A method for quantitatively controlling water seepage from slopes of seasonal open channels in cold regions

Abstract

The present invention provides a method for quantitatively controlling water seepage on the slopes of seasonal open water channels in cold regions. In an open water channel where longitudinal and transverse drainage pipes have been set, a number of water collection wells are arranged along the channel direction. The spacing between the water collection wells is determined according to the principle of balance between the collected seepage flow and the pumping volume. The water collection wells are connected to the transverse drainage pipes, and submersible pumps are placed to continuously pump out the leaking water in the transverse drainage pipes of the channel. At the same time, a pumping flow meter is installed; a post-membrane water level observation pipe is buried between the water collection wells to obtain post-membrane water level data. Based on the acquired data, a fitting model of the post-membrane water level, the channel operating water level, and the pumping volume of the water collection well is constructed. The optimal daytime pumping volume of the water collection wells in different periods is determined by combining the post-membrane water level threshold that stabilizes the slope, the operating period water level, and the fitting model. Pumping operations are performed based on the determined optimal daytime pumping volume. From the perspective of disaster reduction, the present invention provides a precise and quantitative solution for improving the operational safety of channel projects.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy projects and long-distance water diversion projects, and particularly relates to a method for quantitatively controlling water seepage from slopes of seasonal open water delivery channels in cold regions. Background Art

[0002] Long-distance water diversion projects, primarily constructed through open channels, often experience seepage in their embankments, leading to water safety issues such as cracks in the lining, heaving of the channel bottom, and embankment collapse. Furthermore, open channels located in northern China, constrained by harsh climates, often operate only from spring to autumn each year, with no water remaining in the channels during the winter. Consequently, in addition to seepage, these channels also experience significant water level rises and falls in their embankments. From an engineering perspective, this process further weakens the stability of the channel slopes.

[0003] The "behind-the-membrane" zone is a transitional area between the impermeable membrane and sub-membrane mortar beneath the channel lining and the channel foundation soil. It is often formed during construction and through long-term deformation. While not very thick, typically only a few centimeters, this area is particularly sensitive to water seepage from the channel slope. Without effective drainage measures, leaked water will initially accumulate in this area. In engineering, the "behind-the-membrane water level" is often used to characterize the head of leaking water. When channel slope leakage is severe, the behind-the-membrane water level will be roughly equal to the water level within the channel. As the water level within the channel drops, the retained water within the channel foundation will initially flow into this area and then seep back into the channel, causing "internal water seepage" and compromising the stability of the channel slope. Recording the behind-the-membrane water level during operation provides a more intuitive understanding of the leakage situation within this channel section.

[0004] Installing longitudinal and transverse drainage pipes in the channel can effectively collect and drain water leaking from the channel embankment. The usual practice is to install a longitudinal drainage pipe along the direction of water flow in the channel, using the channel's natural longitudinal slope to collect the seepage water that has infiltrated the anti-seepage membrane in a short period of time. Then, at regular intervals, a transverse drainage pipe is installed to connect to the longitudinal drainage pipe to drain the seepage water to the outside of the channel embankment. However, this approach has certain drawbacks. First, it can cause siltation. When using the natural longitudinal slope for drainage, the gravity flow rate in the longitudinal drainage pipe is relatively low. The soil properties of the channel subgrade vary along the hundreds of kilometers of channels. Drainage pipes in poor geological sections are prone to crystallization and blockage, resulting in reduced drainage efficiency. Second, there is the problem of water waste. Typically, seepage water from fill channels is discharged directly to the outside of the channel embankment after being discharged through gravity drainage, and the seepage water is not utilized. Excavated channels, on the other hand, require the installation of longer transverse drainage pipes for external drainage, which in turn increases losses along the entire channel. Third, the degree to which it improves channel operation safety is limited. For seasonal water transfer channels, the rate of water level drop in the channel during water recedes is much faster than the rate of water leakage from the channel embankment, resulting in the aforementioned "internal water seepage" situation. Once the pumping is not timely or the amount is excessive, the uplift pressure generated at this time will damage the channel embankment and channel bottom, and the "unloading effect" during water recedes will be fatal to the stability of the slope.

