A system and method for staged removal of sediment and silt for a side-in / side-out water intake in a canyon-type riverbed

Abstract

The application provides a kind of suitable for canyon type riverbed side type water inlet / outlet grading dredging and desilting system and method, including primary desilting structure and secondary dredging facilities;The primary desilting structure is arranged in the lower reservoir river channel section position between the lower reservoir dam and the lower reservoir sand dam, and the section side is the rear slope of the water inlet / outlet, and the other side is the opposite bank slope;The secondary dredging facilities are used to process the silt accumulated in the front pool and the reverse slope section due to the over-standard flood. In the direction from the rear slope to the opposite bank slope, it includes side type water inlet / outlet, front pool, reverse slope section, sand dam and desilting channel in turn. The primary desilting structure is used to dredge the silt of the frequently encountered flood;The application effectively solves the silt accumulation problem of the front edge and the reverse slope section of the side type water inlet / outlet of the canyon type riverbed through the grading management mode of "structure sand blocking and guiding as the main, mechanical dredging as the auxiliary", and ensures the safety and reliability of long-term operation.

Description

Technical Field

[0001] This invention belongs to the technical field of water conservancy and hydropower engineering facilities, specifically relating to a graded dredging and sand removal system and method suitable for side-mounted inlets / outlets of canyon-type riverbeds. Background Technology

[0002] As crucial nodes in the water conveyance system of pumped storage power stations, the inlet / outlet plays a vital role in regulating the flow patterns of incoming and outgoing water, ensuring a smooth transition of water flow, and facilitating efficient energy conversion. This structure primarily exists in two typical forms: side-mounted and well-mounted. It is generally located at the head of the water intake system and the front of the tailrace system, and has significant engineering value in ensuring the overall operational efficiency of the water conveyance line.

[0003] Side-mounted inlets / outlets offer advantages such as convenient construction, low head loss, and stable flow conditions due to their proximity to the reservoir bank. However, because they directly connect to the natural riverbed, they are more susceptible to sediment transport in narrow hydraulic conditions such as canyon-type riverbeds, leading to continuous siltation at the inlet's leading edge and severely impacting flow capacity and operational safety. Traditional engineering often employs a front-mounted reverse-slope silt-trapping structure to initially intercept coarse-grained sediment through elevation differences. While effective for a certain period, this design has significant limitations in long-term operation: firstly, continuous siltation in front of the silt forms permanent sediment bodies, reducing the effective sediment discharge volume year by year; secondly, fine suspended sediments are prone to seepage around the silt under turbulent flow, affecting structural durability.

[0004] To address the aforementioned issues, existing design approaches often face a dilemma: if only flood defenses are designed according to the standards for common floods, the influx of sediment from floods exceeding the standard will cause severe siltation risks; on the other hand, comprehensively raising the design standards will lead to larger-scale projects, a surge in investment, and economic waste. Therefore, finding effective solutions to these problems is of great significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a graded dredging and sand removal system and method suitable for side-mounted inlets / outlets in canyon-type riverbeds, which can effectively solve the above-mentioned problems.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a graded dredging and sediment removal system suitable for side-mounted inlets / outlets of canyon-type riverbeds, including a primary sediment removal structure;

[0008] The primary sediment discharge structure is located at the cross-section of the lower reservoir river channel between the lower reservoir dam and the lower reservoir sediment control dam. One side of the cross-section is the rear slope of the inlet / outlet, and the other side is the opposite bank slope (6). In the direction from the rear slope to the opposite bank slope (6), it includes the side inlet / outlet (1), the forebay (2), the reverse slope section (3), the sediment control embankment (4), and the sediment discharge channel (5).

[0009] The side inlet / outlet (1) is located on the side away from the back slope, and the bottom elevation of the front pool (2) is lower than the bottom elevation of the side inlet / outlet (1), forming a sedimentation zone; the left slope bottom of the reverse slope section (3) overlaps with the right bottom of the front pool (2); the reverse slope section (3) is an upward sloping surface from left to right in the cross-section of the lower reservoir channel, and the right slope top of the reverse slope section (3) is close to the opposite bank slope (6) and near the lower reservoir. Water surface line; the sand-blocking embankment (4) is set along the longitudinal direction of the river channel at the right slope top edge of the reverse slope section (3); the sand-blocking embankment (4) and the opposite bank slope (6) form the sand-discharging channel (5), the sand-discharging channel (5) is set along the longitudinal direction of the river channel, and its front and rear ends are connected to the lower reservoir sand-blocking dam and the lower reservoir river-blocking dam respectively; the elevation of the sand-discharging channel (5) is level with the bottom of the reservoir downstream of the lower reservoir sand-blocking dam and the bottom of the reservoir upstream of the lower reservoir river-blocking dam.

[0010] Furthermore, the side inlet / outlet (1) is located in a natural deep and narrow riverbed formed by the compression of the mountains on both sides.

[0011] Furthermore, the side inlet / outlet (1) is constructed of reinforced concrete and, in the direction of water flow from the opposite bank slope (6) to the rear slope, includes, in sequence, an anti-vortex beam section (101), an adjustment section (102), a diffusion section (103), and a gate well section (104) that are connected end to end.

