A method and system for analyzing dam continuous-inundation risk of a stepped hydropower hub group

Abstract

The application discloses a kind of cascade hydropower hub group dam continuous risk analysis method and system.The analysis method includes: constructing the physical model of cascade hydropower hub group dam continuous, and its dam flood flow calculation, dam occurrence condition judgment model, on the basis of above model, according to the dam body material of each dam in hydropower hub group, reservoir capacity, dam height, dam crest elevation etc.data, calculate and determine whether each dam occurs dam break or overtopping and the flood evolution after dam break or overtopping occurs.The method of the application has wide application range, does not need to collect too much basic data, and has high calculation efficiency and accuracy, which significantly improves the cascade hydropower hub group continuous risk prevention and control capability.

Description

Technical Field

[0001] This invention relates to the technical field of methods for analyzing the risk of cascading failures of hydropower hubs. Background Technology

[0002] To better develop water conservancy and hydropower projects, most reservoirs are designed as cascade reservoirs. A cascade hydropower hub is a group of reservoirs and dams continuously developed and constructed from upstream to downstream along a designated river section, forming an engineering complex of multiple hydropower projects. As the scale and number of cascade hydropower hubs continue to increase, the consequences of their failures become increasingly severe. If a cascade hydropower hub fails in succession, it will cause enormous losses to downstream lives and the economy. Therefore, risk analysis of cascade hydropower hubs is essential. In risk analysis, obtaining accurate flow rates and flood evolution processes of dam-break floods is crucial for analyzing their impact on downstream reservoirs.

[0003] Existing patent document CN 112749475 discloses a method for determining the risk of successive dam failures in a cascade reservoir group. This method involves collecting, determining, and modeling basic data such as the main characteristic parameters of the selected dams for successive dam failure risk analysis. This method requires acquiring various basic data for each dam, making it difficult to operate and apply in practice. Existing patent document CN11046563 discloses a method for simulating successive dam failure floods in a cascade reservoir group. This method includes extracting river network information, calculating the evolution of floods within the river channel, performing flood regulation calculations for the reservoirs, and treating the entire outflow process of a dam failure as the inflow process of the downstream river section. This method has high requirements for the information obtained, a complex calculation process, and focuses primarily on the flood evolution process, resulting in insufficient applicability of the analysis results. Existing patent document CN107330274 discloses a method for calculating the safety of cascade discharge control in an earth-rock dam group considering upstream dam failure floods. This method analyzes the calculation results of the upstream, midstream, and downstream dam failure flood evolution and flood regulation processes to obtain methods for improving the safety of downstream dams. However, this method is only applicable to earth-rock dams and cannot be applied to other types of dams.

[0004] It can be seen that existing technologies still lack mature and complete calculation and analysis methods for the problem of cascade hydropower hub failures. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to propose a new method and system for analyzing the risk of successive failures of cascade hydropower hubs. This method has a wide range of applications, does not require the collection of excessive basic data, greatly improves computational efficiency, and can accurately analyze the situation when all dams in the basin that would have a downstream impact fail. It can also intuitively identify the controlling reservoirs in the basin, significantly enhancing the risk prevention and control capabilities of successive failures of cascade hydropower hubs.

[0006] The technical solution of the present invention is as follows:

[0007] A method for analyzing the risk of successive failures of dams in a cascade hydropower hub group, comprising:

[0008] S1 constructs a physical model of the cascade hydropower hub group of dam failures, wherein the failures include successive dam failures and / or overtopping;

[0009] S2 constructs a dam-break flood flow calculation model based on the dam-break flood physical model, and obtains the flow rate of the flood that evolves to the next dam after any dam (excluding the final dam) breaks or overflows.

[0010] S3 constructs a dam failure analysis model based on the dam failure physical model. Through the dam failure analysis model, it obtains the following information: whether the next dam will fail or overflow after any dam (excluding the final dam) fails or overflows; the dam failure flow or weir flow after the dam failure or overflow occurs; and the progress of the dam failure and overflow.

