A double vertical shaft compound section spillway and its design method

Abstract

The present application relates to the field of hydraulic power engineering, and particularly relates to a double vertical shaft compound section spillway discharge structure and a design method thereof. The discharge structure comprises a water diversion channel connected with an upstream reservoir; a first vertical shaft with a cylindrical section, a lower part of the first vertical shaft being in communication with a downstream end of the water diversion channel, and a lower part of the first vertical shaft being provided with a transverse communication pipe; a second vertical shaft with a square section, the second vertical shaft being in communication with a downstream end of the transverse communication pipe; and a spillway comprising an overflow weir, a compound section spillway section and a bucket nose in sequence, an upstream end of the overflow weir being in communication with an upper part of the second vertical shaft, and a flow section of the compound section spillway section comprising a semicircular channel, a trapezoidal channel and a rectangular channel from bottom to top. Water flows from the upstream reservoir, through the water diversion channel, the first vertical shaft, the second vertical shaft and the compound section spillway, and finally is discharged into a downstream river channel from the bucket nose. The double vertical shaft compound section spillway discharge structure can keep the water tongue discharge distance substantially stable.

Description

Technical Field

[0001] This invention belongs to the field of hydropower engineering, and specifically relates to a drainage structure with a double vertical shaft and a double cross-section spillway, and its design method. Background Technology

[0002] In western my country, rivers are often characterized by deep V-shaped valleys, narrow flood discharge sections, large flow variations, and steep rises and falls in water level. The spillway structures used in engineering projects are mostly bank-side spillways or flood tunnels, with energy dissipation achieved through jet flow. For high-head spillway structures, due to the high operating head and high flow velocity in the spillway, aeration and erosion mitigation facilities must be installed when the flow velocity exceeds 35 m / s to reduce the risk of cavitation damage. When the cross-section of the spillway is a single rectangular section, the main characteristics of the water flow are as follows: (1) When the flow rate is small, the water depth of the spillway is shallow, the hydraulic radius is small, the roughness of the flow wall is relatively large, the flow loss along the flow increases, the flow velocity at the tip of the spillway is low, which leads to the flow not meeting the requirements for the tipping, forming a vortex flow in the reverse arc section, or due to insufficient tipping distance, the flow directly hits the foundation of the tipping nose or the slope of the bank; (2) When the flow rate is medium, the flow rate increases, the water depth and hydraulic radius of the spillway increase, the roughness of the flow wall decreases relatively, the flow velocity at the end of the spillway increases, the tipping point is located at the center line of the river channel, and the downstream flow is in a good connection state with the downstream river channel; (3) When the flow rate is large, the water depth and hydraulic radius of the spillway are larger, the roughness of the flow wall is relatively smaller, the flow velocity at the end of the spillway increases significantly, the tipping distance of the tipping point increases significantly, and the tipping point of the tipping point crosses the center line of the river channel and directly impacts the toe of the opposite bank slope or hits the opposite bank slope. This analysis, along with engineering practice, demonstrates that under varying flow conditions, a single rectangular cross-section spillway cannot maintain a relatively stable water jet distance. The impact of the water jet on riverbank slopes leads to complex slope protection design, difficult construction, and substantial investment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a drainage structure with a double vertical shaft duplex cross-section drainage channel that can maintain the basic stability of the water tongue distance and its design method.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: an irrigation canal connected to an upstream reservoir; The first vertical shaft has a cylindrical cross-section. The upper part of the first vertical shaft is connected to the downstream end of the water diversion channel, and the lower part of the first vertical shaft is equipped with a horizontal connecting pipe. The second vertical shaft, which has a square cross-section, is connected to the downstream end with a transverse connecting pipe; The spillway includes, in sequence, an overflow weir, a double-section spillway section, and a sluice gate. The upstream end of the overflow weir is connected to the upper part of the second vertical shaft. The cross-section of the double-section spillway section includes, from bottom to top, a semi-circular arc channel, a trapezoidal channel, and a rectangular channel. Water flows from the upstream reservoir through the water diversion canal, the first vertical shaft, the second vertical shaft, and the double-section spillway, and finally is ejected from the sluice gate into the downstream river channel.

[0005] In one embodiment, the transverse connecting pipe is provided with multiple branch connecting pipes in the height direction, and the cross-sectional area of ​​the lower branch connecting pipe is not less than the cross-sectional area of ​​the upper branch connecting pipe.

[0006] In one embodiment, the cross-sectional area of ​​the second vertical shaft is not less than the total flow area of ​​the transverse connecting pipe.

