the properties of rock and soil mass, geological structure, rock mass structure, in-situ stress and so on They often play a major controlling role External factors include the action of surface water and groundwater, earthquake, weathering, manual excavation, blasting and engineering load Surface water and groundwater are the most important and active external factors affecting slope stability Finding out and mastering these influencing factors is very necessary to understand the occurrence and development law of slope instability and formulate prevention and control measures
1. Internal conditions of landslide formation
The internal conditions of landslide are related to the properties, structure, structure and occurrence of rock and soil constituting the slope Different rocks and soils have different shear strength, weathering resistance and water erosion resistance. For example, hard and dense hard rocks have high shear strength and weathering resistance, and the lithology basically does not change under the action of water. Therefore, the slopes formed by them are often not prone to landslide On the contrary, shale, schist and general soil are just the opposite. Therefore, the slope composed of them is more prone to landslide In terms of the structure and structure of rock and soil, it is mainly the tendency of rock (soil) layer surface, fault surface and crack, which has a great relationship with the development of landslide At the same time, these parts are easily weathered and have low shear strength When their tendency is consistent with that of the slope surface, bedding landslide and sliding along the bedrock surface in the accumulation layer are easy to occur; Otherwise, vice versa The section size of the slope also has a great relationship with the stability of the slope. The steeper the slope is, the worse its stability is and the more prone it is to slide If the slope height and the horizontal length of the slope are the same, but one is to grade to the top, while the other is to set a platform in the middle of the slope, the stability of the slope will be increased due to the back pressure of the platform on the slope In addition, if the landslide wants to slide forward, there must be a certain space at its front edge, otherwise the landslide cannot slide forward The scouring of rivers in mountainous areas, the deepening of river valleys and a large number of unreasonable cutting slopes can form a high and steep free surface, which provides good conditions for the development of landslides In short, landslide can occur when the lithology, structure and occurrence of the slope are conducive to the development of the slope and cause changes in the lithology, structure and occurrence of the slope under certain external conditions
2. External conditions of landslide formation
The external conditions of landslide development mainly include the action of water, unreasonable excavation and loading, vibration and mining on the slope The investigation shows that more than 90% of landslides are related to the action of water The source of water is nothing more than atmospheric precipitation, surface water, groundwater, seepage of farmland irrigation, leakage of high-level pool and drainage pipeline, etc Regardless of the source, once the water enters the rock and soil mass of the slope, it will increase the gravity of the rock and soil and produce softening effect, reduce the shear strength of the rock and soil, produce hydrostatic pressure and hydrodynamic force, scour or erode the slope toe, and lubricate the overlying rock and soil layer on the impermeable layer. When the local groundwater collects into the layer on the top surface of the impermeable layer, it will also produce buoyancy effect on the overlying layer, etc In short, the action of water will change the nature, state, structure and structure of the rock and soil constituting the slope Therefore, many landslides were close to stability in the dry season, but they moved rapidly in the rainy season, forming "big fish sliding, light rain sliding, no rain sliding" This also shows the relationship between rain and landslide In the construction of mountainous areas, the slope often slides due to unreasonable excavation of slope toe or improper filling and abandonment of soil, construction of houses or stacking of materials on the slope, which destroys the equilibrium conditions of the slope In addition, vibration also has a certain impact on the occurrence and development of landslides. For example, large landslides are often accompanied by large earthquakes, and sometimes landslides can be caused by blasting
First, geological and geomorphic conditions; The second is the influence of internal and external forces (power) and human actions. The first condition relates to the following aspects:
(1) rock and soil type: rock and soil mass is the material basis of landslide. Generally speaking, all kinds of rocks and soils may form landslide mass, among which the structure is loose, the shear strength and weathering resistance are low, and the properties of rocks and soils that can change under the action of water, such as loose overburden, loess, red clay, shale, mudstone, coal measure strata, tuff, schist, slate, phyllite, etc. and the slope composed of soft and hard rock layers are prone to landslide.
(2) geological structure conditions: the rock and soil mass constituting the slope can slide downward only when they are cut and separated into discontinuous states by various structural planes. At the same time, the structural plane provides a channel for rainfall and other water to enter the slope. Therefore, slopes with various joints, fissures, bedding planes and faults are most prone to landslide, especially when the steep dip structural plane of parallel and vertical slopes and the gently inclined structural plane along the slope are developed.