[0005] The deep integration of next-generation information technology with the current economy and society has posed new requirements for the operation and management of water conservancy projects. However, canal engineering safety issues, primarily caused by leakage, involve complex soil-water-heat processes, making disaster warnings difficult to detect. Various monitoring methods have very limited coverage in long-distance linear water diversion projects, often limited to cross-section monitoring, making comprehensive awareness impossible across canals stretching hundreds of kilometers. Furthermore, penetrating sensing devices such as drones, ground-penetrating radar, and electromagnetic methods are far from meeting the precision requirements of smart water conservancy for disaster identification and early warning.

[0006] With the deepening of the operation of a number of long-distance water diversion projects in China, various engineering problems caused by water leakage have become increasingly prominent. Therefore, it is urgent to find a solution that can scientifically improve the safety of channel projects and meet the needs of water conservancy information construction, so as to achieve the goal of significantly improving the stability of channel embankments, improving operational safety, and reducing maintenance costs with a small amount of funding, and provide invention support for the intelligent operation and maintenance of projects. Summary of the Invention

[0007] The present invention aims to provide a method for quantitatively controlling water seepage from slopes of seasonal open water delivery channels in cold regions.

[0008] Based on this, the present invention focuses on the key factors and indicators that reflect the stability of the slopes of seasonal water supply open channels. By setting up certain engineering measures, the long-distance linear channels are artificially divided into several sections, and the leaking water is effectively collected in sections. Furthermore, the quantifiable and easy-to-monitor properties of the channel slopes in these sections in their stability are monitored. By analyzing the data generated by long-term monitoring and combining it with numerical analysis methods, measures are finally given that can maintain the stability of the channel slopes and significantly improve the management efficiency along the line.

[0009] In order to achieve the above technical objectives, the present invention adopts the following scheme:

[0010] A method for quantitatively controlling water seepage from slopes of seasonal open channels in cold regions, comprising:

[0011] Several water collection wells are set up along the outer side of the canal embankment of the water supply open channel with longitudinal and transverse drainage pipes. The bottom of each water collection well is connected to the transverse drainage pipe. A water pump is set at the connection between the water collection well and the transverse drainage pipe. The water pump is equipped with a pumping volume recording instrument to record the pumping volume of the water collection well.

[0012] A post-membrane water level observation pipe is set between every two water collection wells to record the post-membrane water level;

[0013] Run the open channel water diversion project to obtain data on the pumping capacity of the water collection well, the water level after the membrane, and the channel operating water level. Based on the obtained data, a fitting model for the water level after the membrane, the channel operating water level, and the pumping capacity of the water collection well is constructed;

[0014] The water outage stage of seasonal water diversion open channels in cold regions and spring thaw landslide conditions are identified as the most unfavorable conditions. The finite element strength reduction method is used to inversely calculate the water level threshold behind the membrane under the critical state of the slope under the most unfavorable conditions. The water level threshold behind the membrane and the water level during the operation period are brought into the fitting model to determine the optimal daytime pumping rate of the water collection wells in different periods. Pumping operations are carried out based on the determined optimal daytime pumping rate.

[0015] As a preferred embodiment, the spacing of the water collection wells is determined according to the principle of balance between the seepage flow rate and the pumping and drainage volume, and the calculation formula is as follows:

[0016]

[0017] Among them, L is the spacing between the water collection wells, D is the diameter of the longitudinal drainage pipe, i is the gradient of the longitudinal drainage pipe, k is the permeability coefficient, and h is the burial depth of the longitudinal drainage pipe.

[0018] As a preferred embodiment, the depth of the water collection well is greater than or equal to the buried depth of the longitudinal drainage pipe at the bottom of the channel.

[0019] As a preferred embodiment, the water collection well is set 50m outside the channel embankment, and the diameter of the water collection well is ≥2m.

[0020] As a preferred embodiment, the water pump is a submersible pump with a continuous pumping and drainage function, which is used to automatically control the pumping and drainage operations and observe the daily drainage data in real time.

[0021] As a preferred embodiment, the post-membrane water level observation pipe is parallel to the channel embankment slope and is in close contact with the mortar cushion layer under the membrane.

[0022] As a preferred embodiment, the pumping capacity of the water collection well is used as the dependent variable, denoted as (x, y), and the operating water level in the channel and the water level after the membrane are used as independent variables, denoted as x and y respectively, to establish a fitting model of the following form:

[0023] f(x, y) = cf(x) + df(y)

[0024] Among them, c and d are fitting coefficients.

