10.2. 1. 1 geological disaster investigation and evaluation
Since 199 1 year, the state has carried out regional environmental geological surveys in 31:500,000 or1:200,000 provinces (autonomous regions and municipalities) and compiled a geological hazard map of1:5 million in China. Since 1999, the investigation and zoning of geological disasters threatening residential areas have been carried out in counties (cities). By the end of 2003, surveys in 545 counties (cities) had been completed, covering an area of about 654.38+570,000 square kilometers. Basically find out the types and distribution of geological disasters in various provinces (cities) across the country.
In the theoretical method of geological hazard risk assessment, Yan He and Yin Kunlong (1987) used the multivariate regression model of two-state variables to predict the landslide space in Ankang and Xunyang reach of Hanjiang River basin. Huang Runqiu et al. (1992) applied the logical information model to the bank slope stability prediction in the Three Gorges reservoir area. Xu Qiang, (1994) and Zhou Pinggen (1997) also introduced the neural network method into the spatial prediction of slope and ancient landslide stability. Fuzzy mathematics method is also one of the methods with mature theory and wide application in spatial prediction of geological disasters.
200 1 Chengdu university of technology completed the key project of the Ministry of land and resources "GIS system for geological environment and geological disaster evaluation in mountain basins", which further promoted the development of geological disaster risk zoning technology and initially realized the risk zoning of small watershed collapse and landslide.
In the research of karst collapse, the Institute of Karst Studies of the Chinese Academy of Geological Sciences has successively carried out such projects as "Study of Karst Collapse in South China", "Study of Karst Collapse in the Yangtze River Basin" and "Study of Karst Collapse in North China". In addition, the relevant units have also carried out the work of "karst collapse along the railway and its prevention and control", basically found out the present situation and macro-distribution law of karst collapse in China, and determined the basic types of karst collapse in China. 1993 karst research institute has carried out experimental research on the development mechanism of karst collapse through large-scale physical model test and seepage deformation test. Since 1997, the GIS of karst collapse in Guilin, Yulin and Liupanshui have been developed, and the hazard of karst collapse has been evaluated. In 2002, Karst Institute completed the work of "1∶ 40,000 national land collapse risk zoning".
10.2.10.2 geological disaster monitoring and forecasting technology
(1) Meteorological Early Warning of Geological Disasters
In May, 2003, in the national meteorological early warning technology of geological disasters sponsored by China Institute of Geological Environment Monitoring, the rainfall early warning criterion model diagram of critical process was established by using the rainfall 15 days before the occurrence of landslide and debris flow, and was revised in combination with specific areas. The α-line (critical occurrence) and β-line (explosive boundary) are identified as two critical rainfall lines for landslides and mudslides in specific areas. The possibility of geological disasters in the area below the α line is small (the possibility of being close to the α line is high), and the possibility of geological disasters in the area between the α-β line is high. The area above the β line is an alarm area (with high possibility), and three areas represent three forecast levels. The application from June to July proves that the early warning function of landslide and debris flow disaster is obvious.
In 2002, Zhejiang Province started the local key project "Research and Application Demonstration of Early Warning and Forecasting System of Sudden Geological Disasters in Zhejiang Province", and Sichuan and Zhejiang provinces have done a lot of exploratory work in exploring the probability early warning of sudden geological disasters.
In 2003, the Ministry of Science and Technology launched the key project "Demonstration Research on Early Warning and Forecasting System of Landslide Disaster in Rainfall Region". In Shangrao, Jiangxi Province, the rainstorm conditions induced by landslide were studied by using radar remote sensing automatic detection technology, and the formation mechanism and early warning and forecasting model of regional landslide disasters were studied by combining with the monitoring of ground instruments on the landslide site.
(2) Monitoring and early warning of geological disasters
China has established land subsidence monitoring and early warning networks in Shanghai, Tianjin, Suzhou, Xi and other cities. In particular, Shanghai has established a land subsidence monitoring and early warning system that combines conventional monitoring with automatic monitoring, such as groundwater, layered standard, geodesy and GPS, and has reached the international leading level.
