"Where are the hidden dangers?" and "When will it happen?" The two major problems have always plagued my country's natural resources departments and practitioners of geological disasters. Today, thanks to the efforts of geological disaster practitioners, especially Xu Qiang, vice president of Chengdu University of Technology and executive deputy director of the State Key Laboratory of Geohazard Prevention and Geoenvironmental Protection, has used optical satellite remote sensing, InSAR, airborne LiDAR, and drone photography Surveying, aerial geophysical prospecting, SLAM, multi-beam and other technologies, the "sky-space-ground-inside" full-time and space-time real-scene 3D geological disaster prevention and control system has made people see the dawn of solving the problem .
The so-called "sky-space-ground-inside" full-time and space-time three-dimensional geological disaster prevention and control system refers to the optical remote sensing + InSAR on the spaceborne platform to identify surface deformation, the airborne LiDAR + UAV photogrammetry on the aviation platform to accurately identify landslide hazards, and the ground platform professional Monitoring + investigation and verification to obtain accurate and reliable deformation information, aerial geophysical prospecting to detect geological internal structure + multi-beam detection of underwater terrain + SLAM surveying and mapping indoor form, through multi-technical collaborative monitoring and comprehensive utilization, realize ground + underground, indoor + outdoor, water + Underwater full-element and full-space geological disaster hidden danger identification, real-time monitoring and risk assessment can ensure the safety of people's lives and property to the greatest extent.
"I will introduce any technology that is easy to use now. Because the richer the technical means, the more sufficient the identification and early warning conditions for geological disaster hazards, the more accurate and real the results will be . This is like a doctor seeing a doctor. Through a variety of technologies Only by obtaining multiple indicators can we accurately judge the disease, find out the cause, and prescribe the right medicine." Xu Qiang said.
From civil air defense to technical defense "three checks" system
Affected by factors such as the uplift of the Qinghai-Tibet Plateau and global climate change, my country is one of the countries in the world with the most serious geological disasters such as landslides, collapses, and mudslides, and the most threatened population. The severe situation of disaster prevention and mitigation has given birth to batch after batch of scientific and technological workers who, like Xu Qiang, devote all their energy to the cause of geological disaster prevention.
In the early days when Xu Qiang dealt with geological disasters, limited by the level of equipment technology, it was impossible to use professional monitoring methods to identify disaster hazards and professional monitoring and early warning (that is, technical defense), so he could only use civil air defense. "Civil air defense refers to the discovery of hidden dangers through on-site investigation and visits by people, and the local people's own observation and self-prevention of disasters." Xu Qiang pointed out that civil air defense has gone through two stages:
The first stage
Geological surveyors have carried out comprehensive surveys and investigations of hidden dangers of geological disasters in the "net and carpet style" across the country. A total of about 300,000 hidden dangers of geological disasters have been found across the country.
second stage
Group monitoring and group defense, that is, self-observation (observation) and self-prevention by local people, and monitoring personnel (usually local people) are arranged at each hidden danger point to pay close attention to its dynamic changes all day long. Disaster precursor features such as falling trees, and then start the disaster prevention plan to evacuate the threatened people. With the advancement and maturity of technology, professional monitoring methods represented by GNSS, crack gauge, rain gauge, etc. have been introduced into the prevention and control of geological disasters, and together with civil air defense, a geological disaster safety "protection net" has been woven. However, large-scale professional monitoring methods cannot cover all hidden geological hazards in the country. "We can only choose major hidden dangers to carry out professional monitoring." What makes Xu Qiang even more worried is that in recent years, there have been 80 major geological disasters in China . % are not within the scope of the 300,000 hidden danger points that have been found . "How can we more comprehensively identify potential hidden danger points of geological disasters?" This question kept popping up in Xu Qiang's mind, which kept him awake at night.
At that time, Lu Hao, then Minister of Natural Resources, proposed that the core requirement for preventing geological disasters is to find out "where are the hidden dangers" and "when may it happen", which coincides with Xu Qiang's thinking. In order to answer the minister's question, after in-depth research, Xu Qiang proposed a "three-check" system integrating "sky-air-ground", that is, firstly conduct a large-scale "general survey" of geological disaster hazards through optical satellite remote sensing and InSAR , and then use airborne LiDAR and UAV photogrammetry to carry out "detailed investigation" on high-risk areas of geological disasters and hidden dangers of major geological disasters, and finally through ground investigation and review, to realize "checking" and identification of hidden dangers of major geological disasters . Not long after the "Three Checks" system was put forward, an excellent opportunity to "practice" came. On October 10 and November 3, 2018, two large-scale high-level landslides occurred on the right bank of the Jinsha River in Baige Village, Jiangda County, Tibet Autonomous Region, blocking the Jinsha River and forming a barrier lake. It is a typical large-scale high-level landslide hazard . In order to identify hidden dangers, Xu Qiang led the team to first use satellites to conduct retrospective analysis of the deformation before the slide, and then use UAV photogrammetry to generate DSM, DOM and other results to analyze the characteristics of the slide after the slide, providing targets for the deployment of professional monitoring instruments on the ground, and finally use GNSS Real-time monitoring and early warning by ground professional monitoring instruments such as surface crack meter and surface crack meter, three times of precise early warning 30 minutes in advance, ensuring the timely evacuation of construction workers on the site of the discharge chute of the dam body and ensuring the safety of relevant personnel.
