Yunfeng Power Plant is located in the middle reaches of the Yalu River and in Qingshi Town of Ji’an City, Jilin Province. In 1959, China and North Korea jointly invested in construction, water storage power generation in 1965, completed in 1967, the installed capacity of 40MW, the total reservoir capacity of 3.895 billion m3, effective storage capacity 26. (5.2 billion m3. The main hydraulic structures have a dam, Diversion tunnels and power plants.
The Yunfeng Dam is 828m in length with a total of 55 dam sections, the highest dam section m, and the top elevation of the project is 321.75m. The normal high water level is m. Except No. 8 and No. 48, No. 50 and No. 53, No. 56 are outside the gravity dam section. The rest are wide seam gravity dams.
The displacement of the crest is an important project for dam safety monitoring and is a comprehensive reflection of the displacement of the dam. The horizontal displacement of the crest of the Yunfeng Dam was observed using the line-of-sight method from April 1972 to October 1981. After November 1981, it was replaced by the draw line method. The vertical displacement of the crest has always been observed using precision leveling methods. Due to the large workload of manual observation, vulnerability to external environmental impact, and low accuracy, it is difficult to promptly and promptly propose accurate dam displacement data, and it is not possible to meet the requirements of modernization of hydraulic operation and management for dam safety monitoring. Therefore, many Repeated demonstrations, decided to install a set of vacuum laser collimation automatic deformation measurement system (hereinafter referred to as the laser system).
1 System Introduction Yunfeng laser system is currently an advanced dam deformation observation system in China. The system is jointly designed and constructed by the Changchun Chaoyang Monitoring Technology Institute, the Northeast Electric Power Testing and Research Institute Hydropower Station and the Yunfeng Power Plant. The system has a total length of 892.797m and a total of 53 measuring points. It can simultaneously monitor the horizontal displacement and vertical displacement of the measuring point. The entire system consists of transmitter, receiver, measurement point, vacuum system and other components (see).
The Yunfeng laser system began designing and constructing in 1996. In June 1998, artificial observations were put into trial operation. In April 1999, automatic observation was put into operation. After more than two years of construction and more than five years of operation, comparative observations and multiple system tests, a large amount of system installation, operation data and observation data have been accumulated.
2 System Design 2.1 System Axis Determination The determination of the system axis (pipeline centerline) is also to determine where the system is specifically installed. According to the crest structure of the Yunfeng Dam, the axis position of the system is set to be 6.5m downstream of the dam axis and 322.140m in elevation, and g is about 20cm in the downstream railing and 39cm above the crest elevation (321.75m). The center line is parallel to the original deformation system.
2.2 System Type Determination The laser system is now serialized and qualitative. According to the length of the dam and the size of the displacement, the vacuum laser collimation system is mainly divided into four types: I, n, in, and IV. The pipe diameters are: Type I 159mm, Type 219mm, Type IE 273mm, Type IV 325mm. According to the specific conditions of Yunfeng Power Plant, the first three types are selected, ie: Type I from the launch end to the 9th dam section. , Length about 137m; from dam section 9 to dam section 39, with a length of about 450m; from dam section 40 to the receiving end with type 01, about 297m. 2.3 Design of the transmitting end, receiving end, measuring point of the system The launching end of the laser system is located in the North Korea (left bank) flat hole, 21m from the left dam head, where the vertical displacement observation base point and the draw line end point are all located here. After years of observational data analysis, the rock mass is stable here.
The receiving end of the laser system is located in the Shangba traffic on the right bank, and the laser system layout of the pipeline center line is shown. 4 Selection of vacuum system In order to ensure that the vacuum degree of the pipeline is less than 34Pa, a 2X70 vacuum pump can be used to meet the requirements. However, due to the use of a vacuum pump, it takes 70 minutes to pump from atmospheric pressure to 34Pa, and the pumping time is longer. . In order to shorten the vacuuming time, it is more important to be used as a backup to ensure the reliability of the entire system. Two 2X70 vacuum pumps were finally selected.
2.5 Considerations for Other Factors There are many other factors to be considered in the design process. For example, during the construction of the Yunfeng system, there are the moving positions of the left bank guide line, the ground elevation in front of the elevator door, the road surface elevation on the left bank and the right bank, and the right bank dam test. Improvements to the displacement monitoring system, etc., while also taking into account various difficulties in the actual construction.