[0011] S4 obtains the physical parameters of the major dams in the cascade hydropower hub group to be analyzed for cascading failure risk. Through the dam cascading failure physical model, the dam failure flood flow calculation model, and the dam failure occurrence analysis model, it determines whether the major dams will fail or overtopping, and the flood evolution after the failure or overtopping occurs.

[0012] According to some preferred embodiments of the present invention, the physical model for dam failure is constructed as follows:

[0013] The cascade hydropower hub group comprises n dams connected in series from upstream to downstream, namely the first-level, second-level, ..., nth-level dams. If any dam (except the final-level dam) experiences a dam breach or overtopping, the breach or overtopping process ceases when the water level falls below its dead water level. Subsequently, the breach flood generated by the breach or overtopping propagates to the next dam. When the breach flood reaches the next dam, the water volume of that dam is the difference between its upstream inflow, its own water volume, and its own discharge. The discharge includes the water volume generated for power generation plus the water volume discharged; specific values ​​can be obtained by consulting relevant dam data. If at a certain moment, the water level of the next-level dam exceeds the crest of the dam, then the dam will breach or overflow. After that, the water volume of the next-level dam will be the sum of the upstream inflow and its own water volume, minus its own discharge and the breach or overflow flow. The breach or overflow process will stop when the water level of the next-level dam drops to its dead water level. Within a certain time step, the water levels of all dams will not change.

[0014] According to some preferred embodiments of the present invention, the self-discharge volume includes the power generation volume of the dam and its discharge volume.

[0015] The calculation model for the evolution of the dam-break flood is constructed as follows:

[0016]

[0017] Where, q mx The flow rate of the flood reaching the next dam is the maximum flow rate at a distance x from the dam site where the dam breach or overtopping occurs. The maximum flow rate at the dam site where a dam breach or overtopping is likely to occur is the breach flow rate of the dam where a breach is likely to occur or the weir flow rate of the dam where overtopping is likely to occur; w is the total flood volume, which is the difference between the calculated maximum reservoir capacity and the dead reservoir capacity obtained from the literature; m 3 i0 represents the riverbed slope, i.e., the gradient; n represents the Manning roughness coefficient; x represents the distance between the dam that breached or overtossed and the next dam; λ and r represent the following parameters:

[0018]

[0019]

[0020] Where A and m are the riverbed cross-sectional coefficient and exponent, respectively. If the river channel cross-section is considered to be rectangular, then m = 1.

[0021] According to some preferred embodiments of the present invention, the construction of the dam failure analysis model includes:

[0022] S31 sets the time step to 10s to obtain the reservoir capacity calculation model before the subsequent dam failure or overtopping, as follows:

[0023] W b0 =W b +10q 来 -10q 泄

[0024] Among them, W b0 W represents the reservoir capacity before the subsequent dam collapses or overflows. b q represents the original reservoir capacity of the dam. 来 The upstream inflow rate, q, represents the flow rate of the flood reaching the first-stage dam after the evolution obtained from S2. 泄 This indicates the dam's own discharge flow rate;

[0025] S32 obtains the water level change before the dam breaks or overflows based on the calculated reservoir capacity before the subsequent dam breaks or overflows and the water level-reservoir capacity curve of the subsequent dam.

[0026] S33 Based on the water level changes before the dam breach or overtopping, analyze the dam breach or overtopping situation of the next-level dam to obtain whether the next-level dam has breached or overtopping and the dam breach flow or weir flow flow generated after the breach or overtopping.

[0027] S34 sets the time step to 10s. Based on the analysis results of the dam failure or overtopping situation of the subsequent dam, the reservoir capacity after the failure or overtopping of the subsequent dam is obtained as follows:

[0028] W b1 =10q 来 +W b -10q 泄 -10q 溃

[0029] Among them, W b1 Indicates the reservoir capacity after the subsequent dam fails or overflows; q 溃 This indicates the dam break flow or weir flow obtained from S33.

[0030] S35 obtains the water level change after the dam breaks or overflows based on the reservoir capacity after the subsequent dam breaches or overflows and the water level-reservoir capacity curve of the dam.

