"6" Landslide Disaster in Dangkou Primary School, Yihuang County, Jiangxi Province

20 14 On the morning of June 20th 1, a landslide occurred in the back hill of Dangkou Primary School in Shenzhen-Hong Kong Township, Yihuang County, Jiangxi Province, causing the collapse of four buildings of Dangkou Primary School Teaching Building 1, resulting in four deaths. 1 School toilet, two residential utility rooms, 1 mobile base station.

2 Geological hazard characteristics

2. 1 Regional geological environment conditions

The landslide area belongs to the landform of low mountains and hills. The top of the mountain is 420m above sea level, the relative height difference is about 140m, and the original slope is about 35. The formation lithology is fine-grained porphyritic biotite granite, fine-grained porphyritic biotite granite and fine-grained porphyritic dolomite granite () in the early Yanshan period. The surface is strongly weathered, showing loose sandy soil shape, with strongly weathered fragments locally. There are two fault zones in the area, of which 1 is a compression-torsion fault zone, which strikes northeast and tends to northwest with an inclination of about 45; 1 strip is compressive, inclined to northeast and southeast, with an inclination of about 76.

There is abundant rainfall in the landslide area. In recent 30 years, the average annual precipitation has reached 1907.0mm, the accumulated rainfall in the week before the disaster is about 400mm, and the accumulated rainfall in the three hours before the disaster is107.5 mm.

According to the China Earthquake Peak Acceleration Zoning Map (Jiangxi Part) (JB [200 1] 156), Code for Seismic Design of Buildings (GB 50011-2010) and

2.2 Characteristics of disaster geological bodies

The landslide occurred on the west slope of Qilongtai Mountain, about 70m away from the foot of the slope. The length of the landslide is about 50m, the width is 30m, the thickness is 1.5m, the volume is 2250m3, and the main sliding direction is 3 10. The main sliding bodies are silt and sand (including gravel), with gravel content of 5% and diameter of 5-30cm.

The landslide slid down the slope and rushed to Dangkou Primary School, resulting in the collapse of four teaching buildings in Building 1, and four people were buried and killed. At the same time, the landslide also damaged 1 school toilet, two residential utility rooms and 1 mobile base station, resulting in direct economic loss of about 2 million yuan (photo 1 ~ 2).

Photo 1 Landslide Panorama

Photo 2 Houses washed away by landslides

3 Geological hazards cause analysis and trend judgment

The landslide area is located in the hilly area, and the natural slope of the western slope of Longtai Mountain is about 35. The surface layer is residual silty clay with a thickness of 0.5 ~ 2.5m, and the underlying bedrock is Yanshanian granite with severe surface weathering and poor geological environment conditions.

There are two main reasons for the formation of landslides:

(1) The fully weathered sandy soil and residual silty clay with steep local slopes and loose surface structure on the western slope of Longtai Mountain have significantly reduced friction with the underlying bedrock surface after saturation, and are easy to slide under their own gravity and saturation pressure. The fragile natural geological environment is the internal factor for the formation of geological disasters.

(2) The accumulated rainfall in the week before the disaster is about 400mm, which is a quarter of the average rainfall for many years (1600mm), and the soil water content tends to be saturated; There was a torrential rain of 100 mm or more within 3 hours before the disaster, and the rapid infiltration of rainwater reduced the shear strength and friction of slope soil and increased the sliding force. The short-term concentrated slope flow forms strong erosion on the slope, which is the main inducing factor of landslide formation.

To sum up, due to the steep mountain slope, loose topsoil and high water content, landslides and mudslides occurred on the western slope of Longtai Mountain under the action of rainfall.

4. Emergency prevention and control of geological disasters

After the disaster, the Yihuang County Party Committee and the county government attached great importance to it, immediately launched emergency response, demarcated dangerous areas in time, set up warning lines, set up warning signs, arranged personnel to carry out monitoring, actively organized local people to avoid disasters, and properly handled the aftermath and temporary resettlement work. The Land and Resources Bureau took the initiative to intervene in the investigation in time. The day after the disaster, Yihuang County Land and Resources Bureau sent a working group to the scene to assist in disaster relief; Subsequently, Fuzhou Municipal Bureau of Land and Resources organized an expert working group to rush to the disaster site for investigation; The leaders of the Provincial Department of Land and Resources led a team to the site for guidance. Within 1 hour after receiving the report, the first batch of geological disaster emergency investigation experts composed of the provincial geological disaster emergency center have set off from Nanchang. On June 2 1 day, the provincial geological disaster emergency center, the provincial geological environment monitoring station and the Fuzhou geological team jointly conducted an emergency investigation on the landslides in Dangkou Primary School and its surrounding areas according to the disaster situation provided by the villages and towns.

5 Experience and Enlightenment

(1) The emergency mechanism for geological disasters is sound. After the occurrence of geological disasters, relevant responsible units and personnel can act quickly and carry out emergency disposal of geological disasters in an orderly manner.

(2) The information channel is unblocked and the response is rapid. After the disaster, governments at all levels and relevant departments can get information in time and send personnel to the scene for emergency treatment to avoid the occurrence of secondary disasters.

(3) Strengthen the investigation of natural slopes behind residential houses in densely populated areas such as hills, mountains, schools, hospitals and market towns, do a good job in geological disaster risk assessment, and formulate emergency plans in case of sudden extreme weather.