"6·" Landslide on Dapo Street, Rong'an County, Guangxi Zhuang Autonomous Region

1 Introduction

At 2:30 a.m. on June 19, 2014, a landslide geological disaster occurred in Dapo Street, Dapo Township, Rong'an County, Liuzhou City, Guangxi Zhuang Autonomous Region. The central location is: Longitude 109°31′16″ East, latitude 25°09′07″ North. There are two landslides, one is located at the top of the artificial slope on the west side of Dapo Street and the river bank below the east side of Dapo Street. One of the landslides is 120m wide, 7.5m long, 6m thick, with a volume of 5400m3. The sliding direction is 123°; another landslide has a width of 70m, an oblique length of 25m, an average thickness of 2m, a volume of 3500m3, and a main sliding direction of 95°. Two landslides caused damage to eight 2- to 4-story buildings on Dapo Street, and a motorcycle repair shop slid into the river, causing a direct economic loss of approximately RMB 300,000. Due to the timely evacuation, the death of 173 people from 39 households was avoided. casualties. According to the "Regulations on the Prevention and Control of Geological Disasters", the disaster was considered small.

2 Overview of geological disasters

2.1 Geological environmental conditions

(1) Topography

The landslide is located in a structural erosion hilly landform area. The peak elevation of the hill where it is located is 256m, the relative height difference is 76m, the natural slope of the mountain is 25°-45°, the vegetation is lush, and the coverage rate is greater than 90%. The middle and lower part of the hill is Dapo Township Street, with a ground elevation of 180m. The construction of buildings on both sides of the street has formed an artificial slope with a height of 24-36m and a slope of 56° on the west side; the spoil pile on the east side has formed an artificial slope with a height of 22m and a slope of 56°. Artificial slope around 50°. At the foot of the slope is the Dapo River. The river bed elevation is 158m. The river bank slope height is 15-22m. The average bank slope is about 45°. The river water flows from east to west.

(2) Stratum lithology and engineering geological characteristics

The area where the landslide is located is overlain by Quaternary slope residual gravel soil, with a thickness of 3-5m and a gravel content of about 40% ~50%, with loose structure and good water permeability. The soil is prone to landslides and collapses along the contact surface between the residual sediment layer and the bedrock. The underlying Cambrian Qingxi Formation ( ) is yellow-brown mudstone and argillaceous sandstone, with weak water resistance, easy weathering, and low mechanical strength. The dry compressive strength of fresh rock is 26.6-192MPa, and the softening coefficient is 0.25-0.94.

(3) Geological structure

According to regional data, the landslide is located in the core of the Dapo-Yayao syncline. The inclination angle of the syncline rock layers changes greatly and is composed of Cambrian strata. , axially NE, 38km long and 18km wide. The occurrence of regional rock formations is 140°∠68°.

(4) Hydrogeological conditions

The type of groundwater in the area where the landslide is located mainly includes clastic rock fissure water, which is present in sandstone fissures. It is mainly supplied by atmospheric rainfall and flows in creeks and ditches. The bottom, ditch sides and other places discharge to the surface to form ditch tail springs, etc. The flow rate of the spring in the dry season is 0.3L/s, the groundwater runoff modulus is generally 6-6L/s.km2, and the water volume is abundant.

2.2 Geological hazard characteristics

The landslide at Dapo Street, Dapo Township, Rong'an County, Liuzhou City, Guangxi Province includes two landslides, located on the top of the slope above the mountain behind Dapo Street and on the river bank below , among which:

H1 landslide: located at the top of the artificial cut slope, with a slope height of 24 to 36m and a slope of 56°. The upper 4 to 5m of the slope is residual gravel soil, and the lower part is strongly weathered mudstone and mud. The landslide is made of sandstone, with a width of 120m, an oblique length of 7.5m, a thickness of 6m, a volume of 5400m3, and a main sliding direction of 123°. The landslide is mainly composed of residual soil on the slope, and the sliding surface is the soil-rock contact surface. A nearly north-south arc-shaped crack occurred along the ridge line at the trailing edge of the landslide. The crack was 0.1 to 0.8m wide and offset by 1m. Several small-scale landslides occurred at the front edge, and nearly 800m3 of earth and rock had collapsed from the top of the slope. The impact on the houses at the foot of the slope caused damage to eight 2- to 4-story buildings on Dapo Street, and the landslides had accumulated to the third floor of some houses.

