A safety monitoring method for earth-rock cofferdam during operation period

Abstract

This invention provides a method for safety monitoring of earth-rock cofferdams during operation. This method monitors seepage safety during the operation of earth-rock cofferdams. Due to the permeability of the cofferdam materials, seepage safety issues are prone to occur during operation. This invention performs routine seepage safety monitoring in earth-rock cofferdams while considering the effects of rainfall and the water content of the cofferdam. By real-time monitoring of upstream water level, water content, rainfall, and seepage flow, and using mathematical analysis methods to calculate the seepage flow threshold, an alarm is triggered. This overcomes the shortcomings of traditional seepage flow monitoring methods that do not consider rainfall and the actual operating conditions of the earth-rock cofferdam, improving the accuracy of safety monitoring during operation and achieving safety analysis and alarm functions.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering construction, specifically to a method for safety monitoring of earth-rock cofferdams during operation. Background Technology

[0002] In the construction of water conservancy projects, cofferdams are needed to create a dry construction environment and impound water in the corresponding water bodies. Cofferdams, as temporary water-retaining structures, are widely used in water diversion, hydropower stations, reservoirs, and other projects. Earth-rock cofferdams are the most common type of construction cofferdam due to their high material utilization and simple construction process. Because their filling material is earth and rock, which has high permeability, a seepage barrier is usually built in the middle of the earth-rock cofferdam to improve its seepage resistance and ensure its safety and stability. Earth-rock cofferdams are susceptible to seepage during operation due to factors such as upstream water level, the performance of filling materials, foundation settlement, construction technology, and external construction environment. Once the seepage exceeds the allowable value of the earth-rock cofferdam, it will cause structural damage to the cofferdam, and in severe cases, even cause the cofferdam to collapse. This not only causes the cofferdam to fail, but also causes irreversible construction damage to the downstream protection project, resulting in serious engineering losses. Ensuring the safe operation of earth-rock cofferdams during their operation is one of the difficulties in cofferdam construction and operation.

[0003] With the in-depth application of digital sensing technology, the status perception of equipment or structures has been effectively solved. After the earth-rock cofferdam is filled, monitoring equipment such as water level, seepage, seepage pressure, and deformation are buried inside or outside the cofferdam. This can effectively implement status perception and monitoring of the earth-rock cofferdam. Among them, seepage is one of the most important monitoring items during the operation of the earth-rock cofferdam. During operation, fixed alarm values ​​are usually set. Once the measured seepage flow exceeds the alarm value, an alarm signal is issued. The seepage flow of the earth-rock cofferdam is closely related to the upstream water level, rainfall, and water content of the cofferdam body. Using only a single alarm value cannot achieve accurate safety monitoring during the operation period, nor can it meet the intelligent management and control requirements of the earth-rock cofferdam during the operation period. Summary of the Invention

[0004] This invention addresses the problems of existing technologies by providing a method for safety monitoring of earth-rock cofferdams during operation.

[0005] This invention provides a method for safety monitoring of an earth-rock cofferdam during its operation. The cofferdam is equipped with a water level monitoring device upstream to obtain the upstream water level H. A drainage ditch is located downstream of the cofferdam, and a seepage flow monitoring device is installed within the drainage ditch to obtain the seepage flow Q of the cofferdam. A moisture content monitoring device is installed inside the cofferdam to obtain the moisture content M. The invention is characterized in that the cofferdam is also equipped with a rainfall monitoring device to obtain real-time rainfall P. The safety monitoring method includes the following steps: S1: Real-time monitoring of upstream water level H, infiltration flow Q, water content M, and real-time rainfall P, wherein the real-time rainfall P is hourly rainfall intensity; S2: Based on the upstream water level H, water content M, and real-time rainfall P, calculate the threshold QA of the infiltration flow Q. The method for calculating the threshold QA is as follows: S21: When the real-time rainfall P is 0, the threshold QA = F(H), where F(H) is a function related to the upstream water level H; S22: When the water content M is less than the set first water content M0 and the real-time rainfall P>0, the threshold QA=F(H)+G(P), where G(P) is a function related to the real-time rainfall P and G(P) is related to the shape of the drainage ditch; S23: When the water content M is greater than or equal to the set first water content M0 and less than the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + K1×J(P), where K1 is a proportionality coefficient, K1 = (M-M0) / (M1-M0), and J(P) is a function related to the real-time rainfall P, and J(P) is related to the shape of the downstream slope of the cofferdam; S24: When the water content M is greater than or equal to the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + J(P). S3: Monitor the seepage flow rate Q in real time, and activate a safety alarm when the seepage flow rate Q is greater than or equal to the threshold QA calculated in S2.

[0006] Preferably, the security alarm methods include: on-site loudspeaker alarm and mobile phone SMS push.

