Affected by typhoon "Nanmadu"/KOOC-0/No.20//KOOC-0/,Taishun County, Zhejiang Province experienced heavy rain, with a cumulative rainfall of 300mm in 24 hours. On August 3/KOOC-0/day/KOOC-0/7: 30, Jiu Feng Village, Jiu Feng Office, sixi town/KOOC-0.

This landslide is an old landslide. Affected by Typhoon Morakot in 2009, many cracks appeared in the mountain where the landslide was located, which seriously threatened the lives and property of more than 39 households 160 people and a primary school. Hidden danger points are included in the patrol monitoring points of group defense and group treatment. The building at the toe of the slope was excavated, with a slope length of 200m, a slope height of10 ~16m and a slope of 40 ~ 70. The landslide area belongs to the landform unit of low mountain slope, with natural slope15 ~ 25, the lowest elevation is 888m, the highest elevation is 925m, and the relative height difference is 37m. The vegetation is mainly Phyllostachys pubescens.

The exposed strata in the landslide area are mainly the Lower Cretaceous Guantou Formation (K 1g) and Quaternary eluvial layer (Q4EL-DL). The lithology of Guantou Formation is siltstone with weak weathering resistance. The soil thickness of the fully weathered layer is 10~20m ~ 20m, and the rocks of the strongly weathered layer are broken and the cracks are developed. The lithology of residual slope deposit is clayey silt containing gravels, which is plastic to hard plastic, and the thickness is1~ 2.5m. The slope body is mainly composed of fully weathered rocks, residual slope deposit and locally strongly weathered rocks. The hydrogeological conditions in the area are simple, and the groundwater is mainly pore phreatic water of Quaternary loose rocks and bedrock fissure water, and the water quantity is poor. There are four factors leading to landslide: stratum lithology, heavy rainfall, open cutting slope in front, and poor root fixing ability of Phyllostachys pubescens vegetation on the slope.

Figure 1 Schematic plan (before landslide)

Fig. 2 Landslide disaster in Jiu Feng village

Fig. 3 Schematic diagram of geological disaster avoidance in Jiu Feng Village.

2 Monitoring and emergency hedging

2. 1 monitoring and early warning

In 2009, this point was listed as a monitoring point for group monitoring and prevention inspection, and a special emergency plan and a schematic diagram of risk avoidance were compiled. Jiu Feng village director was once employed as a monitor (20 10 was awarded the title of "National Excellent Group Prevention and Treatment Officer" by the Ministry of Land and Resources) and signed a letter of responsibility.

Affected by typhoon "Nanmadu", there was a general rainstorm of 20 1 1 in Taishun County on August 29th. At about August 3 1 day 12, Sixi Land Institute of Taishun County Land and Resources Bureau received a phone call from the squad leader Zeng to report a hidden danger in Jiu Feng Village. After receiving the report, Yang Guohuai, the Sixi Institute, immediately rushed to the scene and found that new cracks appeared in the mountain, bamboo tilted and soil loosened, and local small landslides appeared at the foot of the slope, accompanied by a large amount of muddy water flowing out. After preliminary analysis and judgment, there is a danger of decline at any time.

2.2 Emergency hedging

After briefly reporting the situation to the bureau leaders, Yang Guohuai immediately launched the emergency plan for geological disasters, quickly evacuated 47 people from the dangerous zone 14 households, and warned the masses not to go home without authorization before the danger was lifted. 17: 30, the western slope of Jiu Feng village, a hidden danger point, fell sharply, with a sliding amount of about 4000m3, causing damage to the back wall of 15 house, with a direct economic loss of about 800,000 yuan. Because the threatened people evacuated earlier, no casualties were caused.

2.3 Subsequent disposal

After receiving the danger report, the government departments immediately started the Grade IV emergency response to geological disasters, and the county government organized the departments of land, meteorology, water conservancy, public security, civil affairs and sixi town government to rush to the disaster site, hold an emergency meeting, and deploy emergency work such as disaster cleaning and mass transfer and resettlement through disaster analysis. Delineate dangerous areas, set warning signs and safety barriers, timely resettle people in dangerous areas, and discuss the next emergency measures.

On September 1 day, experts from Wenzhou Geological Environment Monitoring Station and the 11th Geological Brigade of Zhejiang Province visited the site and held a meeting on disaster analysis and emergency response. On September 2nd, the 11th Geological Brigade of Zhejiang Province submitted a written disaster emergency investigation report and emergency treatment suggestions. Subsequently, the government quickly organized rescue teams to clean up the landslide, and adopted emergency measures such as covering with plastic film, building temporary drainage ditches, and stacking sandbags at the foot of the slope.

Figure 4 Emergency treatment of slope toe

During the emergency response, the local government made proper arrangements for the evacuated people, some of whom stayed at relatives and friends' homes, while others stayed at hotels for free. The county civil affairs department distributed rice, oil, clothes and other daily necessities to the affected people. On September 15, the landslide was cleared on site, the reinforcement and emergency treatment of damaged houses were basically completed, and the threatened people moved back to live one after another. The government will also carry out further exploration and engineering treatment of landslide disaster sites.

3 Experience and Enlightenment

The success of this hedge is mainly due to the establishment of a relatively complete geological disaster monitoring and prevention system in the local area. With a high sense of responsibility, grass-roots staff and monitoring personnel conscientiously implement the geological disaster inspection and monitoring system, find dangerous situations in time, report and issue early warning information, transfer threatened people in advance, and avoid heavy casualties.

Problems faced: There are still some problems in emergency avoidance of geological disasters, such as insufficient equipment, insufficient personnel and funds, and people's lack of understanding and cooperation.

(This part of basic information is provided by Zhejiang Provincial Department of Land and Resources and edited by Chu Hongliang)