The harm and prevention of landslide from Fushun West open Pit Mine, the largest in Asia

I. Definition of landslide

Landslide is the movement of the mountain surface along the slope under the action of gravity after being disturbed by various factors. Engineering geological experts divide the movement of landslide into collapse, landslide, debris flow, rolling stone and so on.

Landslide is caused by a variety of factors, mostly due to the influence of precipitation, in addition to earthquakes, freeze-thaw, mountain excavation, underground mining, reservoir filling, tsunami, etc., is not only a natural phenomenon, but also the result of human activities. Therefore, landslides often occur on slopes with loose rock and soil structure, poor geological conditions and a certain slope, and are affected by the above natural or human activities or after a period of time.

Second, the harm of landslide

If the landslide occurs in the residential business district, it usually destroys buildings, houses, schools, office buildings, power facilities, casualties and animals, etc., occurs in the transportation and other infrastructure areas, will destroy roads, Bridges, water conservancy, etc., if it occurs in agriculture, industry and mining areas, it can damage farmland, production facilities, mining equipment, etc., causing major economic losses.

When landslides occur accompanied by heavy rain, flood, snow and ice melting and other large bodies of water, debris flow disasters often occur. Due to the inclusion of a certain amount of solid soil, silt and stone in the flood and other solid mixtures, usually the volume content of at least 15%, up to about 80%, so it is more destructive than floods and landslides, and the disaster has sudden occurrence, large impact area, faster fluidity and other characteristics. Compared with a single landslide disaster, debris flow may merge into the river, cause changes in the river, indirectly damage other buildings, transportation facilities and farmland, silting reservoirs, affecting the safety of water conservancy facilities, etc., and because of the large amount of water-solid mixed materials, silting is more difficult for post-disaster rescue and recovery.

If the landslide in the reservoir area impacts the reservoir water, it will cause landslide surge, affect the dam body safety, and even cause dam damage, which poses a serious security threat to the water conservancy hub itself and downstream residents and facilities. For example, in March 1961, Tangyanguang large-scale landslide occurred in Zhexi Reservoir, Hunan Province. After rushing into the reservoir, a 21-meter surge wave crossed the dam roof under construction, resulting in more than 40 casualties. In 2003, a landslide in Qianjiangping village, Zigui County, entered the Qinggan River and caused a 20-meter-high surge, killing or missing 24 people, upsetting 22 ships and causing economic losses of more than 80 million yuan.

Weir lake refers to the lake formed after the landslide rock and soil bodies block the valley, river bed and so on. As the body of the barrier lake is a scattered rock or debris flow that collapses down, its structure and mechanical properties are extremely unstable. With the rise of water level and the erosion, dissolution and collapse of the water body, once the dam break occurs, it will bring devastating damage to the downstream. The landslide on the Jinsha River occurred on October 11 and November 3, 2018, forming a barrier lake with a length of about 5,600 meters, a width of about 200 meters and a height of about 70 meters, and a water body of about 200 million cubic meters, resulting in the interruption of the main stream of the Jinsha River and the rapid rise of the water level. Although the artificial drainage channel has been excavated, the barrier lake has successfully relieved the crisis of dam break and eliminated the hidden dangers. However, after the flood discharge, the river water still brought huge losses to the downstream, transferring more than 40,000 people, 7 Bridges were destroyed, more than 8,000 houses collapsed, a large number of farmland was damaged, and direct economic losses reached 4,27155 million yuan.

3. Signs and prevention of landslides before they occur

1. Landslide signs

Landslide precursors are first manifested in the structural precursors of the mountain, such as radial cracks in the front of the landslide, soil uplift in the front of the landslide, rapid expansion of transverse cracks in the rear edge, shear cracks and acceleration of longitudinal rock and soil bodies on both sides, deformation of buildings near the hillside, inclined structures, and local collapse of the mountain.

Landslides often cause many abnormal phenomena when they appear structural signs. Including abnormal sounds in the valley, the water quality of springs and Wells near the hillside is suddenly cloudy, dry or resurrected, the water level is sudden, and animals have abnormal reactions, etc., there will be a landslide. In the summer and autumn concentrated rainfall season, disaster weather such as persistent rainfall and heavy rain are often the main external factors inducing debris flow.

2. Landslide engineering reinforcement and prevention measures

There are many methods for landslide hazard reinforcement. Generally, different reinforcement methods are adopted according to different landslide rock and soil properties, instability modes and external construction conditions. The main reinforcement methods include active rockfall protection net, spray (grouting) method, anti-slide pile reinforcement, retaining wall, anchor rod, prestressed anchor cable, steel grid beam, etc. In addition, slope cutting and load reduction, ground and underground drainage, etc. The above methods are combined with comprehensive treatment and other measures.

3, landslide disaster man-made response measures

When a landslide occurs, the following measures should be taken:

(1) When the landslide occurs, you should run to the sides or high ground perpendicular to the sliding direction, and avoid running up or down the sliding direction.

(2) Do not stay in a low place with thick soil under a steep slope of Rolling Stones or a large number of deposits.

(3) When the landslide slides as a whole and cannot run to both sides, holding a solid fixed object is also a self-rescue measure.

(4) When encountering long-term rainfall or heavy rain, we should be alert to the occurrence of debris flow; If the debris flow occurs, do not run along the debris flow ditch, should run to the hillside on both sides of the ditch bank.

(5) Should try to run out of the building, to the open area, while protecting the head, do not return to the landslide area in a short time to stay in residence, to avoid secondary disasters.

(6) When escaping, abandon all items that affect the running speed, and carry communication tools to facilitate external contact and help.

(7) Timely reporting of the disaster situation to the government or relevant units is conducive to disaster relief and mitigation of disaster losses.

Iv. Conclusion

Due to the complexity of landslide geological material and its engineering, as well as the diversity of environment, the study of landslide stability and the prediction of landslide disaster have always been a very challenging field, and also a scientific and engineering problem to be solved urgently. In recent years, with the development of modern computing technology and landslide information monitoring technology, the application of modern mechanics in the field of landslide engineering safety has become more and more mature. Based on numerical simulation, combined with monitoring information and efficient large-scale parallel computing technology, landslide disaster prediction and early warning have been preliminarily realized. It is believed that the difficult problem of accurate prediction of landslide disaster will be completely solved in the near future.