There are two schemes for designing the launching end position: 1 It is about 20m away from the right abutment head, which is the end point of the original drawing line. Because the rock body is not stable here, it is necessary to drill inverted and double metal target holes, set upside down and double The metal mark is used as the base point for measuring the displacement of the receiving end, and the observation room needs to be built. It will occupy a large space in the traffic hole. 2 The receiving end will be extended to the right again, passing through the traffic hole, and then excavated at the upstream wall of the traffic hole. The 6m deep hole is used as the observation room and the chestnut room. The rock mass is already about 40m deep, and the rock body is stable. There is no need to set upside down and double metal marks, but it is necessary to raise the ground elevation of the traffic hole and affect the appearance of the traffic hole. After comprehensive analysis, the Yunfeng laser system finally selected the second set of solutions, which not only improved the accuracy of the observed values, but also reduced the future maintenance workload and project investment costs, and ensured that the measured displacement was the absolute displacement of the dam.
The Yunfeng Dam has a total of 55 dam sections. Since the No. 2 and No. 3 dam sections are close to the launch end, no survey points have been set. One survey point is set at each dam section of No. 56 dam section No. 4, a total of 53 Measuring point. Among them, the measuring points of the retaining dam sections (No. 27, No. 49, No. 49, No. 49) are set in the middle of each dam section, and the measuring points of the overflow dam section (No. 28, No. 28) are set near the piers measured by the Chinese side. . Each measuring point is equipped with a steel measuring point box, a built-in wave plate and a remote control inversion device. The measuring point box is installed on the steel plate for measuring point sensitivity. In order to ensure the stability of the measuring point and prevent the pipe from being affected by the temperature deformation on the measuring point, the stainless steel bellows at both ends of each measuring point box is used to realize the soft connection of the box.
The laser system layout is as shown.
3 System Construction 3.1 System Centerline Stakeout The Yunfeng laser system center line uses T3 theodolite and NA3003 digital level. The location of the line is based on the axis of the dam, and the elevation is based on the benchmark Ai. It is worth noting that the centerline elevation of the system should be corrected by the curvature of the earth. Because the same height horizontal line equidistantly laid out by geometric levels, due to the influence of the curvature of the earth, is actually an arc, that is, a geodetic level line, and the laser beam is a straight line in the vacuum pipeline, and the vacuum pipeline is also required to be a straight line. The result of the elevation lofting should be corrected with the curvature of the earth. Correction can be made from the middle point to both ends.
3.2 Device Base The equipments at the launching end, receiving end and measuring point of the construction system shall be installed on a solid and reliable base steel plate. The base of the equipment should be drilled, reinforced, poured concrete, and then installed 16mm thick base steel. Because the positions of the transmitting end and the receiving end are already stable, the inserting bars can be directly drilled. The Yunfeng Dam surface is about 25cm thick second-phase concrete. There is catchment between the old and new, and it is vulnerable to freezing and thawing. Therefore, the location of each measuring point should be excavated to about 30cm below the concrete of the second phase, and then proceed. Drilling, inserting, pouring concrete, installation, etc. In order to make the base firm and reliable, and the measuring point can correctly reflect the displacement change in the position, the base inserts use a rebar with a diameter of 30mmXl500mm and one end of which is threaded, and each of the insertion points of the base points is one. Each measurement point is 4 roots.
In addition, the base steel plate should be installed immediately after the insertion of the steel bars. When the steel plate is fixed, nuts should be installed above and below the steel plate. This facilitates adjustment and fixation of the position and height of the steel plate.
3.3 Piping System Installation Laser pipe uses seamless steel pipe. Before the welding, the rust of the inner wall of the pipeline shall be removed. To ensure the concentricity of the pipeline connection during welding, a simple platform such as an iron pipe or a channel steel may be welded first and then welded on the platform.
Each section of the pipeline should be subjected to pressure test after welding, and the leakage point should be treated in a timely manner. This can avoid that the leakage of all pipelines is too large to find leaks.
In order to prevent the pipeline from increasing the temperature gradient in the pipeline under the direct sunlight, affecting the accuracy of the measured displacement, chemical foaming is performed outside the pipeline before installation to form an insulating layer. In order to make the insulation layer durable and beautiful, a layer of nylon fiber tape is additionally wrapped outside the insulation layer and brushed twice with silver powder. In addition, each measurement point box and bellows can not be directly covered with heat insulation material, therefore, each measurement point should be processed with a certain strength, and the inner wall is affixed with a protective sheet of steel insulation.
