Study on monitoring and early warning of geological disasters in Wanzhou-Wushan section of Three Gorges reservoir area

Ouyang Zuxi Zhang Zongrun Chan Meng Kam Shijieshan Chen Zheng Han Wenxin

(Institute of Geostress, Seismological Bureau of China, Beijing, 100085)

In order to solve the problem of high uncertainty in landslide monitoring, various monitoring systems need to cooperate with each other. This paper systematically introduces the research work of geological disaster monitoring and early warning in Wanzhou, Fengjie and Wushan in the Three Gorges reservoir area, including the landslide monitoring network in typical areas of the research area based on 3S technology and ground deformation monitoring network, a new wireless landslide telemetry network developed, and special equipment such as mobile inclinometer and laser rangefinder. According to some typical monitoring results obtained in recent years, the effectiveness of different technologies and methods in monitoring and early warning of geological disasters is analyzed.

Keywords: 3S technology landslide monitoring and early warning system in Three Gorges reservoir area

1 Introduction

Since 1998, the geological disaster project team of the Institute of Geostress, Seismological Bureau of China (hereinafter referred to as the Institute of Geostress) has relied on the "Demonstration Study on GPS Landslide Monitoring in Wanzhou Reservoir Area of Three Gorges Project" by the Immigration Bureau of the State Council Three Gorges Construction Committee and the "Study on New and Efficient Remote Sensing Network Technology System of Geological Disasters in Demonstration Area" by the Tenth Five-Year Plan of the Ministry of Science and Technology. With the support of Chongqing Municipal Government and Immigration Bureau's project of "Monitoring the Stability of High Slope and High Retaining Wall in Fengjie and Wushan" and the project of "Monitoring the Landslide and Bank Slope Deformation in Three Gorges Reservoir Area by Using PSInSAR Remote Sensing Technology", and with the cooperation of Immigration Bureau and Land and Resources Bureau in Wanzhou, Wushan and Fengjie, the research of geological disaster monitoring and early warning system in the reservoir area has been extensively and deeply carried out. The monitoring object extends from landslide, dangerous rock and reservoir bank deformation to the stability of high retaining wall, high slope and immigrant building foundation. Monitoring technology embodies the integration of many disciplines.

In recent years, on the basis of geological survey, the project team established a geological hazard geographic information system by using 3S technology. Carry out global satellite positioning (GPS) landslide deformation monitoring and multi-means instrument monitoring; It also integrates mature and advanced sensor and measurement technology, computer information processing technology and communication technology. The wireless telemetry network based on GSM/GPRS communication platform can choose to connect different sensors to monitor surface deformation, deep displacement, groundwater dynamics, acoustic emission, crack changes, rainfall, and internal forces and thrust of engineering structures such as reservoir banks and anti-slide piles. In the application of remote sensing (RS) technology, the corner reflector technology newly proposed in the world is adopted to assist InSAR signal processing, and a test bed network is established. Up to now, the project team has made many achievements in the deformation monitoring and disaster early warning system of reservoir banks and landslides in the reservoir area. The monitoring results in some typical areas provide an important basis for government decision-making on disaster reduction.

2. The guiding ideology of the design of geological disaster monitoring network in reservoir area.

The main purpose of monitoring the collapse and landslide in the reservoir area is to fully understand and master the evolution process of the collapse and landslide, capture the characteristic information of the collapse and landslide disaster in time, and provide reliable data and scientific basis for the correct evaluation, analysis, prediction and treatment of the collapse and landslide disaster. At the same time, the monitoring results are also the scale to test the analysis and evaluation of collapse and landslide and the effect of landslide control.

In order to achieve the above objectives, the overall design idea of the geological disaster monitoring system in the reservoir area is:

(1) According to the geological structure and deformation stage characteristics of different landslides, different schemes and means are adopted for monitoring;

(2) In view of the high uncertainty of landslide and collapse deformation and failure process, it is advisable to monitor the same landslide by various means, and form a three-dimensional monitoring network combining point, line, surface, surface and underground, which complement and restrict each other;

(3) On the basis of group monitoring and prevention, develop conventional artificial instrument observation and wireless automatic telemetry technology, and establish a monitoring and early warning network combining static and dynamic monitoring to serve the long-term, medium-term prediction and short-term early warning of geological disasters respectively.