[0012] The anti-vortex beam section (101) and the adjustment section (102) are constant cross-section water pipelines along the direction of water flow; the diffuser section (103) is a variable cross-section water pipeline with a gradually decreasing cross-section along the direction of water flow, and its cross-sectional dimensions are the same as those of the adjustment section (102) and the diffuser section (103); the gate well section (104) is a constant cross-section water pipeline along the direction of water flow, and its cross-sectional dimensions are the same as those of the diffuser section (103) and the gate well section (104).

[0013] Furthermore, two side-mounted inlets / outlets (1) are arranged side by side, and the right ends of the two side-mounted inlets / outlets (1) are connected to the forebay (2); the left ends of the two side-mounted inlets / outlets (1) are connected to form a whole through the gate well platform (12);

[0014] There is a gap between the two side inlets / outlets (1); along the center line of the gap, from the forebay (2) to the gate well platform (12), there are in sequence a trash rack maintenance platform (9), a trash rack connecting bridge (10) and a slope (11) below the gate well platform.

[0015] Furthermore, the forebay (2) is a rectangular reinforced concrete structure with a bottom plate thickness of 250mm; the elevation difference between the bottom elevation of the forebay (2) and the bottom plate elevation of the side inlet / outlet (1) is 1.5~2.5 meters.

[0016] Furthermore, the excavation slope ratio of the reverse slope section (3) is 1:4, and the slope ratio of the excavation slopes on both sides is 1:1.2; the sand retaining wall (4) is a truncated concrete structure with a top width of 1 meter and a height of 2.5~3 meters; the sand discharge channel (5) is 10 meters wide, and a layer of cement mortar (7) with a thickness of not less than 5 cm is laid at the bottom as a leveling layer.

[0017] Furthermore, it also includes secondary dredging facilities; the secondary dredging facilities include dredging devices, long-distance sand discharge pipelines (14) and short-distance sand discharge pipelines (15).

[0018] The dredging device is a cutter suction dredger, used to agitate the silt and sand accumulated in the forepool (2) and the reverse slope section (3) to form mud;

[0019] The laying path of the short-distance sand discharge pipeline (15) is as follows: on the slope surface of the reverse slope section (3), it is laid in a serpentine manner from the top of the slope to the bottom of the slope; then it reaches the forepool (2), after passing the bottom of the forepool (2), it reaches the trash rack maintenance platform (9), and after passing the trash rack connecting bridge (10), it is laid in a straight line on the slope surface of the side slope (11) below the gate well platform, and it reaches the gate well platform (12) the closest.

[0020] The laying path of the long-distance sand discharge pipeline (14) is as follows: it is laid in a straight line at the bottom of the forebay (2) to the bottom of the reverse slope section (3), and then laid in a serpentine pattern from the bottom to the top of the slope on the slope surface of the reverse slope section (3). Then, it passes through the left shoulder of the lower reservoir sand-blocking dam from the top of the reverse slope section (3), and is laid along the reservoir surface of the lower reservoir sand-blocking dam, finally reaching the top of the lower reservoir sand-blocking dam.

[0021] The present invention also provides a dredging and sand removal method applicable to a graded dredging and sand removal system for a canyon-type riverbed side-mounted inlet / outlet, including a primary sand removal method and a secondary dredging method;

[0022] Step S1, Primary Sand Removal Method:

[0023] Step S101: When the lower reservoir is in the pumping state, the water stored in the lower reservoir dam and the lower reservoir silt barrier is collected and flows into the silt discharge channel (5) under the action of the topography. Under the interception of the silt barrier (4), the main sediment in the water is blocked in the silt discharge channel (5).

[0024] In step S102, water containing a small amount of sediment flows into the reverse slope section (3) after crossing the sand-blocking embankment (4); after the deceleration and energy dissipation of the reverse slope section (3), a small amount of sediment is deposited on the slope surface of the reverse slope section (3);

[0025] In step S103, after the action of the reverse slope section (3), the water containing a small amount of silt flows into the forepool (2), and the forepool (2) removes the small amount of silt in the water by sedimentation;

[0026] After removing silt, the water flows into the side inlet / outlet (1) and is transported to the upper reservoir by the action of the turbine to complete the pumping operation.

[0027] Step S104: When replenishing water in the lower reservoir, the water in the lower reservoir's sand-blocking dam flows into the lower reservoir through the sand-blocking dam. During the water flow, the sediment deposited in the sand discharge channel (5) is flushed and the sediment is directed to the bottom of the lower reservoir's dam to ensure that there is no sediment at the front edge of the sand-blocking sill (4) when pumping water.

[0028] Step S2, Secondary Dredging Method:

[0029] Step S201: When the siltation thickness in the front pool (2) and the reverse slope section (3) exceeds the design standard of the primary sand discharge structure, the dredging device is activated to agitate the siltation in the front pool (2) and the reverse slope section (3) to form mud.

[0030] In step S202, the mud is discharged to the design location through a long-distance sand discharge pipeline (14) and / or a short-distance sand discharge pipeline (15) under the action of the pump.

