Dam turning water depth calculation method for moraine lake surge

Abstract

The invention discloses a dam turnover water depth calculation method for moraine lake surge, belongs to the technical field of disaster prevention and control, and can solve the problem that the dam turnover water depth cannot be accurately calculated in the prior art. The method comprises the steps that S1, a freeboard of the moraine lake is determined according to the water level height of the moraine lake and the dam crest height of a dam of the moraine lake; s2, determining the wave height and the wave velocity of the surge propagating to a preset position in front of the dam; s3, calculating a first ratio of the wave height to the freeboard, and calculating a second ratio of the kinetic energy of the wave velocity to the potential energy of the freeboard; and S4, the dam turning water depth of the surge is determined according to the first ratio, the second ratio and the freeboard. The method is used for calculating the dam turning water depth of moraine lake surges.

Description

TECHNICAL FIELD

[0001] The application relates to a dam-breaking water depth calculation method for surge waves of an ice lake, and belongs to the technical field of disaster prevention. BACKGROUND

[0002] Ice lakes in alpine regions often break, which causes floods, mudslides and secondary disasters, and seriously threatens the safety of surrounding residents and engineering facilities. Surge waves formed in the ice lake are the main cause of the ice lake break, and the dam-breaking water depth of the surge waves after surmounting the dam of the ice lake is an important factor affecting the damage degree of the surge waves and the ice lake break process. In order to prevent and control the ice lake break disaster, it is necessary to accurately calculate the dam-breaking water depth of the surge waves.

[0003] At present, the existing technology usually calculates the dam-breaking water depth based on the simplified surge wave motion process, ignores various motion characteristics and actual energy conversion processes of the surge waves, and thus a large deviation exists between the calculated dam-breaking water depth and the actual situation. SUMMARY

[0004] The application provides a dam-breaking water depth calculation method for surge waves of an ice lake, and can solve the problem that the prior art cannot accurately calculate the dam-breaking water depth.

[0005] The application provides a dam-breaking water depth calculation method for surge waves of an ice lake, and the method comprises the following steps:

[0006] S1, determining a freeboard of the ice lake according to a water level height of the ice lake and a dam top height of a dam of the ice lake;

[0007] S2, determining a wave height and a wave speed of the surge waves at a preset position before the surge waves propagate to the dam;

[0008] S3, calculating a first ratio of the wave height to the freeboard, and calculating a second ratio of kinetic energy of the wave speed to potential energy of the freeboard;

[0009] S4, determining a dam-breaking water depth of the surge waves according to the first ratio, the second ratio and the freeboard.

[0010] Optionally, S1 specifically comprises the following steps:

[0011] calculating a difference value between the dam top height of the dam of the ice lake and the water level height of the ice lake, and determining the difference value as the freeboard of the ice lake.

[0012] Optionally, the second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard in S3 specifically comprises the following steps:

[0013] calculating a square value of the wave speed, and calculating a double value of a product of the freeboard and gravitational acceleration;

[0014] A ratio of the square value to the double value is determined as a second ratio of kinetic energy of the wave speed to potential energy of the freeboard.

[0015] Optionally, S4 specifically includes:

[0016] S41, determining a third ratio of the breaking wave depth of the surge to the freeboard according to the first ratio and the second ratio;

[0017] S42, determining the breaking wave depth of the surge according to the third ratio and the freeboard.

[0018] Optionally, S41 specifically includes:

[0019] calculating a first product of a power of the first ratio and a power of the second ratio; a and b are respectively a first preset coefficient and a second preset coefficient;

[0020] calculating a second product of the first product and a third preset coefficient, and determining the second product as the third ratio of the breaking wave depth of the surge to the freeboard.

[0021] Optionally, S42 specifically includes:

[0022] calculating a third product of the third ratio and the freeboard, and determining the third product as the breaking wave depth of the surge.