H2 landslide: Located on the river bank below Dapo Street, the landslide is 70m wide, 25m long and 2m thick on average, with a volume of 3500m3 and a main sliding direction of 95°. The front edge of the slide body was washed by the river water, and most of the slide body had slid into the river, while a small amount of slide body accumulated on the slope. The landslide caused a motorcycle repair shop at the top of the slope to slide into the river.

2.3 Analysis of the causes of geological disasters

According to field surveys, the occurrence of landslides is mainly caused by natural factors, followed by human factors. It is the result of the combined effect of natural factors and human factors.

Among them:

H1 landslide: The upper part of the mountain slope where the landslide is located is 4-5m thick slope soil, and the underlying bedrock is mudstone; in 1997, the construction of Dapo Street cut the slope to build houses, forming a 24-meter-high The 36m artificial slope with a gradient of 56° has changed the natural state of the slope. The slope cuts through the soil-rock contact surface, forming a high and steep free surface, creating spatial conditions for the formation of landslides and collapses. There was a sudden heavy rain on June 18, 2014. It rained nearly 200mm in about 3 hours. The rainwater seeped down, causing the soil to be quickly saturated, the strength of the soil to decrease, and its own weight to increase. In addition, due to the water-proofing effect of the mudstone, the rainwater seeped down to After the strongly weathered mudstone seeps along the soil-rock contact surface, the friction on the soil-rock contact surface decreases and causes sliding.

H2 landslide: During the construction of Dapo Street, the spoil excavated from the slope cutting was dumped at the nearest river bank, forming an artificial slope with a height of 22m and a slope of about 50°. It is easy to slide along the original terrain slope. Landslides and collapses; in addition, this area is a bend of the Dapo River, and the river erosion is relatively strong. On June 18, 2014, a sudden heavy rain caused the river water level to surge. The floods strongly washed away the river banks and eroded the foot of the slope, causing the river bank slope to slide and cause a landslide.

3 Geological Disaster Inspection and Monitoring

According to meteorological warning information, starting from June 17, 2014, affected by factors such as tropical high pressure and low-altitude shear lines, most areas of the Guangxi Zhuang Autonomous Region There will be a heavy rainfall process, local heavy rain or heavy rain. The Department of Land and Resources of the Autonomous Region, the Meteorological Bureau and the Hydrological Bureau of the Autonomous Region used various early warning and forecast information platforms to promptly issue yellow early warning forecasts for geological disaster risks to all cities and counties in the region. Dapo Township, Rong'an County, Liuzhou City is the yellow early warning area for geological disaster risks. one. According to the geological disaster early warning and forecast information from the land and resources and other departments, the Party Committee and Government of Dapo Township, Rong'an County, Liuzhou City promptly launched geological prevention and control work according to the predetermined geological disaster prevention and control plan, convened a meeting of all cadres and workers, and urgently deployed the township's geological disaster prevention and flood fighting For disaster relief and other prevention and response work, relevant responsible persons, monitors and residents threatened by geological disasters are required to strengthen the duty, inspection and monitoring of rain conditions, river water conditions and geological disaster-prone areas and hidden danger points, and make every effort to do a solid job Carry out various prevention and response tasks. Affected by heavy rainfall, the cumulative rainfall in Dapo Township, Rong'an County, Liuzhou City in the 48 hours before 16:00 on June 18 had reached 195 mm. By 2:30 a.m. on June 19, geological disaster-prone Dapo Street A resident in the development area heard the sound of the back wall of the house being smashed. He immediately got up to investigate and found that the back wall was hit by a small piece of soil avalanche on the back hillside. He realized that it might be a precursor to a landslide on the back hillside. Therefore, Immediately inform neighbors affected by the landslide and report to the local land and resources department. The inspection and monitoring team of the local land and resources department strengthened monitoring. As of 6 a.m. on June 19, the cracks on the trailing edge of the landslide on the hillside widened and the soil on the front edge accelerated. This was a phenomenon of accelerated landslide sliding. The inspection and monitoring team immediately reported it to Dapo Township. The party committee and government leaders, the township party committee and the government immediately initiated emergency response to the landslide geological disaster, and organized Dapo Township government staff and all police officers from the police station to enter the scene according to the plan to carry out emergency response. At 10 a.m. on June 19, the mountain slid. In accordance with the instructions of the main leaders of Liuzhou City, the Rong'an County Party Committee and County Government quickly organized a rescue team to rush to the disaster site, and together with the Dapo Township Party Committee, the government and other major responsible persons formed a frontline command post to rely on As a frontline commander, we went all out to carry out emergency rescue work, organized the evacuation of affected residents urgently and orderly, and properly conducted resettlement work. Due to timely early warning, adequate monitoring, decisive decision-making and powerful measures, Dapo Township, Rong'an County, successfully avoided the casualties of 173 people in 39 households, and all the affected people were properly resettled.