[0031] Furthermore, the short-distance sand discharge pipeline (15) is used to discharge sand in the following way: the mud in the reverse slope section (3) and the forebay (2) area is discharged to the gate well platform (12) through the sand discharge pipeline, and then transported out by vehicles at the gate well platform (12);

[0032] The long-distance sand discharge pipeline (14) is used to discharge sand in the following way: the mud in the forebay (2) and the mud in the reverse slope section (3) are discharged into the top of the sand-blocking dam of the lower reservoir through the sand discharge pipeline, and then transported out by vehicles at the top of the sand-blocking dam of the lower reservoir.

[0033] Furthermore, the initiation velocity of sediment in front of the sand-retaining embankment (4) and sediment starting particle size It has the relation (1):

[0034] (1)

[0035] in: , These are the densities of water and sediment, respectively. The initiating particle size of the sediment; It is the acceleration due to gravity; The water depth inside the sand discharge channel (5);

[0036] The flow velocity at the front section of the sand-blocking embankment (4) is used as the starting velocity of the sediment flow in the sand discharge channel (5). Based on relation (1), the initiation particle size of sediment was calculated. Therefore, when the actual sediment particle size at the bottom of the reservoir is larger than the initial sediment particle size... This indicates that the sediment will not cross the sand-retaining sill (4) and enter the reverse slope section (3) and the forebay (2), and the sand-retaining sill (4) is reasonably set. Therefore, the sand-retaining sill (4) on the outer edge of the side inlet / outlet (1) should be designed so that the flow velocity in front of the sill is lower than the starting flow velocity of the sediment at the bottom of the reservoir. This will enable the sand removal channel (5) to effectively remove sand.

[0037] The present invention provides a graded dredging and sediment removal system and method suitable for side-mounted inlets / outlets in canyon-type riverbeds, which has the following advantages:

[0038] This invention effectively solves the problem of sediment accumulation at the front edge and reverse slope of the side inlet / outlet of canyon-type riverbeds by adopting a graded treatment model of "structural sand interception as the main method and mechanical dredging as the auxiliary method", thus ensuring the safety and reliability of its long-term operation. Attached Figure Description

[0039] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic plan view of a graded dredging and sand removal system for side-mounted inlets / outlets of canyon-type riverbeds according to the present invention;

[0041] Figure 2 This is a partially enlarged view of the sand discharge channel profile of a graded dredging and sand discharge system for side-mounted inlets / outlets of canyon-type riverbeds according to the present invention.

[0042] Figure 3 This is a schematic diagram of a long-distance dredging and sand removal method applicable to side-type inlets / outlets of canyon-type riverbeds according to the present invention;

[0043] Figure 4 This is a schematic diagram of a short-distance dredging and sand removal method applicable to side-mounted inlets / outlets of canyon-type riverbeds according to the present invention;

[0044] The components are as follows: 1---Side inlet / outlet; 2---Forebay; 3---Reverse slope section; 4---Sediment trap; 5---Sediment discharge channel; 6---Opposite bank slope; 7---Cement mortar; 8---Excavation boundary line; 9---Trash rack maintenance platform; 10---Trash rack connecting bridge; 11---Slope below gate well platform; 12---Gate well platform; 13---Riverbed surrounding rock; 14---Long-distance sediment discharge pipeline; 15---Short-distance sediment discharge pipeline; 16---Water level line; 101---Anti-vortex beam section; 102---Adjustment section; 103---Diffusion section; 104---Gate well section;

[0045] The arrows indicate the direction of the dredging operation. Detailed Implementation

[0046] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0047] This invention provides a graded dredging and sediment removal system and method suitable for side-mounted inlets / outlets of canyon-type riverbeds. It is a graded dredging and sediment removal system adapted to the characteristics of canyon-type riverbeds. By combining sediment removal facilities with measures to clean up siltation exceeding the standard, it takes into account both engineering economy and operational reliability.

[0048] Specifically, this invention is a graded dredging and sediment removal system and method applicable to side-mounted inlets / outlets of canyon-type riverbeds. Based on optimizing the sediment-trapping structure, it introduces the concept of graded treatment and constructs a sediment control system that mainly relies on structural sediment trapping and is supplemented by mechanical dredging. This forms an efficient and economical dredging and sediment removal scheme throughout the entire life cycle, providing a reliable guarantee for the long-term safe and stable operation of pumped storage power stations.

[0049] This invention provides a graded dredging and sediment removal system suitable for side-mounted inlets / outlets of canyon-type riverbeds, including a primary sediment removal structure. The primary sediment removal structure achieves graded sediment removal from the side-mounted inlets / outlets through the coordinated operation of various components based on elevation differences and spatial structures.

[0050] See Figures 1 to 4 The primary sediment discharge structure is located at the cross-section of the lower reservoir river channel between the lower reservoir dam and the lower reservoir sediment control dam. One side of the cross-section is the rear slope of the inlet / outlet, and the other side is the opposite bank slope 6. In the direction from the rear slope to the opposite bank slope 6, it includes, in sequence, a side inlet / outlet 1, a forebay 2, a reverse slope section 3, a sediment control embankment 4, and a sediment discharge channel 5.