[0007] Preferably, the water level monitoring device, seepage flow monitoring device, water content monitoring device and rainfall monitoring device all adopt a dual power supply mode combining municipal power and solar power to ensure uninterrupted data collection.

[0008] Preferably, the moisture content monitoring device is installed on the downstream slope of the cofferdam, and the depth of the moisture content monitoring device from the surface of the downstream slope is less than 20 cm.

[0009] The working principle of this invention is as follows: Due to the material properties of earth-rock cofferdams, some seepage will occur, especially after the cofferdam construction is completed. A dry construction surface forms downstream of the cofferdam, while water is blocked upstream. As the upstream water level changes, water will seep into the cofferdam, forming seepage. The seepage rate of earth-rock cofferdams is an important factor affecting the operational safety of earth-rock cofferdams. Once the seepage rate exceeds the set value, it may cause piping and other problems. In severe cases, it may even cause the cofferdam to collapse, resulting in serious losses.

[0010] During the construction of earth-rock cofferdams, drainage ditches are built downstream to promptly discharge seepage. These ditches not only serve as seepage discharge channels but also act as monitoring points objectively reflecting changes in seepage flow. This invention incorporates a seepage flow monitoring device within the drainage ditch. This device can be a flow meter or a water level gauge. The water level gauge must be able to calculate the seepage flow based on the layout of the drainage ditch. When the monitored seepage flow in the drainage ditch is less than a set value, it indicates that the seepage of the earth-rock cofferdam is normal and without abnormalities (under normal operating conditions, seepage that does not affect structural safety is permissible in earth-rock cofferdams). If the seepage data is abnormal, a threshold will be used for judgment. If the threshold is exceeded, an alarm will be issued promptly for alarm processing. Upon receiving the alarm, operation and management personnel must conduct a comprehensive inspection of the cofferdam to promptly identify and address any seepage anomalies, ensuring the safe operation of the earth-rock cofferdam.

[0011] Unlike traditional seepage flow monitoring for earth-rock cofferdams, this invention proposes three components for the seepage flow of earth-rock cofferdams, enabling differentiated and precise threshold determination. First, the seepage of earth-rock cofferdams is related to the upstream water level; the higher the upstream water level, the greater the allowable normal seepage flow. Therefore, it is necessary to monitor the upstream water level in real time and calculate the upper limit of the allowable seepage flow based on the upstream water level. Second, the rainfall directly falling into the drainage ditch can be calculated through the size and structure of the drainage ditch. Generally, the upper surface of the top of the drainage ditch should be slightly higher than the downstream construction surface to ensure that the water discharged into the drainage ditch is mainly the seepage flow within the cofferdam and the runoff from the downstream slope of the cofferdam. When calculating only this part of the flow, it should be ensured that no runoff occurs on the slope. The main criteria for judgment are: the rainfall is relatively small, and the water content of the earth-rock cofferdam is less than the first water content M0, so that all the rainfall on the downstream slope of the earth-rock cofferdam is absorbed by the soil.

[0012] When the water content of the earth-rock cofferdam is greater than the first water content M0 and less than the second water content M1, it is considered that the water content of the earth-rock cofferdam is sufficient to form a runoff on the slope of the earth-rock cofferdam. It is also considered that the closer the water content is to the second water content M1, the more obvious the runoff is, and the larger the corresponding K1 proportionality coefficient is. When the water content M is greater than the second water content M1, it can be considered that the water content of the earth-rock cofferdam has reached saturation, and all rainfall will form a runoff on the slope.

[0013] By calculating and analyzing the threshold QA, we can analyze the dynamic threshold of seepage flow during rainfall periods and upstream water level changes, thereby enabling reasonable alarm analysis and avoiding false alarms caused by excessively low threshold settings during rainfall periods.

[0014] The advantages of this invention are: (1) Intelligent digital sensing and monitoring: By deploying seepage flow monitoring devices, real-time digital monitoring of seepage flow is realized. At the same time, by digitally monitoring the water level in front of the dam, the water content of the earth and rock cofferdam and the rainfall, the digital sensing of the cofferdam's operating status is realized, overcoming the disadvantages of low efficiency and poor accuracy of traditional manual inspection. (2) Uninterrupted data acquisition: Uninterrupted data acquisition is achieved through a dual power supply system. In particular, considering the operating environment of the earth-rock cofferdam, the construction interference and operation overlap are strong, and power outages are likely to occur. The use of dual power supply can effectively avoid data acquisition interruption. Furthermore, solar power is given priority to achieve green energy conversion and form low-carbon green technology. (3) Accurate data decision-making: Fully consider the factors that generate seepage flow, establish a multi-dimensional seepage flow threshold calculation method, realize accurate calculation of seepage flow threshold, adopt automated analysis in the calculation process, realize accurate discrimination under data-driven, and improve the safety performance of cofferdam seepage monitoring.

