Seepage flow monitoring method based on measuring weir-hydraulic gradient cooperation

Abstract

The invention provides a seepage flow monitoring method based on measuring weir-hydraulic gradient cooperation. The seepage flow monitoring method comprises the following steps: S1, mounting a measuring weir and a pressure measuring pipe; s2, collecting seepage flow data of the measuring weir and water level data of pressure measuring pipes in front of and behind the cutoff wall at regular time, analyzing and comparing data at different time points through data processing, and calculating the seepage flow of the cutoff wall; and S3, synthesizing the seepage flow of the cutoff wall and the seepage flow value of the measuring weir obtained by calculation to obtain the total seepage flow for comprehensive assessment of dam safety. According to the method, the water level monitoring data source is added, the seepage flow of the cutoff wall is subjected to inversion analysis in combination with a hydraulic gradient method, the change of the seepage flow of the dam can be reversely deduced under the condition that the measuring weir does not overflow (such as low-water-level operation), and the technical problem that the seepage flow of the dam cannot be monitored through a conventional means in part of time periods is effectively solved; the total seepage flow of the dam can be approximately obtained through coupling analysis, and key data support and analysis basis are provided for accurately evaluating the seepage behavior safety of the dam.

Description

Technical Field

[0001] This invention belongs to the field of dam safety monitoring, specifically involving a seepage flow monitoring method based on the coordination of water measuring weir and hydraulic gradient. Background Technology

[0002] In earth-rock dam failures, seepage failure accounts for the highest proportion, and seepage flow is the most direct indicator reflecting the seepage behavior of earth-rock dams. Seepage flow mainly comes from leakage in the dam body and foundation. The conventional method for monitoring seepage flow is to set up a cutoff wall at the downstream toe of the dam, with drainage ditches laid on top of the cutoff wall to collect seepage from the dam body and foundation, and a measuring weir set up at the drainage ditches to monitor the seepage flow.

[0003] The main riverbeds in Southwest China are characterized by overburden geology, with depths often exceeding 50 meters. Constructing cutoff walls on such deep overburden is challenging, often necessitating the use of suspended cutoff walls, which are typically quite deep. During actual observations, many projects exhibit periods of no or minimal flow at the downstream weirs, significantly contradicting the actual dam seepage flow. This makes accurate assessment of the dam's seepage behavior impossible and severely impacts the evaluation of the dam's operational safety.

[0004] Existing methods for monitoring seepage at dams with deep overburden layers suffer from incomplete monitoring and inaccurate data. Due to the significant difference in stiffness and dimensions between the concrete cutoff wall and the overburden foundation, the types of loads borne by the cutoff wall are highly complex. Furthermore, as it is a concealed structure, localized damage is difficult to detect. Localized damage to the cutoff wall easily creates seepage channels, reducing its effectiveness. Additionally, the cutoff wall may not penetrate deeply into the bedrock, leaving seepage at the bottom, meaning the drainage ditches do not collect all the seepage. Moreover, the seepage flow at damaged areas or the bottom of the cutoff wall cannot be directly observed. Summary of the Invention

[0005] The main objective of this invention is to provide a seepage flow monitoring method based on the coordination of a water measuring weir and hydraulic gradient, addressing the aforementioned problems.

[0006] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A seepage flow monitoring method based on the coordination of water measuring weir and hydraulic gradient includes the following steps:

[0008] S1. Install the measuring weir and piezometers: Install the measuring weir at a predetermined position downstream of the dam, and arrange piezometers at predetermined positions in front of and behind the water-cutting wall of the measuring weir downstream of the dam.

[0009] S2, Calculate the seepage flow of the cutoff wall. Regularly collect data on seepage flow from the weir. The water level data from the piezometers before and after the cutoff wall are analyzed and compared at different time points to calculate the seepage flow of the cutoff wall. This calculation is then combined with the hydraulic gradient method to determine the final seepage flow. ;

[0010] S3. Calculate the total seepage flow of the dam. The calculated seepage flow rate of the cutoff wall and the seepage flow rate of the measuring weir are combined to obtain the total seepage flow rate data used for the comprehensive assessment of dam safety. The comprehensive seepage coefficient of the cutoff wall is obtained by data fitting. Then, output the total seepage flow of the dam. .