[0051] The side-type inlet / outlet 1 is located in a natural deep and narrow river channel formed by the compression of the mountains on both banks. The forebay 2 is set on the side away from the back slope. The bottom elevation of the forebay 2 is lower than the bottom elevation of the side-type inlet / outlet 1, forming a sedimentation zone. The left slope bottom of the reverse slope section 3 overlaps with the right bottom of the forebay 2. The reverse slope section 3 is an upward sloping surface from left to right in the cross-section of the lower reservoir river channel. The right slope top of the reverse slope section 3 is close to the opposite bank slope 6 and close to the water surface line of the lower reservoir. The sand-retaining embankment 4 is installed along the longitudinal direction of the river channel at the top edge of the side slope to prevent sediment from being transported towards the side inlet / outlet 1. The sand-retaining embankment 4 and the opposite bank slope 6 form the sand-discharging channel 5, which is installed along the longitudinal direction of the river channel and is connected to the lower reservoir sand-retaining dam and the lower reservoir river-blocking dam at its front and rear ends, respectively. The elevation of the sand-discharging channel 5 is level with the bottom of the reservoir downstream of the lower reservoir sand-retaining dam and the bottom of the reservoir upstream of the lower reservoir river-blocking dam. The sand-discharging channel 5 is used to guide the deposited sediment to the bottom of the lower reservoir river-blocking dam.

[0052] In this invention, as a specific implementation structure, the side inlet / outlet 1 is constructed of reinforced concrete and, in the direction of water flow from the opposite bank slope 6 to the rear slope, sequentially includes an anti-vortex beam section 101, an adjustment section 102, a diffusion section 103, and a gate well section 104 connected end to end.

[0053] The anti-vortex beam section 101 and the adjustment section 102 are constant cross-section water conveyance pipelines along the direction of water flow; the diffuser section 103 is a variable cross-section water conveyance pipeline with a gradually decreasing cross-section along the direction of water flow, and its cross-sectional dimensions are the same as those of the adjustment section 102 and the diffuser section 103; the gate well section 104 is a constant cross-section water conveyance pipeline along the direction of water flow, and its cross-sectional dimensions are the same as those of the diffuser section 103 and the gate well section 104.

[0054] As a preferred embodiment, two side-mounted inlets / outlets 1 are arranged side by side, and the right ends of both side-mounted inlets / outlets 1 are connected to the forebay 2; the left ends of the two side-mounted inlets / outlets 1 are connected to form a whole through a gate well platform 12.

[0055] There is a gap between the two side inlets / outlets 1; along the center line of the gap, from the forebay 2 to the gate well platform 12, there are sequentially a trash rack maintenance platform 9, a trash rack connecting bridge 10, and a slope 11 below the gate well platform.

[0056] In this invention, as a specific implementation structure, the forebay 2 is a rectangular reinforced concrete structure with a bottom slab thickness of 250mm; the bottom elevation of the forebay 2 is lower than the bottom slab elevation of the side inlet / outlet 1, and the height difference between the bottom elevation of the forebay 2 and the bottom slab elevation of the side inlet / outlet 1 is 1.5~2.5 meters. The excavation slope ratio of the reverse slope section 3 is 1:4, and the slope ratio of the excavation slopes on both sides is 1:1.2; the sand retaining wall 4 is a frustum-shaped reinforced concrete structure with a top width of 1 meter and a height of 2.5~3 meters; the sand discharge channel 5 is 10 meters wide, and a layer of cement mortar 7 with a thickness of not less than 5 cm is laid at the bottom as a leveling layer. There is an excavation boundary line 8 between the cement mortar 7 and the riverbed surrounding rock 13 below.

[0057] Furthermore, the present invention also includes a secondary dredging facility; the secondary dredging facility is used to treat siltation exceeding the design standard of the primary silt discharge structure; the secondary dredging facility includes a dredging device, a long-distance silt discharge pipeline 14 and a short-distance silt discharge pipeline 15;

[0058] The dredging device is a cutter suction dredger, used to agitate the silt and sand accumulated in the forepool 2 and the reverse slope section 3 to form slurry;

[0059] The laying path of the short-distance sand discharge pipeline 15 is as follows: on the slope surface of the reverse slope section 3, it is laid in a serpentine manner from the top of the slope to the bottom of the slope; then it reaches the forepool 2, passes the bottom of the forepool 2, reaches the trash rack maintenance platform 9, and then passes the trash rack connecting bridge 10. It is laid in a straight line on the slope surface of the side slope 11 below the gate well platform, and reaches the gate well platform 12 the closest.

[0060] The laying path of the long-distance sand discharge pipeline 14 is as follows: it is laid in a straight line at the bottom of the forebay 2, reaching the bottom of the reverse slope section 3, and then laid in a serpentine pattern on the slope surface of the reverse slope section 3, from the bottom of the slope to the top of the slope. Then, from the top of the reverse slope section 3, it passes through the left shoulder of the lower reservoir sand control dam, and is laid along the reservoir surface of the lower reservoir sand control dam, finally reaching the top of the lower reservoir sand control dam.

[0061] Therefore, in this invention, the long-distance sand discharge pipeline 14 and the short-distance sand discharge pipeline 15 respectively form a long-distance sand discharge scheme and a short-distance sand discharge scheme. Both schemes are used to transport the mud formed by the cutter suction dredger to a designated location for discharge through the laid mud discharge pipeline.

