Distinguishing method for setting up sand blocking and discharging system

Abstract

The invention relates to the field of water conservancy projects, in particular to a judgment method for setting up a sand blocking and discharging system, which comprises the following steps of: calculating a multi-year average sand storage amount at the upstream of a dam site drainage basin according to a regional sand transportation modulus; according to the initial hub arrangement scheme of the hydropower station, estimating the total sand storage amount after the hydropower station is operated; according to geological and topographic conditions of a reservoir area, water inlet and outlet bottom plate elevations and sand blocking ridge top elevations are drawn up; calculating the sediment deposition thickness of the reservoir and the silt preparation thickness in front of a water inlet and a water outlet by adopting an estimation method; calculating the ratio lambda1 of the total warehousing sand amount to the average warehousing sand amount for many years, and the ratio lambda2 of the sediment deposition thickness of a water inlet and a water outlet to the silt preparation thickness; when lambda2 is equal to 1 and lambda1 is larger than or equal to the designed service life, the sand blocking and discharging system does not need to be arranged, and when lambda1 is smaller than the designed service life, the sand blocking and discharging system needs to be arranged. The method has the effect of improving the accuracy of setting judgment of the sand blocking and discharging system.

Description

Technical Field

[0001] The invention relates to the field of water conservancy projects, and in particular to a method for determining the establishment of a sand interception and drainage system. Background Art

[0002] In some areas with little rainfall, low vegetation coverage, soil erosion and other problems, river water often contains a lot of sand. The harm of sediment to pumped storage power stations is mainly concentrated in two aspects: blade wear of the unit and reduction of effective storage capacity of the upper and lower reservoirs. At the same time, excessive sediment content will also have an adverse effect on the water filtration equipment and cooling water system sealing devices of the power station.

[0003] Therefore, for pumped storage power stations built on rivers with a lot of sediment, the layout design of the sediment retention and drainage system is an important consideration. However, there are also some situations where it is not necessary to arrange a sediment retention and drainage system. Therefore, in the early stage of the design of a pumped storage power station, it is necessary to determine whether to set up a sediment retention and drainage system. The current method is to conduct a sediment physical model test and propose whether to set up a sediment retention and drainage system based on the test results. However, sediment physical model experiments are often not adopted because they are time-consuming and costly, resulting in large deviations in engineering design, which further affects the dispatching and operation mode and economic benefits of the power station. Summary of the invention

[0004] In order to improve the accuracy of determining whether to establish a sand interception and drainage system, the present invention provides a method for determining whether to establish a sand interception and drainage system.

[0005] The present invention provides a method for determining the establishment of a sand interception and drainage system, which adopts the following technical solutions:

[0006] A method for determining the establishment of a sand interception and drainage system comprises the following steps:

[0007] Calculate the multi-year average sediment inflow upstream of the dam site basin based on the regional sediment transport modulus;

[0008] According to the preliminary hub layout plan of the hydropower station, estimate the total amount of sediment entering the reservoir after the hydropower station is put into operation;

[0009] According to the geological and topographical conditions of the reservoir area, the elevation of the bottom plate of the water inlet and outlet and the elevation of the top of the sand barrier are formulated;

[0010] The estimation method is used to calculate the reservoir sedimentation thickness and the reserve sedimentation thickness before the inlet and outlet;

[0011] Calculate the ratio of the total amount of sediment entering the reservoir to the average amount of sediment entering the reservoir over many years, λ1, and the ratio of the sediment accumulation thickness at the inlet and outlet to the reserve sediment accumulation thickness, λ2;

[0012] When λ2=1, λ1≥design service life, there is no need to set up a sand interception and drainage system; when λ1<design service life, a sand interception and drainage system needs to be set up.

