"8" Landslide in Bibeikou Village, Ruyuan Yao Autonomous County, Guangdong Province

On August 17, 2065438, affected by continuous rainfall, a landslide occurred in Bibeikou Village, Bibei Town, Ruyuan Yao Autonomous County. Due to the timely monitoring and measures taken by the local town government and the National Land Institute, 47 local households 180 people successfully avoided danger, causing no casualties. The landslide made 280 houses uninhabitable, and the surrounding 183 households and 1 100 people were threatened, resulting in a direct economic loss of 20 million yuan and a potential economic loss of more than 1 100 million yuan.

1 general situation of geological disasters

1. 1 geological environment conditions

Topography: According to the landform characteristics, Bibei Town belongs to the landform type of Gaozhongshan. The mountain peaks in this area are 800 ~ 1900 m above sea level, and most of the mountains are distributed in north-south direction and northeast direction. According to field observation, the micro-topography of the disaster site is a V-shaped valley with high and steep slopes on both sides, with a natural slope of about 60. The hillsides on both sides were transformed into terraces by local villagers, and there was a stream flowing in the north-south direction at the bottom. The rain in the valley flows into the stream and then into the Yangxi River.

Formation lithology: The stratum exposed at the disaster point is Sinian Lechangxia Group, and the lithology is mainly shallow metamorphic sandstone, sericite parent rock and top siliceous rock. The field investigation shows that the landslide is mainly located in shallow metamorphic sandstone, and the surface layer is strongly weathered, and the original rock has been strongly weathered into sand.

Geological structure: Ruyuan county is located between the east-west structural belt of Jiu Feng and the east-west structural belt of Dadongshan-Guidong in Nanling belt. Since Caledonian, it has experienced many tectonic movements, with developed folds and faults and frequent magmatic activities. In the seismic intensity zoning map of Guangdong province, Ruyuan county is an area with seismic intensity less than six degrees, with stable crust and inactive neotectonic movement.

Engineering rock group combination: Upper Quaternary residual soil and lower Sinian lightly metamorphic sandstone of Lechangxia Formation belong to loose rock engineering geological rock group and semi-hard engineering geological rock group. After long-term physical and chemical weathering, the original rock structure has changed from hard to soft, and its stability has gradually deteriorated, which is easy to form landslide geological disasters under the infiltration of rainfall.

Groundwater: Rainfall infiltration is the main source of groundwater recharge in this area. After the groundwater is replenished by rainfall, it flows into the valley along the hillside or along the karst passage, and part of it is exposed to the surface in the form of spring water.

1.2 disaster scale and inducing factors

Disaster scale: landslide * * * caused 70 houses to collapse, 2 10 houses were damaged into dangerous houses, and the direct economic loss reached 20 million yuan, which was particularly harmful (disaster classification). At the same time, because some landslides in this landslide group are still in the stage of creep deformation, obvious cracks appear at the rear edge, and the landslide body is unstable. Poxia 183 households, 1 100 people are threatened, and the potential economic loss exceeds 1 100 million yuan. The risk grade (danger grade) of geological disasters is relatively high.

Figure 1 Village that must pass after landslide disaster

Fig. 2 Houses toppled by landslides in Bikou Village.

