"9" Landslide Disaster in Shijiadao Village, Wang Xi Sub-district Office, Baqiao District, Xi City, Shaanxi Province

At 2011September1July 14 10, a landslide occurred on the north slope of Bailuyuan Village, Wang Xi Sub-district Office, Baqiao District, Xi City, killing 32 people and injuring 5 others, resulting in a direct economic loss of 8 million yuan.

Figure1Panorama of the "9. 17" landslide in Baqiao District of Xi City.

2 regional geological environment conditions and genetic trend analysis

2. 1 Regional geological environment conditions

The climate in Baqiao District of Xi City belongs to warm temperate and semi-humid continental monsoon climate, with annual average temperature11.3 ~13.7℃ and annual average precipitation of 584. 9mm。 Rainfall is concentrated from July to September, and autumn showers often occur. Due to the special geological and topographic conditions, geological disasters such as collapse and landslide often occur in the rainy season in the Loess Plateau. The rainfall intensity is directly proportional to the occurrence of geological disasters.

Baqiao district is located in the eastern suburb of Xi, in the middle of Guanzhong basin in Weihe fault depression valley, with high terrain in the southeast and low terrain in the northwest. There are loess tablelands in Hong Qing in the east, Bailuyuan in the south, Longshou tablelands in the west, and alluvial plains in Bahe and Weihe rivers in the north. The landform in this area is dominated by alluvial-diluvial valley terraces, followed by loess tableland and low mountains and hills in the east.

The landslide is located on the north slope of Bailuyuan on the left bank of Bahe River (west bank), with a slope angle of 50 ~ 70, and vegetation and farmland are developed in some areas. The upper part of the landslide is Malan loess with loose soil, the lower part is Lishi loess, and the middle part is multi-layered ancient soil.

2.2 Geological characteristics of disasters

The landslide is located in the north slope of Bailuyuan, Shijiadao Village, Wang Xi Sub-district Office, Baqiao District, Xi City. The main accumulation area of landslide is 180m long and 230m wide, with an average thickness of 6m and a maximum thickness of 10m, and the total sliding amount is about 248,000m3 (Figure 2). The landslide slipped 320 meters, destroying some factories and dormitories of Qi 'an Yanta Ceramics Company, killing 32 people and injuring 5 others.

Fig. 2 "9. 17" landslide profile in Baqiao District, Xi City.

2.3 Cause analysis and trend judgment

The main causes of landslides are as follows:

First, formation lithology. Landslides are located at the edge of the Loess Plateau. The upper part of the landslide is Malan loess with loose soil, the lower part is Lishi loess, and the middle part is multi-layered ancient soil. The loess plateau is high and steep, vertical joints are developed, and rainwater is easy to penetrate, while the ancient soil is dense, waterproof and the geological structure is easy to slide. Under the action of heavy rainfall, loess is prone to instability and sliding at the interface between loess and paleosol.

Second, the original abandoned old brick factory cut slopes to borrow soil. Xi Anruifeng Hollow Brick Factory, formerly known as Xi Anji Tile Factory, was built in 1965. During the period of 1965 ~ 1996, a steep slope with a gradient of 50 ~ 70 was formed, which was unstable and prone to landslides. According to the interpretation and field verification of the high-resolution satellite remote sensing image of the second land survey of land and resources in April 20 1 1, vegetation is developed here, and there are no signs of interference such as artificial slope cutting in the near future (Figure 3).

Third, continuous rainfall. According to meteorological data, the cumulative rainfall in this area reached 284. 5mm from September 1 to September 17. According to statistics for many years, the rainfall in this half month is nearly three times the average monthly rainfall in this area (the average monthly rainfall for many years is 95. 2mm)。 It is concluded that rainfall-induced landslides occur from time to time.

Development trend: the trailing edge and both sides of the landslide are steep, and the rainfall continues, which may lead to another landslide. The trailing edge of the landslide and steep slopes on both sides are in an unstable state.

3 emergency response and disposal measures

At 2011September1July 14 10, a landslide occurred on the north slope of Bailuyuan, Shijiadao Village, Wang Xi Sub-district Office, Baqiao District, Xi City, causing heavy casualties. Shaanxi Provincial Department of Land and Resources and Shaanxi Geological Survey Institute immediately formed an emergency investigation team and rushed to the scene together with xi Municipal Bureau of Land and Resources and xi Geological Survey.

4 Experience and Enlightenment

Strengthen the investigation of units, enterprises, villagers and households affected by high and steep loess slopes, strengthen monitoring and inspection, and take timely measures to avoid casualties and reduce property losses once hidden dangers of geological disasters are discovered.

In the future, we should draw lessons from this loess landslide disaster in the process of engineering construction, further strengthen the safety guarantee of geological environment and avoid dangerous slope areas; Especially in areas prone to geological disasters, it is necessary to carry out geological disaster risk assessment and related research work.

(The basic information in this section is provided by Shaanxi Provincial Department of Land and Resources and edited by Wei)

Fig. 3 Satellite remote sensing image of the second land survey of land and resources in April 2011(no obvious disturbance was found in the vegetation development of the steep slope at the rear edge).