(Institute of Prospecting Technology, Chinese Academy of Geological Sciences, Chengdu, Sichuan, 6 1008 1)

Geological hazard prevention and control projects need to monitor geological hazard bodies. This paper briefly introduces the main methods of geological disaster monitoring in China and the application of new technology in engineering practice, points out the main problems existing in geological disaster monitoring engineering practice, and looks forward to the development trend of technology in this field in China.

Keywords: application prospect of geological disaster monitoring technology

Natural geological environment and human activities are the two main causes of geological disasters. In recent 20 years, with the increase of population and the rapid development of economic construction, especially the expansion of infrastructure construction scale, the contradiction between construction and land use is very prominent. The serious destruction of vegetation has led to frequent geological disasters such as landslides, mudslides and land subsidence in many parts of the country, which has seriously hindered the economic construction and social development in the disaster areas.

1 Main forms and hazards of geological disasters in China

1. 1 Geological disasters and common forms

Geological disasters refer to all kinds of unique natural environmental disasters formed by natural geological processes and human activities, which may cause harm to human survival and engineering construction.

The common forms of geological disasters are collapse, landslide, debris flow, land subsidence, ground fissures and land subsidence, which are referred to as collapse, slip, flow, collapse, crack and subsidence for short.

1.2 major geological disasters in the three Gorges reservoir area

After the completion of the Three Gorges Water Conservancy Project, it will produce great economic and social benefits. However, its construction has also had a direct or potential impact on the natural environment of the reservoir area. The impoundment of the first and second phases of the Three Gorges Project and the construction of new towns have brought many geological disasters to the reservoir area. In the construction of new towns in flood-stricken areas, due to insufficient consideration of geological environment factors in site selection, some new towns have formed an "indissoluble bond" with geological disasters from the beginning of construction. The main manifestations are landslides and collapses induced by man-made high-cut slopes and deep foundation pits. Badong and Zigui in Hubei, Wushan, Fengjie, Yunyang and Wanxian in Chongqing have all caused a lot of geological disasters in the construction of new cities. How to seek advantages and avoid disadvantages is a major issue before us.

1.3 Main hazards of geological disasters

The harm of geological disasters is obvious. China has a vast territory, complex geological structure and diverse landforms, with mountains and hills accounting for more than two-thirds of the total land area. There are different forms and degrees of geological disasters in 34 provinces, municipalities, autonomous regions and special administrative regions in China, which cause heavy casualties and property losses every year. Among them, sudden geological disasters, such as landslides, mudslides, flash floods, etc., have been designated as the main disasters of international disaster reduction by 10. Because of their potential and suddenness, once they happen, they will be fierce, often causing road interruption, navigation interruption, damage to structures, casualties and property losses. The total number of deaths due to geological disasters in China reaches 800 ~ 1000 every year, and the economic loss exceeds 1000 billion yuan.

1.4 characteristics of geological disaster monitoring

Deformation bodies such as (1) landslides are usually dispersed and the genetic mechanism is complex. Before monitoring, it is necessary to have a certain foundation of geological environment investigation and research;

(2) Geological disasters are mostly located in areas with inconvenient transportation and communication, and it is also difficult to access power supply;

(3) At present, most of the monitoring is mainly manual, with slow data acquisition speed and high labor cost;

(4) Compared with the safety monitoring of fixed buildings and structures such as dams, bridges and tunnels, geological disaster monitoring has open monitoring boundaries and complex conditions. Attention should be paid to the environmental adaptability and anti-interference performance of instruments and equipment in the selection, fixed installation and operation of monitoring means such as automatic monitoring and telemetry to ensure normal use and safe operation.

