Stilling basin with heightened tail sill and underwater construction method

Abstract

According to the stilling pool with the heightened tail sill and the underwater construction method, the heightened tail sill is arranged on the downstream side of an original tail sill, the original tail sill is located on the downstream side of a dam and an apron, a tail sill top platform is arranged on the top of the heightened tail sill, and heightened side walls are arranged on the basis of original side walls on the outer sides of the two ends, in the transverse river direction, of the heightened tail sill; the slope ratio and the transverse river width of the heightened tail sill are kept consistent with the slope ratio and the transverse river width of the original tail sill; the length of the platform on the top of the tail sill in the river direction meets the requirement for arranging the movable flood control baffle and is used for temporarily retaining water when the stilling pool is overhauled. An arc-shaped chamfer is arranged at the turning position of the tail end of the tail sill top platform. On the premise that the construction quality is guaranteed, the engineering investment is saved, the original energy dissipation effect is not affected, and a dry land environment is provided for stilling pool maintenance.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic structure design and construction, and in particular relates to a stilling pool with a heightened tail sill and an underwater construction method. Background Art

[0002] The water flow from the discharge structure has a lot of mechanical energy, which will cause strong scouring on the riverbed. In order to reduce the damage of the water flow to the riverbed and the foundation of the building, energy dissipation and anti-scouring facilities are usually arranged downstream of the discharge structure. The energy dissipation pool is one of the widely used structures. During the operation, the energy dissipation pool is affected by hydraulic scouring, hard object wear, etc., and is prone to structural damage, so it needs regular maintenance.

[0003] Some new projects did not build maintenance cofferdams during the construction period due to tight construction schedules; some projects that have been in operation for many years have poor anti-seepage performance of maintenance cofferdams due to complex material sources and other reasons, resulting in leakage and other problems. The above reasons lead to some new or long-running projects being unable to provide effective dry land maintenance conditions for energy dissipation pools when they need maintenance. In addition, the construction of maintenance cofferdams has the disadvantages of long construction period, low reusability, and large project investment.

[0004] However, due to the tight construction schedule and the impending flood discharge of the flood discharge structure, the deep tailwater environment makes it difficult to drain the foundation pit, clean the foundation and compact the underwater concrete, which is prone to problems such as poor bonding between the new and old concrete surfaces and the foundation surface. How to raise the tail sill of the original energy dissipation pool through underwater construction technology in the case of deep tailwater, while ensuring the construction quality, saving project investment and not affecting the original energy dissipation effect, is a key technology in the design, construction and maintenance of hydraulic energy dissipation and anti-scouring structures. Summary of the invention

[0005] The first purpose of the present invention is to provide an energy dissipation pool with a raised tail sill, which provides a dry land maintenance environment for the energy dissipation pool without affecting the original energy dissipation effect, avoids the construction of a maintenance cofferdam during the maintenance period, and saves project investment.

[0006] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A stilling pool with a raised tail sill, which is arranged on the downstream side of a dam, comprises a guard tank and an original tail sill arranged in sequence, and is characterized in that a raised tail sill is arranged on the downstream side of the original tail sill, a tail sill top platform is arranged on the top of the raised tail sill, and raised side walls are respectively arranged on the outer sides of both ends of the transverse river of the raised tail sill.

[0008] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0009] As a preferred technical solution of the present invention: the heightened side wall is connected to the foundation of the original side wall.

[0010] As a preferred technical solution of the present invention: the slope ratio and the transverse width of the raised tail sill are respectively consistent with the slope ratio and the transverse width of the original tail sill.

[0011] As a preferred technical solution of the present invention: the length of the top platform of the tail sill in the river direction is sufficient to arrange a movable flood prevention baffle for temporarily blocking water during the maintenance of the energy dissipation pool.

[0012] As a preferred technical solution of the present invention: an arc chamfer is provided at the turning point of the tail sill top platform toward the end along the river.

[0013] As a preferred technical solution of the present invention: anchor piles are provided between the raised tail sill and the foundation.

[0014] Another object of the present invention is to provide an underwater construction method for raising the tail sill structure of the energy dissipation pool under deep tailwater conditions, so as to raise the original tail sill when the foundation pit is deeply flooded, thereby ensuring the construction quality and the strength and stability of the raised tail sill.

[0015] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0016] An underwater construction method for raising the tail sill structure of a stilling pool in deep tailwater conditions, characterized in that it comprises the following steps:

[0017] S1. Use a water pump to pump water from the foundation pit to lower the water level to below the elevation line of the underwater concrete top surface; perform underwater foundation cleaning on the foundation surface of the raised tail sill on the downstream side of the original tail sill, try to remove underwater blocks and silt, and ensure that the silt on the contact surface between the new and old concrete is removed;

[0018] S2. Use the conduit method to pour underwater concrete, ensuring that the conduit mouth is close to the contact surface of the new and old concrete and extends to the bottom of the silo under water-proof conditions. After the first batch of concrete reaches the bottom of the silo, the conduit should be buried in the concrete to a certain depth; during the pouring process, gradually lift the conduit so that the unremoved rocks and silt are squeezed and pushed by the concrete toward the temporary cofferdam on the downstream side; raise the height between the tail sill and the temporary cofferdam, and the part below the elevation line of the underwater concrete top surface is the underwater concrete overfill part; during the pouring process, ensure that the lower end of the conduit is always buried in the concrete;

[0019] S3. Pour normal concrete above the underwater concrete top elevation line;

[0020] S4. After pouring, the bonding quality between the newly poured concrete and the foundation should be checked. If the quality does not meet the requirements, consolidation grouting should be carried out after the underwater concrete has finally set, and anchor piles should be arranged using the grouting holes.