The "three investigations" system that has been tested in actual combat has become a watershed for technical prevention in geological disasters: the professional monitoring stage has evolved to the hidden danger identification + professional monitoring stage . Although the role of technical defense is becoming more and more prominent, Xu Qiang does not blindly praise technical defense, but repeatedly emphasizes that the prevention and control of geological disasters must be the organic combination of technical defense and civil defense to achieve the effect of "1+1>2". "After all, after discovering the hidden dangers of disasters through technical means, people still need to investigate and review." He pointed out that the current relationship between civil air defense and technical defense is in the second stage, that is, the stage of "remote sensing first, geological survey to keep up". The role of Chinese technology prevention is to improve the refinement and accuracy of geological survey work. The previous stage was called by Xu Qiang as "mainly geological survey, supplemented by remote sensing". In this stage, the role of technical defense is to solve operational problems that cannot be reached by humans. "In the next stage, the relationship between the two may evolve into 'remote sensing-based, geological survey review'." Xu Qiang said, "No matter what stage, the relationship between technical defense and civil defense is always an organic combination, and one is indispensable."
Build a three-dimensional disaster prevention and control system in real time and space
Utilize the "three checks" system to enable our country to identify hidden dangers in the deformation zone (areas or parts that are undergoing deformation and have obvious signs of deformation) and historical deformation and damage areas (instability failures have occurred in history but are not currently deformed) has been greatly improved . "For areas that are undergoing deformation, high-resolution optical remote sensing and InSAR technology can be used to identify them; for historically deformed and damaged areas, airborne LiDAR, which can effectively remove vegetation, can be used for identification, supplemented by optical satellite remote sensing." Xu Xu Qiang explained.
However, he changed the subject and said: "The 'Three Checks' system is powerless to identify the hidden dangers of potentially unstable slopes." The potentially unstable slopes that Xu Qiang mentioned meant that no deformation or failure had occurred in history, and there were no obvious signs of deformation at present. However, its stability is relatively poor, and it is prone to sudden instability and destruction of the slope under the influence of rainfall. So, how to solve the hidden danger identification problem of potentially unstable slopes? Xu Qiang's answer is to implement the "trilogy" refined operation method:
first step
Use lidar to carry out refined surveying and mapping, draw 1:1000 or even higher-resolution topographic maps, and find the slopes most likely to be unstable.
second step
Use Doppler radar to carry out refined meteorological early warning. By making the time accuracy of weather forecast to the minute and hour level and the spatial accuracy to the kilometer level, we can accurately grasp the temporal and spatial change process and dynamics of rainfall, narrow the range of threatened areas, and achieve accurate forecasting. Judgment and timely evacuation minimize the number of evacuated personnel while avoiding casualties.
third step
Develop airborne geophysical prospecting technology to quickly find out the internal structure and water content of slopes, quantitatively analyze and evaluate the stability of slopes in different regions and parts under different rainfall conditions, so as to delineate relatively dangerous areas and dangerous parts, and use scientific and technological means to truly realize the risk. dual control.
While tackling the problem of hidden danger identification on potentially unstable slopes, Xu Qiang is also tackling the problem of monitoring and early warning of sudden landslides. "Because this type of landslide is sudden and there are no signs before the rainfall is induced, it is extremely difficult to monitor and warn." In order to overcome this problem, Xu Qiang led the team to develop a monitoring system that adaptively adjusts the sampling frequency. Mechanism and supporting instruments and equipment, related instruments and equipment will automatically adjust the sampling frequency according to the change speed of the monitored indicators, so that not only can meet the requirements of on-site power supply and transmission, but also can comprehensively obtain the complete information of accelerated deformation, especially in the sliding stage. It helps to accurately warn sudden landslides in advance. On the other hand, the Newton force remote monitoring and early warning system for landslide disasters was introduced to monitor the force changes during the formation of the landslide; the seismic network and microseismic were introduced to capture the precursor signals before the landslide, and the development and evolution process of the sliding surface inside the landslide and its precursor characteristics were analyzed ; At the same time, monitoring and early warning equipment such as GNSS, crack meter, pore piezometer, and rain gauge are installed to monitor slopes with thick covering layers or relatively poor stability. "Through these methods, we can monitor the relevant physical quantities and external factors in the process of landslide formation and evolution in an all-round way, greatly improving the accuracy of landslide early warning." Xu Qiang said.