4 Geological disaster avoidance arrangements

The main measures taken for the Dapo Street “6.19” landslide geological disaster emergency response work are:

(1) Advance Make good preparations for geological disaster prevention and response

Since the flood season in 2014, the autonomous region has held a video and telephone work conference on flood prevention and drought relief to comprehensively strengthen flood prevention and disaster prevention and response work. On May 18, an autonomous region flood prevention and emergency drill was held in Nanning City to enhance the ability of all levels to handle flood season emergencies. On May 28, the Emergency Office of the Autonomous Region Government, the Department of Land and Resources, and the Qinzhou Municipal People's Government jointly held the 2014 geological disaster emergency avoidance and relief drill in Pubei County, and organized cities and counties to watch the live TV broadcast, using innovative methods to effectively improve flood prevention and control in various places. disaster response level, and timely strengthen the awareness and knowledge of geological disaster prevention and control among the cadres and the masses in our district before the flood season.

(2) Strengthen geological disaster monitoring, early warning and forecasting work

Before the “6·19” landslide geological disaster occurred in Dapo Township, according to the rainfall weather process in Rongan County, the autonomous region The land and resources department promptly issued yellow warning information on geological disaster risks to cities and counties. After receiving the early warning information, the Rongan County Government promptly organized the land and resources department and the meteorological department to strengthen emergency coordination and liaison, do a good job in real-time monitoring and forecasting of rain conditions, make short-term predictions of geological disasters based on real-time monitoring data and forecast data of rain conditions, and make predictions about possible geological disasters. Forecast the time, location, disaster scope and impact of the disaster; at the same time, the Dapo Township Government is required to strengthen on-duty emergency response, strengthen inspection and monitoring of geological disaster hazard areas and geological disaster-prone areas, and report dangers in a timely manner. On June 18, a large-scale heavy rainfall occurred in Rongan County. Rongan County repeatedly released weather forecast information and real-time rainfall information through rural meteorological warning loudspeakers. Among them, at 7:26 on June 18, the 2-hour rainfall amount in Dapo Township was announced. 62mm, and the rainfall exceeded 195mm at 16:00 on the 18th. The Dapo Township Party Committee and Government immediately organized staff to strengthen inspections and monitoring, and informed the people in the township to take precautionary measures. In the early morning of June 19, after the disaster-stricken people discovered signs of geological disasters, geological disaster technicians from the local land and resources department went to the site to inspect the cracking and deformation of the back mountain. Through strengthened monitoring, they quickly reported the danger to the Dapo Township Party Committee and Government when it occurred, so as to provide Scientific decision-making provides the necessary basis and buys valuable evacuation time for successful risk avoidance.

(3) Establish a frontline headquarters to be responsible for the emergency response to geological disasters

After the disaster occurred, the Dapo Township Party Committee and the government promptly launched the geological disaster prevention and control plan and organized cadres and workers to take Loudspeakers were used to inform the threatened people from door to door to quickly evacuate to safe areas; the main leaders of Rongan County also rushed to the scene as soon as possible, launched the geological disaster emergency response according to the plan, and established a geological disaster emergency rescue and relief headquarters, with the county party committee secretary as the commander. Other county leaders serve as deputy commanders, and five emergency rescue teams are established: monitoring team, security team, rescue team, resettlement team, and logistics support team. Each team leader is served by a county leader, and the team members are composed of leaders from relevant departments and bureaus. Each emergency team immediately carried out disaster relief and rescue work according to their work responsibilities. The monitoring team is responsible for investigating and verifying dangerous situations, organizing monitoring and predicting the development trends and potential threats of geological disasters, delineating dangerous areas, setting up 4 monitoring piles at the cracks of the landslide body, and implementing 24-hour monitoring and early warning of changes in the landslide body; security The team is responsible for traffic control on important road sections where geological disasters occur, maintaining traffic order and on-site public security order, setting up warning lines and warning signs in dangerous areas, closing dangerous areas with wooden boards, arranging dedicated personnel to be on duty 24 hours a day, and strictly prohibiting people from entering and exiting; the rescue team Responsible for emergency rescue and health care of the affected residents. Under the guidance of experts, we excavated drainage ditches on the mountain 3m above the cracks at the rear edge of the landslide, filled and consolidated the landslide cracks, covered the landslide body with colored strips of cloth, etc. to prevent surface water. Infiltrate cracks, reduce the infiltration of rainwater and ground water, and play a sliding role; the resettlement team is responsible for the transfer and resettlement of threatened people and important properties, and adopts methods such as seeking relatives and friends, setting up temporary resettlement sites, etc. to resettle the affected people; the logistics support team Responsible for the emergency repair and restoration of power and communication facilities in disaster areas, and the distribution of disaster relief materials and other logistical support work. Under the unified command of the headquarters, various emergency response teams gave full play to their functions and organized rescue work in a coordinated and orderly manner, allowing 173 people from 39 threatened households to successfully escape danger.