[0031] S36 determines the progress of the dam breach or overtopping based on the water level changes after the dam breach or overtopping, including: determining that the dam breach or overtopping process stops when the water level after the dam breach or overtopping drops to the dead water level.

[0032] According to some preferred embodiments of the present invention, S33 includes:

[0033] (1) Based on the water level changes before the dam breaks or overflows, determine whether the highest water level of the dam before the dam breaks or overflows exceeds its crest elevation. If it does not exceed the crest elevation, it is determined that the dam will not break and the downstream dams will not break. Otherwise, it is determined that the dam will break or overflow.

[0034] (2) Determine whether the dam will break or overflow based on the dam type. If a dam break occurs, calculate the dam break flow rate. If an overflow occurs, calculate the weir flow rate.

[0035] According to some preferred embodiments of the present invention, the dam type includes earth-rock dam and concrete dam. When the dam type is earth-rock dam, it is prone to dam failure, and when the dam type is concrete dam, it is prone to overtopping.

[0036] According to some preferred embodiments of the present invention, the dam-break flow rate is obtained through the following calculation model:

[0037]

[0038] Among them, Q m λ is the dam failure flow rate; λ is the flow rate parameter, which can be taken as 8 / 27; B0 is the width of the valley at the dam site; g is the gravitational acceleration; H0 is the upstream water depth before the dam failure.

[0039] According to some preferred embodiments of the present invention, the weir flow rate is obtained through the following calculation model:

[0040] If δ / H < 0.67, then the weir flow is a thin-walled weir flow, and the weir flow discharge is...

[0041] If 0.67 < δ / H < 2.5, then the weir flow is a practical weir flow, and the weir flow discharge is...

[0042] If 2.5 < δ / H < 10, then the weir flow is a broad-crested weir flow, and the weir flow rate Q = σ S mnε1bH 3 / 2 ;

[0043] Where δ represents the weir crest thickness, H represents the weir crest head, m is the flow coefficient; c is the upstream weir slope influence coefficient, which is taken as 1.0 when the upstream is vertical, and can be assumed to be vertical during the flow process; ε1 is the contraction coefficient; σ s denoted as , where b is the submergence coefficient; b is the weir width; and g is the gravitational acceleration.

[0044] Based on the above analysis methods, the present invention can further provide a cascade hydropower hub group dam failure risk analysis system, which includes: a hydropower hub group dam group database module for acquiring and storing dam type, dam height and dam crest elevation data; a dam failure calculation module for constructing and storing the dam failure flood flow calculation model and dam failure occurrence analysis model; and a dam failure result analysis module for obtaining analysis results based on the data and models.

[0045] The present invention has the following beneficial effects:

[0046] This invention can calculate the failure or overtopping scenarios of all non-final-stage dams in a cascade hydropower hub group, based on dam type considerations. It can obtain the failure scenarios of all dams in the basin, accurately identify the key dams with the ability to block upstream reservoir dam failure floods, i.e., the control dams in the cascade hydropower hub group, and conduct multi-faceted analysis of the failure results to accurately assess the risk of cascading failures.

[0047] The analytical method of this invention has a wide range of applications and a simple and easy calculation process. It can be selected according to different dam types, requires less basic data and is easy to obtain, and has high calculation efficiency and accuracy, and wide applicability. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the risk analysis method in a specific embodiment of the present invention.

[0049] Figure 2 This diagram illustrates the construction method of the physical model in a specific embodiment of the present invention. Detailed Implementation

[0050] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0051] In some specific implementations, refer to the appendix. Figure 1 The method for analyzing the risk of successive failures of cascade hydropower hub dams in this invention includes the following steps:

[0052] S1 constructs a physical model of cascade hydropower hub group dam failures, where failures include consecutive dam failures and / or consecutive overtopping.