[0007] In one embodiment, the total flow area of ​​the transverse connecting pipe is not less than twice the cross-sectional area of ​​the first vertical shaft.

[0008] In one embodiment, the elevation of the overflow weir crest is not lower than the elevation of the top surface of the uppermost branch connecting pipe of the transverse connecting pipe.

[0009] In one embodiment, the roughness of the semi-circular arc channel in the flow section of the compound cross-section drain section is... ≤ Trapezoidal channel roughness ≤Roughness of rectangular channel .

[0010] In one embodiment, the downstream end of the overflow weir is connected to the upstream end of the compound cross-section spillway section via an inclined plane, and the downstream end of the compound cross-section spillway section is connected to the upstream end of the sluice gate via an inclined plane.

[0011] In one embodiment, the cross-sectional area of ​​the semi-circular arc channel, trapezoidal channel, and rectangular channel gradually increases.

[0012] Based on the same inventive concept, a design method for a drainage structure with a double vertical shaft and a double cross-section spillway is also provided, including: S1. Based on the engineering topography, geology, and hydrological conditions, determine the discharge flow rate Q, discharge drop Z, discharge channel width B, and discharge channel velocity V of the spillway structure in accordance with the design specifications. S2. Using a moderate flow rate as the calculation condition, preliminarily determine the angle θ of the sill and the head difference between the sill and the river surface. ; S3. Calculate the water jet distance according to the theoretical parabolic equation, and verify the positional relationship between the water jet landing point and the river centerline. If the water jet landing point deviates from the river centerline by more than ±5%, return to S2 and adjust the jet angle θ of the jet nose and the drop from the jet nose to the river water surface. At least one parameter in the parameters, until the point where the water tongue falls deviates from the center line of the river channel by no more than ±5%; S4. Assuming the water flow in the compound cross-section spillway is uniform, calculate the total drop of the compound cross-section spillway. Hydraulic gradient of the compound cross-section spillway section ,include: The basic dimensions of the semi-circular arc channel, trapezoidal channel and rectangular channel, as well as the comprehensive roughness n of the channel wall of the compound cross-section drainage section, were initially determined. Based on the discharge flow rate Q, the discharge channel velocity V, the discharge channel width B, the overflow weir flow coefficient m, and the velocity coefficient... Calculate the water level difference between the water surface in the second vertical shaft and the starting section of the spillway. :

[0013] Calculate the head loss along the flow path The water level difference in the double-section spillway section Calculated according to the Cheshire formula: ,in:

[0014] In uniform flow, the change in water potential energy is equal to the head loss along the flow path. The water level difference in the compound cross-section spillway section... for:

[0015] Total drop of the trough for:

[0016] Hydraulic gradient of the double-section spillway section for:

[0017] In the formula, V is the discharge channel velocity (m / s); Q is the discharge flow rate (m³ / s). 3 / s; L - length of the drain channel, m; A - flow area of ​​the drain channel, m² 2 P - Total wetted perimeter of the drain tank, P = P 1+ P2+...+P i ,m;P i - Wetted perimeter of the i-th morphological boundary segment of the spillway, m; R - Hydraulic radius, m; n - Overall roughness coefficient, n i - Roughness of the i-th morphological boundary segment of the groove; C - Chezy coefficient m - overflow weir flow coefficient, which can be found in the hydraulic calculation manual; - Flow velocity coefficient, taken as ; S5. Verify the calculated water jet distance. If the water jet landing point deviates from the river centerline by more than ±15%, adjust the basic dimensions of the semi-circular arc channel, trapezoidal channel, and rectangular channel, as well as at least one parameter of the comprehensive roughness n of the channel wall of the compound cross-section spillway section, until the water jet landing point deviates from the river centerline by no more than ±15%. S6. Calculate the total head of water level in the vertical shaft. ,Right now:

[0018] S7. Determine the total head difference of the vertical shaft water level in the spillway structure. Total drop of the trough And the cross-sectional shape of the complex cross-section chute section.