3S technology has made great progress in the monitoring of geological disasters in the Three Gorges. During the "Sixth Five-Year Plan" to the "Ninth Five-Year Plan", the former Ministry of Geology and Mineral Resources and the Ministry of Land and Resources conducted many remote sensing flights in the Three Gorges reservoir area, which were widely used in the field of geological disaster monitoring and early warning, and established standards and norms for geological disaster interpretation based on remote sensing technology; In the study of reservoir bank stability, the collapse and landslide are interpreted by color infrared aerial photographs; In April, 2003, China Geological Survey took a color infrared aerial photograph of the reservoir area, obtained the background value of geological environment before the second impoundment (water level in front of the dam 135m), and interpreted the geological disasters.
1999 65438+ 10, the Ministry of Land and Resources established the "Experimental (Demonstration) Area for Landslide Monitoring in the Three Gorges Reservoir Area", initially established the GPS reference network for geological disasters in the reservoir area, established a single monitoring network for local landslides, and emphatically studied the feasibility of GPS for landslide monitoring.
During the period of 1999, the Ministry of Land and Resources completed the construction of the demonstration project "Geological Disaster Information System (GGIS) and Prediction and Early Warning System". In 2000, China Institute of Geological Environment Monitoring completed the special scientific and technological plan of the Ministry of Land and Resources, namely, the project development of geological hazard information system (GHGIS) in the Three Gorges reservoir area, and applied it to the investigation of major engineering geological hazards in 19 county (city) and reservoir area (Fu Xiaolin et al., 2003). Wuhan University has completed the high-precision and fast GPS software development project of "Monitoring and Prediction of Geological Disasters in the Three Gorges of the Yangtze River".
Since 2002, the relevant state departments have invested 654.38+0.5 billion yuan to establish a comprehensive and systematic geological disaster monitoring network in the Three Gorges reservoir area. At present, this work is in the implementation stage.
In 2002, the Ministry of Science and Technology set up a key research project, and the Institute of Geomechanics of the Chinese Academy of Geological Sciences was responsible for the early warning research of geological disasters in the Three Gorges reservoir area. The project uses rainfall monitoring, geological survey, fractal dimension calculation method and GIS automatic mapping technology to predict and warn geological disasters.
In recent years, the monitoring of geological disasters in other areas of China has also made great progress. Taking Xiakou landslide in Ya 'an, Sichuan as the object, the new technologies and methods of landslide monitoring are studied by using GPS technology, borehole inclinometer, automatic water level observation instrument, automatic displacement monitor, TDR, pile arrangement and automatic rain gauge, and the data are transmitted in real time by using automatic transmission technology. In hydropower, railways, highways, mines and other departments, dozens or even hundreds of single landslides (including surface displacement and deep displacement) and pore water pressure have been monitored for a long time, and many valuable data have been obtained.
In the monitoring and prediction of karst collapse, through the model test of karst collapse, it is concluded that the change of karst water pressure has an important triggering effect on collapse, which is of great predictive significance as a critical condition to measure the occurrence of collapse (Jiang Xiaozhen, 1998). In 2000, the Karst Research Institute established a monitoring station for karst collapse disaster in Zhemu Town, Guilin, Guangxi, which mainly monitors the dynamic changes of water (gas) pressure in karst pipeline fracture system, and water (gas) pressure is the trigger factor for collapse. The monitoring results of more than one year show that the new collapse is related to the great change of karst water vapor pressure in the past month.
10.2.10.3 geological disaster prevention technology
Since 1992, the former Ministry of Geology and Mineral Resources has carried out a series of geological disaster investigation, evaluation and prevention, and accumulated experience in theoretical research, design theory and design method of geological disaster prevention. Especially in the "treatment of dangerous rocks in Lianziya of the Three Gorges of the Yangtze River", computer-aided design technology was fully used and parametric and intelligent design was started. In the prevention and control project, pre-stressed anchorage prevention and control projects have been carried out for Lianziya dangerous rock mass in the Three Gorges, Douyapeng landslide in Wanxian, Sichuan, Hanyuan landslide in Sichuan and Cuipingshan landslide in Yibin, Sichuan. Technology such as large-tonnage prestressed anchor cable and anchor pile is adopted.
