Underground rainwater pipe network generalization method

Abstract

The invention relates to the technical field of urban inland inundation model construction and application, and discloses an underground rainwater pipe network generalization method which comprises the following steps: S10, acquiring underground drainage pipe network data which comprises a complete topological structure of an underground drainage pipe network, and upstream and downstream pipe bottom elevations, pipe diameters and pipe lengths of each pipeline; s20, according to the data of the underground drainage network in the S10, firstly calculating the inclination angle of the pipeline, then giving water level classification from the lowest point to the highest point of the underground drainage network by combining the inclination angle of the pipeline and the water flow state in the pipeline, calculating the water volume in each pipeline under each classification water level, and counting the water level-volume relationship of the underground drainage network, according to the underground rainwater pipe network generalization method provided by the invention, the calculation efficiency can be greatly improved when urban inland inundation is simulated.

Description

Technical Field

[0001] The present invention relates to the technical field of urban waterlogging model construction and application, and in particular to a method for generalizing an underground rainwater pipe network. Background Art

[0002] The construction of digital twins for the "four pre-emptive" aspects of water conservancy in the new era places higher demands on the timeliness of specialized water conservancy models. While traditional hydrodynamic models offer high simulation accuracy, they are computationally intensive and time-consuming to run in large-scale areas or at fine resolutions. Because urban flooding events are often sudden, with only a short time between rainfall and surface waterlogging, traditional hydrodynamic models, constrained by computational efficiency, often struggle to provide rapid, real-time surface waterlogging information, hindering real-time decision-making for flood prevention, disaster reduction, and population evacuation.

[0003] For some research areas lacking measured pipe network data, making physical mechanism modeling impossible, experts and scholars have proposed an "equivalent drainage" approach to generalize the drainage capacity of pipe networks. These methods include the "rainfall reduction method," the "equivalent drainage method," and the "pipeline network generalization method." This generalization method, to some extent, omits the hydrodynamics of the underground pipe network. While the simulation results are inferior to those of mechanistic models, it significantly improves the efficiency of urban waterlogging simulations.

[0004] The equivalent drainage method is specifically divided into "global equivalent drainage method", "road equivalent drainage method" and "rainwater well equivalent drainage method". The global equivalent drainage method quantifies the drainage capacity of the pipe network, and according to the principle of water conservation, generalizes the drainage effect of the pipe network into a fixed infiltration parameter, which is accumulated on the actual infiltration rate of all areas; the road equivalent drainage method takes into account the actual layout range of the pipe network, such as roads and construction areas, and quantifies the drainage capacity of the pipe network within the actual layout range, and only modifies the infiltration parameters of the road; the rainwater well equivalent drainage method takes into account the impact of the actual surface morphology on the rainwater generation and convergence process, and understands the actual layout range and size of the rainwater well through actual surveys, remote sensing satellites and other methods. When rainwater flows into the rainwater well, the actual layout range and size of the rainwater well are calculated.

[0005] When the well is located in the grid, the amount of rainwater flowing into the pipe network is calculated using the weir flow formula. According to the principle of water conservation, this amount of water is subtracted on the surface to accurately generalize the drainage capacity of the pipe network.

[0006] The existing equivalent drainage generalization method only generalizes the drainage capacity of the underground rainwater pipe network into a strength parameter, without considering the actual bearing capacity of the underground rainwater pipe network. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a generalization method for underground rainwater pipe networks, which can greatly improve the calculation efficiency when simulating urban waterlogging.

[0008] The present invention provides a method for generalizing an underground rainwater pipe network, comprising: S10: Acquire underground drainage network data, which includes the complete topological structure of the underground drainage network, the upstream and downstream bottom elevations of each pipe, the pipe diameter, and the pipe length; S20: Based on the underground drainage network data in S10, first calculate the inclination of the pipeline, and then combine the pipeline inclination and the water flow state in the pipeline to give a water level classification from the lowest point to the highest point of the underground drainage network. Calculate the water volume in each pipeline at each graded water level, and statistically calculate the water level-volume relationship of the underground drainage network. Construct a pipeline network generalization model based on the water level-volume relationship, generalize the underground rainwater pipeline network into an equivalent water tank model with a water level-volume relationship curve, and combine the topological structure of the underground rainwater pipeline network to generalize the actual carrying capacity of the underground rainwater pipeline network.

