Tail widening type step flood discharge tunnel

Abstract

The utility model belongs to the technical field of water conservancy and hydropower engineering, and discloses a tail widening type step flood discharge tunnel which comprises a conventional section, a transition section and a widening section, the conventional section and the widening section are in transition connection through the transition section, each section is composed of a straight wall, a bottom plate and a vault, the bottom plate of the conventional section is a smooth section bottom plate, and the bottom plate of the widening section is a flat section bottom plate. The bottom plates of the transition section and the widening section are energy dissipation section bottom plates, and the energy dissipation section bottom plates are arranged at the tail of the flood discharge tunnel and composed of a plurality of steps connected end to end. According to the utility model, the energy dissipation effect is improved, and the investment cost is saved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of water conservancy and hydropower engineering, and particularly relates to a tail part widening type stepped flood discharge tunnel. BACKGROUND

[0002] The construction of the reservoir area of a pumped storage power station project blocks the flood discharge route of the original mountain torrent, and the mountain torrent has a high sediment content. In order to prevent the flood from entering the reservoir, a flood discharge tunnel is often built to discharge the flood from the flood discharge tunnel to the downstream. These flood discharge tunnels are characterized by large drop and long distance. Taking the flood discharge tunnels of two in-construction pumped storage power stations in Gansu as examples, the drop of the flood discharge tunnel of A power station is 102 m, and the length of the tunnel is 860 m. The drop of the flood discharge tunnel of B power station is 152 m, and the length of the tunnel is 979 m. It is difficult to dissipate the energy by means of a downstream stilling basin due to such a large drop, and therefore, a stepped energy dissipation structure needs to be arranged in the tunnel to reduce the flow velocity at the outlet of the tunnel.

[0003] Research shows that the energy dissipation effect of the stepped energy dissipation structure is most affected by the single-width flow (flow / drainage width). The larger the single-width flow, the worse the energy dissipation effect. For example, the width of the flood discharge tunnel of B power station is 3.5 m, the single-width flow is about 29 m 2 / s, and the energy dissipation effect is not good. Therefore, the width needs to be increased to 6 m, the single-width flow is about 17 m 2 / s. Increasing the width of the nearly-kilometer-long tunnel requires a large investment cost, which is not in line with the concept of "building a quality project". How to improve the energy dissipation effect while saving costs is a problem that needs to be solved for this type of project.

[0004] Through model test research on the flood discharge tunnels of A and B power stations, it is found that the water flow through the steps can form uniform flow after about 100 m, that is, after the flow velocity is reduced to a certain speed, the gravitational potential energy makes the flow velocity increase, and the effect of friction and air entrainment energy dissipation makes the flow velocity decrease, so that the flow velocity is maintained stable. The flow velocity at the outlet of the tunnel is the same when longer steps are arranged or 100 m steps are arranged. Based on this, the utility model provides a tail part widening type stepped flood discharge tunnel.

[0005] Chinese patent application "CN217710604U" discloses a gradually expanding stepped spillway, which comprises a gentle chute section, a apron section and a steep slope gradually expanding section. The gentle chute section is an inclined chute structure with gentle slope. The steep slope gradually expanding section comprises a plurality of gradually expanding sections. Each gradually expanding section comprises a gradually expanding section bottom plate, gradually expanding section side walls and a plurality of gradually expanding section steps arranged on the gradually expanding section bottom plate. The gradually expanding section side walls are fixed on the gradually expanding section bottom plate, and the gradually expanding section side walls form a gradually expanding flow channel with small upper part and large lower part between the two gradually expanding section side walls. The upstream end of the gradually expanding flow channel is equal in width to the downstream end of the adjacent gradually expanding flow channel upstream, and the downstream end of the gradually expanding flow channel is equal in width to the upstream end of the adjacent gradually expanding flow channel downstream. The gradually expanding flow channels of adjacent gradually expanding sections are connected to form a gradually expanding spillway flow channel which connects the gentle chute section at the upper end and the apron section at the lower end. The spillway structure of the utility model is simple, has excellent energy dissipation effect, and greatly facilitates construction.

[0006] But the application still has certain limitations: the application is suitable for general spillway because the spillway is short, so for the long flood drainage tunnel of nearly one thousand meters, the full width expansion and the full step laying increase the investment cost, and the auxiliary energy dissipater is not suitable for the mountain flood drainage tunnel with large stone particle size and high silt content (the stone will hit the energy dissipater). Practical new type content

[0007] The tail part expansion type step flood drainage tunnel improves the energy dissipation effect and saves the investment cost.