(4) Do a good job in post-disaster disposal work

After the disaster, the Rongan County Government entrusted the geological disaster technical support unit Guangxi Geological Environment Monitoring Station to propose a technical plan for landslide emergency response and held a special topic in a timely manner Meeting. We discussed the emergency response plan for the "6·19" landslide geological disaster in Dapo Township, and finally decided on the plan to cut the slope to clear the hidden danger of the landslide, and quickly entrusted a professional technology company to be responsible for the cleanup and engineering supervision. The plan is scientific and reasonable, the entrusted company has strong professional skills and good reputation. The post-disaster follow-up work is carried out in an orderly, timely and solid manner in a short period of time, and the hidden dangers are expected to be fundamentally eliminated.

5 Experience and Enlightenment

(1) Leadership attention is a prerequisite

After the occurrence of danger, the municipal and county governments and relevant departments attach great importance to it. The city's main leading comrades gave important instructions, and the county leaders took command from the front. All units responded quickly and organized evacuation, hidden danger investigation, and resettlement of victims at the landslide site to ensure the safety of people's lives and property in the landslide danger area.

Rong'an County leading cadres strongly support geological disaster prevention and control work. Every year, the county government holds a special meeting on geological disaster prevention and control; it issues documents to clarify the key points of prevention. Every year during the flood season, county leaders lead teams to inspect and supervise key hidden danger points, and clearly implement prevention responsibilities and prevention and control measures.

(2) Publicity and training are the foundation

Rong'an County focuses on publicity and training on geological disaster prevention and control. Nearly 70,000 yuan is allocated for earthquake publicity and training funds every year, and geological disaster prevention and control knowledge is widely publicized through media such as radio and television, newspapers and periodicals, and festivals such as "Earth Day", "Land Day" and "March 3" are used to adopt Promote knowledge on geological disaster prevention and control in various forms; distribute more than 10,000 promotional materials and more than 1,200 clear cards every year, and set up 260 warning signs in geological disaster-prone areas, important disaster points and along highways, making geological disaster prevention and control knowledge truly Go to the "point" of entry.

Before the flood season every year, the Rongan County Government organizes professional and technical personnel from the land and resources department to conduct geological disaster prevention and control knowledge training for 12 township cadres, village cadres, primary and secondary school principals, monitors and other relevant personnel in the county. Types and characteristics of geological disasters. Use easy-to-understand language to teach cadres and the masses the knowledge of geological disaster prevention and control, so that they can master the classification of geological disasters, the characteristics and precursors of various geological disasters, learn to use simple tools for monitoring, and master correct Emergency and avoidance measures for geological disasters, etc., to achieve "four things to know" and "four things to know". The county government also organizes land and resources and other relevant departments to go deep into the county's important geological hazard hidden danger points every year, and conduct targeted emergency geological disaster emergency avoidance drills, so that the masses can truly master and apply geological disaster prevention and control knowledge, and continuously improve the geological disaster prevention and control knowledge. Ability and level of self-rescue and mutual rescue.