[0053] More specifically, the physical model for the dam's cascading failures is constructed as follows:

[0054] See attached document Figure 2 The study area to be risk analyzed contains n cascaded dams, numbered 1, 2, 3...n from top to bottom. After dam 1 experiences a breach or overtopping, the breach or overtopping process stops when the water level falls below its dead water level. Subsequently, the breach flood from dam 1 propagates towards dam 2. When the breach flood reaches dam 2, the water volume of dam 2 is equal to the upstream inflow volume (i.e., the volume of the advancing flood) plus the difference between its own water volume and its own discharge volume. If the water volume of dam 2... If the water level of dam 2 exceeds the crest of dam 2, dam 2 will breach or overflow. Afterward, the water volume of dam 2 will be the sum of the upstream inflow and its own water volume, minus its own discharge and the breach / overflow discharge. This process continues until the water level of dam 2 drops to its dead water level, at which point the breach / overflow process of dam 2 will cease. Subsequently, the breach / overflow flood from dam 2 will propagate towards dam 3. The breach / overflow occurrence at each dam will then follow the same pattern as dam 2, and within a certain time step, the water levels of all dams will remain unchanged.

[0055] The physical model of the present invention does not consider factors such as water inflow and earthquakes, which simplifies the calculation process and improves calculation efficiency.

[0056] The self-discharge volume mentioned here refers to the water volume during normal dam operation or flood discharge, which can be obtained by consulting dam data.

[0057] Preferably, the time step is set to 10s.

[0058] Based on the dam failure physical model of S1, S2 constructs a flood evolution flow calculation model for dam failure, obtaining the flow rate of the flood that evolves to the next dam level after any dam level fails or overflows.

[0059] Preferably, the dam-break flood evolution flow calculation model calculates the maximum value of the dam-break flow or weir flow. The distance x between the dam and the flood peak is used to construct the formula for flood peak flattening.

[0060] More specifically, the calculation model for the evolution of the dam-break flood flow is constructed as follows:

[0061]

[0062] Where, q mx The evolution represents the flood flow reaching the next stage dam, which is the maximum flow at a distance x from the dam site where a dam breach or overtopping occurs, in meters. 3 / s; The maximum flow rate at the dam site where a dam breach or overtopping is likely to occur, i.e., the breach flow rate of a dam that is likely to breach or the weir flow rate of a dam that is likely to overtopping, is expressed in m. 3 / s; w represents the total flood volume, i.e., the flood discharge, and m represents the difference between the calculated maximum reservoir capacity and the dead storage capacity obtained from consulting data. 3 ; i0 represents the riverbed slope, i.e., gradient; n represents the Manning roughness coefficient; x represents the distance between the dam that has breached or overtossed and the next dam; λ represents the parameters.

[0063]

[0064]

[0065] Where A and m are the riverbed cross-sectional coefficient and exponent, respectively. In this study, the river channel cross-sectional shape is assumed to be rectangular, and m = 1 is determined based on relevant data.

[0066] Based on the dam failure physical model of S1, S3 constructs a dam failure analysis model to analyze whether the subsequent dam will fail or overflow after the failure or overtopping of any first-level dam, the dam failure flow or weir flow generated after the failure or overtopping, and the progress of dam failure and overtopping.

[0067] Preferably, the construction of the dam failure occurrence analysis model includes:

[0068] S31 sets the time step to 10s to obtain the reservoir capacity calculation model before the subsequent dam failure or overtopping, as follows:

[0069] W b0 =W b +10q 来 -10q泄

[0070] Among them, W b0 W represents the reservoir capacity before the subsequent dam collapses or overflows. b q represents the original reservoir capacity of the dam. 来 The upstream inflow rate, q, represents the flow rate of the flood reaching the first-stage dam after the evolution obtained from S2. 泄 This indicates the dam's own discharge flow rate.

[0071] S32 uses a reservoir capacity calculation model before the collapse or overtopping of a subsequent dam to obtain the water level changes before the collapse or overtopping of the dam based on the water level-reservoir capacity curve of the subsequent dam.

[0072] The water level-reservoir capacity curve of the next-level dam is a curve drawn based on the correspondence between the water level and reservoir capacity of the next-level dam, which can be obtained by consulting relevant materials.