[0023] The present application can produce beneficial effects, including:

[0024] The present application is based on the movement process and movement characteristics of the surge overtopping the moraine lake dam, and the breaking wave depth of the surge is calculated according to multiple key factors of the breaking wave depth such as wave height, wave speed and freeboard, and the mutual conversion process of kinetic energy and potential energy, so that the calculation of the breaking wave depth is more in line with the actual movement process of the surge, and the rationality and accuracy of the calculation of the breaking wave depth are improved. At the same time, the calculation method of the present application combines the freeboard of the moraine lake, and can be used to calculate the breaking wave depth of the surge of the moraine lake with different freeboards, and has wide applicability. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The flowchart of the breaking wave depth calculation method of the surge of the moraine lake provided by the embodiment of the present application;

[0026] Figure 2 The schematic diagram of the moraine lake provided by the embodiment of the present application;

[0027] Figure 3 The schematic diagram of the surge propagation process provided by the embodiment of the present application;

[0028] Figure 4 The schematic diagram of the surge overtopping process provided by the embodiment of the present application. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0030] The embodiment of the present invention provides a method for calculating the water depth of a moraine lake surge, such as Figure 1 As shown, the method includes:

[0031] S1. The freeboard of the moraine lake is determined based on the water level of the moraine lake and the height of the dam crest of the moraine lake.

[0032] Specifically, calculate the difference between the dam crest height of the moraine lake and the water level of the moraine lake, and determine the difference as the freeboard of the moraine lake. Figure 2 As shown, Figure 2 in The freeboard of the moraine lake, that is, the difference in height between the water level and the dam top, can be obtained by measurement.

[0033] S2. Determine the wave height and wave speed at the preset location before the surge reaches the dam.

[0034] The preset position can usually be set according to the actual situation. To improve the accuracy of the calculation, a position as close to the dam as possible can be selected, such as Figure 3 shown. Figure 3 in Indicates the wave speed of the surge wave propagating to the preset location, Indicates the height of the swell wave that reaches the preset location. and wave height All of them can be calculated according to existing technology.

[0035] When a landslide, ice slide or ice avalanche occurs upstream of the moraine lake, a large amount of sediment or ice will quickly enter the moraine lake, often forming a surge with a wave speed exceeding 10m / s and a wave height exceeding 10m. Figure 4 As shown in Figure 2, the surge quickly overran the dam of the moraine lake, flowed into the back slope of the dam, and eroded the moraine earth dam body on the back slope. Figure 4 in This represents the water depth at which a surge overturns a dam. According to hydraulic principles, when the surge overturn depth reaches a certain level, the shear stress generated by the water flow will cause sediment on the backslope to mobilize, exposing the bottom and directly eroding the coarse rocks on the backslope. The accumulated erosion will cause the moraine earth dam on the backslope to be undercut, further eroding the dam and triggering a moraine lake outburst. Therefore, the surge overturn depth is a key factor influencing the extent of surge damage and the process of moraine lake outburst. Accurate calculation of this surge overturn depth is essential to prevent and control moraine lake outburst disasters.

[0036] S3, calculate a first ratio of the wave height to the freeboard, and calculate a second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard.

[0037] In the embodiment, the calculation formula of the first ratio is:

[0038] (1)

[0039] In the formula (1), represents the first ratio, represents the wave height of the swell propagating to the preset position, represents the freeboard of the glacial lake.

[0040] The second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard in S3 specifically includes:

[0041] calculating a square value of the wave speed, and calculating a double value of the product of the freeboard and the gravitational acceleration;

[0042] determining the ratio of the square value to the double value as the second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard. Wherein, the kinetic energy of the wave speed represents the kinetic energy of the swell when moving at the wave speed, and the potential energy of the freeboard represents the potential energy when the wave speed moves to the height of the freeboard, i.e. to the highest point of the freeboard.

[0043] In the embodiment, the calculation formula of the second ratio is:

[0044] (2)

[0045] In the formula (2), represents the second ratio, represents the wave speed of the swell propagating to the preset position, represents the freeboard of the glacial lake, represents the gravitational acceleration.

[0046] S4, determining the dam-breaking water depth of the swell according to the first ratio, the second ratio and the freeboard, specifically including:

[0047] S41, determining a third ratio of the dam-breaking water depth of the swell to the freeboard according to the first ratio and the second ratio.