[0021] The present invention provides an energy dissipation pool with a raised tail sill and an underwater construction method. A raised tail sill is arranged on the downstream side of an original tail sill, the original tail sill is located on the downstream side of a dam and a protection tank, a tail sill top platform is arranged on the top of the raised tail sill, and raised side walls are arranged on the outer sides of the two ends of the raised tail sill in the transverse river direction on the basis of the original side walls; the slope ratio and the transverse river width of the raised tail sill are consistent with the slope ratio and the transverse river width of the original tail sill; the length of the tail sill top platform along the river direction meets the requirements for arranging a mobile flood control baffle, which is used for temporary water blocking during the maintenance of the energy dissipation pool; an arc chamfer should be arranged at the turning point of the tail sill top platform. The present invention can save engineering investment under the premise of ensuring construction quality, does not affect the original energy dissipation effect, and provides a dry land environment for the maintenance of the energy dissipation pool.

[0022] Specifically, the present invention has the following beneficial effects:

[0023] 1) The present invention eliminates the need to build temporary cofferdams during the maintenance of the stilling pool, thus saving engineering investment and construction period;

[0024] 2) By maintaining the original tail sill slope ratio and setting an arc chamfer at the turning point of the tail sill top platform, the water flow pattern and energy dissipation effect after the tail sill is raised can be ensured to avoid adverse effects on other buildings;

[0025] 3) By setting up a platform on the top of the tail sill, a space is provided for installing a mobile flood baffle, which can temporarily block water during the maintenance period, avoid excessive heightening of the tail sill, save engineering investment, and avoid excessive impact on the flow pattern;

[0026] 4) Through the construction and displacement of underwater pipes, underwater concrete overfill is generated to avoid the formation of weak structural surfaces due to silt between the underwater concrete and the foundation surface. Reinforcement measures such as consolidation grouting and anchor piles are adopted to ensure the strength and stability of the raised tail sill. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A structural diagram of the stilling pool with a raised tail sill provided by the present invention;

[0028] Figure 2 Details of the heightened tail sill, the tail sill top platform and the curved chamfer;

[0029] Figure 3 It is a diagram of the underwater construction process of the stilling pool tail sill heightening structure under deep tailwater conditions;

[0030] Figure 4 This is a structural diagram of another type of structure with a higher tail sill;

[0031] Figure 5 A photo of the flow pattern of the water flow behind the sill of the tail sill heightening structure provided by the present invention;

[0032] Figure 6This is a photo of the flow pattern of water behind the sill of another type of tail sill heightening structure;

[0033] The figure shows: 1-dam; 2-tank protection; 3-original tail sill; 4-raised tail sill; 5-top platform of tail sill; 6-raised side wall; 7-arc chamfer; 8-temporary cofferdam; 9-contact surface between new and old concrete; 10-elevation line of underwater concrete top surface; 11-underwater concrete overfill part; 12-anchor piles. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1-Figure 2 As shown, an energy dissipation pool with a raised tail sill is arranged on the downstream side of a dam 1, and includes a protective tank 2 and an original tail sill 3 arranged in sequence, a raised tail sill 4 is arranged on the downstream side of the original tail sill 3, a tail sill top platform 5 is arranged on the top of the raised tail sill 4, and raised side walls 6 are respectively arranged on the outer sides of both ends of the transverse river of the raised tail sill 4.

[0036] The heightened side wall 6 is connected to the foundation of the original side wall.

[0037] The slope ratio and the width in the transverse direction of the raised tail sill 4 are kept consistent with the slope ratio and the width in the transverse direction of the original tail sill 3.

[0038] The length of the platform 5 at the top of the tail sill in the river direction is sufficient to arrange a mobile flood prevention baffle for temporarily blocking water during the maintenance of the stilling pool.

[0039] An arc chamfer 7 is provided at the turning point of the tail sill top platform 5 along the river to the end.

[0040] Anchor piles 12 are provided between the raised tail sill 4 and the foundation.