3. Geological hazard monitoring methods and techniques

According to the physical quantities of landslide and landslide deformation monitoring, considering the accuracy requirements of deformation measurement and the efficiency of monitoring work, combined with the current development level of monitoring technologies and methods at home and abroad, GPS, InSAR, laser ranging, flow inclination and crack monitoring technologies are used to measure surface deformation in practical applications, and traditional methods such as total station and leveling are also used in some sections. Borehole inclinometer monitors deep displacement; Pore water pressure gauge monitors the dynamic change of groundwater; The steel bar stress gauge and anchor cable (rod) stress gauge are used to monitor the stress changes of steel bars, anchor cables and anchor rods in anti-slide piles respectively; At the same time, telemetry network technology is used to collect a variety of dynamic monitoring data including surface deformation, deep displacement, groundwater, steel bar meter, acoustic emission of dangerous rocks and so on. The characteristics and application fields of these methods are briefly introduced below.

3. 1 GPS geodetic network

Global Positioning System (GPS) is a navigation, positioning and timing system developed by the US Department of Defense. It consists of 24 satellites, equally spaced on six orbital planes, with a height of about 20,000 kilometers. Anywhere on the earth, at any time, at the altitude of 15. At least four or more satellites can be observed at the same time in the above sky. Users can calculate the three-dimensional coordinates of the receiving point by receiving the signals transmitted by these satellites with the ground receiver and measuring the distance from the receiver antenna to the satellite. In recent years, the development and application of GPS positioning technology in China have developed rapidly. For example, a GPS monitoring network was established in the dam area of the Three Gorges Project. Practice has proved that the horizontal positioning accuracy of high-performance GPS can reach millimeter level, and it can be used for displacement monitoring of collapse and landslide.

Compared with traditional geodetic methods, the application of GPS measurement technology in landslide monitoring has the following advantages: ① there is no need for intervisibility between observation points, and it is convenient to select points; (2) it is not limited by weather conditions and can be observed all day; ③ Three-dimensional coordinates of observation points can be determined at the same time; ④ The new generation GPS receiver has the characteristics of simple operation, small size and low power consumption. Therefore, this method has been widely used in landslide deformation monitoring, construction safety monitoring and landslide control effect monitoring. However, due to the long period of monitoring station construction and data collection, this method is rarely used for short-term early warning of disasters.

3.2 Special Instrument Monitoring Network

Among these measuring methods, many traditional measuring instruments are still widely used, such as theodolite, total station, level and borehole inclinometer, which are mainly used for construction safety monitoring of various engineering management projects. In addition to the above instruments, we also developed portable inclinometers, mobile laser rangefinders and other equipment from the specific environmental conditions of the Three Gorges reservoir area, combined with the needs of other aspects of geological disaster monitoring, to make up for the shortage that GPS observation is not convenient to measure because of the shelter of houses and hillsides, so as to comprehensively monitor the landslide surface deformation, house and foundation deformation of new towns in the reservoir area located on the sloping terrain of valleys. In some key landslides and deformed bodies after engineering treatment, combined with the monitoring of treatment effect, a large number of steel bar meters and anchor rod (cable) meters are also used to monitor the internal stress and landslide thrust of anti-slide piles.

The observation of various mobile instruments on the surface has the characteristics of many monitoring parameters, high sensitivity, large measuring range, high efficiency, low cost and simple operation. Therefore, this measurement method is suitable for the safety monitoring and effect monitoring of landslide control construction, which is the same as the previous GPS mobile station observation method, and is also widely used in the medium and long-term monitoring and prediction of various geological disasters.

3.3 Wireless Telemetry Network for Geological Hazards

At present, the monitoring and early warning technology of collapse and landslide abroad has developed to a higher level. First, the telemetry network with automatic and multi-parameter monitoring is widely used; Secondly, in the aspect of geological disaster model prediction and early warning system, the spatial analysis, model prediction and early warning system of geological disasters are studied by using 3S(GPS, GIS and RS) technology. Although there is still a big gap in the above aspects in China, in recent years, some scientific research institutes and a few mining areas, such as the Ministry of Railways and the Ministry of Communications, have tried to monitor and predict landslide disasters by using small telemetry network. In 2002, the multi-parameter wireless telemetry network for geological disaster monitoring and early warning was built for the first time in the Three Gorges reservoir area where the crust of China Seismological Bureau is located.