[0009] Optionally, the underground drainage network data obtained in S10 includes: Step S101: Eliminate sewage pipes and corresponding nodes, and only retain rainwater pipes and mixed rainwater and sewage pipes. Rainwater pipes and mixed rainwater and sewage pipes are collectively referred to as pipes. Step S102: Delete duplicate nodes, pipes and drains; Step S103: Delete isolated nodes that are not connected to both ends of the pipeline to ensure that each node is connected to at least one pipeline.

[0010] Optionally, obtaining underground drainage network data in S10 further includes: Step S104: Correcting the top elevation of the pipeline node to ensure that it is not higher than the ground surface elevation; Step S105: Correct the bottom elevation of the pipeline node to ensure that it is lower than the buried depth of any pipeline connected to the node; Step S106: Modify the topology of the pipe network by adding new connecting pipes or drainage outlets to ensure that each isolated pipe node and pipe is connected to at least one drainage outlet downstream.

[0011] Optionally, correcting the top elevation of the pipeline node in step S104 includes: when the top elevation of the pipeline node is higher than the ground elevation, taking the ground elevation as the top elevation of the pipeline node.

[0012] Optionally, correcting the bottom elevation of the pipeline node in step S105 includes: when the bottom elevation of the pipeline node is higher than the buried depth of the pipeline connected to the node, taking the buried depth of the pipeline connected to the node as the bottom elevation of the pipeline node.

[0013] Optionally, the topological structure of the pipe network is corrected in step S106, including: if the isolated pipe is adjacent to a river, adding the node with the lowest bottom hole elevation in the isolated pipe as a new discharge outlet; if the isolated pipe is far from the river, connecting the part of the isolated pipe to the main pipe by adding a new pipe, and thus connecting to the downstream discharge outlet.

[0014] Optionally, the water flow state in the pipeline includes four pressure-free water flow states: The water level is higher than the downstream pipe bottom elevation, but lower than the upstream pipe bottom elevation; The water level is higher than the upstream pipe bottom elevation, but lower than the downstream pipe top elevation; The water level is higher than the downstream pipe top elevation, but lower than the upstream pipe bottom elevation; The water level is higher than the upstream pipe bottom elevation and higher than the downstream pipe top elevation.

[0015] Optionally, calculating the water volume in each pipeline at each graded water level in S20 includes: According to the four no-pressure water flow states and the corresponding pipe inclination angles, the horizontal projection lengths of the water body in the pipe corresponding to the four no-pressure water flow states are obtained; Divide the water body in the pipe into n equal parts along the length direction to obtain the length of the water body of a single pipe unit; Obtain the water depth of the cross section of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross section of the pipe unit water body corresponding to different pipe shapes; The cross-sectional water flow area of ​​the pipe unit water body is obtained according to the horizontal projection length of the water body, the cross-sectional water depth of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross-sectional area of ​​the pipe unit water body; The volume of each pipe unit water body in each pipe is obtained based on the cross-sectional water flow area of ​​the pipe unit water body. The volumes of all pipe unit water bodies in a single pipe are summed to obtain the total volume of water in a single pipe, that is, the total water volume. Then, the volume of water in all pipes is summed at each graded water level.

[0016] Optionally, the pipe shape includes a circular cross-section pipe and a rectangular cross-section pipe.

[0017] Optionally, S10 also includes: processing the underground drainage network data into an inp file.