[0013] In a specific feasible implementation plan, the method for calculating the average amount of sand entering the reservoir over many years includes the following steps:

[0014] If there is sediment observation data in the basin, the average amount of sediment entering the reservoir over many years, W, can be calculated based on the sediment content S at the hydrological station and the flow at the dam site Q. s , the calculation formula is: s =Q*S;

[0015] If there is no sediment observation data in the basin, the regional sediment transport modulus M s Calculate the average annual sediment inflow W based on the basin area A above the dam site s , the calculation formula is: s =M s *A.

[0016] In a specific implementation plan, the total amount of sand entering the warehouse is calculated as follows: W = N*W s *η,

[0017] Among them, W is the total amount of sand entering the reservoir;

[0018] N is the design service life of the power station;

[0019] η is the sediment discharge ratio;

[0020] W s It is the average amount of sand entering the reservoir over many years.

[0021] In a specific implementation scheme, the sediment discharge ratio η can be obtained according to an empirical formula or calculated using the Brune formula, which is as follows:

[0022]

[0023] In the above formula, V is the storage capacity below the normal water level;

[0024] Q z is the annual runoff into the reservoir.

[0025] In a specific embodiment, the siltation thickness Z before the inlet and outlet is b The calculation formula is: b =G k -G j ,

[0026] In the formula, G k G is the top elevation of the sand barrier; j is the elevation of the bottom plate of the water inlet and outlet;

[0027] The thickness of reservoir sedimentation is estimated using the equilibrium gradient method.

[0028] In a specific implementation plan, the top elevation of the sand barrier G k The calculation formula is: k =G s -H k ,

[0029] In the formula, H k The water depth is at the top of the ridge;

[0030] G s It is the lowest elevation of dead water level.

[0031] In a specific embodiment, the water depth H of the top of the ridge k The calculation formula is:

[0032]

[0033] In the above formula, Q f Fully pump flow for the power station;

[0034] V k The flow velocity over the sand bank;

[0035] L k The length of the sand barrier.

[0036] In a specific embodiment, the lowest dead water level G s The calculation formula is: s =G j +H y +G z，

[0037] Among them, G j G is the elevation of the bottom plate of the water inlet and outlet; z H is the elevation of the inlet and outlet gate holes; y It is the minimum submergence depth of the inlet and outlet.

[0038] In a specific possible implementation manner, after the ratio λ1 and the ratio λ2 are calculated, a correlation diagram of the ratio λ1 and the ratio λ2 is established.

[0039] In summary, the present invention has the following beneficial effects:

[0040] 1. Be able to reasonably judge whether it is necessary to establish a sediment interception and drainage system based on the sediment production in the basin, engineering layout and other conditions.

[0041] 2. Whether it is necessary to set up a sand interception and drainage system is simple to calculate and has wide adaptability.

[0042] 3. It can effectively solve the engineering sediment problem and save engineering investment. It can be widely used in various reservoir projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of the determination method for setting up a sand interception and drainage system.

[0044] Figure 2 It is a schematic diagram showing the thickness of silt deposits in the reservoir.

[0045] Figure 3 It is a correlation diagram between the ratio λ1 and the ratio λ2. DETAILED DESCRIPTION

[0046] The following combination Figure 1-Figure 3 The present invention is described in further detail.

[0047] Reference Figure 1 A method for determining the establishment of a sand interception and drainage system comprises the following steps:

[0048] S100, calculates the multi-year average sediment inflow upstream of the dam site based on the regional sediment transport modulus.

[0049] If there is sediment observation data in the basin, the average amount of sediment entering the dam site over the years is W s It is calculated based on the product of the sediment content S at the hydrological station and the flow Q at the dam site, that is, W s =Q*S, the average amount of sediment entering the reservoir over many years W s The unit of is t, and the unit of flow Q at the dam site is m 3 / s, the unit of sand content S is kg / m 3 .

[0050] If there is no sediment observation data in the basin, according to the regional sediment transport modulus M s Calculate the average annual sediment inflow W in the upstream of the dam site s Regional sediment transport modulus M s Generally, the regional sediment transport modulus M can be obtained from the local hydrological atlas. s The product of the watershed area A above the dam site is the average annual sediment inflow W. s , that is, W s =M s *A, regional sand transport modulus M s The unit is t / (km 2 a) The unit of drainage area A is km 2 .