"RDA wireless remote sensing network for geological disasters" is a new wireless remote sensing network based on GSM/GPRS technology developed by the earth's crust. The system is mainly composed of monitoring substation group, monitoring and early warning data center and GPRS data communication public network (see figure 1 for system composition). GPRS is a wireless packet-switched data bearer service developed on the basis of GSM. Compared with the circuit-switched data transmission mode of GSM/SMS, GSM/GPRS adopts the packet-switched data transmission mode, which improves the transmission rate, effectively utilizes the channel resources of wireless network, fully realizes the function of mobile Internet, and has obvious advantages for every user to always be online.

Figure 1 GPRS Landslide Wireless Telemetry System

According to the needs of a single landslide monitoring, the number of telemetering substations can be determined, and each telemetering substation can be connected with different sensors to monitor the surface displacement and deep displacement of landslide, or the surface dip angle, crack change and rainfall, as well as the internal force and thrust of engineering structures such as revetment and anti-slide piles. The software functions of the monitoring and early warning data center system include receiving the data of telemetering substations at various geological disaster points, putting the data into storage, displaying the deformation trend curve, and automatically giving an alarm if the data exceeds the limit. At the same time, the data center station can send instructions to each telemetry substation to change its working parameters, such as data sampling interval (5 minutes, 1 hour, 24 hours, etc. The system can be connected to the local computer network of the regional monitoring and early warning center to support the operation of the disaster reduction decision support system based on GIS. The computer screen of the city and county geological disaster monitoring and command center can closely monitor the accelerated deformation trend of landslide in quasi-real time, support the short-term and imminent landslide prediction of reservoir bank and landslide damage events, and also conduct on-site monitoring and rescue command of geological disaster events. Since we built the first telemetering network in Wanzhou WJW landslide in 2002, nearly 20 landslides and landslides in Wanzhou and Wushan have been monitored by RDA wireless telemetering network, and a wealth of data has been accumulated. The wireless remote sensing system for geological disasters mainly has the following characteristics:

(1) has many monitoring parameters and high accuracy.

The system integrates eight kinds of landslide monitoring instruments, including: landslide surface deformation (displacement and settlement), inclination deformation measuring instrument, crack measuring instrument, landslide micro-fracture acoustic emission signal recorder, underground sliding deformation inclinometer, pore water pressure measuring instrument, steel bar dynamometer and anchor cable (pole) tensiometer. These measuring instruments have high measuring accuracy and large dynamic range.

(2) automatic telemetry, unattended

The telemetry instrument has built-in microprocessor and wireless data transmission module, which has a large dynamic range, can be automatically monitored and transmitted wirelessly, and can be powered by AC power supply or solar cells.

(3) Barrier-free design

The developed instrument meets the barrier-free design requirements of measurement and data transmission, and has the advantages of convenient installation and good environmental adaptability.

(4) Relying on advanced communication technology

This telemetry network comprehensively uses the latest GSM/GPRS communication technology, which not only adapts to the terrain conditions of the Three Gorges reservoir area, but also has the characteristics of high capacity, wide coverage and low cost.

3.4 Emergency Monitoring System for Collapse and Landslide

In the past, no matter in the Three Gorges reservoir area or other areas of China, people often lost their lives because of lack of emergency monitoring means, failure to accumulate detailed data and missed the opportunity of research. On the basis of RDA telemetry network, we changed the communication to GSM/SMS, that is, short message mode, to make the system more suitable for public communication network and set it up more simply and reliably. This is especially important in remote monitoring environment and emergency monitoring occasions.

The emergency monitoring system optimizes the means of surface inclination, laser ranging and crack measuring instrument. Once people report or instrument monitoring shows signs of accelerated deformation of the landslide, they can rush to the scene, install the network in time and implement 24-hour continuous monitoring. It can not only effectively avoid the occurrence of emergencies, but also accumulate valuable data for studying the deformation and failure stages of landslides. In 2003, at the request of Wanzhou local government, the emergency monitoring of highway bridges received good results.