[0018] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology: An embodiment of the present invention provides a method for generalizing an underground rainwater network. Based on the physical properties of the underground drainage network, namely, the underground drainage network data, the method combines the pipe inclination angle and the water flow state within the pipe. The underground drainage network is given a water level classification from the lowest point to the highest point, and the water volume within each pipe corresponding to each water level classification is calculated. The water level-volume relationship curve of the drainage network is statistically calculated, and the underground rainwater network is generalized into an equivalent water tank model with a water level-volume relationship curve. Combined with the topological structure of the underground rainwater network, the actual carrying capacity of the underground rainwater network is generalized, providing a new approach for urban waterlogging simulation. Because the method for generalizing an underground rainwater network provided by the embodiment of the present invention generalizes the underground rainwater network into a water tank with a water level-volume relationship, it ignores the hydraulic solution of the pipe and instead obtains the water level within the water tank under a certain water volume by querying the water level-volume relationship curve. Therefore, it can significantly improve computational efficiency when simulating urban waterlogging. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the storage and drainage state of an inclined pipeline provided by an embodiment of the present invention, wherein: Figure 1 a is a schematic diagram of the inclined pipe storage and drainage state in state 1. Figure 1 b is a schematic diagram of the inclined pipe storage and drainage state in state 2. Figure 1 c is a schematic diagram of the inclined pipe storage and drainage state in state three. Figure 1 d is a schematic diagram of the storage and drainage state of the inclined pipe in state four; Figure 2 A schematic diagram of a cross-sectional water depth less than a radius provided in an embodiment of the present invention; Figure 3 A schematic diagram of a cross-sectional water depth greater than a radius provided in an embodiment of the present invention; Figure 4 A schematic diagram of a first pipeline water state provided by an embodiment of the present invention; Figure 5 A schematic diagram of a second pipeline water state provided by an embodiment of the present invention; Figure 6 A schematic diagram of a third pipeline water state provided by an embodiment of the present invention; Figure 7 A schematic diagram of a fourth pipeline water state provided by an embodiment of the present invention; Figure 8 A schematic diagram of the pipe network storage and drainage status provided by an embodiment of the present invention; Figure 9 A schematic diagram of a water level-volume relationship curve provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] A specific embodiment of the present invention is described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the technical solutions of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] The present invention is described below by means of several specific embodiments. To keep the following description of the embodiments of the present invention clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numeral in each drawing.

[0023] An embodiment of the present invention provides a method for generalizing an underground rainwater pipe network, comprising: S10: Acquire underground drainage network data, which includes the complete topological structure of the underground drainage network, the upstream and downstream bottom elevations of each pipe, the pipe diameter, and the pipe length; S20: Based on the underground drainage network data in S10, first calculate the inclination of the pipeline, and then combine the pipeline inclination and the water flow state in the pipeline to give a water level classification from the lowest point to the highest point of the underground drainage network. Calculate the water volume in each pipeline at each graded water level, and statistically calculate the water level-volume relationship of the underground drainage network. Construct a pipeline network generalization model based on the water level-volume relationship, generalize the underground rainwater pipeline network into an equivalent water tank model with a water level-volume relationship curve, and combine the topological structure of the underground rainwater pipeline network to generalize the actual carrying capacity of the underground rainwater pipeline network.

[0024] An embodiment of the present invention provides a method for generalizing an underground rainwater network. Based on the physical properties of the underground drainage network, namely, the underground drainage network data, the method combines the pipe inclination angle and the water flow state within the pipe. The underground drainage network is given a water level classification from the lowest point to the highest point, and the water volume within each pipe corresponding to each water level classification is calculated. The water level-volume relationship curve of the drainage network is statistically calculated, and the underground rainwater network is generalized into an equivalent water tank model with a water level-volume relationship curve. Combined with the topological structure of the underground rainwater network, the actual carrying capacity of the underground rainwater network is generalized, providing a new approach for urban waterlogging simulation. Because the method for generalizing an underground rainwater network provided by the embodiment of the present invention generalizes the underground rainwater network into a water tank with a water level-volume relationship, it ignores the hydraulic solution of the pipe and instead obtains the water level within the water tank under a certain water volume by querying the water level-volume relationship curve. Therefore, it can significantly improve computational efficiency when simulating urban waterlogging.

[0025] Optionally, the underground drainage network data obtained in S10 includes: Step S101: Remove sewage pipes and corresponding nodes, retaining only rainwater pipes and mixed rainwater and sewage pipes. Rainwater pipes and mixed rainwater and sewage pipes are collectively referred to as pipes. Since most urban drainage systems currently separate rainwater and sewage, rainwater pipes (non-pressure gravity drainage) and sewage pipes (pressure pump drainage) are two drainage systems. This embodiment of the present invention is targeted at gravity drainage rainwater pipe networks and is used to study urban waterlogging under heavy rainfall. Due to issues such as the age of construction, some mixed rainwater and sewage pipes may still exist. Therefore, only rainwater pipes and mixed rainwater and sewage pipes are retained. Step S102: Delete duplicate nodes, pipes and drains; Step S103: Delete isolated nodes that are not connected to both ends of the pipeline to ensure that each node is connected to at least one pipeline.