[0015] (4) Dynamic alarm control: The alarm threshold is different for different operating conditions of earth and rock cofferdams, so as to realize the dynamic alarm control system driven by upstream water level, earth and rock cofferdam water content and rainfall, and realize synchronization with the actual operating status of earth and rock cofferdam. Attached Figure Description

[0016] Figure 1 Layout diagram of monitoring devices for earth-rock cofferdams; Figure 2 This is a flowchart of the safety monitoring method for earth-rock cofferdams during operation. Detailed Implementation

[0017] The following provides a detailed explanation of the limitations of this invention.

[0018] This invention provides a method for safety monitoring of an earth-rock cofferdam during its operation. The method includes a water level monitoring device 1 installed upstream of the cofferdam to obtain the upstream water level H; a drainage ditch installed downstream of the cofferdam; a seepage flow monitoring device 2 installed in the drainage ditch to obtain the seepage flow Q of the cofferdam; and a moisture content monitoring device 3 installed inside the cofferdam to obtain the moisture content M. The method is characterized in that the cofferdam is also equipped with a rainfall monitoring device 4 to obtain the real-time rainfall P. The safety monitoring method includes the following steps: S1: Real-time monitoring of upstream water level H, infiltration flow Q, water content M, and real-time rainfall P, wherein the real-time rainfall P is hourly rainfall intensity; S2: Based on the upstream water level H, water content M, and real-time rainfall P, calculate the threshold QA of the infiltration flow Q. The method for calculating the threshold QA is as follows: S21: When the real-time rainfall P is 0, the threshold QA = F(H), where F(H) is a function related to the upstream water level H; S22: When the water content M is less than the set first water content M0 and the real-time rainfall P>0, the threshold QA=F(H)+G(P), where G(P) is a function related to the real-time rainfall P and G(P) is related to the shape of the drainage ditch; S23: When the water content M is greater than or equal to the set first water content M0 and less than the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + K1×J(P), where K1 is a proportionality coefficient, K1 = (M-M0) / (M1-M0), and J(P) is a function related to the real-time rainfall P, and J(P) is related to the shape of the downstream slope of the cofferdam; S24: When the water content M is greater than or equal to the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + J(P). S3: Monitor the seepage flow rate Q in real time, and activate a safety alarm when the seepage flow rate Q is greater than or equal to the threshold QA calculated in S2.

[0019] The upstream water level monitoring device 1 can be an immersion water level gauge, which can be directly immersed in the water body in front of the weir; the seepage flow monitoring device 2 can be a Doppler flow meter or a water level gauge. When a water level gauge is selected, the seepage flow should be converted according to the structural form of the drainage ditch. In order to ensure the accuracy of seepage flow monitoring, the drainage ditch should be made of hardened material, such as cement or concrete cross-section, to ensure that the monitoring cross-section is straight and regular, so as to ensure the accuracy of flow monitoring.

[0020] Multiple moisture content monitoring devices 3 can be deployed, with the placement location chosen on the downstream slope of the earth-rock cofferdam near the top of the dam to ensure real-time sensing of the moisture content of the downstream slope of the earth-rock cofferdam. The moisture content monitoring needs to reflect the moisture content of the downstream slope of the earth-rock cofferdam. Multiple moisture content monitoring devices are buried at the same depth in the dam body, and the depth from the downstream slope surface is less than 20cm. The slope of the road on the top of the dam is inclined to the upstream of the earth-rock cofferdam, so that the rainwater drainage from the top of the dam is discharged into the upstream of the cofferdam, while the downstream drainage ditch only collects the rainwater from the downstream slope of the cofferdam.

[0021] The rainfall monitoring device 4 is mounted on a pole. The monitoring device can be a rain gauge, which returns the cumulative rainfall. The hourly rainfall intensity is calculated by converting the hourly rainfall into the cumulative rainfall of the most recent hour. For example, from 3:00 to 3:59, the hourly rainfall intensity for that period is calculated as: the cumulative rainfall at 3:00 minus the cumulative rainfall at 2:00. Similarly, from 4:00 to 4:59, the hourly rainfall intensity is calculated as: the cumulative rainfall at 4:00 minus the cumulative rainfall at 3:00.

[0022] The function F(H) is the upstream water level and seepage flow function of the earth-rock cofferdam. Its calculation method can be combined with the structural form and material properties of the earth-rock cofferdam to perform seepage simulation calculations and obtain the seepage flow corresponding to different upstream water levels H. This function does not consider the influence of rainfall. The upstream water level H can be set at intervals (such as 0.2m) to obtain multiple sets of upstream water level-seepage flow arrays. For the water level within the upstream water level interval, linear interpolation can be performed.