1997 ~ 2003, the "Study on Prevention and Control of Major Geological Disasters in Resettlement in the Three Gorges Reservoir Area" was carried out, and the karst and karst geological disasters in the resettlement area, the engineering geological characteristics of mudstone slip layer in Badong Formation, the protection technology of engineering reservoir bank, the harm of civil air defense works in the reservoir area to new resettlement sites, the stability evaluation and protection technology of artificial high slope, and the stability of reinforced earth retaining wall for garbage disposal were deeply studied. The prevention and control demonstration zones in Wushan and Badong counties have been initially established, and the research on landslide development and utilization based on treatment has been carried out. On the basis of studying the relevant technical specifications and mature technical methods of landslide prevention and control design and construction at home and abroad, combined with the characteristics of the Three Gorges reservoir area, the Technical Specifications for Landslide Prevention and Control Engineering Design and Construction in the Three Gorges Reservoir Area of the Yangtze River is compiled.
In the construction of railways, hydropower, highways and cities, China has carried out a lot of research on landslide prevention technology, and established technical regulations including surface drainage engineering, underground drainage engineering, slope cutting and load reduction engineering, buttress back pressure engineering, anti-slide pile (key), supporting pile engineering, anchoring engineering, concrete bearing anti-slide engineering, grouting engineering and so on.
In the prevention and control of railway debris flow, open tunnels, tunnels, aqueducts, rapids, gravity dams and rail bars are used to prevent and control debris flow; The model test is used to scientifically demonstrate the prevention and control project of large debris flow gully, which makes the prevention and control project scheme more reasonable.
In recent years, in the practice of highway collapse and landslide prevention engineering in China, the technology of mutual cooperation between optical network protection system and biological slope protection system has been applied in the landslide disaster prevention engineering. For example, spraying thick planting substrate for greening is a biological slope protection system developed in recent years. It is a new type of slope protection technology that uses machinery to spray organic matrix containing plant seeds on the slope to restore natural vegetation quickly. Its construction technology is simple and the greening effect is good, and it is especially suitable for the treatment of rock slopes with slopes greater than 1∶0.5.
Problems in 10.2.2
(1) lacks a set of high-tech rapid investigation and evaluation methods.
Rapid investigation and identification technology (such as high-precision remote sensing image and its identification technology) is relatively backward. There is still a big gap between the evaluation index system and technical methods of geological disasters, especially the comprehensive application of 3S technology.
Because the gestation, occurrence and development of geological disasters are influenced and controlled by many factors, the genetic mechanism is extremely complicated. Not only the controlling factors and inducing factors of different types of geological disasters (such as landslides and mudslides) are quite different, but even the same type of geological disasters are also quite different because of their different geological environment conditions (such as loess areas in southwest, east and west China, etc.), and the genetic mechanism and critical value induced by external factors (such as rainfall) are also quite different. Due to various reasons, the spatial prediction and risk zoning of geological disasters are extremely complicated. It is unrealistic to put forward a unified and universal index system, model and standard for geological disaster prediction and evaluation. Only by formulating different evaluation index systems, choosing different weights and adopting different prediction and evaluation models and standards for a typical region and various disasters can geological disasters be objectively predicted. At present, the comprehensive application of 3S technology in geological hazard assessment is in the initial stage, which needs a lot of in-depth and meticulous work.
(2) The formation mechanism and inducing mechanism of geological disasters need further study.
There are various types of landslides in Chinese mainland, and the formation mechanism of rainfall landslides has its own characteristics. The formation mechanism of cluster landslides and large landslides in China needs further study.