2 the necessity of monitoring in the prevention and control of geological disasters

According to the different stages of the project, the monitoring of geological disaster prevention project can be divided into construction safety monitoring, prevention effect monitoring and long-term stability monitoring. At present, it is generally simply called monitoring. In the past work practice, it is often found that there is blindness in the process of geological disaster control besides economic reasons. Some geological disasters are dealt with on the grounds of instability. Some people have no governance because they feel stable. Except some simple and rough survey data, there is hardly enough evidence to prove whether a deformed body is stable or not and whether it needs engineering treatment. If necessary monitoring is carried out on deformed bodies such as landslides, this blindness will be reduced and the effect of getting twice the result with half the effort will be achieved.

2. 1 refers to geological disasters for which engineering measures have been taken.

For the geological disaster prevention and control projects that have taken engineering measures, in the process of governance, the effect is evaluated according to the monitoring results, the construction is guided, and the design is revised in time; After the completion of the prevention and control project, with the change of surrounding environmental conditions, the constraint conditions will also change. For example, the corrosion and relaxation of anchor cable, the change of groundwater level, the increase of free surface, the low quality of engineering, and the huge external force (such as earthquake and big blasting) may make some landslides that are temporarily in a relatively stable state lose stability after treatment. If they are not monitored for a long time, they are more deceptive and dangerous, so they cannot sit back and relax. It is still necessary to judge their therapeutic effect and long-term stability through necessary monitoring.

2.2 For geological disasters without engineering measures,

It is also necessary to monitor some untreated and potentially harmful geological disasters. Some large-scale landslide deformation bodies that have no funds for engineering renovation for the time being, but pose a great potential threat to people's lives and property, are effective ways and means to make up for them with less investment in monitoring work. Effective monitoring can not only evaluate its stability, but also provide design basis for whether and how to control it. Effective monitoring of deformed bodies such as landslides by monitoring means is a method with less investment and quick results, which has been gradually accepted and respected by some government officials and owners. They also realized that monitoring data should be used to verify the repair of engineering means, otherwise it would be blind. However, at present, there are still quite a few management and design departments that only pay attention to passive governance and mending after the sheep is dead, but do not pay attention to nip in the bud.

3 the main methods of geological disaster monitoring at present

In the past, as the object of monitoring work, it mainly monitored the deformation, displacement and settlement of some important structures and large-scale construction projects, such as water conservancy and hydropower dams, large bridges, important workshops, large underground concealed works, mine slopes and tailings dams. The monitoring of complex geological disasters has only been gradually applied in recent years, and the main monitoring methods currently adopted are as follows.

3. 1 absolute ground displacement monitoring

Absolute displacement monitoring is the most basic conventional monitoring method. By measuring the three-dimensional coordinates of landslide measuring points, the three-dimensional deformation displacement, displacement direction and deformation displacement rate of the measuring points can be obtained. This paper mainly uses theodolite, level, infrared rangefinder, laser collimator, total station and GPS to measure the three-dimensional coordinates of a point on the deformed body by geodetic method.

3.2 Monitoring of relative ground displacement

Ground relative displacement monitoring is a common deformation monitoring method, which is used to measure the changes of relative displacement (opening, closing, sinking, lifting, dislocation, etc.). ) between the key deformation parts of the landslide. It is mainly used for monitoring and settlement observation of cracks, landslide zone, roof and floor of goaf, etc. It is one of the important contents of displacement monitoring. At present, the commonly used monitoring instruments include vibrating wire displacement meter, resistance displacement meter, crack meter, displacement meter, convergence meter and so on.

3.3 Drilling Deep Displacement Monitoring

For deformed geological bodies such as landslides, it is necessary to monitor not only their surface displacement, but also their deep displacement to judge and monitor the overall displacement. The method comprises the following steps: firstly, drilling holes on deformed bodies such as landslides, passing down from the sliding zone to the stable section, directionally lowering special inclinometer tubes, and backfilling the consolidated inclinometer tubes with cement mortar (suitable for drilling in rock mass) or sand and earth and stone (suitable for drilling in loose accumulation body) in the annular gap between tube holes; Run the borehole inclinometer, take the hole bottom as the zero displacement point, and measure the displacement of each depth point in the hole relative to the hole bottom at a certain interval (generally 0.5m or 1m). Commonly used monitoring instruments include borehole inclinometer and borehole multi-point displacement meter.

