Why is the landslide in Xuyong, Sichuan in winter？ Expert： The slope with sudden temperature change is very sensitive to temperature and water.

Cctv news(Reporter He Chuan) At 16: 20 on December 9, a landslide occurred near a construction site of Xuwei Expressway in xuyong county, Sichuan Province. As a result, three houses collapsed, 11 people were buried and one lost contact. The reporter learned that as of noon on the 10th, all the buried people had been rescued, four people were confirmed dead and seven survivors were being treated in the hospital. The disaster also caused more than 30,000 cubic meters of landslides, which blocked the provincial road from Xuyong, Sichuan to Weixin, Yunnan, and cut off power for more than 7,000 villagers.

Sichuan is one of the areas with frequent landslides, especially after the flood season in summer, which is more likely to cause such disasters because of heavy rain. Then, why did the landslide in Xuyong, Sichuan occur in winter? What warning does this landslide have for the prevention and control of natural disasters in winter in the future?　

Diagram of the relationship between the position of the bridge and the disaster occurrence point.

There is a bridge under construction more than 100 meters away from the landslide. After the landslide, many people speculate whether there is some relationship between the landslide and the bridge construction.

It is understood that this bridge is called the Xuwei Expressway Bridge, which was built in the middle of the river valley. The mountain where the landslide occurred this time is on both sides of the river, and there is a distance of more than 100 meters between the bridge and the landslide position. Among the 11 people who were rescued, four were workers at the bridge construction site, and they rented one of the three destroyed houses. The rescued workers said that they would not live in this area if building a bridge would have such a great impact on the mountain.

Chen Hongqi, director of the Comprehensive Office of the Geological Disaster Prevention and Control Center of the Ministry of Natural Resources, said in an online interview: "What if we only look at the drawings, I don’t find any evidence of a relationship between the two. But there is a simple road in the middle of the landslide, so it is easy to guess that (building a bridge) is related to this incident. Our country has very clear procedures for understanding the causes of disasters. I believe that the expert group on the spot will make a scientific judgment, and everything will be based on the data. "

It is reported that Luzhou City has set up an expert investigation team to investigate the cause of the disaster. Whether the bridge construction is related to the landslide will not be conclusive until the official investigation report is released.

In 2016, Sichuan Province published a list of 35 geological hazards, among which xuyong county was one. According to local villagers, just below the landslide is the provincial highway. In 2017, a vehicle was hit by a stone falling from the mountain at the disaster site.

Through aerial camera observation, we can see that the whole mountain is a mountain shape with loess mixed with boulders. It is reported that in 2015, a similar disaster occurred in Bailu Miao Autonomous Township on the other side of this mountain, when a flash flood in summer killed 11 people.

Why did this disaster happen in winter? Chen Hongqi said that the freezing and thawing caused by the sudden rise and fall of temperature in winter caused damage to rock mass, especially some slopes were sensitive to temperature and water, which also caused landslides and landslides.

On the evening of 10th, Chen Hongqi said in an online interview that the formation of landslides is influenced by many factors such as geology, topography and rainfall, and most of them are caused by rainfall in our country. Because of the heavy rainfall in summer, it is relatively easy to occur, so everyone feels a little confused. In fact, according to previous records, landslides sometimes occur in winter, which is a normal phenomenon. In winter, when the weather suddenly rises and falls, it will bring the influence of freezing and thawing, which will destroy the rock mass and cause landslides and landslides. Especially some slopes are sensitive to water and temperature.

Chen Hongqi said that the prevention and control of geological disasters cannot be achieved overnight. Only through meticulous and dynamic investigation and monitoring can we grasp the information of these risk changes and try to avoid similar disasters from happening again.