[0019] In one embodiment, the overall roughness n of the channel wall in the compound cross-section drainage section is adjusted by adjusting the roughness of the semi-circular arc channel. Trapezoidal channel roughness and the roughness of rectangular channels Adjustment.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The above-mentioned double-shaft duplex cross-section spillway uses a double-shaft arrangement. The upstream first shaft is mainly used to receive the upstream water and reduce most of the mechanical energy (potential energy and kinetic energy) of the water flow. The cylindrical structure has good pressure-bearing performance and is suitable for withstanding the rotation and impact of the water flow. The transverse connecting pipe and the downstream second shaft are mainly used to reduce the water flow volume, adjust the water flow pattern, maintain the stability of the water surface in the shaft, and smoothly guide the water flow to the downstream spillway, while keeping the spillway flow velocity within a range that does not cause cavitation damage. The composite cross-section of the spillway section adopts a composite cross-sectional shape, forming a flow pattern similar to the "deep channel + shallow shoal" of a natural river channel. At low flow rates, the wetted perimeter is small, the hydraulic radius is large, and the head loss along the flow path is reduced; at high flow rates, the wetted perimeter is large, the hydraulic radius is small, and the head loss along the flow path increases. Under different flow conditions, the head loss along the flow path remains essentially the same, thus ensuring that the flow velocity at the sill is essentially the same, maintaining a relatively stable water jet distance, and ensuring that the water jet landing point is located in the centerline area of ​​the river channel. This simplifies the design of riverbank protection and reduces engineering investment. The semi-circular bottom conforms to the natural flow lines of the water, especially at high flow rates, effectively preventing negative pressure at the bottom of the channel and thus preventing cavitation damage. The trapezoidal and rectangular cross-section structures are simple, with clear stress distribution, reliable connection to the sidewalls, and high overall rigidity, capable of resisting the vibration and impact of high-speed water flow. The composite cross-section spillway of this invention allows the water flow to have different hydraulic radii at different water depths, which helps optimize the flow velocity distribution and reduce adverse phenomena such as water flow shock waves. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a longitudinal cross-sectional schematic diagram of a double-shaft duplex cross-section drainage structure according to an embodiment of the present invention. Figure 2 This is a schematic plan view of the drainage structure of the double vertical shaft duplex cross-section drainage channel according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a cross-sectional AA-shaped drainage channel according to an embodiment of the present invention; Figure 4 This is a longitudinal section and hydraulic calculation parameters diagram of a double vertical shaft duplex cross-section spillway according to an embodiment of the present invention. Figure 5 This is a flowchart illustrating the design method of a drainage structure with a double vertical shaft and a double cross-section drainage channel according to an embodiment of the present invention.

[0023] In the diagram: 1: Water diversion channel; 2: First vertical shaft; 3: Horizontal connecting pipe; 31: Branch connecting pipe one; 32: Branch connecting pipe two; 33: Branch connecting pipe three; 4: Second vertical shaft; 5: Spillway; 51: Overflow weir; 52: Compound cross-section spillway section; 521: Semi-circular arc channel; 522: Trapezoidal channel; 523: Rectangular channel; 53: Flow-lifting nose sill; 6: Downstream river channel. Detailed Implementation

[0024] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0027] Please see Figure 1-5One embodiment of the double-shaft duplex cross-section spillway includes a cylindrical water diversion channel 1, a first vertical shaft 2, a transverse connecting pipe 3, a second vertical shaft 4, and a spillway 5, which are sequentially connected to an upstream reservoir. The spillway 5 is connected to a downstream river channel 6. Specifically, the upper part of the first vertical shaft 2 is connected to the downstream end of the water diversion channel 1, the upstream end of the transverse connecting pipe 3 is connected to the middle and lower part of the first vertical shaft 2, and the downstream end of the transverse connecting pipe 3 is connected to the middle and lower part of the second vertical shaft 4. The discharge channel 5 includes an overflow weir 51, a double-section discharge channel section 52, and a flow-lifting nose sill 53. The flow cross section of the double-section discharge channel section 52 is composed of a semi-circular arc channel 521, a trapezoidal channel 522, and a rectangular channel 523. The upstream end of the overflow weir 51 is connected to the upper part of the second vertical shaft 4. Preferably, the downstream end is connected to the upstream end of the double-section discharge channel section 52 via an inclined plane, and the downstream end of the double-section discharge channel section 52 is connected to the upstream end of the flow-lifting nose sill 53 via an inclined plane. The water flows through the flow-lifting nose sill 53 and is ejected into the downstream river channel 6.

[0028] The water flow from the upstream reservoir enters the first cylindrical vertical shaft 2 through the water diversion channel 1 in a horizontal swirling manner, so as to convert the horizontal momentum of the water flow into vertical momentum and improve the energy dissipation efficiency.