[0051] S200, based on the preliminary hub layout plan of the hydropower station, estimate the total amount of sediment entering the reservoir after the hydropower station is put into operation.

[0052] According to the geological conditions of the river section, select the appropriate dam axis and the location of the inlet and outlet, preliminarily determine the project scale, hub layout plan and reservoir characteristic water level and other parameters, and use the empirical formula to deduce the sediment discharge ratio η based on the preliminary project layout plan to estimate the total sediment volume W entering the reservoir after the power station has been in operation for N years, that is, W=N*W s *η, N are selected according to the requirements of "Design Specification for Reasonable Service Life and Durability of Hydropower Projects" NB / T 10857-2021, and the unit of total sediment volume W is t. The sediment discharge ratio η can be calculated using Brune's formula, as follows:

[0053]

[0054] Where V is the reservoir capacity below the normal water level, in m 3 , Q z is the annual runoff into the reservoir, in m 3 .

[0055] S300, based on the geological and topographical conditions of the reservoir area, formulate the elevations of the inlet and outlet bottom plates and the top elevation of the sand retaining embankment.

[0056] According to the geological and topographic conditions and installed capacity of the inlet and outlet, the size of the inlet and outlet gate holes is preliminarily determined. At the same time, the inlet and outlet bottom plates are arranged on stable bedrock, and the inlet and outlet bottom plate elevation G is determined. j .

[0057] Calculate the minimum submergence depth H of the inlet and outlet y .

[0058] According to the inlet and outlet bottom plate elevation G j , Inlet and outlet gate hole elevation G z and the minimum submergence depth H of the inlet and outlet y , calculate the lowest dead water level G s , that is, G s =G j +H y +G z , the lowest dead water level G s、 Inlet and outlet bottom plate elevation G j , Inlet and outlet gate hole elevation G z and the minimum submergence depth H of the inlet and outlet y The unit is m.

[0059] Sand barrier top elevation G k =G s -H k , G k The unit is m. k It is the water depth at the top of the dam that meets the flow velocity requirement of the dam under the full pumping flow of the power station, in meters. k The calculation formula is as follows:

[0060]

[0061] In the above formula, Q f is the full pumping flow of the power station, in m 3 / s; V k The flow velocity over the sand bank is generally 0.5-1m 3 / s;L k The length of the sand barrier is generally 2.5-3m.

[0062] S400, using the estimation method to calculate the reservoir sediment thickness Z y and the siltation thickness Z before the inlet and outlet b .

[0063] Thickness of siltation before inlet and outlet Z b The calculation formula is: b =G k -G j , in m. Reservoir sediment thickness Z y The equilibrium slope method is generally used for estimation, that is, according to J and L k Determine Z y , where J = βJ0, L k , =αL0, J0 is the natural riverbed gradient, J0 = (G z -G b ) / L0,G z is the normal water level elevation, G b is the bottom elevation of the dam site, J is the gradient after sedimentation balance, L0 is the distance from the dam to the intersection of the normal water level and the bottom of the reservoir, L k The distance between the starting point of reservoir tail sedimentation and the dam, α is the coefficient, generally 1.1-1.3, β is the coefficient, generally 0.4-0.7, see for details Figure 2 .

[0064] S500, based on the operating years of the power station, calculate the total amount of sand entering the reservoir W and the average amount of sand entering the reservoir over many years W s The ratio of λ1, the thickness of sediment deposited at the inlet and outlet Z y and the thickness Z b The ratio λ2 of the two ratios is established, such as Figure 3 .