(3) topographic and geomorphic conditions: landslides may occur only on slopes with a certain slope at a certain geomorphic position. Generally, the slopes of rivers, lakes (reservoirs), seas and ditches, the open hillsides at the front edge, the slopes of railways, highways and engineering buildings are all geomorphic parts prone to landslide. The slope with a gradient of more than 10 degrees and less than 45 degrees, steep in the lower part, gentle in the middle, steep in the upper part and annular in the upper part is the favorable terrain for landslide.
(4) hydrogeological conditions: groundwater activity plays a major role in the formation of landslide. Its function is mainly manifested in: softening rock and soil, reducing the strength of rock and soil, generating hydrodynamic pressure and pore water pressure, eroding rock and soil, increasing the unit weight of rock and soil, and generating buoyancy force on permeable rock stratum. In particular, the softening effect and strength reduction effect on the sliding surface (belt) are the most prominent.
In terms of the second condition, the area with current crustal movement and the area with frequent human engineering activities are landslide prone areas. External factors and effects can change the basic conditions of landslide and induce landslide. The main factors that cause the erosion of the surface water body, such as the continuous immersion of the snow and the slope toe by the earthquake are the scouring of the surface water body and the slope toe; Unreasonable human engineering activities, such as excavation of slope toe, loading on the upper part of slope, blasting, reservoir water storage (discharge) and mining, can induce landslides, as well as tsunami, storm surge, freezing and thawing.
Through the above introduction to the morphological characteristics and formation conditions of landslide, it is not difficult for us to find out the relevant engineering measures to control landslide However, the occurrence of a landslide is often the result of the comprehensive action of multiple factors, because only after detailed investigation, analysis and calculation can we formulate practical prevention and control measures In general, landslide treatment should adhere to the principle of prevention first, comprehensive treatment and timely treatment Combined with the factors of slope instability and the internal and external conditions of landslide formation, the treatment of landslide can be started from the following two aspects:
1. Eliminate and reduce the harm of surface water and groundwater
The occurrence of landslide is often closely related to the action of water, which is often the main factor causing landslide. Therefore, it is particularly important to eliminate and reduce the harm of water to the slope. Its purpose is to reduce the pore water pressure and hydrodynamic pressure, prevent the softening and dissolution decomposition of rock and soil mass, and eliminate or reduce the scouring and wave impact of water The specific methods are as follows: to prevent the peripheral surface water from entering the landslide area, intercepting ditches can be built at the boundary of the landslide; In the landslide area, drainage ditches can be built on the slope Mortar rubble or artificial vegetation can be used to cover the overburden to prevent surface water infiltration For rock slope, shotcrete can also be used for surface protection or hanging reinforcement mesh for shotcrete There are many measures to remove groundwater, which should be selected according to the geological structure characteristics and hydrogeological conditions of the slope The commonly used methods are: 1. Horizontal drilling and drainage; 2. Vertical hole drainage; 3. Shaft pumping; 4. Tunnel drainage; 5. Support blind ditch
2. Improve the mechanical strength of slope rock and soil mass
Through certain engineering and technical measures, improve the mechanical strength of slope rock and soil mass, improve its anti sliding force and reduce the sliding force The common measures are: 1. Slope cutting and load reduction; Reduce the slope height or gentle slope angle to improve the stability of the slope In slope cutting design, the height of unstable rock and soil mass shall be reduced as much as possible, while the rock and soil mass resisting sliding shall not be reduced This method is not always the most economical and effective measure. Economic and technical comparison should be made before construction. 2. Artificial reinforcement of slope; The commonly used methods are: 1. Building retaining walls and retaining walls to support unstable rock mass; 2. Reinforced concrete anti slide pile or reinforced pile as anti slide support works; 3. Prestressed anchor bolt or anchor cable is suitable for strengthening rock slope with crack or weak structural plane; 4. Strengthen the strength of slope rock mass or soil mass by consolidation grouting or electrochemical reinforcement; 5. SNS slope flexible protection technology, etc
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