3.4 Pressure monitoring

For deformation bodies such as landslides, it is necessary to monitor not only the change of displacement, but also the change of internal stress. Because the deformation (or movement) of geological body is inevitably accompanied by the change and adjustment of the internal stress of the deformed body, it is very necessary to monitor the stress change. Commonly used instruments include anchor stress gauge, anchor stress gauge, vibrating string soil pressure gauge and so on.

3.5 Water environment monitoring

For landslides, besides natural geological conditions and human interference, water is the most important factor directly affecting the stability of landslides, so it is very important to monitor the water environment (including process rainfall and rainfall intensity, surface water flow, groundwater level, seepage flow, seepage pressure, pore water pressure, groundwater temperature, etc.). ). The commonly used monitoring instruments include measuring weir, telemetering rain gauge, clock, electric water level gauge, telemetering water level gauge, osmometer, seepage meter, electric thermometer, etc.

3.6 Earthquake monitoring

Earthquake monitoring is applicable to all landslide monitoring. Seismic force is one of the special loads acting on landslide, so it plays an important role in the stability of landslide. When geological disasters are located in earthquake-prone areas, data from nearby seismic stations should be collected frequently and timely; If necessary and conditions permit, seismographs and other instruments can be used to monitor the intensity and occurrence time of earthquakes in this area and its surroundings. The epicenter location, focal depth and seismic intensity are analyzed, and the influence of earthquake action on landslide stability in this area is evaluated.

3.7 Monitoring human-related activities

Human activities, such as digging holes, cutting slopes and taking soil, blasting and quarrying, and loading and running of water conservancy facilities, often cause man-made geological disasters or induce geological disasters. When this happens, we should monitor and stop an activity. In the monitoring of human activities, we should monitor the projects that have an impact on landslides, and monitor their scope, intensity and speed.

3.8 Macro-geological survey and monitoring

Using conventional geological survey methods, the macroscopic deformation traces (such as the occurrence and development of cracks, ground subsidence, collapse, expansion, uplift, building deformation, etc.) are analyzed. ) and abnormal phenomena related to deformation (such as ground sound and groundwater anomaly, etc.). ) Conduct regular surveys and records. This method is intuitive, adaptable and reliable. It is the main means of landslide monitoring and the main content of group prevention and treatment. It is suitable for all landslides and has accurate prediction function.

Research and engineering practice of new monitoring technology

4. 1 Research and application of new monitoring technology abroad

Developed countries not only have traditional monitoring methods and instruments in the field of geotechnical engineering and geological disaster monitoring, but also apply high and new technology to geological disaster prediction and early warning engineering in recent years. PDI, Geokon, Sisgeo, Leica, Sweden, Zeiss and Nikon are all in the leading position in the innovation of monitoring methods and the application of new technologies. Infrared technology, laser technology, microwave technology, optical fiber technology, grating technology, mechatronics, automation technology, satellite communication technology, computer and artificial intelligence have been widely used in the development and research of monitoring technology and instruments. It can be said that geological disaster monitoring and monitoring instruments, as a branch of geotechnical engineering monitoring, are no longer geodetic instruments in the traditional sense, but have realized the perfect combination of traditional methods and instruments with modern high technology, pushing the technical level of monitoring instruments to a brand-new stage and developing to a higher level. Representative foreign products include Leica TCR 1800 total station, TCR2003 measuring robot, Geomos system, DNA electronic level, GPS, Zeiss DiNi 12 series electronic level, North American drilling multi-point displacement meter, Sicon geotechnical engineering monitoring series instruments, etc.