[0023] The function G(P) is related to the shape of the drainage ditch, mainly to the area of ​​its upper surface. It can be calculated as: G(P) = P × A1 ÷ 3600000, where P is the hourly rainfall intensity in mm and A1 is the area of ​​the upper surface of the drainage ditch in m². 2 The function J(P) is related to the shape of the downstream slope of the cofferdam, mainly to its surface area. It can be calculated as: J(P) = P × A² ÷ 3600000, where P is the hourly rainfall intensity in mm and A² is the surface area of ​​the downstream slope in m². 2 The seepage flow rate calculated using G(P) and J(P) is in m³ / s.

[0024] The first moisture content M0 and the second moisture content M1 can be determined empirically, or through simulation calculations or experiments.

[0025] Preferably, the safety alarm methods include: on-site loudspeaker alarm and mobile phone SMS push notification. After the monitoring data is collected and sent to the cloud backend, it can be analyzed and calculated. Once the analysis results trigger an alarm, it will be pushed through the on-site loudspeaker to remind construction personnel to investigate, and simultaneously pushed to project management personnel via mobile phone SMS for handling.

[0026] Preferably, the water level monitoring device 1, seepage flow monitoring device 2, water content monitoring device 3 and rainfall monitoring device 4 all adopt a dual power supply mode combining municipal power and solar power to ensure uninterrupted data collection.

[0027] Preferably, the moisture content monitoring device 3 is installed on the downstream slope of the cofferdam, and the depth of the moisture content monitoring device 3 from the surface of the downstream slope is less than 20 cm. Multiple moisture content monitoring devices 3 can be installed along the cofferdam to accurately reflect the moisture content of the cofferdam and achieve precise judgment.

[0028] The collected data is sent to the cloud server via 4G. The cloud server analyzes and calculates the data through a background application to determine whether the cofferdam has triggered an alarm. When an alarm is triggered, the alarm mechanism is activated in a timely manner to send an alarm message, thereby ensuring the safe operation of the cofferdam throughout its entire operation period.

[0029] The above embodiments are merely preferred embodiments of the present invention. The scope of protection of the present invention should not be considered as limited to the specific forms described in the embodiments. The scope of protection of the present invention also includes equivalent technical means that can be conceived by those skilled in the art based on the concept of the present invention.

Claims

1. A method for safety monitoring during the operation of an earth-rock cofferdam, wherein a water level monitoring device is installed upstream of the earth-rock cofferdam to obtain the upstream water level H, a drainage ditch is installed downstream of the earth-rock cofferdam, a seepage flow monitoring device is installed in the drainage ditch to obtain the seepage flow Q of the earth-rock cofferdam, and a moisture content monitoring device is installed inside the earth-rock cofferdam to obtain the moisture content M of the earth-rock cofferdam, characterized in that: The earth-rock cofferdam is also equipped with a rainfall monitoring device to obtain real-time rainfall P. The safety monitoring method includes the following steps: S1: Real-time monitoring of upstream water level H, infiltration flow Q, water content M, and real-time rainfall P, wherein the real-time rainfall P is hourly rainfall intensity; S2: Based on the upstream water level H, water content M, and real-time rainfall P, calculate the threshold QA of the infiltration flow Q. The method for calculating the threshold QA is as follows: S21: When the real-time rainfall P is 0, the threshold QA = F(H), where F(H) is a function related to the upstream water level H; S22: When the water content M is less than the set first water content M0 and the real-time rainfall P>0, the threshold QA=F(H)+G(P), where G(P) is a function related to the real-time rainfall P and G(P) is related to the shape of the drainage ditch; S23: When the water content M is greater than or equal to the set first water content M0 and less than the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + K1×J(P), where K1 is a proportionality coefficient, K1 = (M-M0) / (M1-M0), and J(P) is a function related to the real-time rainfall P, and J(P) is related to the shape of the downstream slope of the cofferdam; S24: When the water content M is greater than or equal to the set second water content M1, and the real-time rainfall P>0, the threshold QA = F(H) + G(P) + J(P). S3: Monitor the seepage flow rate Q in real time, and activate a safety alarm when the seepage flow rate Q is greater than or equal to the threshold QA calculated in S2.

2. The method for safety monitoring of earth-rock cofferdams during operation as described in claim 1, characterized in that: The security alarm methods include: on-site loudspeaker alarm and mobile phone SMS push.

3. The method for safety monitoring of earth-rock cofferdams during operation as described in claim 1, characterized in that: The water level monitoring device, seepage flow monitoring device, water content monitoring device, and rainfall monitoring device all adopt a dual power supply mode combining municipal power and solar power to ensure uninterrupted data collection.

4. The method for safety monitoring of earth-rock cofferdams during operation as described in claim 1, characterized in that: The water content monitoring device is installed on the downstream slope of the cofferdam, and the depth of the water content monitoring device from the surface of the downstream slope is less than 20cm.

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