[0011] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0012] As a preferred technical solution of the present invention: in step S2, the seepage flow of the cutoff wall... As shown in the formula below:

[0013] ;

[0014] In the formula, The number of cross-sections for which piezometers are installed on the cutoff wall. This refers to the seepage flow rate of sub-regions after dividing the cross-section. The permeability coefficient of the sub-region The flow area of ​​the sub-region The comprehensive seepage coefficient of the sub-region , These represent the water levels in front of and behind the cutoff wall at each cross-section.

[0015] As a preferred embodiment of the present invention: in step S3, data fitting includes: Each data pair includes a weir seepage flow value. Water level difference before and after the cutoff wall - ; Calculation obtained Based on the correlation expression between the seepage flow rate of the medium-sized weir and the water level difference before and after the cutoff wall, the comprehensive seepage coefficient of the cutoff wall is obtained. .

[0016] As a preferred technical solution of the present invention: In step S3, the total seepage flow of the dam... As shown in the formula below:

[0017] ;

[0018] In the formula, For the seepage flow data of the weir, This represents the comprehensive seepage coefficient for the sub-region. , These represent the water levels in front of and behind the cutoff wall at each cross-section.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) By adding water level monitoring data sources and combining the hydraulic gradient method to perform inverse analysis on the seepage flow of the cutoff wall, it is possible to infer the change of dam seepage flow under the condition that the water measuring weir does not flow (such as when the water level is low), effectively solving the technical problem that the dam seepage flow cannot be monitored by conventional means during certain periods.

[0021] 2) The total seepage flow of the dam can be approximated through coupling analysis, providing key data support and analytical basis for accurately assessing the seepage behavior safety of the dam. Attached Figure Description

[0022] Figure 1 The flowchart shows the seepage flow monitoring method based on the coordination of water measuring weir and hydraulic gradient provided by the present invention.

[0023] Figure 2 This is a plan view of the water measuring weir.

[0024] Figure 3 This is a cross-sectional view of the water measuring weir. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1-3 As shown, a seepage flow monitoring method based on the coordination of a water measuring weir and hydraulic gradient includes the following steps:

[0027] S1. Installation of the measuring weir and piezometers: A measuring weir is installed at a predetermined location downstream of the dam to measure the dam's seepage flow data in real time; piezometers are installed at predetermined locations before and after the weir's cutoff wall to monitor the water level before and after the cutoff wall. , ;

[0028] S2, Calculate the seepage flow of the cutoff wall. Regularly collect data on seepage flow from the weir. The water level data from the piezometers before and after the cutoff wall are analyzed and compared at different time points to calculate the seepage flow of the cutoff wall. This calculation is then combined with the hydraulic gradient method to determine the final seepage flow. As shown in the formula below:

[0029] ;

[0030] In the formula, The number of cross-sections for which piezometers are installed on the cutoff wall. This refers to the seepage flow rate of sub-regions after dividing the cross-section. The permeability coefficient of the sub-region The flow area of ​​the sub-region This represents the comprehensive seepage coefficient for the sub-region. , These are the water levels in front of and behind the cutoff wall at each cross-section;

[0031] S3. Calculate the total seepage flow of the dam. The calculated seepage flow rate of the cutoff wall and the seepage flow rate of the measuring weir are combined to obtain the total seepage flow rate data used for the comprehensive assessment of dam safety. The comprehensive seepage coefficient of the cutoff wall is obtained by data fitting. Then, output the total seepage flow of the dam. As shown in the formula below:

[0032] ;

[0033] In the formula, For the seepage flow data of the weir, This represents the comprehensive seepage coefficient for the sub-region. , These represent the water levels in front of and behind the cutoff wall at each cross-section.

[0034] Data fitting includes: Each data pair includes a weir seepage flow value. Water level difference before and after the cutoff wall - ; Calculation obtained Based on the correlation expression between the seepage flow rate of the medium-sized weir and the water level difference before and after the cutoff wall, the comprehensive seepage coefficient of the cutoff wall is obtained. .

[0035] Example:

[0036] Step 1: Install the measuring weir and piezometers: Install the measuring weir at a predetermined location downstream of the dam to measure the dam's seepage flow data in real time; arrange piezometers at predetermined locations before and after the weir's cutoff wall to monitor the water level before and after the cutoff wall.