[0026] Optionally, obtaining underground drainage network data in S10 further includes: Step S104: Correcting the top elevation of the pipeline node to ensure that it is not higher than the ground surface elevation; Step S105: Correct the bottom elevation of the pipeline node to ensure that it is lower than the buried depth of any pipeline connected to the node; Step S106: Modify the topology of the pipe network by adding new connecting pipes or drainage outlets to ensure that each isolated pipe node and pipe is connected to at least one drainage outlet downstream.

[0027] The above methods ensure that the topology structure is complete and reasonable.

[0028] Optionally, correcting the top elevation of the pipeline node in step S104 includes: when the top elevation of the pipeline node is higher than the ground elevation, taking the ground elevation as the top elevation of the pipeline node. Taking the top elevation of the rainwater pipeline node as an example, which must not be higher than the ground elevation, just like the rainwater grates that can be seen everywhere on the road, they are basically flush with the ground. If the rainwater outlet is higher than the ground, the rainwater cannot be effectively discharged into the rainwater pipe network. Therefore, the correct topology or design will require that the top elevation of the rainwater well node be less than or equal to the ground elevation.

[0029] like Figure 8 As shown, in step S105, correcting the bottom elevation of a pipeline node includes: when the bottom elevation of a pipeline node is higher than the buried depth of the pipeline connected to the node, the buried depth of the pipeline connected to the node is used as the bottom elevation of the pipeline node. For example, the bottom elevation of a rainwater well node must be lower than the bottom elevation (i.e., the buried depth) of the connected pipeline; otherwise, only the upper half of the pipeline will be connected to the rainwater well.

[0030] Optionally, the topological structure of the pipe network corrected in step S106 includes: if the isolated pipe is adjacent to a river, the node with the lowest bottom elevation in the isolated pipe is added as a new outlet; if the isolated pipe is far from the river, the isolated pipe is connected to the main pipe by adding a new pipe, thereby connecting it to the downstream outlet. The rainwater pipe network is used to collect rainwater and discharge it into the river. If there is an isolated rainwater pipe network that is not connected to any outlet, the rainwater therein cannot be drained away, and the rainwater will accumulate more and more, causing it to emerge from the pipe network and form surface waterlogging. Therefore, it is necessary to ensure that each node and pipe is connected to at least one outlet downstream. This is the correct and reasonable pipe network topology.

[0031] refer to Figure 1 , Figure 1 This is a schematic diagram of the storage and drainage state of an inclined pipeline provided by an embodiment of the present invention, wherein: Figure 1 a is a schematic diagram of the inclined pipe storage and drainage state in state 1. Figure 1 b is a schematic diagram of the inclined pipe storage and drainage state in state 2. Figure 1 c is a schematic diagram of the inclined pipe storage and drainage state in state three. Figure 1 d is a schematic diagram of the inclined pipe storage and drainage state in state four, as shown in Figure 1 As shown in the figure, the water flow state in the pipeline includes four pressure-free water flow states: State 1: The water level is higher than the downstream pipe bottom elevation, but lower than the upstream pipe bottom elevation; State 2: The water level is higher than the upstream pipe bottom elevation, but lower than the downstream pipe top elevation; State 3: The water level is higher than the downstream pipe top elevation, but lower than the upstream pipe bottom elevation; State 4: The water level is higher than the upstream pipe bottom elevation and higher than the downstream pipe top elevation.

[0032] The calculation of the water volume in each pipe at each graded water level in S20 includes: refer to Figures 2 to 7 , Figure 2 A schematic diagram of a cross-sectional water depth less than a radius provided in an embodiment of the present invention, Figure 3 A schematic diagram of a cross-sectional water depth greater than a radius provided by an embodiment of the present invention, Figure 4 A schematic diagram of the first pipeline water state provided by an embodiment of the present invention, Figure 5 A second schematic diagram of a pipeline water state provided by an embodiment of the present invention is shown. Figure 6 A schematic diagram of a third pipeline water state provided by an embodiment of the present invention, Figure 7 The fourth pipeline water state diagram provided by the embodiment of the present invention is to obtain the horizontal projection length of the water body in the pipeline corresponding to the four no-pressure water flow states according to the four no-pressure water flow states and the corresponding pipeline inclination angles, specifically: calculate the inclination angle of each pipeline : , in, is the pipeline inclination; is the bottom elevation of the upstream (up) pipeline; is the bottom elevation of the downstream pipeline (down), m; is the horizontal projection length of the pipeline, m; Determine the water level of a given grade Below, the water status in each pipeline is: State 1: If Figure 4 As shown, and .