3.5 InSAR measurement technology of synthetic aperture interferometric radar

Short for Synthetic Aperture Radar (Interferometric Synthetic Aperture Radar).

Measurement technology is a measurement technology that uses the phase difference of two SAR images in the same area observed on adjacent routes to obtain ground data. Its main feature is to use the phase information in radar data.

Interferometric radar has many advantages: it has all-weather working ability, the emitted microwave has certain penetration ability to ground objects, and it can provide information that optical remote sensing can not provide, so it is an active working mode. For European radar satellite ERS- 1/2 and Canadian radar satellite RADRSAT- 1, DEM generated by interferometry is used to monitor the ground displacement change, and the accuracy can reach millimeter order. Therefore, this technical means is especially suitable for monitoring and forecasting large-scale geological disasters such as landslides, collapses, mudslides, ground fissures and land subsidence, and it is a fast and economical high-tech space detection means.

The Three Gorges area is rich in vegetation, abundant in rainfall and quite different in landforms, which is not conducive to jamming radar signal processing. Someone tried in this respect, but it didn't work. Therefore, the Crustal Stress Research Institute cooperates with the German Geoscience Center (GFZ) and adopts the newly introduced corner reflector technology to assist InSAR signal processing. Corner reflector is a device made of three angular metal plates, which can reflect the radar wave irradiated in it back to the original direction, and the reflected signal is obviously enhanced relative to the surrounding environment. By arranging artificial corner reflectors evenly in the workspace and determining some stable points as natural reflection points, it is convenient for image registration and accurate calculation of the displacement of corner reflectors. For such a large area of the Three Gorges reservoir area, it is limited to measure landslide deformation at a limited point only with GPS or other instruments and equipment. Therefore, it is of great significance to explore the use of InSAR technology to carry out landslide monitoring in the Three Gorges reservoir area. In 2003, we have installed 14 corner reflectors in Wanzhou and Wushan for experimental monitoring and research, and also jointly carried out GPS deformation monitoring as a comparison.

4. Geological disaster monitoring and early warning GIS system

Geological hazard monitoring geographic information system is an information system that can effectively manage all kinds of four-dimensional space (including geographical coordinates and time changes) data. Based on monitoring objects such as landslides, it stores spatial data such as topography, urban planning and monitoring point distribution into the computer according to their spatial positions. Through database module, curve display module and data analysis module, the functions of monitoring data storage, update, query, trend analysis, drawing display, chart and table output are realized.

The system mainly consists of four parts: geographic information subsystem, geological basic data document management subsystem, geological disaster monitoring database subsystem and monitoring data analysis subsystem.

Since the monitoring and research of geological disasters were carried out in Wanzhou District of Chongqing from 65438 to 0998, Crustal Institute first devoted itself to establishing a GIS-based geological disaster data and information management platform, and successfully developed the "Wanzhou Reservoir Area Migration Geographic Information System" in 2000. After that, the related database management system was gradually improved, the data analysis module was enriched, the automatic alarm function was added, and the landslide monitoring and early warning GIS system with data management and analysis was realized, which was extended to Wushan and Fengjie counties one after another.

The system uses the object-oriented programming language Visual C++6.0 as the development tool and MapInfo as the basic development platform. The geological disaster monitoring database was created by Microsoft SQL Server 2000, and the database connection and access adopted ADO technology. Geological disaster monitoring and early warning GIS system takes large-scale electronic map as working map, which can zoom and roam at will, automatically find map targets and associate with database. The system provides an effective platform for the management of various engineering geological and hydrogeological data, the monitoring network of the above-mentioned geological disasters, the analysis and display of monitoring data, including the management of group monitoring and prevention work, thus laying a good foundation for the study of landslide stability (the overall structure of the system is shown in Figure 2).

Fig. 2 overall structure block diagram of geological disaster monitoring and early warning GIS system

According to the requirements of the above functions, the system can output various visual forms, such as graphs, charts and three-dimensional simulation diagrams, which express the results of data processing and spatial analysis. Figure 3 is an interface of GIS system in Wushan County, showing the distribution of landslides, roads and four types of monitoring stations, which is an example.

Fig. 3 distribution map of GPS and tilt monitoring stations displayed by Wushan GIS system.