[0041] like Figure 3 As shown, an underwater construction method for raising the tail sill structure of a stilling pool in deep tailwater conditions comprises the following steps:

[0042] S1. Use a water pump to pump water from the foundation pit to lower the water level to below the underwater concrete top surface elevation line 10; perform underwater foundation cleaning on the foundation surface of the elevated tail sill 4 on the downstream side of the original tail sill 3, try to remove underwater blocks and silt, and ensure that the silt on the contact surface 9 of the new and old concrete is removed;

[0043] S2. Use the conduit method to pour underwater concrete, ensuring that the conduit mouth is close to the contact surface 9 of the new and old concrete and extends to the bottom of the warehouse under the condition of water isolation. After the first batch of concrete reaches the bottom of the warehouse, the conduit should be buried in the concrete to a certain depth; during the pouring process, gradually lift the conduit so that the blocks and silt that have not been removed are squeezed and pushed by the concrete toward the temporary cofferdam 8 on the downstream side; raise the height between the tail sill 4 and the temporary cofferdam 8, and the underwater concrete top surface elevation line 10 is below the underwater concrete overfill part 11; during the pouring process, ensure that the lower end of the conduit is always buried in the concrete;

[0044] S3, pouring normal concrete above the elevation line 10 of the underwater concrete top surface;

[0045] S4. After pouring, the bonding quality between the newly poured concrete and the foundation should be checked. If the quality does not meet the requirements, consolidation grouting should be carried out after the underwater concrete has finally set, and anchor piles 12 should be arranged using the grouting holes.

[0046] In addition, the inventors also compared the structure type of the energy dissipation pool tail sill heightening provided by the present invention (hereinafter referred to as type I) with another structure type of tail sill heightening (hereinafter referred to as type II), such as Figure 4 As shown in the red part in the middle, Type II is vertically elevated, with the original tail sill connected to a reverse slope.

[0047] Through hydraulic model tests, a comparative study of the two tail sill heightening types was conducted. After comparative analysis of test data such as flow patterns, pressure distribution, velocity distribution, water surface line, water surface fluctuation, and riverbed scour in the stilling pool and downstream river under typical test conditions, it was found that:

[0048] Adopting (Type I) the 1:2 slope heightening scheme along the original scoop sill, under the appropriate sill top elevation, the dynamic water pressure in the scoop sill, the fluctuation of the tailwater level of the scoop sill and the power station are relatively close to the original scoop sill elevation design, and the water flow pattern is as follows: Figure 5 shown.

[0049] When the tail sill is vertically raised and then connected to the reverse slope (Type II), the vertical sill has a significant effect of raising the water level of the scoop pool. The water surface drops sharply behind the sill, forming secondary energy dissipation in the apron area. The water flow pattern is as follows: Figure 6 The water tongue at the bottom hole outlet was completely submerged below the water surface at the tail sill outlet of the scoop pool, and the water surface at the bottom hole outlet rolled over the side wall and overflowed to the side of the power plant building, seriously affecting the outflow of the bottom hole and endangering the safety of the power plant building.

[0050] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A stilling pool with a raised tail sill, the stilling pool is arranged at the downstream side of the dam, comprising a guard tank (2) and an original tail sill (3) arranged in sequence, characterized in that: A raised tail sill (4) is arranged on the downstream side of the original tail sill (3), a tail sill top platform (5) is arranged on the top of the raised tail sill (4), and raised side walls (6) are respectively arranged on the outer sides of both ends of the raised tail sill (4).

2. The stilling pool with elevated tail sill according to claim 1, characterized in that: The heightened side wall (6) is connected to the foundation of the original side wall.

3. The stilling pool with elevated tail sill according to claim 1, characterized in that: The slope ratio and transverse width of the raised tail sill (4) are respectively consistent with the slope ratio and transverse width of the original tail sill (3).

4. The stilling pool with elevated tail sill according to claim 1, characterized in that: The length of the tail sill top platform (5) along the river is sufficient for arranging a movable flood prevention baffle.

5. The stilling pool with elevated tail sill according to claim 1, characterized in that: An arc chamfer (7) is provided at the turning point of the tail sill top platform (5) toward the end along the river.

6. The stilling pool with elevated tail sill according to claim 1, characterized in that: Anchor piles (12) are provided between the elevated tail sill (4) and the foundation.

7. An underwater construction method for raising the tail sill structure of a stilling pool in deep tailwater conditions, characterized in that: The steps include: S1. Use a water pump to pump water from the foundation pit to lower the water level to below the underwater concrete top surface elevation line (10); perform underwater foundation cleaning on the foundation surface of the raised tail sill (4) on the downstream side of the original tail sill (3), remove underwater rocks and silt, and ensure that the silt on the contact surface (9) between the new and old concrete is removed; S2. Use the conduit method to pour underwater concrete, ensuring that the conduit opening is close to the contact surface (9) of the new and old concrete and extends to the bottom of the silo under water-proof conditions. After the first batch of concrete reaches the bottom of the silo, the conduit should be buried in the concrete to a certain depth; during the pouring process, gradually lift the conduit so that the rocks and silt that have not been removed are squeezed and pushed by the concrete toward the temporary cofferdam (8) on the downstream side; raise the height between the tail sill (4) and the temporary cofferdam (8), and the underwater concrete top surface elevation line (10) is below the underwater concrete overfill part (11); during the pouring process, ensure that the lower end of the conduit is always buried in the concrete; S3, pouring normal concrete above the underwater concrete top elevation line (10); S4. After pouring, the bonding quality between the newly poured concrete and the foundation should be checked. If the quality does not meet the requirements, consolidation grouting should be carried out after the underwater concrete has finally set, and anchor piles (12) should be arranged using the grouting holes.

Images