Trillion-dollar national debt flood control and disaster reduction response: MYUAV UAV-dam piping identification scheme
Uavs dam pipe identification scheme
Policy environment
In the fourth quarter of 2023, an additional 1 trillion yuan of government bonds will be issued, all of which will be allocated to local governments through transfer payments, focusing on supporting post-disaster recovery and reconstruction, making up for weak points in disaster prevention and relief, and improving China’s overall ability to withstand natural disasters. According to the Ministry of Finance, the funds will focus on eight major areas: Post-disaster recovery and reconstruction, key flood control projects, projects to improve natural disaster emergency capacity, other key flood control projects, construction and renovation of irrigation areas and key soil erosion control projects, actions to improve urban drainage and waterlogging prevention capabilities, key projects to build a comprehensive natural disaster prevention and control system, and construction of high-standard farmland in Northeast China and the disaster-stricken areas of the Beijing-Tianjin-Hebei region. The additional issuance of national debt not only released multiple positive signals, but also highlighted the urgent task of improving China’s disaster prevention, mitigation and relief capabilities.
Piping hazard
Piping is the phenomenon of the water table rising above the ground and gushing out of the ground or buildings. Under the action of seepage, the fine particles in the soil are carried away or rushed out of the pores of the coarse particles. Also called sand drum water, bubble springs and so on. During the flood, due to the high water level of the river, higher than the ground inside the embankment, there is a pressure difference inside and outside the levee, if there is a permeable layer at the bottom of the levee, seepage will occur. Where there is percolation, there will be percolation force, when the percolation force is large to a certain value, the fine particles in the soil will be carried and transported by the seepage flow, this groundwater erosion is called subduction.
The continuous development of submerged corrosion will form holes in the weak areas, and the holes will make the penetration path shorter, the hydraulic gradient will increase, more seepage will be concentrated in the holes, the submerged corrosion effect is stronger, the holes continue to develop, and finally develop into a pipeline, a large number of fine particles are carried into the holes by the seepage, gushing out along the pipeline, that is, the formation of piping.
Piping can not only cause damage to the surrounding buildings and infrastructure, but also may cause geological disasters. Swell monitoring and identification is of great significance for preventing geological disasters, protecting buildings and infrastructure, treating groundwater problems and improving early warning ability. Piping is one of the common hazards in dike engineering. Piping will cause the soil at the bottom of the dam to discharge outwards continuously under the action of seepage force. After a long period of time, the soil skeleton of the dam foundation will be damaged, the pores will be expanded, and the foundation soil will be hollowed-out, causing the dam to collapse, resulting in dam bursting, dam collapse and other dangerous situations.
System composition
When the UAV is used for pipe surge identification, its load, imaging system, algorithm, data processing and transmission capabilities and cloud management platform comprehensive control capabilities are considered to improve the efficiency and accuracy of the UAV in flood prevention and rescue.
Pipe identification technology
Based on the principle of infrared radiation, infrared thermal imaging technology uses infrared radiation measurement technology and methods to measure the transmission of heat waves inside the object, and displays it through the thermal imager. Finally, the collected thermal images are processed to determine whether there are defects inside the object. The flow chart of infrared detection technology is as follows:
1. Technical principles
The current detection principle is to determine the low temperature point as the leak point, but this criterion has a high misjudgment rate, which is because the dam itself is neglected in management and maintenance, and there are widespread uneven pits, water, moisture and vegetation growth, which are often low temperature points. Only the water downstream of the dam comes from the river or reservoir water, can be judged as the leakage point, so the principle of unstable leakage detection of the dam is to distinguish the reservoir water and the water on the surface of the dam. Because of the small volume of water on the surface of the dam, its temperature is greatly affected by the air temperature, and it is close to the air temperature. Due to the large volume of reservoir water, its temperature is less affected by air temperature, so there is a big difference between it and the air temperature. Therefore, the difference between the temperature of reservoir water (river) and the air temperature is used as the identification condition for leakage, which can realize the accurate identification of unstable leakage.
2. Algorithm principle
Data acquisition: The drone collects both visible and thermal imaging data as it flies, as well as related water flow and environmental data.
Image preprocessing: Preprocessing the collected visible and thermal imaging data, including image correction, enhancement and filtering, to improve image quality.
Feature extraction: Extracting from the pre-processed image helps to identify the features of the pipe, and extract the temperature distribution and color information.
Recognition algorithm: Combining visible light and thermal imaging data with deep learning algorithm to train the pipe recognition model.
Real-time monitoring/early warning: During the flight of the UAV, the collected image data is input into the pipe surge identification model in real time, and the model will determine whether there is a pipe surge phenomenon. Once a surge is detected, the system will give a real-time warning and mark the location information.
Uav surge identification inspection process overview
(1) Set the UAV inspection route, determine the temperature and reservoir water temperature, determine the weather conditions and vegetation coverage on the surface of the dam body.
(2) The UAV was used to carry an infrared thermal imager to comprehensively inspect the downstream surface of the embankment according to the preset inspection route, and the thermal image of the downstream surface of the embankment was captured by the infrared thermal imager during the inspection; If the temperature > storage water temperature, the lowest temperature in the thermal image is lower than the threshold, or the storage water temperature > air temperature, alarm and record the suspected leakage site; Continue the inspection until the entire downstream surface of the dam is completed; If the inspection is completed and there is no alarm sound, it is determined that the dam body is not leaking and the inspection is ended.
(3) Fly around and approach the suspected leakage site to take the thermal image again. If the alarm conditions are still met, the location is identified as the leakage point, and the area of the low temperature area (>) or high temperature area (<) in the thermal image is calculated.
(4) After T time interval, reset the temperature threshold, fly around again and approach the leakage point to take a thermal image, calculate the area of low/high temperature region in the thermal image, and compare the changes in the area of low/high temperature region in steps (3) and (4) to determine whether there is early unstable leakage. It is worth noting that in the flood season, the interval T should not be too long, controlled within 2 hours.
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