1.GPS static monitoring station; 2.GPS dynamic monitoring station; 3. Mobile tilt monitoring station; 4.GPS coordinate control points

The data analysis process basically has the following three aspects:

(1) The data obtained by the whole monitoring system, including automatic transmission and mobile observation, can be stored in the basic database of the local geological environment monitoring station after verification.

(2) Research on GIS-based geological disaster trend analysis and early warning technology, including statistical analysis of monitoring results, time series analysis, surface displacement vector diagram analysis, landslide depth-displacement curve analysis, displacement-rainfall analysis, etc. And then determine the landslide warning threshold under different geological environments.

(3) The obtained time-varying curve of landslide deformation and its two-dimensional plane distribution image results can be used for further landslide stability analysis and research.

5 Application of various monitoring technologies and typical monitoring results

5. 1 GPS technology for landslide deformation monitoring

Since the end of 1999, a GPS landslide deformation monitoring network with more than 120 mobile stations has been built in Wanzhou reservoir area. By the end of 2002, * * * has completed eight surveys. The results show that the recent deformation rate of most landslides is low, below 5 mm/year; The annual deformation rates of a few landslides, such as Banbianshiba and Experimental Primary School, are 84mm and 49mm respectively. Landslides such as Guantangkou and Qingcaobei also have obvious deformation. Figure 4 shows the zoning characteristics of landslide deformation in Wanzhou city: most of the areas with large deformation are steep slopes, and some are ancient landslide distribution areas; The recent deformation is mainly related to human engineering activities and heavy rainfall.

Schematic diagram of landslide deformation distribution in Wanzhou District.

1.GPS landslide monitoring point; 2. Landslide; 3. Sliding vector; 4. Stable region with small deformation

The above results are of guiding significance to the urban construction planning in the reservoir area. It is understood that some infrastructure projects have been selected in the above-mentioned deformation zone. Since the start of construction in early 2002, the three links and one leveling have been blocked repeatedly, and it took three years to carry out capital construction, which paid a heavy price. Monitoring and research on these landslides with poor stability have been strengthened. For example, in 2003, the SMB landslide in Wanzhou continued to deform and collapse, and its northern area has been seriously deformed since May. Figure 5 shows three representative baseline changes, and the ordinate represents the change of daily rainfall and GPS baseline length in mm. As can be seen from the figure, the deformation rate in this area was not high in the first quarter of 2003. In April 18 (in the figure 108), after the rainstorm of 84mm, the landslide deformation was obviously accelerated. G 123- 134 is the measurement baseline close to the main sliding direction, and the cumulative deformation reached about 400 meters by June. In addition to the landslide deformation caused by human engineering activities in this area, the influence of heavy rainfall can not be underestimated.

Another example is that there are more than 50 collapses and landslides in Fengjie new county, among which Sanmashan, Baotaping, Baiyi Temple and Nanzhuyuan have the greatest influence on the newly-built county. Because Xinxian County is located in a complex geological structure, the rock stratum is relatively broken, the gullies are developed, the high-order land is narrow and the continuity is poor. Most of the newly-built resettlement areas are distributed on steep ditches and valley slopes, and high and steep slopes excavated by hand can be seen everywhere, which has the characteristics of high height and long continuous distribution. The height of the slope can reach 30 ~ 40 meters and the length can reach hundreds of meters. High slope stability is one of the biggest potential geological disasters in fengjie county.

In 2002, we established a GPS and surface inclination deformation monitoring network in Fengjie, with a total of 290 monitoring piles. By the middle of 2003, the deformation distribution in the county was nearly 8km2. As shown in Figure 6, the area with the largest deformation was the high slope of the western Zhu Yi Valley slope. Most of these areas are high-order land and steep slopes, and the main geological disasters are the instability of natural high-steep slopes and ancient landslides caused by building loads. Because of leveling the construction site, cutting the slope and filling the toe and valley, the high slope and backfill slope are unstable.