[0073] Based on the water level changes before the dam breach or overtopping, S33 analyzes the dam breach or overtopping situation of the next-level dam as follows:

[0074] If the highest water level of the next-level dam does not exceed its crest elevation, then the next-level dam is considered not to have breached, and neither are any of the downstream dams. If the water level of the next-level dam exceeds its crest elevation at a certain moment, then it is determined whether it will breach or overtopping based on the dam type. The determination process includes:

[0075] (1) If the dam is an earth-rock dam, it is assumed that it will break, and the dam break flow rate is calculated as follows:

[0076]

[0077] Among them, Q m The peak flow rate, i.e., the dam-break flow rate, is m. 3 / s; take λ = 8 / 27 as the flow rate parameter; B0 is the width of the valley at the dam site, in meters; assume the river width is equal to the dam length, in meters; g is the acceleration due to gravity, 9.8 m / s². 2 H0 represents the upstream water depth before the dam collapsed, in meters.

[0078] (2) If the dam is a concrete dam, it is assumed that it will overtopping. The type of weir flow and the flow rate generated during overtopping are determined in the following ways:

[0079] If δ / H < 0.67, then the weir flow is a thin-walled weir flow, and the weir flow discharge is...

[0080] If 0.67 < δ / H < 2.5, then the weir flow is a practical weir flow, and the weir flow discharge is...

[0081] If 2.5 < δ / H < 10, then the weir flow is a broad-crested weir flow, and the weir flow discharge Q = σ S mnε1bH 3 / 2 ;

[0082] Where δ represents the weir crest thickness, H represents the weir crest head, m is the flow coefficient; c is the upstream weir slope influence coefficient, which is taken as 1.0 when the upstream is vertical, and can be assumed to be vertical during the flow process; ε1 is the contraction coefficient; σ s ρ is the submergence coefficient; b is the weir width; g is the acceleration due to gravity.

[0083] S34 sets the time step to 10 seconds. Based on the analysis results of the dam failure or overtopping situation of the next-stage dam, the reservoir capacity after the failure or overtopping of the next-stage dam is obtained as follows:

[0084] W b1 =10q 来 +W b -10q 泄 -100q 溃

[0085] Among them, W b1 Indicates the reservoir capacity after the subsequent dam fails or overflows; q 溃 This indicates the dam break flow or weir flow obtained from S33.

[0086] Based on the reservoir capacity after the collapse or overtopping of the next-level dam obtained in S34 and the water level-reservoir capacity curve of that dam, S35 obtains the water level change after the collapse or overtopping of the dam.

[0087] S36 determines the status of dam breach or overtopping based on the water level changes after the dam breach or overtopping, including: the dam breach or overtopping process stops when the water level drops to the dead water level after the dam breach or overtopping.

[0088] The above analysis fully considers the dam type and can calculate the downstream dam failure situation caused by the instantaneous complete collapse of a non-final-stage dam. The overtopping situation of earth-rock dams can be equated with the dam failure situation. For concrete dams such as gravity dams and arch dams, the discharge flow can be directly calculated based on the weir flow after overtopping. After the dam-break flood reaches the downstream dam, the discharge is calculated as the flood volume transmitted from the upstream + the existing water volume of the downstream dam + the dam's discharge volume. The dam discharge volume can be obtained by consulting relevant data and can specifically include the power generation water volume + the flood discharge volume. Subsequently, the downstream evolution process of the dam-break flood can be calculated using a dam-break flood discharge calculation model.

[0089] In steps S1-S3 above, dam failure refers to the instantaneous and complete collapse of the dam body, and overtopping refers to the water level exceeding the dam crest elevation. Floods resulting from either dam failure or overtopping are called dam-break floods. The water level change at the dam is calculated using the downstream dam's reservoir capacity curve. If the maximum water level at the downstream dam does not exceed its crest elevation, the dam is considered safe, the dam-break transmission is complete, and the dam has the capacity to block upstream reservoir dam-break floods; it is a key dam in the cascade hydropower project. If the water level exceeds its crest elevation, the dam type is then used to determine whether a dam failure or overtopping has occurred, and the corresponding weir flow and discharge flow are calculated.