[0025] As a preferred embodiment, R 2 ≥0.9 was used as the fitting index, and the model was fitted using the measured data.

[0026] As a preferred embodiment, a drop-in water level gauge is placed in the post-membrane water level observation pipe to observe the water level in the pipe.

[0027] As a preferred embodiment, the method further includes performing pumping operations by controlling the water pump start-up power through remote scheduling according to the optimal daytime pumping and drainage volume determined at different times during the operation period.

[0028] In order to scientifically improve the operational safety of channel projects and comply with the needs of digital water conservancy operation and maintenance, the present invention is based on the idea of ​​"dynamic balance" of seepage water control and, from the perspective of disaster reduction, first quantitatively determines the spacing between the layout of the pumping and drainage wells. Secondly, the long-distance channels are divided into sections, and the post-membrane water level value, operating water level and pumping and drainage well flow data of each section during the channel operation are quantitatively captured. On this basis, mathematical analysis methods are used to establish a quantitative mathematical relationship between the observed data. Finally, according to the most unfavorable working conditions during the operation period of the long-distance channel, the corresponding post-membrane water level threshold is proposed, and the flow control index of the pumping and drainage well operation is obtained by using the established mathematical relationship. This technology can quantify the layout and operation management of the vertical and horizontal drainage systems of the channel, improve the stability of channel operation, and provide a more sophisticated scientific solution for the operation and management of long-distance seasonal water transfer channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the layout of the longitudinal and transverse drainage pipes and collection wells in the channel, where A is the cross-sectional view and B is the top view.

[0030] Figure 2 This is the water collection well pump setting diagram.

[0031] Figure 3 This is a schematic diagram of the water level observation tube behind the membrane. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] Based on the concept of "dynamic balance" for seepage control, a comprehensive approach to controlling seepage in seasonal open channel slopes includes the following steps:

[0035] 1. For a specific open channel project where longitudinal and transverse drainage pipes have been installed, a number of water collection wells shall be set up outside the channel embankment. The depth of the water collection wells shall not be lower than the buried depth of the longitudinal drainage pipes at the bottom of the channel and the diameter shall not be less than 2m. The bottom of the water collection wells shall be connected to the transverse drainage pipes.

[0036] The spacing of the water collection wells is determined based on the following formula:

[0037]

[0038] Among them, L is the spacing of the water collection wells, D is the diameter of the longitudinal drainage pipe, i is the gradient of the longitudinal drainage pipe, k is the permeability coefficient, h is the burial depth of the longitudinal drainage pipe, H is the channel water depth, and n is the pipe roughness.

[0039] 2. Set up a water pump at the connection between the water collection well and the horizontal pipe, and install a pumping and discharge volume recorder. The pumping and discharge volume can be collected remotely or read manually according to the specific conditions of the project.

[0040] 3. Divide the channel into sections with two water collection wells. Install a water level observation pipe at the canal crest in each section. Place the pipe parallel to the canal slope, outside the mortar beneath the embankment membrane. The pipe can be made of a filter tube and is called a "behind-membrane water level observation pipe." A submersible water level gauge can be placed inside the pipe, or a manual line can be set to observe the water level.

[0041] 4. During the operation period of the project, the water pump in the water collection well shall be set to working state, and the collection of leaked water in the water collection well shall be manually observed. At the same time, the water level observation data behind the membrane shall be recorded. The observation interval during the operation period shall not exceed 3 days.

[0042] 5. Record the pumping volume of the water collection well, the water level behind the membrane, and the channel operating water level data provided by the management department for 3 to 5 operation periods. The obtained data will be used as a sample for channel leakage data analysis.

[0043] 6. Based on the analysis samples, a fitting model of "water level after membrane - channel operating water level - water collection well pumping capacity" is established. Function fitting key indicator R 2 Should not be lower than 0.9. The fitting model is as follows:

[0044] f(x, y) = cf(x) + df(y) (2)

[0045] Among them: f(x, y) is the pumping capacity of the water collection well, f(x) is the function of the operating water level in the channel, and f(y) is the function of the water level after the membrane. It can be different mathematical transformation forms of the operating water level in the channel / water level after the membrane, such as exponential form, power form, etc., which are determined according to the fitting situation. c and d are fitting coefficients.