Fig. 5 GPS measurement results of surface deformation of SMB landslide

Fig. 6 Deformation contour map of Fengjie New County in 2003

5.2 Monitoring Technology in Safe Construction Stage of Landslide Treatment Project

The monitoring work at this stage is mainly used to evaluate the stability of landslide (dangerous rock) in the construction process, feedback, track and control the construction process in time, provide the most direct basis for the improvement of the original design and construction organization, and send an alarm signal to the possible danger in time, so as to adjust the relevant construction technology and steps and avoid the occurrence of vicious accidents. Realize information construction to achieve the best economic benefits. At present, a large number of special instruments are used in safety monitoring, which is familiar to engineers and technicians. Here is just an example to illustrate the application results of "RDA wireless remote monitoring network for geological disasters". Since May 2002, a wireless telemetry network has been established in WJW landslide area of Wanzhou. The landslide is a geological disaster control project of the second phase of the Three Gorges reservoir area. Construction started in June 2002 and was completed in February 2003. Fig. 7 shows the results of laser ranging and telemetry along the main sliding direction of landslide. Although the construction includes the excavation and pouring of 59 anti-slide piles, due to the reasonable design and construction, the landslide displacement during the whole construction period is only a few millimeters. It can be seen that the continuous monitoring of telemetry network can grasp the deformation dynamics of landslide in time and accurately, and ensure the construction safety.

5.3 Monitoring of engineering governance effect

Take Wanzhou WJW landslide as an example. The landslide treatment project adopts a comprehensive treatment scheme with prestressed anchor anti-slide piles as the main part, supplemented by surface drainage and bioengineering. The monitoring network of treatment effect adopts instruments such as GPS, deep displacement, pore water pressure measurement and steel bar stress gauge, and sets up telemetry network at key positions for continuous monitoring.

Displacement curve of safety monitoring for Wanzhou WJW landslide treatment project.

Fig. 8 shows the daily variation curve of observation results of A2 anti-slide pile in No.3002 telemetry substation from August 2003 to June+February 5438. As can be seen from the figure, the internal force change (observed by steel bar meter and anchor rod meter) and deep displacement change of landslide are obviously related to the change of groundwater pore water pressure (observed by osmometer); According to meteorological data, the change of landslide pore water pressure is also directly related to rainfall. However, from the overall trend, the internal force and deep displacement of anti-slide piles have not changed much, which shows that WJW landslide is basically in a stable state after treatment, which is basically consistent with the instrument measurement results of other monitoring points.

Fig. 8 Curve display of observation results of 3002 telemetry substation

Fig. 9 is the vector diagram of WZB slope inclination deformation analyzed and displayed on Wushan GIS system, which is an example of monitoring the engineering treatment effect by using instrument monitoring network. It can be seen from the vector diagram that the dip angles of the four measuring points are basically consistent with the slope direction, and the cumulative angle variable in 2003 is ≤ 0.02, which indicates that the slope stability after treatment is good.

5.4 Emergency Monitoring of Landslide Deformation

Wushan county disabled persons' Federation landslide is located in the center of Wushan new county. The elevation of the landslide area is between 278 and 492 m, which is a valley slope with a slope angle of 10 ~ 30. The landslide is Quaternary slope deposit, containing gravel and silty clay, with a thickness of 0 ~ 12m and a total volume of about 15000 m3. Because this area is a slope area, the original slope must be excavated and cut in different degrees in the construction of roads and houses, and the deformation has been found in 200 1. According to the geological survey data, the boundary of the Disabled Persons' Federation landslide is obvious, and the sliding surface is gradually forming, which belongs to progressive landslide. Although it was treated twice in 2002, its western area still showed obvious deformation in 2003, endangering the safety of the roads and immigrant buildings under it.

Fig. 9 vector diagram of inclined deformation of WZB slope in Wushan County

Figure 10 laser ranging curve of Wushan Disabled Persons' Federation landslide (September 2003 ~ February 2004)

At the request of Wushan County Land and Resources Bureau, a telemetry network was installed in September 2003. The telemetering network of the Disabled Persons' Federation landslide is installed in the part that can best reflect the deformation characteristics of the landslide, and four telemetering substations form a survey line along the main sliding direction.

The monitoring data of laser ranging changes with time, as shown in figure 10. The last curve is the result of ranging, the length of the survey line is 5 1.3m, and the survey line shortened due to the downward sliding of the landslide is in mm; The next one is the ambient temperature curve, the unit is℃, and the abscissa is the measurement time, which is displayed in the format of year-month-day-hour.