[0008] To achieve the above object, the practical new type adopts the following technical scheme:

[0009] A tail part expansion type step flood drainage tunnel, comprising a conventional section, a gradual change section and an expansion section, the conventional section and the expansion section are connected through the gradual change section, each section is composed of a straight wall, a bottom plate and an arch top, the bottom plate of the conventional section is a smooth section bottom plate, the bottom plates of the gradual change section and the expansion section are energy dissipation section bottom plates, the energy dissipation section bottom plate is arranged at the tail part of the flood drainage tunnel, and the energy dissipation section bottom plate is composed of a plurality of steps connected in head-tail mode.

[0010] Preferably, the steps are arranged only within a range of 100 m at the end of the flood drainage tunnel.

[0011] Preferably, the step size gradually transitions to the designed standard size from small to large in the direction from the gradual change section to the expansion section.

[0012] Preferably, the width of the expansion section is designed according to the single-width flow, and the single-width flow is less than 20 m / s. 2 / s.

[0013] The practical new type has the following beneficial effects:

[0014] (1) Compared with the flood drainage tunnel without expansion and with large single-width flow, the energy dissipation effect is improved;

[0015] (2) Compared with the flood drainage tunnel with full width and small single-width flow, the investment cost is saved;

[0016] (3) The steps are arranged only within a range of 100 m at the end of the outlet, and the step engineering quantity of several hundred meters is reduced. DRAWINGS

[0017] Fig. 1 It is a top view of the practical new type.

[0018] Fig. 2 It is a side view of the practical new type.

[0019] Fig. 3 This is a cross-sectional view of the present invention.

[0020] In the diagram: 1. Straight wall; 2. Base plate; 3. Arch; 4. Regular section; 5. Gradual section; 6. Widening section; 21. Smooth section base plate; 22. Energy dissipation section base plate; B1 is the width of the regular section; B2 is the width of the widening section; θ is the diffusion angle of the gradual section; H is the height of the straight wall. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0022] like Figs. 1-3 As shown, a tail-widening stepped flood discharge tunnel includes three sections: a conventional section 4, a transition section 5, and a widening section 6. The conventional section 4 and the widening section 6 are connected by the transition section 5. Each section consists of a straight wall 1, a base plate 2, and an arch 3. The straight wall 1 and the base plate 2 are set vertically, and the arch 3 is set on top of the straight wall 1. The base plate 2 of the conventional section 4 is a smooth section base plate 21, and the base plate 2 of the transition section 5 and the widening section 6 is an energy dissipation section base plate 22. The energy dissipation section base plate 22 is arranged at the tail of the flood discharge tunnel and is composed of numerous steps connected end to end.

[0023] The steps are arranged on the transition section 5 and the widening section 6. Through experimental research, the steps of the flood discharge tunnel are only arranged within 100m of the end of the flood discharge tunnel, that is, the horizontal length of the transition section 5 and the widening section 6 is about 100m. The diffusion angle θ of the transition section 5 should be less than 3°.

[0024] The step size gradually transitions from small to large in the direction from the transition section 5 to the widening section 6, thus improving the flow pattern.

[0025] The size of the steps arranged on the widening section 6 is fixed and can be determined through experimental research. Generally, the step height is about 0.6m. The size of the steps arranged on the transition section 5 gradually increases from small to large. This avoids the high-speed water flow on the bottom plate 21 of the smooth section from directly encountering large-sized steps without being reduced, which would cause severe splashing and poor flow. The gradual transition from small to large can effectively avoid splashing and improve the flow.

[0026] The width B1 of the standard section 4 and the height H of the straight wall 1 are designed according to the relevant design specifications for spillway structures, only needing to meet the flow capacity. The width B2 of the widened section 6 is designed based on the unit width flow rate, aiming to make the unit width flow rate q less than 20 m³ / h. 2 / s (unit width flow rate q equals discharge Q / width B2), after the width B2 is determined, the height H of the straight wall 1 is determined according to the water surface line after the energy dissipation of the steps (the flow velocity decreases and the water depth increases).

[0027] Because of the width of the widening section 6, the single-width flow q is small, and the step energy dissipation effect is obviously improved.

Claims

1. A tail-widened stepped flood discharge tunnel, characterized in that, It includes three sections: a regular section, a transition section, and a widening section. The regular section and the widening section are connected by the transition section. Each section consists of a straight wall, a base plate, and an arch. The base plate of the regular section is a smooth section base plate, and the base plates of the transition section and the widening section are energy dissipation section base plates. The energy dissipation section base plates are located at the tail of the flood discharge tunnel and are composed of numerous steps connected end to end.

2. The tail-widened stepped flood discharge tunnel according to claim 1, characterized in that, The steps are only located within 100m of the end of the drainage tunnel.

3. The tail-widened stepped flood discharge tunnel according to claim 1, characterized in that, The dimensions of the steps gradually transition from small to large in the direction from the transition section to the widening section, eventually reaching the designed standard dimensions.

4. The tail-widened stepped flood discharge tunnel according to claim 1, characterized in that, The width of the widened section is designed based on the unit width flow rate, which is less than 20m³ / h. 2 / s.

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