[0062] This invention provides a graded dredging and sediment removal system suitable for side-mounted inlets / outlets of canyon-type riverbeds, comprising a primary sediment removal structure and a secondary dredging facility, together forming a graded treatment system. The method of this invention is novel, with good dredging and sediment removal effect, simple construction, and low cost, effectively solving the problems of sediment accumulation at the front edge of the sand retaining wall and the inability to remove sediment from the reverse slope section during the operation of pumped storage power stations.

[0063] The present invention also provides a dredging and sand removal method applicable to a graded dredging and sand removal system for a canyon-type riverbed side-mounted inlet / outlet, including a primary sand removal method and a secondary dredging method;

[0064] Step S1, Primary Sand Removal Method:

[0065] Step S101: When the lower reservoir is in the pumping state, the water stored in the lower reservoir dam and the lower reservoir silt barrier flows into the silt discharge channel 5 under the action of the topography. Under the interception of the silt barrier 4, the main sediment in the water is blocked in the silt discharge channel 5.

[0066] In step S102, the water containing a small amount of sediment flows into the reverse slope section 3 after passing over the sand-blocking dam 4; after the deceleration and energy dissipation of the reverse slope section 3, a small amount of sediment is deposited on the slope surface of the reverse slope section 3.

[0067] In step S103, after the action of the reverse slope section 3, the water containing a small amount of silt flows into the forepool 2, and the forepool 2 removes the small amount of silt in the water by sedimentation.

[0068] After removing silt, the water flows into the side inlet / outlet 1 and is transported to the upper reservoir by the turbine to complete the pumping operation.

[0069] Step S104: When replenishing water to the lower reservoir, the water in the lower reservoir's silt-blocking dam flows into the lower reservoir through the silt-blocking dam. During the water flow, the sediment deposited in the silt discharge channel 5 is flushed out and guided to the bottom of the lower reservoir's silt-blocking dam, ensuring that the leading edge of the silt-blocking sill 4 is free of sediment during pumping operations.

[0070] Step S2, Secondary Dredging Method:

[0071] Step S201: When the siltation thickness in the forepool 2 and the reverse slope section 3 exceeds the design standard of the primary siltation structure, the dredging device is activated to agitate the siltation in the forepool 2 and the reverse slope section 3 to form slurry.

[0072] In step S202, the slurry is discharged to the design location through the long-distance sand discharge pipeline 14 and / or the short-distance sand discharge pipeline 15 under the action of the pump.

[0073] The short-distance sand discharge pipeline 15 discharges sand in the following way: the mud in the reverse slope section 3 and the forebay 2 area is discharged to the gate well platform 12 through the sand discharge pipeline, and then transported out by vehicles at the gate well platform 12.

[0074] The long-distance sand discharge pipeline 14 discharges sand in the following way: the mud in the forebay 2 and the mud in the reverse slope section 3 area are discharged into the top of the lower reservoir sand-blocking dam through the sand discharge pipeline, and then transported out by vehicles at the top of the lower reservoir sand-blocking dam.

[0075] As a further improvement, the present invention also increases the initiation velocity of the sediment in front of the sand-retaining embankment 4. and sediment starting particle size The relationship between the two is studied, and the expression of formula (1) is proposed:

[0076] (1)

[0077] in: , These are the densities of water and sediment, respectively. The initiating particle size of the sediment; It is the acceleration due to gravity; The water depth inside the sand discharge channel 5;

[0078] The flow velocity at the front section of the sand-retaining embankment 4 is used as the initiation velocity of the sediment flow in the sand discharge channel 5. Based on Equation 1, the initiation particle size of sediment was calculated. Therefore, when the actual sediment particle size at the bottom of the reservoir is larger than the initial sediment particle size... This indicates that sediment will not cross the sediment trap 4 and enter the reverse slope section 3 and the forebay 2, and the sediment trap 4 is reasonably designed. Therefore, the sediment trap 4 on the outer edge of the side inlet / outlet 1 should be designed so that the flow velocity in front of the trap is lower than the sediment initiation velocity at the bottom of the reservoir. This will enable the sand removal channel 5 to effectively remove sand.

[0079] This invention discloses a graded dredging and sediment removal system and method suitable for side-mounted inlets / outlets in canyon-type riverbeds, belonging to the field of dredging and sediment removal technology for pumped storage power station projects. The system includes a side-mounted inlet / outlet 1, a forebay 2, a reverse slope section 3, a sediment trap 4, and a sediment removal channel 5 connected in sequence. The bottom elevation of the forebay 2 is lower than the bottom plate of the side-mounted inlet / outlet 1, forming a sedimentation zone. A sediment trap 4 is circumferentially arranged around the outer edge of the reverse slope section 3, and a sediment removal channel 5 is provided between its end and the opposite bank slope 6, together forming a primary sediment removal structure for diverting sediment from frequent floods. The method defines an implementation scheme for secondary dredging operations using dredging devices such as cutter suction dredgers to remove sediment deposited in the forebay 2 and reverse slope section 3 due to floods exceeding standard levels. This invention effectively solves the problem of sediment accumulation at the front edge and reverse slope of the side inlet / outlet of canyon-type riverbeds by adopting a graded treatment model of "structural sand interception as the main method and mechanical dredging as the auxiliary method", thus ensuring the safety and reliability of its long-term operation.