In the process of tackling the two major problems of hidden danger identification of potentially unstable slopes and sudden landslide monitoring and early warning, Xu Qiang also introduced new technologies such as SLAM, multi-beam, and communication optical fibers into the " In the "Three Checks" system. Among them, SLAM technology is used for rapid mapping and construction of indoor 3D models of buildings to realize quantitative risk assessment of geological disaster-affected bodies; multi-beam technology is used to detect underwater topography and landforms to provide data support for the prevention and control of geological disasters in water areas and surrounding areas . Through the continuous absorption of new technologies, the "three investigations" system has gradually expanded to the "sky-space-ground-inner" full-time and space-time three-dimensional geological disaster prevention and control system. Relying on optical satellite remote sensing, InSAR, airborne LiDAR, UAV photogrammetry, aerial geophysical prospecting, SLAM, multi-beam and other technologies, the new system realizes the organic integration and synergy of ground and underground, water and underwater, indoor and outdoor, which will help In our country, we can maximize the hidden danger identification, real-time monitoring and scientific early warning of landslide disasters. "In the future, I will continue to improve this system so that it can play a greater role in geological disaster prevention and control." Xu Qiang said.
Play a new system role in multi-hazard early warning
According to Xu Qiang, the "sky-space-ground-inside" full-time and space-time real-scene 3D geological disaster prevention and control system has been successfully applied in Sichuan, Guizhou, Gansu, Yunnan, Shaanxi, Tibet and other provinces, and achieved good results. Among them, Guizhou Province used InSAR and airborne LiDAR to conduct a professional investigation of high-level hidden disasters in the province, and found nearly 2,000 new geological disaster hidden dangers, including nearly 900 high-level hidden hidden dangers; Sichuan Province used InSAR and optical remote sensing Combined, hidden dangers were identified in 60,000 square kilometers of high-risk areas of geological disasters, and 840 new deformation areas were discovered; Yunnan Province identified more than 50 hidden dangers of geological disasters by using the combination of optical remote sensing and InSAR.
With the advantages of multi-technology collaboration, Xu Qiang believes that the "sky-space-ground-inner" full-time and space-time real-scene 3D geological disaster prevention and control system can also make great achievements in the fields of earthquake prediction and mine slope monitoring .
He pointed out that in the field of earthquake prediction, InSAR and airborne LiDAR can be used to accurately locate active faults in the national key earthquake monitoring and defense areas and key earthquake risk areas, and then use ground professional monitoring equipment, communication optical fibers, and seismic network and other means for real-time monitoring and early warning. "In this way, earthquakes that will obviously rupture the surface will be predicted in advance in the next 30 to 50 years ." Xu Qiang said. In the field of mine slope monitoring, first use optical satellite remote sensing and InSAR to monitor mine surface deformation, identify areas where surface deformation is occurring, and provide targets for the deployment of ground professional monitoring instruments, and then use GNSS, surface crack meter, ground-based SAR and other ground professional monitoring instruments to conduct real-time monitoring and early warning of targets to ensure the safety of mine slopes. At present, the "sky-space-ground-inside" full-time and space-time real scene 3D geological disaster prevention and control system has been applied to mine slope monitoring in Guizhou, Xinjiang and other provinces.
Xu Qiang emphasized that a unified management mechanism is inseparable from the "sky-space-ground-inner" full-time and spatial three-dimensional geological disaster prevention and control system in order to play its biggest role in multi-hazard monitoring and early warning. "Currently, the data of various departments cannot be fully shared, and there are still certain difficulties in promoting multi-hazard early warning." Therefore, he hopes that the Ministry of Emergency Management can take the lead in establishing an organization for unified coordination and management.
At the same time, he also believes that the product level represented by surveying and mapping geographic information companies also determines the effect of this system. Therefore, he hopes that surveying, mapping and geographic information companies will put scientific and technological innovation in the first place, and develop geological disaster monitoring and early warning equipment with excellent performance and stable quality.
Xu Qiang believes that with the joint efforts of multiple parties, the "sky-space-ground-inner" full-time and space-time real-time 3D geological disaster prevention and control system can better benefit my country's multi-disaster monitoring and early warning, so that the safety of people's lives and property can be guaranteed to the maximum extent. .