[0046] Where: h 膜 is the water level behind the membrane, h 渠 is the channel operating water level, Q 排 is the pumping capacity of the water collection well, c is the anti-seepage coefficient, and d is the pumping efficiency coefficient.

[0047] 7. Through a comprehensive analysis of the design and operation data of the specific project, including the lining structure type, channel foundation soil properties, and the type and location of damage during operation, a numerical calculation model for channel slope stability is established. The two most unfavorable working conditions, uplift pressure damage and slope instability, which occur during the water level drop during the water outage period, are analyzed in detail. The post-membrane water level threshold h that can ensure channel lining safety and slope stability is obtained. 膜’ .

[0048] 8. The determined water level threshold h behind the membrane 膜’ , water level during operation h 渠 Substitute the fitting model and give the recommended optimal drainage volume Q 排opt .

[0049] 9. Get the optimal displacement Q 排opt Afterwards, the management department can use this data to coordinate the pumping and drainage operation settings of the water collection wells during the channel operation period, as well as the arrangement of inspection personnel, which will greatly improve work efficiency and reduce unnecessary investment.

[0050] Example 2

[0051] Now, relying on the main canal of a long-distance water supply project in Northwest China, the specific examples of the present invention are further elaborated.

[0052] The project is located in the northern Xinjiang region. The length of the project is more than 100km. The cross section is a traditional trapezoid. The lining is manually laid with prefabricated hexagonal blocks. "One cloth and one membrane" anti-seepage is laid under the lining. The mortar cushion layer under the membrane is 30cm thick. The channel is put into operation in late April and shut down in early October every year. Longitudinal and transverse drainage pipes are set up along the channel. According to the method described in the present invention, a batch of water collection wells are set up within 50m outside the horseway on the top of the channel. The position, diameter and connection method of the water collection wells with the transverse drainage pipes are as follows: Figure 1 It is applicable to both cut channels and fill channels.

[0053] Determine the spacing between water collection wells. It is known that the permeability coefficient of this section of soil is 1×10 -6 m / s, the diameter of the longitudinal drainage pipe is 120 cm, the gradient of the longitudinal drainage pipe is 1 / 5000, the burial depth is 2.5 m, the channel water depth is 5.5 m, and the pipe roughness is 0.01. According to formula (1), the maximum spacing is 556.84 m. For the convenience of construction, the integer 500 m is taken as the spacing of the water collection wells.

[0054] A mechanical water pump is installed at the connection between the water collection well and the horizontal pipe, such as Figure 2 The water pump should have the function of recording the pumping and discharge volume.

[0055] A water level observation pipe behind the membrane is installed on the water collection well side of the channel section between two adjacent water collection wells. The installation method is as follows: Figure 3 The reading method can be arranged flexibly. If conditions permit, a immersion water level gauge can be set up for remote data collection, or manual measurement and reading can be carried out during manual canal inspections, and records should be kept.

[0056] Before water is released into the channel, the effectiveness of relevant facilities, equipment or methods such as water pumps, water level observation after the membrane, and channel operation water level observation should be checked.

[0057] After the channel is opened to water, the outflow of each well is manually observed, and continuous pumping and drainage operations are started (uninterrupted). If the water level in the collection well is higher than the wellhead, that is, there is excessive leakage, it is necessary to consider discharging the water level of the collection well.

[0058] During operation, data should be recorded for the channel's operating water level, the water level behind the membrane, and the pumping rate of the water collection well. The operating water level and the water level behind the membrane should be measured at least every three days. Towards the end of the operation period, especially when the water level in the channel begins to drop, the frequency of data observation should be increased.

[0059] Organize the data from one operation period and repeat the above data observation steps until 3-5 operation periods are completed. Organize and compile the above collected data to form a water level observation database related to the water supply period operation.

[0060] The fitting function established in this embodiment is as follows:

[0061]

[0062] Function fitting key indicator R 2 >0.9. In general, c is 0 when the lining and impermeable membrane are intact, and d is 0 when the water collection well is completely blocked and ineffective. Based on the analysis results of the engineering example, the recommended values ​​for c are: 0.1 for partial damage to the lining and impermeable membrane, and 0.05 for severe damage; the recommended values ​​for d are: 0.017 for unblocked pumping and drainage wells, and 0.008 for partial blockage.