[0080] The following description, using a large-scale hydropower station project employing the technical solution of this invention as an example, is further illustrated with reference to the accompanying drawings:

[0081] The project has a total installed capacity of 1400MW and a rated generating head of 449m. The water conveyance system consists of two parts: a water intake system and a tailrace system. Both systems are arranged in a single tunnel with two turbines, forming two independent water conveyance systems (No. 1 and No. 2). The lower reservoir's inlet / outlet is a side-type inlet / outlet 1, which consists of an anti-vortex beam section 101, an adjustment section 102, a diffuser section 103, and a gate well section 104, with a total length of 58.22m. The bottom elevation of side-type inlet / outlet 1 is 878.0m. The topography of side-type inlet / outlet 1 is characterized by a deep and narrow river channel formed by the compression of the riverbed by the mountains on both banks. To ensure smooth water flow at the side inlet / outlet 1, a tailrace channel is provided at the end of the side inlet / outlet 1 to connect to the lower reservoir. The tailrace channel is arranged in the following order along the direction of the power generation water flow: forebay 2, reverse slope section 3, sand retaining wall 4, and sand discharge channel 5.

[0082] At the 885m elevation section of the main flow point of the side inlet / outlet 1, the flow velocity at the junction of the forebay 2 and the reverse slope section 3 is 0.19~0.63 m / s, and the flow velocity at the middle section of the reverse slope section 3 is 0.21~0.84 m / s. The flow velocity at the middle measuring line of the two side inlets / outlets 1 is relatively low, and the transverse velocity distribution of each section is relatively uniform. At the 895m elevation section, the flow velocity at the junction of the forebay 2 and the reverse slope section 3 is -0.04~-0.16 m / s, the flow velocity at the middle section of the reverse slope section 3 is 0.05~0.16 m / s, and the flow velocity on both sides of the open channel is 0.43~0.57 m / s. The transverse velocity distribution of each section is relatively uniform. When the dead water level of the lower reservoir is 896m, the starting flow velocity in front of the 4th sediment trap is 0.12 m / s. Using the sediment starting formula, the sediment starting particle size is found to be 0.263 mm. It can be assumed that sediment particles larger than 0.263 mm will not trigger the influx. Based on years of suspended sediment particle size distribution analysis from the hydrological station of this power station, the median particle size of the suspended sediment is 0.02 mm, the average particle size is 0.033 mm, and the percentage of sediment particles smaller than 0.25 mm is approximately 99.5%. Therefore, it is considered that a flood exceeding a 30-year return period entering the reservoir will not require overall dredging of the lower reservoir. Considering factors such as hydrological characteristics, power station operation mode, and flow patterns at the side inlet / outlet under power generation conditions, most of the open channel sediment can be carried out of the side inlet / outlet. Sedimentation at the lower reservoir's side inlet / outlet will not significantly affect the normal operation of the power station, and separate dredging is not necessary.

[0083] During the operation of the power station, the probability of a flood with a return period greater than 50 years is low. However, if multiple floods with a return period greater than 30 years occur during the operation of the power station, or if floods of the above frequency occur during unit maintenance, and the amount of siltation exceeds the dead storage capacity, then overall dredging is required.

[0084] Sediment carried away during power generation is not considered. A calculation and analysis of sediment deposition at side-mounted inlets / outlets is performed using a 50-year flood as an example:

[0085] A 50-year flood event resulted in a total siltation of 510,000 cubic meters in the reservoir. 3 The total area of ​​the lower reservoir at its normal storage level is approximately 324,590.509 m². 2 The siltation area of ​​the side inlet / outlet 1 of the lower reservoir is approximately 5763.063 m². 2 (Forebay 2 and reverse slope section 3 area). Based on the flat layout of the forebay 2 and reverse slope section 3 of the lower reservoir's side inlet / outlet, a conservative estimate is that a 50-year flood will cause a total sedimentation of 0.9055 million m³ at the lower reservoir's side inlet / outlet 1. 3 The siltation thickness at the side inlet / outlet 1 of the lower reservoir during a 50-year flood event is 1.571m, which is less than the 2.25m height of the sill at the front end of the forebay.

[0086] The dredging and sand removal plan for the side-mounted inlet / outlet section is as follows: Hydraulic dredging or cutter suction dredgers will be used for dredging and sand removal. A CZ650 dredger with a nameplate capacity of 1200 m³ can be used. 3 / h; When using hydraulic dredging and pumping, assuming a sand content of no more than 20%, the total amount of water and sand to be pumped is 45,300 m³. 3 Pumping capacity is based on 1000 m³. 3 At a scale of / h, it would take approximately 2 days to pump.

[0087] By adopting the above-disclosed technical solution of this invention, the following beneficial effects are obtained:

[0088] The sediment discharge scheme and structure of this invention can effectively allow most of the sediment brought by the riverbed to flow out smoothly through the sediment discharge channel, preventing it from entering the side inlet / outlet, and intercepting a small portion of the sediment that crosses the sediment barrier in the forebay section; by selecting the corresponding sediment discharge scheme, the sediment in the forebay and reverse slope section can be discharged to the designated location, further improving the sediment removal effect.