Inducing factors: The area near Bibeikou Village, Bibei Town, Ruyuan Yao Autonomous County belongs to the landform of Gaosan Valley. At the bottom of the valley is a village with high and steep slopes on both sides. The natural slope is about 60, and the hillside is terraced by local villagers. Under the condition of long-term farmland irrigation and heavy rainfall, slope water can not be discharged in time, which is easy to cause slope water to flow into and infiltrate, and soften the soil. The surface residual soil layer of the slope is thick, belonging to Quaternary loose engineering rock (soil) group, which is composed of sandstone with strong weathering, poor cohesive force, loose and easy to liquefy and disintegrate, and its underlying is Sinian shallow metamorphic sandstone, sericite mica schist and siliceous rock, with alternating soft and hard, and weak structural plane. In addition, the catchment area of the two sides of the slope is large, so it is easy to form a large slope water flow to penetrate into the slope in a short time when it rains, and it will concentrate seepage along the soil-rock interface. From the above analysis, it can be seen that this place is a fragile point of geological environment (the distribution and prone area map of geological disasters in Ruyuan County, Guangdong Province belong to the prone area of geological disasters), and it is easy to form landslide geological disasters under disastrous heavy rainfall climate conditions. By extracting the daily rainfall data of Ruyuan County from August 2065 438 12 to August 2065438 19, we can know that due to the influence of Typhoon Ute, there were three consecutive days of rainstorm from June 16 to June 18, and the continuous rainfall made the surface loose the pore water in the soil. August 13, 17, 2065438 Guangdong Geological Disaster Early Warning and Forecasting Center predicts the secondary warning of geological disasters around Ruyuan Yao Autonomous County in the next 24 hours, and relatively accurately predicts the target area of geological disasters. To sum up, the occurrence of geological disasters is the result of the comprehensive action of many factors. The complex terrain, the combination of loose rock engineering geological formations and semi-hard engineering geological formations are the internal causes of the landslide group, but in August, therefore, Bibeikou Village in Bibei Town, Ruyuan Yao Autonomous County is a geological disaster caused by heavy rainfall and natural factors.

2. Geological hazard inspection and monitoring

Before the arrival of Typhoon Ute, the Bureau of Land and Resources of Ruyuan Yao Autonomous County had received the early warning information from the provincial and municipal land and resources departments and the geological disaster early warning and forecasting center, and informed the directors of the towns' land and resources institutes, the persons responsible for the hidden dangers of geological disasters and the monitors to strengthen inspection and monitoring according to the requirements of the emergency plan. On August 12, the Bureau of Land and Resources of Ruyuan Yao Autonomous County, based on the analysis of meteorological information, sent early warning information of geological disasters to the persons in charge of hidden geological disasters, requiring them to be on duty 24 hours a day to investigate hidden geological disasters and possible hidden dangers. At 4 o'clock in the afternoon of August 17, Deng, inspector of Bibeizhen Land and Resources Institute, found that the ground of Bibeikou Village was sunken, and yellow turbid groundwater gushed out in some areas, which was initially identified as a landslide geological disaster. He immediately informed the director of Bibeikou Village Committee, reported it to Bibei Town Government and Ruyuan Yao Autonomous County Land and Resources Bureau, and reported the danger of geological disasters. After receiving the report, the Bureau of Land and Resources of Ruyuan Yao Autonomous County and Bibei Town Government immediately launched the emergency plan. At 4 o'clock in the afternoon, landslides began to appear in some areas.

3. Safe disposal of geological disasters

After receiving the report, the Land and Resources Bureau of Ruyuan County and Bibei Town Government immediately contacted and organized the cadres of the "two committees" in Bibeikou Village, and went door-to-door to inform people living in areas that might be threatened by geological disasters, and organized them to move to Bibei Town Government and residential areas in safety zones. At about 1 on August 8, all the villagers were safely transferred to the town government and surrounding houses. At about 2 o'clock, a landslide geological disaster occurred in residential areas where people were concentrated. Due to the timely discovery and rapid transfer, no local people were killed or injured in this geological disaster. On August 2 1, Guangdong Geological Environment Monitoring Station sent two technicians, together with the staff of Shaoguan Land and Resources Bureau and Shaoguan Mineral Resources and Geological Environment Monitoring Center, to rush to the geological disaster site for emergency investigation, analyze the causes and development trends of landslide groups, and put forward emergency measures and relevant suggestions. As of 20 13, the geological disaster site is under investigation and design of the control project.

4 Experience and Enlightenment

(1) Strengthening the foundation of prevention and control work is the core. The landslide disaster occurred in the early morning, when people were sleeping, and it took only ten hours from the appearance of symptoms to the occurrence. The rapid and successful development of emergency avoidance can not be separated from the solid foundation of geological disaster prevention and control.

(2) It is the key to implement the inspection and monitoring responsibility. The first time to find signs and report them in time won valuable time for the implementation of hedging actions.

(3) It is fundamental to mobilize the masses to take the initiative to prevent disasters. The masses may not only be the object of disasters, but also the subject of active disaster prevention. Only by mobilizing and organizing can the prevention and control of geological disasters proceed smoothly.