Each end of the pipe is connected to the bellows with a flange. In order to facilitate the flange alignment, the flange is preferably one end fixed (welded), the other end with a movable flange, or both ends of the use of movable flange. As shown.
China Water Directional Seals Laser Lines Fixed Flange Bellows To prevent the deformation of the laser pipe, the pipe is supported by the pier and the distance between the piers is about 4m. A small rolling bar is installed between the pier and the pipe to ensure that the pipe is free from temperature influences. Flexibility also facilitates adjustment of the level when the pipe is installed.
When installing measuring points and pipelines, the influence of temperature and water level shall be taken into consideration according to the season at that time, so as to ensure that the measuring points and the axis of the pipeline are compatible with the variation of the displacement of the dam. For this purpose, the measuring point box and the measurement point pier panel should be set inside, so as to ensure the inside of the pipeline is dry and form a space without rust and oxidation, so as to ensure the long-term and stable operation of the internal equipment. The Yunfeng system generally observes once a week. According to the air leakage volume of 1 Pa/h, the vacuum inside the pipeline is much less than 20 kPa. Therefore, the system runs for 5 years and there are no signs of rust in the internal equipment.
The system is running. Due to the large number of high-power electrical equipment on the dam, the laser system power supply is unstable, and it is easy to cause unstable work and equipment damage. Later, the regulator was installed (excluding the vacuum pump) and achieved good results. In addition, because the transmitter and receiver rooms are relatively humid, a leakage protector must be installed before the system power supply to prevent the system from accidentally causing a major accident.
Although the protective layer of the laser pipe is simply protected, because the construction and tourism personnel often go to the pedaling and some of them have been damaged, in order to prevent further damage, the galvanized iron sheet on the outside of the thermal insulation protective layer plays a very good protective role. . For long-term use, it is recommended to wrap the system directly during installation.
Set the appropriate adjustment device.
3.4 Measurement point adjustment According to the analysis of the observation data of the Yunfeng Dam for many years, there are aging displacements in the majority of the left bank. In order to adapt to this situation, it is possible to increase the measuring point range, and add a standard pad under the No. 4 to No. 9 measuring point boxes with large time displacement during construction. When the dam is raised, the measuring point range can be increased by lowering the height of the measuring point box. Among them, No. 4 and No. 5 measuring point pads are three 5mm, No. 6 and No. 7 measuring point pads are two 5mm, No. 8 and No. 9 measuring point pads are 5mm, so that the range is increased by 4 system operation management respectively. Operation management is a long-term process. Only proper and reasonable operation and management can ensure long-term stable operation of the system and truly play the role of automatic monitoring. In the five-year operation and management process, Yunfeng laser system has accumulated the following management experience: it has formulated strict equipment management system and periodic inspection system, and strengthened the training of observers. The laser automation system integrates light, electricity, and machinery into one, and it is difficult for hydraulic observers to maintain it. Therefore, it is necessary to pass training. Continuously improve the operational level and management capabilities of the observers.
In order to improve the observation accuracy, it is best for the laser artificial observer to fix it. There must be someone responsible and manual measurements during vacuum pump operation are prohibited.
Under the conditions permitting, the original manual observation items are retained as much as possible, which facilitates the comparison of manual and automatic measured values, and because the laser system construction time is long (usually a year or two before operation), the system can be guaranteed during the construction process. The continuity of the observation data and the normal observation of the flood season can be observed.
Normally, the degree of vacuum in the laser pipe is to be ensured at 20kPa due to the thin bellows wall of the system, and two dams are leaked during the construction process of the dam downstream reinforcement (the protective cover is temporarily removed due to construction needs), and the bellows More expensive, change trouble. Therefore, at the time holding a try, we asked the welder to use argon-arc welding. As a result, the welding effect was better and it has been used until now. It is worth noting that it is necessary to inflate the pipeline before welding. The welding can be performed only when the internal and external air pressures are the same, so that the pressure in the pipe is too small, the leakage point caused by the welding is larger, or the welding object is sucked to the other side, so that the other side also leaks.