[0029] Preferably, the transverse connecting pipe 3 consists of multiple branch connecting pipes set at different elevations. For example, in one embodiment, it includes branch connecting pipe 1 31, branch connecting pipe 2 32 and branch connecting pipe 33 from top to bottom. The cross-sectional area of ​​the lower branch connecting pipe is not less than the cross-sectional area of ​​the upper branch connecting pipe. The total flow area of ​​the transverse connecting pipe 3 is not less than twice the cross-sectional area of ​​the first vertical shaft 2, so as to facilitate the smooth flow of water from the first vertical shaft 2 into the second vertical shaft 4 and significantly reduce the water flow rate.

[0030] Preferably, the cross-sectional area of ​​the second vertical shaft 4 is not less than the total flow area of ​​the transverse connecting pipe 3, so as to further reduce the water flow, adjust the water flow pattern, and maintain the stability of the water surface in the second vertical shaft 4.

[0031] Furthermore, the crest elevation of the overflow weir 51 is not lower than the top surface elevation of the uppermost branch connecting pipe of the transverse connecting pipe 3, ensuring that the transverse connecting pipe 3 is in a state of complete submersion and the water flow is pressurized.

[0032] Furthermore, the roughness of the semi-circular arc channel of the 52 flow section of the compound cross-section drainage channel... ≤ Trapezoidal channel roughness ≤Roughness of rectangular channel By finely adjusting the roughness of the channel wall, the difference in flow velocity at the exit sill is further reduced, allowing for more precise control of the water jet distance.

[0033] Furthermore, the cross-sectional area of ​​the semi-circular arc channel 521, the trapezoidal channel 522, and the rectangular channel 523 gradually increases.

[0034] Based on the same inventive concept, a design method for a drainage structure with a double vertical shaft and a double cross-section spillway is also provided, including: S1. Based on the engineering topography, geology, and hydrological conditions, determine the discharge flow rate Q, discharge drop Z, discharge channel width B, and discharge channel velocity V of the spillway structure in accordance with the design specifications. S2. Using a moderate flow rate as the calculation condition, preliminarily determine the angle θ of the sill and the head difference between the sill and the river surface. ; S3. Calculate the water jet distance according to the theoretical parabolic equation, and verify the positional relationship between the water jet landing point and the river centerline. If the water jet landing point deviates from the river centerline by more than ±5%, return to S2 and adjust the jet angle θ of the jet nose and the drop from the jet nose to the river water surface. At least one parameter in the parameters, until the point where the water tongue falls deviates from the center line of the river channel by no more than ±5%; S4. Assuming the water flow in the compound cross-section spillway is uniform, calculate the total drop of the compound cross-section spillway. Hydraulic gradient of the compound cross-section spillway section ,include: The basic dimensions of the semi-circular arc channel, trapezoidal channel and rectangular channel, as well as the comprehensive roughness n of the channel wall of the compound cross-section drainage section, were initially determined. Based on the discharge flow rate Q, the discharge channel velocity V, the discharge channel width B, the overflow weir flow coefficient m, and the velocity coefficient... Calculate the water level difference between the water surface in the second vertical shaft and the starting section of the compound spillway. :

[0035] Calculate the head loss along the flow path The water level difference in the double-section spillway section Calculated according to the Cheshire formula: ,in:

[0036] In uniform flow, the change in water potential energy is equal to the head loss along the flow path. The water level difference in the compound cross-section spillway section... for:

[0037] Total drop of the trough for:

[0038] Hydraulic gradient of the double-section spillway section for:

[0039] In the formula, V is the discharge channel velocity (m / s); Q is the discharge flow rate (m³ / s). 3 / s; L - length of the drain channel, m; A - flow area of ​​the drain channel, m² 2 P - Total wetted perimeter of the drain tank, P = P 1+ P2+...+P i ,m;P i - Wetted perimeter of the i-th morphological boundary segment of the spillway, m; R - Hydraulic radius, m; n - Overall roughness coefficient, n i - Roughness of the i-th morphological boundary segment of the groove; C - Chezy coefficient m - overflow weir flow coefficient, which can be found in the hydraulic calculation manual; - Flow velocity coefficient, taken as ; S5. Verify the calculated water jet distance. If the water jet landing point deviates from the river centerline by more than ±15%, adjust the basic dimensions of the semi-circular arc channel, trapezoidal channel, and rectangular channel, as well as at least one parameter of the comprehensive roughness n of the channel wall of the compound cross-section spillway section, until the water jet landing point deviates from the river centerline by no more than ±15%. S6. Calculate the total head of the vertical shaft water level. ,Right now:

[0040] S7. Determine the total head of the vertical shafts of the spillway structures. Total drop of the trough And the cross-sectional shape of the complex cross-section chute section.

