A landslide occurred in Taoyuan County, Hunan Province, causing three people to lose contact. How did the landslide form?

Forced mountain excavation, drainage system construction and engineering blasting are all important causes of landslide.

Forced mountain opening is an important reason for landslide formation. In some mountainous areas, when building a railway or a factory by the mountain, the lower part of the mountain slope will be excavated, making it slip without support. Some projects have changed the stability of the mountain after excavation. When encountering natural disasters such as rainstorm and earthquake, it will lead to the collapse and landslide of the mountain above.

The construction of drainage system is also an important reason for the formation of landslide, because some drainage systems will increase pore water in the mountain with a large amount of water infiltration, which will soften the rock and soil under pressure and increase the bulk density of slope, thus promoting landslide. If a reservoir is built near the mountain, when the water level of the reservoir changes sharply, it will also increase the water pressure on the slope and lead to landslides. The blasting of mining engineering will also lead to the occurrence of landslides and the loss of protection of slopes. When it is washed away by rain, a large amount of rain will penetrate into the slope and landslide will occur.

Before the landslide, there will be some abnormal phenomena, for example, at the slope angle before the landslide, a spring that has been blocked for many years re-gushes, the mountain rises, the rock breaks or makes abnormal sounds. This time is a sign before the landslide. People should evacuate to a safe place as soon as possible and don't stay in this place for a long time. In addition, there will be cracks in the mountain before the landslide, which will expand rapidly and there will be hot air or cold air. At this time, animals will be frightened and trees will be abnormal.

The formation of landslides is also closely related to the occurrence of natural disasters, such as strong earthquakes, storms and tsunamis, storm surges, etc., which will cause serious harm to the body and are prone to landslides. There are also some landslides, which occur after natural disasters such as rainfall, snowfall and tsunami, especially after heavy rain, many mountains become loose, and when encountering strong winds or slight earthquakes, the slopes will slide.