[0090] S4 obtains the dam type, dam height, and dam crest elevation of each dam in the cascade hydropower hub group to be analyzed for cascading failure risk. Through the physical model of dam cascading failure, the flood flow calculation model for dam failure, and the analysis model of dam failure occurrence, it determines whether each dam will fail or overtopping, and the flood evolution after a dam failure or overtopping occurs.

[0091] For a cascade hydropower hub with n dams, dam failure analysis calculations are performed for each dam from the first dam to the (n-1)th dam, thus completing the dam failure analysis calculation for a cascade hydropower hub.

[0092] Example 1

[0093] Based on the above specific implementation methods, the Dadu River Basin was used as the study area for a cascading failure risk analysis. All reservoirs in this basin are arranged in series. The first-stage reservoir is the Houziyan Reservoir, a concrete dam, which experienced overtopping. Its calculated δ / H = 0.1 < 0.67, therefore its weir flow process is classified as thin-walled weir flow. Based on the thin-walled weir flow calculation model... The time step is set to 10 seconds, assuming no change in water level within 10 seconds. The weir flow rate is obtained, which represents the flood flow from the first-stage reservoir's dam break to the second-stage reservoir, Changheba Reservoir. During this process, the water level at each time point is calculated based on the Houziyan water level-reservoir capacity curve plotted from consulted data, until the water level at Houziyan drops below the dead water level of Houziyan Reservoir, at which point the overtopping process is considered to have stopped. Simultaneously, based on the distance between Houziyan Reservoir and its next-stage reservoir, Changheba Reservoir, and the flood's evolution velocity, the time it takes for the flood to reach Changheba is estimated. The flow velocity is assumed to remain constant. The flood evolution velocity calculation model is as follows:

[0094]

[0095] Where m represents the riverbed cross-sectional index; g is the gravitational acceleration; and H0 is the upstream water depth before the dam breach.

[0096] After calculating the arrival time of the flood, the flood flow rate for each time period is calculated according to a time step of 10 seconds.

[0097] The volume of water reaching Changhe Dam is equal to the inflow from the upstream Houziyan Reservoir plus the dam's own volume minus its own outflow. Then, based on the Changhe Dam's water level-reservoir capacity curve, the water level corresponding to the calculated reservoir capacity for each time period is determined. If the calculated highest water level does not exceed the dam crest, the Changhe Dam is considered safe and will not breach, and all downstream dams are also considered safe and will not breach. If any calculated water level exceeds the dam height, the Changhe Dam is considered to have breached. Subsequently, based on the Changhe Dam's dam type (earth-rock dam), a corresponding model is selected to calculate the breach flow.

[0098] By repeating the calculations of dam-break flow and flood progression, the impact of each reservoir's overtopping or dam failure on the downstream cascade reservoirs of the Dadu River basin can be determined. This process continues until the analysis of all reservoirs in the Dadu River basin is completed. The dam-break risk analysis results are shown in Table 1 below:

[0099] Table 1 Results of the sequential failure analysis of non-final-stage dams in the Dadu River Basin

[0100]

[0101]

[0102] Each row in the table represents the impact of a dam breach or overtopping on all downstream dams. "Breach" indicates an instantaneous complete breach, "√" indicates a dam breach, "Overtopping" indicates only the top of the dam is overtopping, and "○" indicates no dam breach.