4.2 Research and Application of New Monitoring Technology in China

Domestic hydropower systems and the Ministry of Land and Resources have carried out research in this field, such as the Academy of Water Conservancy, the relevant research institutes of Chinese Academy of Sciences, and the Institute of Technical Methods of the Ministry of Land and Resources. With the construction of the Three Gorges Project, with the strong support of the Ministry of Land and Resources, our institute has also developed a series of borehole inclinometers, stress measurement series, ground displacement measurement series and other geotechnical engineering and geological disaster prevention monitoring instruments, multi-parameter telemetry systems, etc. It also undertook the research on the project of "Automatic Monitoring System for Landslide Geological Disasters" of the Ministry of Science and Technology, and did a lot of work for the localization of measuring instruments. The products have been well applied in the Three Gorges reservoir area and major national projects. My research achievements and products in recent years mainly include the following eight items:

(1)DMY laser tunnel section measurement system;

(2)BYT type optical fiber landslide thrust monitoring system;

(3)DZQX new multifunctional borehole inclinometer;

(4) Wireless automatic monitoring and forecasting system for collapse;

(5)PSD micro-displacement deformation measurement system;

(6)MS anchor cable (anchor rod) force measuring system;

(7)DHS formation water content meter;

(8) Research on core orientation and coring technology.

4.3 Engineering Monitoring Practice

At the same time of research and development, I actively participated in the monitoring of major national capital construction projects and the monitoring of geological disaster prevention projects in the Three Gorges reservoir area with my own research results, and achieved good economic and social benefits. The main monitoring projects carried out in recent years include:

(1) Deformation measurement of Qingjiang double-track large-section tunnel on Baocheng double-track line;

(2) Deformation measurement of Ma 'anbao South Tunnel in Xichang, chengdu-kunming railway;

(3) Deformation measurement of Beijing Metro Fu-Ba Line;

(4) Deformation measurement of People's Square Station of Shanghai Metro 1 Line;

(5) Deformation measurement of Qingdao metro test section;

(6) Deformation and measurement of high and steep slope of Chang-Cheng Expressway;

(7) Deformation measurement of high slope of Neijiang-Yibin Expressway;

(8) Acceptance of the entire tunnel of Dan-Ben (Xi) section of Dan-Shen-Yang Expressway;

(9) Monitoring of ground displacement, deep displacement and stress of K2794+860 ~ 980 landslide in Erlangshan-Kangding section of National Highway 3 18;

(10) Geological hazard monitoring project in fengjie county and Yunyang counties.

5 Development prospect of monitoring technology

(1) Geological disasters will occur more frequently and do more harm, and monitoring work will receive more attention, and the application of monitoring results will produce greater social benefits.

(2) With the support of China Geological Survey, our monitoring instrument research and operating system software development will receive more funding, and our monitoring means will be more complete, reaching a new level and having stronger market competitiveness.

(3) Automatic monitoring and telemetry are the development direction of geological disaster monitoring, but there are still many difficulties in implementation at present.

(4) Geological disasters are regional and public welfare undertakings, which need the guidance and support of the government.

6 conclusion

Through several years of monitoring engineering practice, we have witnessed many lives and property losses caused by neglecting engineering safety monitoring and poor engineering of geological disasters, and also seen many examples of successfully predicting and avoiding disasters through monitoring. With the implementation of the lifelong accountability system for engineering quality, it is particularly important and urgent to monitor the safety of geological disasters and related geotechnical engineering for a long time.

Monitoring engineering is an important part of geological disaster prevention engineering system. Pay equal attention to governance, prevention and monitoring, and sometimes even pay more attention to engineering management means.

Monitoring landslide deformation for a certain period of time can save a lot of investment.

Geological disaster prevention and control projects should be based on scientific monitoring to guide design, construction and engineering effect evaluation. Facing it with a scientific attitude, it should be upgraded from an empirical and rough investigation to a quantitative stage. Only in this way can we have a profound understanding and scientific evaluation of landslide deformation.

Monitoring is not dispensable, it is the need of engineering diagnosis, and it is the necessary work for geological disaster research and prediction.

Prevention is more important than disaster relief, and monitoring is better than governance.

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