[0048] S41 specifically includes:

[0049] calculating a first product of the power of the first ratio and the power of the second ratio; and are respectively a first preset coefficient and a second preset coefficient;

[0050] ​​​​​The first product and the second product of the third preset coefficient are calculated, and the second product is determined as the third ratio of the dam-breaking water depth of the surge and the freeboard.

[0051] In the embodiment, the calculation formula of the third ratio is:

[0052] (3)

[0053] In the formula (3), denotes the third ratio, denotes the first ratio, denotes the second ratio, , and denote the first preset coefficient, the second preset coefficient and the third preset coefficient respectively, , and can be determined through experiments.

[0054] S42, determining the dam-breaking water depth of the surge according to the third ratio and the freeboard.

[0055] S42 specifically includes:

[0056] The third product of the third ratio and the freeboard is calculated, and the third product is determined as the dam-breaking water depth of the surge.

[0057] In the embodiment, the third ratio , the dam-breaking water depth of the surge and the freeboard of the moraine lake satisfy the following mathematical relationship:

[0058] (4)

[0059] In the formula (4), denotes the third ratio, denotes the dam-breaking water depth of the surge, denotes the freeboard of the moraine lake.

[0060] According to the formula (4), the third ratio is multiplied by the freeboard of the moraine lake to obtain the dam-breaking water depth of the surge .

[0061] In the embodiment, through experiments, , , and the formula (1) to the formula (4), the calculation formula of the dam-breaking water depth is:

[0062] (5)

[0063] in formula (5), represents the dam-breaking water depth of the surge, represents the wave height of the surge propagating to the preset position, represents the wave speed of the surge propagating to the preset position, represents the freeboard of the moraine lake, represents the gravitational acceleration, in the embodiment = 9.81 m / s 2 .

[0064] According to the movement process of the surge, the dam-breaking water depth is closely related to the wave height, wave speed and freeboard of the moraine lake of the surge. The higher the wave height of the surge, the greater the dam-breaking water depth, and the use of the wave height to calculate the dam-breaking water depth ensures the reliability of the calculation. The greater the freeboard of the moraine lake, the smaller the dam-breaking water depth, and the embodiment fully considers the influence of the freeboard on the dam-breaking water depth, so that the calculation method of the embodiment can adapt to moraine lakes with different freeboards and is more reasonable in technology. The greater the wave speed of the surge, the greater the kinetic energy of the surge, the more the potential energy obtained by the conversion of the kinetic energy, and the greater the dam-breaking water depth, and the use of the wave speed to calculate the dam-breaking water depth has high reliability. Therefore, the embodiment combines the wave height, wave speed and freeboard of the moraine lake of the surge, which is beneficial to improve the calculation accuracy of the dam-breaking water depth.

[0065] The reliability of the calculation method of the embodiment will be described below in combination with a verification experiment.

[0066] Since the moraine lakes are all located in high-cold mountainous areas, the formation and dam-breaking process of the surge are difficult to be effectively captured and recorded, so that no on-site examples can be obtained. The indoor experiment is used to verify the reliability of the calculation method in the embodiment.

[0067] The embodiment builds a triangular dam in the room, and the slope of the water-facing slope is 30°, and the dam top height is 20 cm. The embodiment performs 16 verification experiments based on different wave speeds, wave heights or freeboards. Specifically, the embodiment forms a surge by sliding a preset sliding object (such as a water bucket) into the water, and by adjusting the height and sliding angle of the preset sliding object, surges with different wave speeds and wave heights can be obtained. Then the actual dam-breaking water depth can be obtained by on-site measurement, and the calculated dam-breaking water depth can be obtained by using the calculation method of the embodiment, and the specific data of the verification experiment is shown in Table 1.

[0068] Table 1 Verification experiment and error of dam-breaking water depth of surge

[0069] According to Table 1, the relative error of the calculated dam-breaking water depth and the actual dam-breaking water depth ranges from -9.7 to 17.2%, that is, the absolute error is within 20%; and 81.3% of the relative error is within the range of -9.7 to 9.9%, that is, the absolute error is within 10%, the deviation of the calculated dam-breaking water depth and the actual dam-breaking water depth is small, the calculation result has high accuracy, and it is indicated that the reliability of the calculation method of the embodiment is high.