[0089] The present invention has the following advantages:

[0090] (1) Conventional sediment treatment: Initial interception is achieved through the sand-blocking embankment, sediment is collected in the forepool as the sedimentation zone, and finally the sediment is smoothly discharged through the sand discharge channel, forming an efficient and economical closed loop for conventional sediment treatment.

[0091] (2) Flexible dredging scheme for excessive sediment: In response to the sedimentation problem caused by floods exceeding the standard, mechanical dredging is carried out by cutter suction dredgers, and two sand discharge schemes, one for long distance and one for short distance, are equipped. The optimal dredging path can be selected according to the actual situation of the project to ensure the cleaning effect.

[0092] (3) Comprehensive advantages of the graded system: Through the graded combination of “structural sand interception and mechanical dredging of excessive silt”, the efficiency of sand removal under the condition of frequent floods is guaranteed, and reliable countermeasures are provided for floods exceeding the standard. While controlling the engineering cost, the safety and adaptability of the system are significantly improved.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A stepwise dredging and desilting system suitable for a side-type water inlet / outlet of a canyon-type riverbed, characterized in that, The application relates to a sand discharge structure of a lower reservoir. The sand discharge structure is arranged at a lower reservoir riverway section between a lower reservoir dam and a lower reservoir sand retaining dam, one side of the section is a back slope after an inlet / outlet, and the other side is a bank slope (6); the sand discharge structure comprises, in sequence from the back slope to the bank slope (6), a side-type inlet / outlet (1), a front pool (2), an inverse slope section (3), a sand retaining dam (4) and a sand discharge channel (5). The side-type inlet / outlet (1) is provided with the front pool (2) on the side far from the back slope; the bottom elevation of the front pool (2) is lower than that of the side-type inlet / outlet (1), thereby forming a sand setting area; the left side slope bottom of the inverse slope section (3) is connected with the right side bottom of the front pool (2); the inverse slope section (3) is an upwardly inclined slope surface from left to right at the lower reservoir riverway section; the right side slope top of the inverse slope section (3) is close to the bank slope (6) and close to the water surface line of the lower reservoir; the sand retaining dam (4) is arranged on the right side slope top edge of the inverse slope section (3) along the longitudinal direction of the riverway; the sand retaining dam (4) and the bank slope (6) form the sand discharge channel (5); the sand discharge channel (5) is arranged along the longitudinal direction of the riverway, and the front and back ends of the sand discharge channel (5) are communicated with the lower reservoir sand retaining dam and the lower reservoir dam respectively; the elevation of the sand discharge channel (5) is flush with the lower reservoir bottom downstream of the lower reservoir sand retaining dam and the lower reservoir bottom upstream of the lower reservoir dam. The side-type inlet / outlet (1) is made of reinforced concrete and comprises, in sequence from the bank slope (6) to the back slope, a vortex-proof beam section (101), an adjusting section (102), a diffusion section (103) and a gate well section (104) which are connected in sequence. The vortex-proof beam section (101) and the adjusting section (102) are equal-section water pipelines along the water flow direction; the diffusion section (103) is a variable-section water pipeline with gradually reduced cross section along the water flow direction, and the cross section size of the diffusion section (103) is the same as that of the adjusting section (102) and the diffusion section (103); the gate well section (104) is an equal-section water pipeline along the water flow direction, and the cross section size of the gate well section (104) is the same as that of the diffusion section (103) and the gate well section (104). The sand discharge structure further comprises secondary dredging facilities; the secondary dredging facilities comprise a dredging device, a long-distance sand discharge pipeline (14) and a short-distance sand discharge pipeline (15). The dredging device is a cutter suction dredger which is used to twist the accumulated silt in the front pool (2) and the inverse slope section (3) to form slurry. The laying path of the short-distance sand discharge pipeline (15) is as follows: the short-distance sand discharge pipeline (15) is laid in a serpentine shape on the slope surface of the inverse slope section (3) from the top to the bottom of the slope; then the short-distance sand discharge pipeline (15) reaches the front pool (2), passes through the pool bottom of the front pool (2), reaches the trash rack maintenance platform (9), and then is laid in a straight line on the slope surface of the gate well platform below slope (11) after passing through the trash rack connecting bridge (10), and finally reaches the gate well platform (12). The laying path of the long-distance desilting pipeline (14) is: linearly laid on the bottom of the front pool (2), reaches the slope bottom of the reverse slope section (3), then is laid in a serpentine shape on the slope surface of the reverse slope section (3) from the slope bottom to the slope top, then passes through the left dam abutment of the lower reservoir sedimentation dam from the slope top of the reverse slope section (3), is laid along the reservoir surface of the lower reservoir sedimentation dam, and finally reaches the dam top of the lower reservoir sedimentation dam.

2. A step-dredging and sand-discharging system suitable for a side-type water inlet / outlet of a gorge-type riverbed according to claim 1, characterized in that, The side-type inlet / outlet (1) is arranged in a natural deep and narrow river channel topography squeezed by the two-bank mountains.