[0063] Establish a finite element model of channel slope stability, recommend the use of strength reduction method, and use the overall coupling or sequential coupling method to consider water level changes. Combined with the analysis of previous operation data of this section, the minimum water level behind the membrane that will cause uplift pressure to break during the period of sudden drop in the channel water level is finally determined. 膜 The water level threshold behind the membrane to maintain slope stability during the spring thaw is 2.0m.

[0064] Taking the example section of this project as an example, during the water outage period, the water level dropped from 5.5m to 0. Before the water level drop, the water level behind the membrane needs to be controlled below 1.5m. Q is calculated by formula 2. 排 =3.45m 3 / s. During the spring thaw period, the channel water level rises from 0 to 5.5m. During this process, the channel slope infiltrates again, and the intensity decreases. It is necessary to ensure that the water level behind the membrane is lower than 2.0m. Q is calculated by formula 2 排 =1.45m 3 / s.

Claims

1. A method for quantitatively controlling water seepage from slopes of seasonal open channels in cold regions, characterized in that: include: Several water collection wells are set up along the outer side of the canal embankment of the water supply open channel with longitudinal and transverse drainage pipes. The bottom of each water collection well is connected to the transverse drainage pipe. A water pump is set at the connection between the water collection well and the transverse drainage pipe. The water pump is equipped with a pumping volume recording instrument to record the pumping volume of the water collection well; A post-membrane water level observation pipe is set between every two water collection wells to record the post-membrane water level; Run the open channel water diversion project to obtain data on the pumping capacity of the water collection well, the water level after the membrane, and the channel operating water level. Based on the obtained data, a fitting model for the water level after the membrane, the channel operating water level, and the pumping capacity of the water collection well is constructed; The water outage stage of seasonal water transfer open channels in cold regions and the spring thaw landslide condition are identified as the most unfavorable conditions. The finite element strength reduction method is used to inversely calculate the water level threshold behind the membrane under the critical state of the slope under the most unfavorable conditions. The water level threshold behind the membrane and the water level during the operation period are substituted into the fitting model to determine the optimal daytime pumping rate of the collection wells in different periods, and pumping operations are carried out based on the determined optimal daytime pumping rate.

2. The method according to claim 1, characterized in that The spacing of the water collection wells is determined based on the principle of balance between the seepage flow rate and the pumping and drainage volume, and the calculation formula is as follows: Among them, L is the spacing of the water collection wells, D is the diameter of the longitudinal drainage pipe, i is the gradient of the longitudinal drainage pipe, k is the permeability coefficient, h is the burial depth of the longitudinal drainage pipe, H is the channel water depth, and n is the pipe roughness.

3. The method according to claim 1, characterized in that The depth of the water collection well is ≥ the buried depth of the longitudinal drainage pipe at the bottom of the channel.

4. The method according to claim 1, wherein The water collection well is set 50m outside the channel embankment, and the diameter of the water collection well is ≥2m.

5. The method according to claim 1, wherein The water pump is a submersible pump with continuous pumping and drainage functions, which is used to automatically control the pumping and drainage operations and observe the daily water discharge data in real time.

6. The method according to claim 1, characterized in that The water level observation pipe behind the membrane is parallel to the slope of the channel embankment and is close to the mortar cushion layer under the membrane.

7. The method according to claim 1, characterized in that With the pumping capacity of the water collection well as the dependent variable, and the operating water level in the channel and the water level after the membrane as the independent variables, the following fitting model is established: f(x, y) = cf(x) + df(y) Among them, f(x, y) is the pumping capacity of the water collection well, f(x) is the function of the operating water level in the channel, f(y) is the function of the water level after the membrane, and c and d are fitting coefficients.

8. The method according to claim 1 or 7, characterized in that R 2 ≥0.9 was used as the fitting index, and the model was fitted using the measured data.

9. The method according to claim 1, characterized in that A drop-in water level gauge is placed in the water level observation pipe behind the membrane to observe the water level in the pipe.

10. The method according to claim 1, characterized in that It also includes the optimal daytime pumping volume determined at different times during the operation period, and the control of the water pump start-up power through remote scheduling to carry out pumping operations.

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