The service life of the laser tube is generally longer, but after long-term use, the output power will gradually decrease, and the laser output power should be frequently tested during use. When the power drops significantly, it should be replaced in time. In order to ensure the continuity of the observation data before and after the replacement, before the replacement, all observation points should be observed one by one, and records should be made. After the replacement, observations should be made on the same conditions. Do not mobilize the laser tube, aperture plate, and base during normal use. Otherwise, the continuity of the measured value will be affected. Special care should be taken when replacing, do not touch the aperture aperture and the point of light source, just adjust the adjustment screw on the laser tube bracket.
The laser tube is mounted in a separate sealed metal container and connected to the laser tube through a hose (valve on one side of the tube). Its internal vacuum is consistent with the inside of the laser tube. When the Yunfeng laser system replaced the laser tube for the first time, the valve was closed first, and then the container was inflated and replaced. However, after the valve was restored, the laser tube could not work, and several replacements were performed in a row. The conditions were the same. Afterwards, the inside of the pipeline was also inflated and replaced, and the laser tube was operating normally. The preliminary analysis may be due to the fact that the instantaneous pull of the laser tube was too large after the original replacement, but it needs to be further confirmed. Therefore, before replacing the laser tube, it is best to inflate the inside of the tube to change the pressure inside and outside the tube.
The system is best separated from the in-plant MIS network. If it must be connected to the 5 manual ratio measurement system during operation, the manual observation project always insists on measurement. It can be seen from the manual and automatic process lines (see and) that automatic and manual measurements are available. The values ​​are basically close, and their variation laws are exactly the same, which means that the automatic measurement values ​​are credible and can accurately reflect the measurement point displacement. In order to better test the system, compare the measured values ​​of the two. The difference between the two is in accordance with the error theory (The laser automatic continuous measurement of the displacement distribution 5.4 data collection missing rate data missing rate is calculated as follows: W automatic = f moving data missing rate is the number of measured data W is the number of data not collected .
MIS network, you must install anti-virus software and firewalls, and upgrade in time.
5 System Analysis 5.1 Boost Rate Boost rate is an important measure of the laser system and is the key to determining the success of the system. Only by guaranteeing a certain range of boost rate, can the system components be protected from environmental influences such as moisture, ensure long-term stability of the system, reduce failures, and increase observation accuracy. The boost rate of the Yunfeng laser system is always maintained at 7Pa/h20Pa/h, meeting the requirements of the regulations of less than 120Pa/h.
5.2 System Accuracy The accuracy of manual observation and automatic observation of the laser system is less than the requirement of *1.mm in the Technical Specifications for Safety Monitoring of Concrete Dams in 5178-2003.
5.3 System stability In order to examine the stability of the laser system, set up laser automatic monitoring continuous measurement 15 times, calculate the accidental error of each point, in which the maximum value of the horizontal displacement.
079mm, the maximum vertical displacement is 0.054mm, and the 15 observations are close to the respective average, as shown.
Foot full-scale table 1 Comparison of horizontal displacement and laser manual horizontal displacement table Table 45 Stage 45 Dam 46 Section 47 Section 49 Section 49 Section 50 Section 51 Section 52 Section 52 Section 54 Dam Table 2 Leveling and laser Artificial Vertical Displacement Measurement Comparison Table Stage 24 Section 26 Section 27 Section 27 Section 41 Section 50 Section 51 Section 51 Section 52 Section 55 Section 5.6 System Work Efficiency Previously the top of the diversion line observation once required 2 people at most , 4h, dam top level observation once requires 5 people, 5h, and easily affected by the external environment. Now the laser system is vacuumed for about 20 minutes before each observation, manual observation is about 2 persons and 60 minutes, and only one person is required for automatic measurement. 20 minutes. 6 end-note system has high observation accuracy, fast measurement speed, and stability Strong, influenced by the external environment and other characteristics. The application of this system to the Yunfeng Dam has improved the working environment of the observers and greatly improved the efficiency of observations.
The laser system has been operating for 5 years, but it still cannot fully realize remote control. At present, the remote control cannot understand the operation of the vacuum pump; the quality of the vacuum pump must be taken into account to prevent the vacuum pump from sucking into the vacuum pipeline at the moment when the vacuum pump stops operating, causing a greater accident. Now some high-quality vacuum cream can avoid this problem, but the price is higher.
Tomorrow tomorrow (1975-), male, assistant engineer, engaged in hydraulic building safety
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