3. A step-dredging and sand-discharging system suitable for a side-type water inlet / outlet of a gorge-type riverbed according to claim 1, characterized in that, The two side-type inlets / outlets (1) are arranged side by side, and the right ends of the two side-type inlets / outlets (1) are communicated with the front pool (2); the left ends of the two side-type inlets / outlets (1) are connected by a gate well platform (12) to form a whole. The two side-type inlets / outlets (1) have a spacing area; on the center measuring line of the spacing area, there are, in sequence from the front pool (2) to the gate well platform (12), a trash rack maintenance platform (9), a trash rack connecting bridge (10) and a slope (11) below the gate well platform.

4. A step-dredging and sand-discharging system for a side-type water inlet / outlet of a gorge-type riverbed according to claim 1, characterized in that, The front pool (2) is a rectangular reinforced concrete structure, and the thickness of the bottom plate is 250 mm; the height difference between the bottom elevation of the front pool (2) and the bottom plate elevation of the side-type inlet / outlet (1) is 1.5-2.5 m.

5. A step-dredging and sand-discharging system for a side-type water inlet / outlet of a gorge-type riverbed according to claim 1, characterized in that, The excavation slope ratio of the reverse slope section (3) is 1:4, and the excavation slope ratio of the two sides is 1:1.2; the sedimentation dam (4) is a prismatic reinforced concrete structure, the top width is 1 m, and the height is 2.5-3 m; the desilting channel (5) has a width of 10 m, and a layer of cement mortar (7) with a thickness of not less than 5 cm is laid as a leveling layer on the bottom.

6. A method for dredging and desilting according to any one of claims 1 to 5, characterized in that, The method comprises a primary desilting method and a secondary dredging method. Step S1, the primary desilting method: Step S101, when the lower reservoir is in the pumping state, the water stored in the lower reservoir dam and the lower reservoir sedimentation dam flows into the desilting channel (5) under the action of the terrain, and under the interception of the sedimentation dam (4), the main sediment in the water is blocked in the desilting channel (5); Step S102, after the water containing a small amount of sediment flows into the reverse slope section (3) through the sedimentation dam (4), the small amount of sediment is deposited on the slope surface of the reverse slope section (3) through the deceleration and energy dissipation of the reverse slope section (3); Step S103, after the action of the reverse slope section (3), the water containing a small amount of sediment flows into the front pool (2), and the front pool (2) deposits and removes the small amount of sediment in the water; The water after removing the sediment flows into the side-type inlet / outlet (1), and under the action of the water turbine, is transported to the upper reservoir, and the pumping condition is completed; Step S104, when the lower reservoir is replenished, the water in the lower reservoir sedimentation dam flows into the lower reservoir through the lower reservoir sedimentation dam, and in the process of water flow, the deposited sediment in the desilting channel (5) is scoured, and the deposited sediment is guided to the bottom of the lower reservoir dam, so that the front edge of the sedimentation dam (4) is free of sediment in the pumping condition; Step S2, the secondary dredging method: Step S201, when the deposition thickness of the sediment in the front pool (2) and the reverse slope section (3) exceeds the design standard of the first sediment discharge structure, the dredging device is started to dredge the sediment deposited in the front pool (2) and the reverse slope section (3), and form slurry; Step S202, under the action of the pump, the slurry is discharged to the designed location through the long-distance sediment discharge pipeline (14) and / or the short-distance sediment discharge pipeline (15).

7. The method of claim 6, wherein the method is a method of cleaning and desilting a stepped desilting system for a side-type water inlet / outlet of a canyon-type riverbed, characterized in that, The short-distance sediment discharge pipeline (15) discharges in the following way: the slurry in the reverse slope section (3) and the front pool (2) area is discharged to the gate well platform (12) through the sediment discharge pipeline, and is transported out by vehicles at the position of the gate well platform (12); The long-distance sediment discharge pipeline (14) discharges in the following way: the slurry in the front pool (2) and the slurry in the reverse slope section (3) area are discharged to the top of the dam of the lower reservoir sediment barrier through the sediment discharge pipeline, and are transported out by vehicles at the position of the top of the dam of the lower reservoir sediment barrier.

8. The method of claim 6, wherein the method is characterized by, the threshold velocity of flow of sediment in front of the sandbar (4) and the threshold size of sediment has the relationship (1): （1） wherein: , are the water and sediment densities, respectively; is the sediment starting particle size; is the gravitational acceleration; is the water depth in the sediment discharge channel (5); The flow velocity of the front section of the sand barrier (4) is taken as the incipient flow velocity of the sediment in the sediment discharge channel (5) Based on the relationship (1), the incipient sediment particle size is calculated Therefore, when the actual reservoir bottom sediment particle size is greater than the incipient sediment particle size It is shown that the sediment will not cross the sand barrier (4) into the reverse slope section (3) and the front pool (2), and the sand barrier (4) is reasonably set; therefore, the sand barrier (4) on the outer edge of the side-type water inlet / outlet (1) is designed so that the flow velocity of the front section of the sand barrier (4) is lower than the incipient flow velocity of the reservoir bottom sediment That is, the effective sediment discharge effect of the sediment discharge channel (5) can be achieved.

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