[0103] Based on Table 1, the simulation results of dam-break floods under this condition are as follows: When Houziyan Dam breaks, Changhe Dam also breaks, and all other reservoirs overflow; when Changhe Dam breaks, all downstream reservoirs overflow; when Lengzhuguan Dam breaks, downstream reservoirs are safe and do not break; when Luding Dam breaks, Yingliangbao overflows, and the others are safe and do not break; when Yingliangbao Dam breaks, the other reservoirs are safe; when Dagangshan Dam breaks, the other reservoirs overflow; when Longtoushi Dam breaks, Laoyingyan overflows, and the other reservoirs are safe; when Laoyingyan Dam breaks, all downstream reservoirs are safe; when Pubugou, Shenxigou, Zhentouba, and Gongzui Dams break, all downstream reservoirs overflow. Because Changhe Dam breaks instantly and completely, the resulting dam-break flow is extremely large, and all downstream reservoirs overflow, resulting in immense destructive power. It is evident that instantaneous dam breaks are more destructive in a short period of time. Because the reservoir capacity before the Lengzhuguan dam breach was small and the initial water level was low, the resulting breach flow was relatively small. The Luding Hydropower Station successfully blocked the breach flood at Lengzhuguan, protecting all downstream reservoirs and preventing breaches. Luding has the capacity to block upstream floods and is a key control reservoir in the Dadu River basin. When the Luding Hydropower Station breached, the reservoir capacity before the breach was larger than that of Yingliangbao, leading to overtopping. The breach was only stopped by the Dagangshan Hydropower Station blocking the upstream breach flood. Similarly, when the Longtoushi dam breached, Dagangshan again blocked the upstream breach flood, making it an important control reservoir in the Dadu River basin. As the hydropower station with the largest reservoir capacity in the entire basin, Pubugou could block the upstream breach floods when Longtoushi or Laoyingyan dams breached. These comparisons show that whether a dam breach occurs depends primarily on reservoir capacity, dam type, and the pre-break water level. Comparing all the results, it can be concluded that when a dam experiences a sudden and complete collapse, the duration is relatively short, but the collapse flow is extremely large; when a dam only experiences overtopping, the collapse duration is extremely long, but the collapse flow is relatively small.

[0104] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for analyzing the risk of successive failures of dams in a cascade hydropower hub group, characterized in that, It includes: S1 Constructs a physical model of cascade hydropower hub group dam failures, where failures include successive dam failures and / or overtopping; S2 Based on the dam failure physical model, a dam failure flood flow calculation model is constructed. According to the dam failure flood flow calculation model, the flow rate of the flood that evolves to the next dam after any dam (excluding the final dam) fails or overflows is obtained. S3 Based on the dam failure physical model, construct a dam failure occurrence analysis model. Through the dam failure occurrence analysis model, obtain the following information: after any dam (excluding the final dam) fails or overflows, whether the next dam will fail or overflow, the dam failure flow or weir flow generated after the dam failure or overflow, and the progress of the dam failure and overflow. S4 obtains the physical parameters of the major dams in the cascade hydropower hub group to be analyzed for cascading failure risk. Through the dam cascading failure physical model, dam failure flood flow calculation model and dam failure occurrence analysis model, it determines whether the major dams will fail or overtopping and the flood evolution after the failure or overtopping occurs. The physical model for the dam's cascading failures is constructed as follows: The cascade hydropower hub group comprises n dams connected in series from upstream to downstream, namely the first-level, second-level, ..., nth-level dams. When any dam (except the final dam) experiences a dam breach or overtopping, the breach or overtopping process ceases when the water level falls below its dead water level. Subsequently, the breach floodwaters propagate to the next dam. When the breach floodwaters reach the next dam, the water volume of that dam is the difference between its upstream inflow, its own water volume, and its own discharge. If, at any moment, the water volume of the next dam causes its water level to exceed the crest of the dam, then that dam experiences a breach or overtopping. Afterward, the water volume of the next dam is the sum of its upstream inflow, its own water volume, and the difference between its own discharge and the breach or overtopping flow. The breach or overtopping process ceases when the water level of the next dam drops to its dead water level. Within a certain time step, the water levels of all dams remain unchanged. The model for calculating the dam-break flood flow is constructed as follows: ； in, The flow rate of the flood reaching the next dam is the maximum flow rate at a distance x from the dam site where the dam breach or overtopping occurs. The maximum flow rate at the dam site of the dam where a dam breach or overtopping occurs, i.e., the dam breach flow rate of the dam where a dam breach occurs or the weir flow rate of the dam where overtopping occurs. w , where is the total flood volume, and is the difference between the maximum reservoir capacity and the dead storage capacity, in m³. The slope of the riverbed is denoted by n; the roughness coefficient of Manning is denoted by x; and the distance between the dam that has breached or overtossed and the next dam after it is denoted by x. r represents the following parameters: ； ； Where A and m are the riverbed cross-sectional coefficient and exponent, respectively, and m=1 when the river channel cross-sectional shape is set to rectangular.