[0033] State 2: If Figure 5 As shown, .

[0034] State 3: If Figure 6 As shown, .

[0035] State 4: If Figure 7 As shown, and .

[0036] in, is the graded water level (surface), m; is the radius of the pipe, m.

[0037] Calculate the horizontal projection length of the water body in each pipeline according to the situation : State 1: Use the upstream pipe bottom elevation minus the downstream pipe bottom elevation, and then divide it by the sine value of the pipe inclination to obtain the horizontal projection length of the water body in the pipe in state 1, that is, ; State 2: At this time, the water in the pipe covers the entire pipe horizontally, that is, ; State 3: At this time , where the horizontal length of the pressurized water body is ; State 4: At this time, the water in the pipe covers the entire pipe horizontally, that is, , where the horizontal length of the pressurized water body is ; in, is the horizontal projection length of the water body in the pipe, is the horizontal projection length of the pressurized water body, m.

[0038] Divide the water in the pipe into n equal parts along the length direction to obtain the length of the water in a single pipe unit. The more parts the pipe is divided into, the closer the statistical result is to the true value. The length of each small part is In order to use gravity to achieve natural drainage, the pipe is usually set with a certain inclination, but this inclination is often small. The actual length of the pipe is approximately equal to the horizontal projection length. The smaller the inclination, the closer the two are. Secondly, the statistical method of the present invention uses the differential summation method to count the water volume. The volume of each small portion of water is approximately the cross-sectional area multiplied by the height. The cross-sectional area here is perpendicular to the horizontal plane, so is the horizontal length; Obtain the cross-sectional water depth of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross-sectional water body of the pipe unit water body corresponding to different pipe shapes, and calculate the Cross-sectional depth of a water body : Status 1: , State 2: , State three: , State 4: ; like Figure 2 、 Figure 3 As shown, the calculation of the circular cross-section pipeline The circumferential angle corresponding to the free water surface of the cross section of the water body (half of the central angle) : , Calculate the Cross-sectional area of ​​water body : For circular cross-section pipes: , For rectangular cross-section pipes: , in, is the width of the rectangular pipe, m.

[0039] According to the horizontal projection length of the water body, the cross-sectional water depth of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross-sectional area of ​​the pipe unit water body, the cross-sectional water area of ​​the pipe unit water body is obtained, and the volume of each small micro-element water body of each pipe is calculated. , sum up the n infinitesimal water bodies in a single pipe and calculate the total volume of water in a single pipe .

[0040] The volume of each pipe unit water body in each pipe is obtained based on the cross-sectional water flow area of ​​the pipe unit water body. The volumes of all pipe unit water bodies in a single pipe are summed to obtain the total volume of water in the single pipe, i.e., the total water volume. The volumes of water in all pipes are then summed at each graded water level. Steps 302 to 309 are performed at each graded water level. The volumes of water in all pipes are summed at each graded water level (the finer the water level classification, the more accurate the statistical results). This will yield a water level-volume relationship curve for the drainage network, completing the construction of a generalized model of the drainage network.

[0041] Optionally, the pipe shape includes a circular cross-section pipe and a rectangular cross-section pipe.

[0042] Optionally, S10 also includes: processing the underground drainage network data into an inp file, converting the verified network model elements into a digital format, and processing them into a standard input file format (inp file) of the SWMM model as the input file of the network generalization model. Using the inp file format can improve the applicability and compatibility of the network generalization model. For any given inp file, a network generalization model can be constructed according to step S20.

[0043] The above inventions are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A method for generalizing an underground rainwater pipe network, characterized in that: include: S10: Acquire underground drainage network data, wherein the underground drainage network data includes a complete topological structure of the underground drainage network, upstream and downstream bottom elevations of each pipe, pipe diameter, and pipe length; S20: Based on the underground drainage network data in S10, first calculate the inclination of the pipeline, and then combine the pipeline inclination and the water flow state in the pipeline to give a water level classification from the lowest point to the highest point of the underground drainage network. Calculate the water volume in each pipeline at each graded water level, and statistically calculate the water level-volume relationship of the underground drainage network. Construct a pipeline network generalization model based on the water level-volume relationship, generalize the underground rainwater pipeline network into an equivalent water tank model with a water level-volume relationship curve, and combine the topological structure of the underground rainwater pipeline network to generalize the actual carrying capacity of the underground rainwater pipeline network.