[0041] Preferably, the overall roughness n of the channel wall in the compound cross-section drainage section is adjusted by adjusting the roughness of the semi-circular arc channel. Trapezoidal channel roughness and the roughness of rectangular channels Adjustment.

[0042] Examples and Comparative Examples A certain hydropower project has a bank-side spillway with a maximum discharge capacity of Q=2000 m³ / h. 3 / s, total head of flood discharge Z=100m, the spillway inlet adopts WES practical weir, the width of the spillway B=20m, the length L=1000m, and the angle of the spillway nose sill is 28°. The first vertical shaft is circular with a diameter of 20m~25m, the second vertical shaft is square with a side length of 30m, and the diameters of the transverse connecting pipes between the two vertical shafts are 20m, 15m and 15m respectively.

[0043] Comparative Example 1: Under the above conditions, when a conventional rectangular cross-section chute is used, the rectangular channel is 20.0m wide and 7.3m deep. The roughness of the compound cross-section chute section is 0.014. The hydraulic calculation results are shown in Table 1.

[0044] Example 1: When using the compound cross-section drainage channel of the present invention, the drainage channel cross-section consists of a semi-circular arc channel, a trapezoidal channel, and a rectangular channel. The semi-circular arc channel has a radius of 3.5m and a roughness coefficient of 0.014; the trapezoidal channel has a depth of 1.65m and bottom widths of 10.3m and 13.6m respectively, with a roughness coefficient of 0.014; the rectangular channel has a width of 20.0m, a depth of 2.15m, and a roughness coefficient of 0.014. The hydraulic calculation results are shown in Table 2.

[0045] Example 2: When using a compound cross-section drainage channel and adjusting the roughness of the semi-circular arc channel, trapezoidal channel, and rectangular channel, the radius of the semi-circular arc channel is 3.5m, and the roughness is 0.011; the depth of the trapezoidal channel is 1.65m, and the bottom widths are 10.3m and 13.6m respectively, with a roughness of 0.012; the width of the rectangular channel is 20.0m, the depth is 2.15m, and the roughness is 0.014. The hydraulic calculation results are shown in Table 3.

[0046] The calculation results show that: Comparative Example 1: The water jet distance deviated from -59.7% to 17.4%, and the flow velocity was 25.0 m / s to 52.6 m / s; Example 1: Water jet distance deviation -15.8% to 15.2%, flow velocity 26.0 m / s to 34.4 m / s; Example 2: Water tongue distance deviation -2.9% to 2.8%; flow velocity 26.0 m / s to 26.6 m / s.

[0047] It is evident that the hydraulic properties of the compound spillway cross section of the present invention are significantly superior to those of the conventional rectangular cross section. By adjusting the roughness of the semi-circular arc channel, trapezoidal channel and rectangular channel, the deviation of the water jet landing point from the center line at a moderate flow rate can be controlled to no more than ±15%.

[0048] Table 1. Calculation table of hydraulic parameters for the rectangular cross-section spillway in Comparative Example 1

[0049] Table 2 Calculation table of hydraulic parameters for the compound cross-section spillway in Example 1

[0050] Table 3 Calculation Table of Hydraulic Parameters for the Collateral Cross-Sectional Roughness Adjustment Channel in Example 2

[0051] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A drainage structure with a double vertical shaft and a compound cross-section drainage channel, characterized in that, include: The irrigation canal connects to the upstream reservoir; The first vertical shaft has a cylindrical cross-section. The upper part of the first vertical shaft is connected to the downstream end of the water diversion channel, and the lower part of the first vertical shaft is equipped with a horizontal connecting pipe. The second vertical shaft, with a square cross-section, is connected to the downstream end of the horizontal connecting pipe; The spillway includes an overflow weir, a double-section spillway section, and a sluice gate connected in sequence. The upstream end of the overflow weir is connected to the upper part of the second vertical shaft. The cross-section of the double-section spillway section includes a semi-circular arc channel, a trapezoidal channel, and a rectangular channel from bottom to top. Water flows from the upstream reservoir through the water diversion channel, the first vertical shaft, the second vertical shaft, and the double-section spillway, and finally is ejected from the sluice gate into the downstream river channel. The transverse connecting pipe is provided with multiple branch connecting pipes in the height direction, and the cross-sectional area of ​​the lower branch connecting pipe is not less than the cross-sectional area of ​​the upper branch connecting pipe. The elevation of the overflow weir crest shall not be lower than the elevation of the top surface of the uppermost branch connecting pipe of the transverse connecting pipe; In the flow section of the compound cross-section drain section, the roughness of the semi-circular arc channel is... ≤ Trapezoidal channel roughness ≤Roughness of rectangular channel ; The downstream end of the overflow weir is connected to the upstream end of the compound cross-section spillway section via an inclined plane, and the downstream end of the compound cross-section spillway section is connected to the upstream end of the spillway nose via an inclined plane. The cross-sectional area of ​​the semi-circular arc channel, trapezoidal channel, and rectangular channel gradually increases.