2. The analytical method according to claim 1, characterized in that, The self-discharge volume includes the water volume generated by the dam for power generation and the water volume discharged from it.

3. The analytical method according to claim 1, characterized in that, The construction of the dam failure analysis model includes: S31 sets the time step to 10s to obtain the reservoir capacity calculation model before the subsequent dam failure or overtopping, as follows: ； in, This indicates the reservoir capacity before the subsequent dam collapses or overflows. This indicates the original reservoir capacity of the dam. This is expressed as the upstream inflow rate, which is the flow rate of the flood reaching the next stage dam based on the evolution obtained from S2. This indicates the dam's own discharge flow rate; S32 Based on the calculated reservoir capacity before the collapse or overtopping of the next-level dam and the water level-reservoir capacity curve of the next-level dam, the water level change before the collapse or overtopping of the dam is obtained. S33 Based on the water level changes before the dam breach or overtopping, analyze the dam breach or overtopping situation of the next-level dam to obtain whether the next-level dam has breached or overtopping and the dam breach flow or weir flow flow generated after the breach or overtopping. S34 sets the time step to 10s. Based on the analysis results of the dam failure or overtopping situation of the subsequent dam, the reservoir capacity after the failure or overtopping of the subsequent dam is obtained as follows: ； in, This indicates the reservoir capacity after the subsequent dam fails or overflows. This indicates the dam break flow or weir flow obtained based on S33; S35 Based on the reservoir capacity after the subsequent dam breach or overtopping and the water level-reservoir capacity curve of the dam, obtain the water level change after the dam breach or overtopping. S36 Based on the changes in water level after the dam breach or overtopping, determine the progress of the dam breach or overtopping, including: when the water level after the dam breach or overtopping drops to the dead water level, determine that the dam breach or overtopping process has stopped.

4. The analytical method according to claim 3, characterized in that, S33 includes: (1) Based on the changes in water level before the dam breaks or overflows, determine whether the highest water level of the dam before the dam breaks or overflows exceeds its crest elevation. If it does not exceed the crest elevation, it is determined that the dam will not break and the downstream dams will not break. Otherwise, it is determined that the dam will break or overflow. (2) Determine whether the dam will break or overflow based on the dam type. If the dam breaks, calculate the dam break flow rate. If the dam overflows, calculate the weir flow rate.

5. The analytical method according to claim 4, characterized in that, The dam types include earth-rock dams and concrete dams. When the dam type is an earth-rock dam, it is prone to dam failure. When the dam type is a concrete dam, it is prone to overtopping.

6. The analytical method according to claim 5, characterized in that, The dam break flow rate is obtained through the following calculation model: ， in, The dam break flow rate; For the flow rate parameter, take 8 / 27; The width of the valley at the dam site is given by g; g is the acceleration due to gravity. This represents the upstream water depth before the dam collapsed.

7. The analytical method according to claim 5, characterized in that, The weir flow rate is obtained through the following calculation model: like If the value is less than 0.67, then the weir flow is a thin-walled weir flow, and the weir flow discharge is... ; If 0.67 < If the value is less than 2.5, then the weir flow is a practical weir flow, and the weir flow discharge is... ; If 2.5 < If the value is less than 10, then the weir flow is a broad-crested weir flow, and the weir flow rate is... ; in, Indicates the thickness of the weir crest. The value of c represents the head at the top of the weir, m is the flow coefficient, and c is the influence coefficient of the upstream weir slope. When the upstream is vertical, the value of c is 1.

0. In the calculation, it can be assumed that the upstream is vertical during the flow process. To measure the shrinkage coefficient; denoted as the submergence coefficient; b is the weir width; g is the gravitational acceleration.

8. A system for analyzing the risk of successive failures of cascade hydropower dams, implementing the analysis method described in any one of claims 1-7, characterized in that, It includes: a hydropower hub dam group database module for acquiring and storing dam type, dam height and dam crest elevation data; a dam break calculation module for constructing and storing the dam break flood flow calculation model and dam break occurrence analysis model; and a dam break result analysis module for obtaining analysis results based on the data and model.

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