From September 2003 12 to February 3, 2004, it can be roughly divided into two stages:

The first stage: from September 12 to September 27, before the anti-slide pile in the middle of the landslide is completed, the internal stress of the slope is adjusted due to excavation. Affected by the upper load of the landslide, the soil is squeezed forward. The creep deformation of the lower part of the landslide to the free surface is obvious, and the sliding rate is almost uniform, about 2 mm/d, and the total change of 16 days is 30 mm.

The second stage: after the anti-slide pile in the middle part of the sliding body is completed, the displacement rate is slowed down to 0.5 ~1mm/d; By the first half of February, 2004, the change was only 0. 1mm/d/d, which showed that the anti-slide treatment project contained the deformation of the sliding body and achieved the purpose of emergency treatment.

6 conclusion

(1) Based on 3S technology and ground deformation monitoring network, the landslide monitoring system of typical sections in the study area is basically established. The regional distribution of landslide deformation can be obtained by using space technology such as GPS, which is not only conducive to determining the landslide to be monitored, but also has guiding significance for urban reconstruction planning in the reservoir area. Telemetry network can measure the deformation rate quickly, and it is an effective tool to grasp the dynamic deformation trend of landslide and implement emergency monitoring.

(2) In order to solve the problem of high uncertainty in landslide monitoring, various types of instruments are needed. The new landslide wireless telemetering network, mobile inclinometer and laser rangefinder developed by the author have high precision and stable performance, and have great promotion value.

(3) Because the geological environment and influencing factors of landslides and high slopes are different, their failure mechanism and danger degree are also different. It is of great significance for stability monitoring, analysis and evaluation to correctly understand and distinguish the geological landscape of landslide and high slope and rationally arrange the stability monitoring points.

Here, I would like to thank Chen Cheng, Fan, and other comrades who participated in this work.

refer to

[1] Zhuo Baoxi. Establishment of "3s" geological disaster information three-dimensional prevention and control system and its practical significance [J]. chinese journal of geological hazard and control,1998,9 (4): 252 ~ 257.

Cui Zhengquan, Li Ning. Slope engineering-the latest development of theory and practice [M]. Beijing: China Water Resources and Hydropower Press, 1999

Ouyang Zuxi, Zhang Zongrun, Zhang Lu, et al. Geographic Information System of Three Gorges Project Immigrants in Wanzhou District, Chongqing. See: Crustal structure and geostress (12). Beijing: seismological press,1999:140 ~146.

Ouyang Zuxi, Zhang Yong, Zhang Zongrun, et al. Application of global satellite positioning technology in landslide monitoring in Three Gorges reservoir area. See: Crustal structure and geostress (13). Beijing: seismological press, 2000:185 ~191.

Ouyang Zuxi, Ding Kai, Shi Jieshan, et al. A new wireless remote monitoring network for geological disasters. Chinese journal of geological hazard and control, 2003, 14 (1): 90 ~ 94.

Ouyang Zuxi, Wang Mingquan, Zhang Zongrun, et al. Using GPS technology to study the landslide stability in Wanzhou reservoir area of Three Gorges Project. Chinese journal of geological hazard and control, 2003, 14 (2): 76 ~ 8 1.

Ouyang Zuxi, Shi Jieshan, Wang Mingquan, et al. RDA wireless telemetering network for landslide deformation. See: Proceedings of the 9th National Conference on Soil Mechanics and Geotechnical Engineering in china civil engineering society. Beijing: Tsinghua University Publishing House, 2003:1261~1266.

Chan Meng Kam, Ouyang Zuxi, Shi Jieshan, et al. Wireless remote sensing system of geological disasters based on GPRS technology. Journal of Natural Disasters, 2004, 13 (3): 65 ~ 69.

Chan Meng Kam, Ouyang Zuxi. Back calculation of internal force of prestressed anchor anti-slide pile. See: Crustal structure and geostress set (17). Beijing: seismological press, 2004: 139 ~ 145.

[10] Ouyang Zuxi, Zhang Zongrun, Ding Kai, et al. Landslide monitoring system for typical sections of Three Gorges reservoir area based on 3S technology and ground deformation observation. Journal of Rock Mechanics and Engineering, 2005 (to be published).