2. The drainage structure with a double vertical shaft and a compound cross-section drainage channel as described in claim 1, characterized in that, The cross-sectional area of ​​the second vertical shaft shall not be less than the total flow area of ​​the horizontal connecting pipe.

3. The drainage structure with a double vertical shaft and a compound cross-section drainage channel as described in claim 2, characterized in that, The total flow area of ​​the transverse connecting pipe shall not be less than twice the cross-sectional area of ​​the first vertical shaft.

4. A design method for a drainage structure with a double vertical shaft and a compound cross-section as described in any one of claims 1-3, characterized in that, include: S1. Based on the engineering topography, geology, and hydrological conditions, determine the discharge flow rate Q, discharge drop Z, discharge channel width B, and discharge channel velocity V of the spillway structure in accordance with the design specifications. S2. Using a moderate flow rate as the calculation condition, preliminarily determine the angle θ of the sill and the head difference between the sill and the river surface. ; S3. Calculate the water jet distance according to the theoretical parabolic equation, and verify the positional relationship between the water jet landing point and the river centerline. If the water jet landing point deviates from the river centerline by more than ±5%, return to S2 and adjust the jet angle θ of the jet nose and the drop from the jet nose to the river water surface. At least one parameter in the parameters, until the point where the water tongue falls deviates from the center line of the river channel by no more than ±5%; S4. Assuming the water flow in the compound cross-section spillway is uniform, calculate the total drop of the compound cross-section spillway. Hydraulic gradient of the compound cross-section spillway section ,include: The basic dimensions of the semi-circular arc channel, trapezoidal channel and rectangular channel, as well as the comprehensive roughness n of the channel wall of the compound cross-section drainage section, were initially determined. Based on the discharge flow rate Q, the discharge channel velocity V, the discharge channel width B, the overflow weir flow coefficient m, and the velocity coefficient... Calculate the water level difference between the water surface in the second vertical shaft and the starting section of the spillway. : Calculate the head loss along the flow path The water level difference in the double-section spillway section Calculated according to the Cheshire formula: ,in: In uniform flow, the change in water potential energy is equal to the head loss along the flow path. The water level difference in the compound cross-section spillway section... for: Total drop of the trough for: Hydraulic gradient of the double-section spillway section for: In the formula, V is the discharge channel velocity (m / s); Q is the discharge flow rate (m³ / s). 3 / s; L - length of the drain channel, m; A - flow area of ​​the drain channel, m² 2 P - Total wetted perimeter of the drain tank, P = P 1+ P2+...+P i ,m;P i - Wetted perimeter of the i-th morphological boundary segment of the spillway, m; R - Hydraulic radius, m; n - Overall roughness coefficient, n i - Roughness of the i-th morphological boundary segment of the groove; C - Chezy coefficient m - overflow weir flow coefficient, which can be found in the hydraulic calculation manual; - Flow velocity coefficient, taken as ; S5. Verify the calculated water jet distance. If the water jet landing point deviates from the river centerline by more than ±15%, adjust the basic dimensions of the semi-circular channel, trapezoidal channel, and rectangular channel, as well as at least one parameter of the comprehensive roughness n of the channel wall in the compound cross-section spillway section, until the water jet landing point deviates from the centerline by no more than ±15% compared to the landing point at medium flow rate. S6. Calculate the total head of water level in the vertical shaft. ,Right now: S7. Determine the total head difference of the vertical shaft water level in the spillway structure. Total drop of the trough And the cross-sectional shape of the complex cross-section chute section.

5. The design method for the drainage structure of the double-shaft duplex cross-section drainage channel according to claim 4, characterized in that, The adjustment of the overall roughness n of the channel wall in the compound cross-section discharge section is achieved through the semi-circular arc channel roughness. Trapezoidal channel roughness and the roughness of rectangular channels Adjustment.

Images