(3) Group detection and prevention are fundamental

Rong'an County Government has always attached great importance to group detection and prevention, and has always regarded it as an important means of monitoring dangerous situations. Every year, the Liuzhou Municipal Government and county governments, county governments and township governments, township governments, village committees and monitors sign work responsibility letters at various levels to decompose and implement the responsibilities for geological disaster prevention and control, forming a horizontal to edge and vertical to bottom work pattern. The Rongan County government invests more than 200,000 yuan every year to establish and maintain the operation of the county's mass monitoring and prevention system. At present, a total of 307 geological disaster monitors have been implemented, and segmented management is implemented, covering all geological disaster-prone areas in 12 towns in the county. identify risk areas and hidden danger points to ensure that inspections, inspections, and verifications during the annual flood season are carried out effectively. When encountering a disaster or danger, it can link up and down in time to give full play to the role of group detection and group prevention, and effectively prevent and reduce casualties and property losses caused by geological disasters.

(4) Timely geological disaster early warning is the key

Timely and accurate geological disaster early warning information played an important role in this successful avoidance. After receiving the information from the autonomous region and the city, After the early warning information is released by the first-level geological disaster forecast and early warning information platform, Rongan County arranges dedicated personnel to collect and organize geological disaster forecasts and early warnings. When encountering extremely severe meteorological conditions, the early warning information is promptly sent to the county's disaster prevention staff through the SMS platform. On your mobile phone, you can be reminded to do a good job in inspection and prevention of geological disasters. In 2014, more than 21,000 pieces of meteorological warning information for geological disasters were issued. At the same time, the meteorological department of the autonomous region installed 14 rural meteorological warning loudspeakers in 12 towns in Rongan County to release weather warning and forecast information in real time; Four automatic geological disaster monitoring instruments have been installed at important geological disaster hazard points such as Wotun. Real-time and effective monitoring is carried out in a scientific way, so that the general public can understand and prepare for meteorological warning information early, and detect and stop geological disasters early. Early treatment can minimize the losses caused by geological disasters.

(5) A sound geological disaster emergency plan is a guarantee

Rong'an County promptly adjusted the county's geological disaster prevention and control leading group based on the actual situation of geological disasters in each township, and issued the "Rong'an County Emergency Plan" "Emergency Plan for Geological Disasters" and "Rong'an County Geological Disaster Prevention and Control Plan", as well as the corresponding modification and improvement of disaster prevention plans for towns, villages and hidden danger points, and strictly implement various systems such as geological disaster inspection, duty, and rapid reporting to effectively ensure that After discovering a dangerous situation, the county party committee and county government can initiate emergency response in a timely manner and carry out emergency response work in an orderly manner in accordance with the emergency plan, so as to achieve "having a plan in hand and not panicking in the heart."

(6) Scientific handling of geological disasters is the key point

During the heavy rainfall, the Rongan County Party Committee and the county government required all townships and relevant functional departments to strengthen emergency duty for geological disasters and strengthen emergency response to geological disasters. Inspection and monitoring of geological disaster-prone areas and geological disaster-prone areas; short-term real-time early warning and forecasting of geological disasters based on real-time rain monitoring data and forecast data; during the rescue and rescue process, decisions are made decisively and scientific handling is carried out, and the rescue team is guided by experts. , dig drainage ditches on the mountain 3m above the cracks at the rear edge of the landslide, fill the landslide cracks with abandoned solids, cover the landslide body with colored strips of cloth, etc. to prevent surface water from seeping into the cracks, reduce the infiltration of rainwater and ground water, and play a role in blocking to prevent landslides; set up 4 monitoring piles at the cracks of the landslide to provide 24-hour monitoring and early warning of changes in the landslide; cordon off and set up warning signs in dangerous areas to maintain traffic order and on-site public security order, and use wooden boards to seal off dangers It is scientific to arrange dedicated personnel to be on duty 24 hours a day in the area and strictly prohibit people from entering and leaving; adopt methods such as seeking relatives and friends, setting up temporary resettlement sites, etc. to resettle the affected people; regularly report the disaster response situation and speed up the reconstruction progress after the disaster, proactively communicate with the victims, and stabilize the thoughts and emotions of the victims. This is all scientific , effective geological disaster emergency response measures.

(7) Communication innovation is the highlight

Rong'an County also makes reasonable use of modern online media and established the "Rural Rongan" WeChat group using WeChat on mobile phones, bringing together county and township levels. Government leaders and principals of relevant functional departments have not only strengthened daily business communication, effectively realized information sharing, innovated information communication methods, and can better utilize the timeliness in dealing with sudden geological disasters. This makes it easier for the on-site command headquarters to take effective and more complete disposal measures in a timely, scientific and effective manner.