2. The method for generalizing an underground rainwater pipe network according to claim 1, characterized in that: Acquiring underground drainage network data in S10 includes: Step S101: Eliminate sewage pipes and corresponding nodes, and only retain rainwater pipes and mixed rainwater and sewage pipes, which are collectively referred to as pipes; Step S102: Delete duplicate nodes, pipes and drains; Step S103: Delete isolated nodes that are not connected to both ends of the pipeline to ensure that each node is connected to at least one pipeline.

3. A method for generalizing an underground rainwater pipe network according to claim 2, characterized in that: The acquisition of underground drainage network data in S10 further includes: Step S104: Correcting the top elevation of the pipeline node to ensure that it is not higher than the ground surface elevation; Step S105: Correct the bottom elevation of the pipeline node to ensure that it is lower than the buried depth of any pipeline connected to the node; Step S106: Modify the topology of the pipe network by adding new connecting pipes or drainage outlets to ensure that each isolated pipe node and pipe is connected to at least one drainage outlet downstream.

4. A method for generalizing an underground rainwater pipe network according to claim 3, characterized in that: The step S104 of correcting the top elevation of the pipeline node includes: when the top elevation of the pipeline node is higher than the ground elevation, taking the ground elevation as the top elevation of the pipeline node.

5. The method for generalizing an underground rainwater pipe network according to claim 3, characterized in that: Correcting the bottom elevation of the pipeline node in step S105 includes: when the bottom elevation of the pipeline node is higher than the buried depth of the pipeline connected to the node, taking the buried depth of the pipeline connected to the node as the bottom elevation of the pipeline node.

6. The method for generalizing an underground rainwater pipe network according to claim 3, characterized in that: The topological structure of the pipe network is modified in step S106. If the isolated pipe is adjacent to a river, the node with the lowest bottom elevation in the isolated pipe is added as a new discharge outlet. If the isolated pipe is far from the river, the isolated pipe is connected to the main pipe by adding a new pipe, thereby connecting it to the downstream discharge outlet.

7. The method for generalizing an underground rainwater pipe network according to claim 1, characterized in that: The water flow state in the pipeline includes four pressure-free water flow states: The water level is higher than the downstream pipe bottom elevation, but lower than the upstream pipe bottom elevation; The water level is higher than the upstream pipe bottom elevation, but lower than the downstream pipe top elevation; The water level is higher than the downstream pipe top elevation, but lower than the upstream pipe bottom elevation; The water level is higher than the upstream pipe bottom elevation and higher than the downstream pipe top elevation.

8. The method for generalizing an underground rainwater pipe network according to claim 7, characterized in that: Calculating the water volume in each pipeline at each graded water level in S20 includes: According to the four no-pressure water flow states and the corresponding pipe inclination angles, the horizontal projection lengths of the water body in the pipe corresponding to the four no-pressure water flow states are obtained; Divide the water body in the pipe into n equal parts along the length direction to obtain the length of the water body of a single pipe unit; Obtain the water depth of the cross section of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross section of the pipe unit water body corresponding to different pipe shapes; The cross-sectional water flow area of ​​the pipe unit water body is obtained according to the horizontal projection length of the water body, the cross-sectional water depth of the pipe unit water body and the circumferential angle corresponding to the free water surface of the cross-sectional area of ​​the pipe unit water body; The volume of each pipe unit water body in each pipe is obtained based on the cross-sectional water flow area of ​​the pipe unit water body. The volumes of all pipe unit water bodies in a single pipe are summed to obtain the total volume of water in a single pipe, that is, the total water volume. Then, the volume of water in all pipes is summed at each graded water level.

9. The method for generalizing an underground rainwater pipe network according to claim 8, characterized in that: The pipe shapes include circular cross-section pipes and rectangular cross-section pipes.

10. The method for generalizing an underground rainwater pipe network according to claim 1, wherein: The S10 further includes: processing the underground drainage network data into an inp file.

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