[0037] In this embodiment, a trapezoidal measuring weir is installed at the downstream toe of the dam, and a measuring weir meter is arranged 1.5 m upstream of the weir plate to achieve automated monitoring.

[0038] Given the specific operating conditions of this embodiment: ① the water level in front of the interceptor wall is connected to and equal to the water level of the measuring weir; ② the interceptor wall is adjacent to the downstream river channel, and the water level behind the wall is directly controlled by the tailwater level of the dam. Therefore, in order to optimize the monitoring process, this embodiment directly replaces the piezometer level in front of the interceptor wall with the water level of the measuring weir, and directly replaces the piezometer level behind the interceptor wall with the tailwater level of the dam.

[0039] Step 2: Calculate the seepage flow of the cutoff wall: Collect the seepage flow data of the measuring weir and the water level data of the piezometers before and after the cutoff wall at regular intervals. Analyze and compare the data at different time points through data processing to calculate the seepage flow of the cutoff wall.

[0040] The test data came from a set of measured seepage data from the dam, totaling 20 data pairs. Analysis showed a significant linear correlation between the seepage flow rate of the measuring weir and the water level difference before and after the cutoff wall. Through data fitting, the comprehensive seepage coefficient of the cutoff wall was obtained. It is 36.37.

[0041] Step 3: Combine the calculated seepage flow of the cutoff wall with the measured seepage flow of the measuring weir to obtain the total seepage flow data used for the comprehensive assessment of dam safety.

[0042] The total seepage flow of the dam is expressed as

[0043]

[0044] From the above formula, it can be seen that the measuring weir does not allow water to flow (i.e., the water flow does not exceed the standard). Under these conditions, the water level difference before and after the cutoff wall can still be used to determine the water level. Calculate the total seepage flow of the dam This enables effective assessment of dam seepage behavior under low water level conditions.

[0045] The technical solution of the present invention has been described in conjunction with the specific experimental procedures shown in the accompanying drawings. However, the scope of protection of the present invention is not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for monitoring seepage flow based on the coordination of a water-measuring weir and hydraulic gradient, characterized in that, Includes the following steps: S1. Install the measuring weir and piezometers: Install the measuring weir at a predetermined position downstream of the dam, and arrange piezometers at predetermined positions in front of and behind the water-cutting wall of the measuring weir downstream of the dam. S2, Calculate the seepage flow of the cutoff wall. Regularly collect data on seepage flow from the weir. The water level data from the piezometers before and after the cutoff wall are analyzed and compared at different time points to calculate the seepage flow of the cutoff wall. This calculation is then combined with the hydraulic gradient method to determine the final seepage flow. ; S3. Calculate the total seepage flow of the dam. The calculated seepage flow rate of the cutoff wall and the seepage flow rate of the measuring weir are combined to obtain the total seepage flow rate data used for the comprehensive assessment of dam safety. The comprehensive seepage coefficient of the cutoff wall is obtained by data fitting. Then, output the total seepage flow of the dam. .

2. The method according to claim 1, characterized in that: In step S2, the seepage flow rate of the cutoff wall As shown in the formula below: ； In the formula, The number of cross-sections for which piezometers are installed on the cutoff wall. This refers to the seepage flow rate of sub-regions after dividing the cross-section. The permeability coefficient of the sub-region The flow area of ​​the sub-region This represents the comprehensive seepage coefficient for the sub-region. , These represent the water levels in front of and behind the cutoff wall at each cross-section.

3. The method according to claim 1, characterized in that: In step S3, data fitting includes: Each data pair includes a weir seepage flow value. Water level difference before and after the cutoff wall - ; Calculation obtained Based on the correlation expression between the seepage flow rate of the medium-sized weir and the water level difference before and after the cutoff wall, the comprehensive seepage coefficient of the cutoff wall is obtained. .

4. The method according to claim 1, characterized in that: In step S3, the total seepage flow of the dam As shown in the formula below: ； In the formula, For the seepage flow data of the weir, This represents the comprehensive seepage coefficient for the sub-region. , These represent the water levels in front of and behind the cutoff wall at each cross-section.

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