[0070] It is worth noting that the difference between the wave height of the surge and the freeboard of the glacial lake is generally taken as the dam-breaking water depth of the surge in the prior art for the convenience of understanding and calculation. However, the calculation process simplifies the actual movement process of the surge, and ignores the multiple movement characteristics and actual energy conversion process of the surge, that is, after the surge reaches the water-facing slope of the dam, the surge will continue to climb up along the water-facing slope, and the kinetic energy will be converted into potential energy, so that the final movement height of the surge will be higher than the wave height. Obviously, the dam-breaking water depth obtained by calculating the difference between the wave height and the freeboard ignores this process, which leads to a large deviation between the calculated dam-breaking water depth and the actual dam-breaking water depth, and affects the accuracy of the calculation result.

[0071] Meanwhile, the actual movement process of the surge dam-breaking generally includes the movement characteristics of impacting the dam, climbing up along the water-facing slope, generating reflected surge, and crossing the dam top, etc. Among them, the impact on the dam will cause energy loss, the climbing up along the water-facing slope will change the movement direction of the surge, the reflected surge in the opposite direction formed during the climbing up will also reduce the kinetic energy, and the movement state after crossing the dam top will also change. In addition, the slope of the water-facing slope also has an influence on the movement process and energy conversion process of the surge. As can be seen, the actual movement process of the surge dam-breaking has multiple movement characteristics and multiple stages of energy conversion process, and the calculation method of the prior art cannot objectively reflect these movement characteristics and energy conversion process, and is not suitable for fine evaluation of the damage degree of the surge and the breaching process of the glacial lake, and cannot provide a reliable basis for the prevention and control of the breaching disaster of the glacial lake.

[0072] The embodiment fully considers the movement characteristics and energy conversion process of the surge on the water-facing slope of the dam, and calculates the dam-breaking water depth of the surge according to multiple key influencing factors of the dam-breaking water depth such as the wave height, wave speed and freeboard of the surge, and the mutual conversion process of kinetic energy and potential energy, so that the calculation of the dam-breaking water depth is more in line with the actual movement process of the surge, and the rationality and accuracy of the dam-breaking water depth calculation are improved. Meanwhile, the calculation method of the embodiment combines the freeboard of the glacial lake, and can be used to calculate the dam-breaking water depth of the surge of the glacial lake with different freeboards, and has wide applicability.

[0073] The above merely describes several embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with the preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical contents without departing from the scope of the technical solutions of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solutions.

Claims

1. A method for calculating the overtopping depth of a dammed glacial lake outburst wave, characterized in that, The method comprises: S1, determining the freeboard of the moraine lake according to the water level height of the moraine lake and the dam top height of the dam of the moraine lake; S2, determining the wave height and wave speed of the swell propagating to a preset position in front of the dam; S3, calculating a first ratio of the wave height to the freeboard, and calculating a second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard; S4, determining the overtopping depth of the swell according to the first ratio, the second ratio and the freeboard.

2. The method of claim 1, wherein, S1 specifically comprises: calculating the difference between the dam top height of the dam of the moraine lake and the water level height of the moraine lake, and determining the difference as the freeboard of the moraine lake.

3. The method of claim 1, wherein, In S3, the second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard is calculated, specifically comprising: calculating the square value of the wave speed, and calculating the double value of the product of the freeboard and the gravitational acceleration; determining the ratio of the square value to the double value as the second ratio of the kinetic energy of the wave speed to the potential energy of the freeboard.

4. The method according to claim 1, wherein S4 specifically comprises: S41, determining the third ratio of the overtopping depth of the swell to the freeboard according to the first ratio and the second ratio; S42, determining the overtopping depth of the swell according to the third ratio and the freeboard.

5. The method of claim 4, wherein, S41 specifically comprises: calculating a first product of the a-th power of the first ratio and the b-th power of the second ratio; a and b are respectively a first preset coefficient and a second preset coefficient; calculating a second product of the first product and a third preset coefficient, and determining the second product as the third ratio of the overtopping depth of the swell to the freeboard.

6. The method of claim 4, wherein, S42 specifically comprises: calculating a third product of the third ratio and the freeboard, and determining the third product as the overtopping depth of the swell.

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