[0065] S600, when the thickness of sediment accumulation is equal to the reserve sediment thickness (the ratio of the two is 1) as the judgment standard, when the ratio of the total amount of sediment entering the reservoir corresponding to the judgment standard to the average amount of sediment entering the reservoir over many years is greater than the design service life of the power station, no sediment interception and drainage system may be set up, and when it is less than the design service life of the power station, a sediment interception and drainage system needs to be set up. Assuming that the design service life of the power station is T = 50, that is, when λ2 = 1, λ1 ≥ 50 does not require a sediment interception and drainage system, and λ1 < 50 requires a sediment interception and drainage system.

[0066] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the establishment of a sand interception and drainage system, characterized in that: The steps include: Calculate the multi-year average sediment inflow upstream of the dam site basin based on the regional sediment transport modulus; According to the preliminary hub layout plan of the hydropower station, estimate the total amount of sediment entering the reservoir after the hydropower station is put into operation; According to the geological and topographical conditions of the reservoir area, the elevation of the bottom plate of the water inlet and outlet and the elevation of the top of the sand barrier are formulated; The estimation method is used to calculate the reservoir sedimentation thickness and the reserve sedimentation thickness before the inlet and outlet; Calculate the ratio of the total amount of sediment entering the reservoir to the average amount of sediment entering the reservoir over many years, λ1, and the ratio of the sediment accumulation thickness at the inlet and outlet to the reserve sediment accumulation thickness, λ2; When λ2=1, λ1≥design service life, there is no need to set up a sand interception and drainage system; when λ1<design service life, a sand interception and drainage system needs to be set up.

2. The method for determining the establishment of a sand interception and drainage system according to claim 1, characterized in that: The calculation method of the average amount of sediment entering the reservoir over many years includes the following steps: If there is sediment observation data in the basin, the average amount of sediment entering the reservoir over many years, W, can be calculated based on the sediment content S at the hydrological station and the flow at the dam site Q. s , the calculation formula is: s =Q*S; If there is no sediment observation data in the basin, the regional sediment transport modulus M s Calculate the average annual sediment inflow W based on the basin area A above the dam site s , the calculation formula is: s =M s *A.

3. The method for determining the establishment of a sand blocking and drainage system according to claim 1, characterized in that: The calculation formula for the total amount of sand entering the warehouse is: W = N * W s *η, Among them, W is the total amount of sand entering the reservoir; N is the design service life of the power station; η is the sediment discharge ratio; W s It is the average amount of sand entering the reservoir over many years.

4. The method for determining the establishment of a sand interception and drainage system according to claim 3 is characterized in that: The sediment discharge ratio η can be obtained according to the empirical formula or calculated using the Brune formula. The Brune formula is as follows: In the above formula, V is the storage capacity below the normal water level; Q z is the annual runoff into the reservoir.

5. The method for determining the establishment of a sand interception and drainage system according to claim 1, characterized in that: Thickness of siltation before inlet and outlet Z b The calculation formula is: b =G k -G j , In the formula, G k G is the top elevation of the sand barrier; j is the elevation of the bottom plate of the water inlet and outlet; The thickness of reservoir sedimentation is estimated using the equilibrium gradient method.

6. The method for determining the establishment of a sand interception and drainage system according to claim 5, characterized in that: Sand barrier top elevation G k The calculation formula is: k =G s -H k , In the formula, H k The water depth is at the top of the ridge; G s It is the lowest elevation of dead water level.

7. The method for determining the establishment of a sand interception and drainage system according to claim 6, characterized in that: Water depth at top of ridge H k The calculation formula is: In the above formula, Q f Fully pump flow for the power station; V k The flow velocity over the sand bank; L k The length of the sand barrier.

8. The method for determining the establishment of a sand interception and drainage system according to claim 6, characterized in that: Minimum dead water level G s The calculation formula is: s =G j +H y +G z， Among them, G j G is the elevation of the bottom plate of the water inlet and outlet; z H is the elevation of the inlet and outlet gate holes; y It is the minimum submergence depth of the inlet and outlet.

9. The method for determining the establishment of a sand interception and drainage system according to claim 1, characterized in that: After calculating the ratio λ1 and the ratio λ2, a correlation diagram of the ratio λ1 and the ratio λ2 is established.

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