The development of karst collapse in most cities is closely related to the activity of groundwater, but how to determine the critical value? At present, the main focus of physical model test is the qualitative revelation of collapse mechanism, and the observation methods are all manual methods, which can not capture the continuous changes of trigger factors and main influencing factors in the process of collapse development, and can not quantitatively analyze the critical trigger conditions of karst collapse and its relationship with main influencing factors.
(3) The accuracy of early warning and prediction of sudden geological disasters is low.
Limited by the basic data and the number of statistical samples of landslides and debris flows, the accuracy of prediction in space and time needs to be improved. Especially, there is not enough research on the relationship between the basic geological environment conditions and the corresponding critical rainfall in various regions of China. At the same time, the forecasting method is still relatively backward. At present, they are basically in the stage of manual or semi-manual and semi-computerized early warning, which is far from realizing the automation and rapidity of geological disaster prediction and early warning process.
(4) The monitoring technology of geological disasters is backward.
At present, most monitoring technologies of geological disasters still rely on conventional means with low accuracy, low efficiency and high cost. The popularization and application of new technologies and methods developed in recent years (such as high-precision global positioning system (GPS), high-precision interferometric synthetic aperture radar remote sensing INSAR and laser monitoring technology) are not enough.
Because of the late start in geological disaster monitoring, most of them are limited to point monitoring, and only a few are regional monitoring. The optimization of geological disaster monitoring network and the application of computer network have developed slowly.
The monitoring of landslide and debris flow disasters is mainly limited to the monitoring of displacement and pore water pressure, while other indexes related to evolution (such as temperature, hydrochemical field, geostress, thrust, etc. ) is rarely taken into account. At the same time, there is no unified standard for the layout, monitoring instruments and accuracy requirements of landslide and debris flow disaster monitoring network in China, which limits the comparability and appreciation of monitoring data.
The application of synthetic aperture radar interferometry (INSAR) technology in regional land subsidence monitoring needs further study. The optimization scheme of time (frequency), space (bedrock marker, layered marker), method and density of land subsidence monitoring network established by IN-SAR technology, early warning and prediction (simulation prediction) method and information integration are important topics that need to be studied urgently at present.
(5) The research on "post-disaster" widely exists in the early identification of potential disaster bodies.
Because the existing geological disaster investigation mainly investigates geological disasters that harm villages and towns and have obvious precursors, the analysis of related influencing factors and the study of the formation mechanism of geological disasters are not enough, resulting in poor early identification of potential disaster bodies and insufficient prediction ability of potential geological disaster points, and the research on "post-disaster" is more common.
(6) The prevention and control of geological disasters lacks a set of standards.
Lack of a set of technical standards for statistics, investigation, evaluation, exploration, design, construction, governance, emergency investigation and disposal of geological disasters.
10.2.3 the situation we are facing
(1) It is an urgent need for China's economic construction and sustainable development to actively carry out research on geological disaster prevention technology.
With the implementation of China's western development and sustainable development strategy, the focus of national large-scale projects and economies of scale has gradually shifted to the fragile geological environment in the central and western regions, especially some projects, new cities and small towns are threatened by more and more serious geological disasters. The influence and threat of geological disasters on human activities and living conditions are becoming more and more obvious, and the geological disasters induced by human engineering activities are becoming more and more frequent. The prevention and control of geological disasters has become one of the restrictive factors of China's economic construction and sustainable development. The prevention and control of geological disasters urgently needs the scientific and technological support of geological disaster investigation, monitoring and forecasting and prevention technology.
(2) The development of modern new technology, computer and information technology provides sufficient technical support for the study of geological disaster prevention.
The rapid development of modern measurement technology, information technology and computer technology provides advanced technical support for real-time monitoring of geological disasters, integrated transmission of various information, research on dynamic simulation of disasters, research on prediction and early warning model, research on disaster prediction and early warning system and research on rapid information release and feedback system, and creates unprecedented favorable conditions for the research and development of geological disaster monitoring and early warning and information management.