Dike closure method based on whole assembly type double-culvert closure bottom structure

Abstract

The present application belongs to the technical field of water conservancy and hydropower engineering closure construction, and particularly relates to a kind of embankment closure method based on integral assembly type double ridge closure bottom protection structure.The present application precast and accurately throw the integral bottom protection structure formed by rigid connection of bottom protection section and double ridge section in dry season of a year before closure, with standardized reinforced gabion as basic unit, adopt double connection inside and outside to form continuous plate type whole, with high impact resistance and stone blocking foot capacity.Through particle size and impact distance calculation, throw test, GPS joint positioning to realize accurate underwater throwing.After bottom protection construction is completed, embankment pre-advance is implemented in dry season of next year, and large stone and reinforced gabion are continuously thrown in closure stage, which can improve the stability of throwing material, prevent embankment collapse, and realize safe and rapid closure.The present application can solve the problems of traditional dispersed bottom protection, such as easy loss, low precision, interference with flood discharge, etc., and greatly improve the safety and efficiency of closure under complex riverbed conditions.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy and hydropower engineering technology, specifically relating to a method for closure of a levee based on an integrally assembled double-sill bottom protection structure, suitable for conditions of high flow velocity, thick overburden, and poor riverbed erosion resistance. Background Technology

[0002] When constructing hydraulic structures such as dams and sluice gates on rivers, the water flow is usually cut off first (interception) to create a dry construction environment. The difficulty of the interception is mainly concentrated in the stage from the initial placement of materials at the dam's closure point: when the dam's closure point is located on a smooth riverbed rock surface, the high-speed water flow can easily cause the materials to be eroded and lost; when the closure point is located on a riverbed with a thick overburden layer, the high-speed water flow can easily cause the foundation of the dam's head to be hollowed out, become unstable, and collapse, significantly increasing the difficulty and safety risks of the interception.

[0003] Existing bottom protection methods for river mouths mostly employ a dispersed approach, using large stones, concrete structures, and ordinary wire mesh cages. This method has significant drawbacks.

[0004] 1) The overall erosion resistance of the dispersed structure is relatively poor. The time between the placement of the bottom protection and the closure should not be too long, otherwise the blocks placed at the dam opening will be easily washed away by the high-speed water flow over a long period of time. The placement time is generally arranged to be completed before the flood season of the year's closure, and it is only subject to the erosion of one flood season. It is also necessary to maintain its stability through large-scale design to ensure that there is still residual bottom protection available after the flood season erosion.

[0005] 2) The construction process cannot control the width, height and distribution range of the underwater bottom protection structure, resulting in uneven distribution of the projectiles, which affects the roughening effect of the riverbed and cannot effectively intercept the later projectiles. In severe cases, the bottom protection will lose its protective function.

[0006] 3) Irregular bottom protection structures are difficult to control in terms of shape, which will interfere with and affect the flood discharge, diversion and navigation of the river channel before the diversion;

[0007] 4) When the pre-flood construction period is affected by the weather and water level, especially in northern regions where the river is frozen for a long time and the construction period before the closure is short, it is difficult to complete the bottom protection and pouring construction according to the planned schedule. The closure and closure period cannot be guaranteed. The closure is an important node in the main project and will affect the construction of subsequent projects, putting the project construction in a very passive situation.

[0008] To address the aforementioned issues, a method for closure of the embankment based on an integrally assembled double-sill bottom protection structure was invented. This invention can effectively improve the erosion resistance of the interception and dumping materials, prevent scouring of the riverbed at the embankment opening, greatly reduce the loss of dumped materials, virtually eliminate the collapse of the embankment head, reduce the construction intensity and difficulty during the interception period, and accelerate the closure progress. Summary of the Invention

[0009] The purpose of this invention is to overcome the above-mentioned problems existing in traditional technologies and provide a method for closure of dikes based on an integrally assembled double-sill bottom protection structure. By prefabricating and precisely throwing the double-sill bottom protection structure during the dry season one year before the dike closure, a stable, continuous, and high-roughness dike protection system is formed, which improves the erosion resistance stability of the thrown material, protects the dike toe from scouring, and achieves safe and rapid closure.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0011] This invention provides a method for closure of a double-sill bottom protection structure with integral assembly, comprising the following steps:

[0012] 1) During the dry season one year before the closure, a prefabricated, integrally assembled double-sill embankment bottom protection structure is constructed. The bottom protection structure is composed of a bottom protection section and a double-sill embankment section rigidly connected in sequence along the water flow direction. Standardized steel gabions are assembled into a whole through double internal and external connections.

[0013] 2) The bottom protection structure is assembled in sections using a bottom-opening barge platform. The relationship between current velocity and distance is determined through throwing tests. GPS and floating objects are used for joint positioning to carry out precise underwater throwing.

[0014] 3) After the bottom protection structure is completed, the dike will be pre-entered during the dry season of the following year to form the head of the dam;

[0015] 4) Large stones and reinforced gabions were continuously thrown in, and the full-section advancement method and the protruding upstream corner method were combined to advance and complete the closure of the sluice gate.

[0016] Furthermore, the core component of the overall assembled double-slope bottom protection structure is a reinforced gabion; the bottom protection reinforced gabion has a size of 1.0m×1.0m×0.5m or 1.0m×1.0m×1.0m, and the retaining sill reinforced gabion has a size of 2.0m×2.0m×2.0m.

[0017] Furthermore, the reinforced gabion frame is welded with Φ20mm HRB400 steel bars, and the mesh is welded with Φ14mm HRB400 steel bars into a 10cm×10cm grid; the filling stone is hard stone with saturated compressive strength >40MPa, softening coefficient >0.8, freeze-thaw loss rate <1%, and particle size ≥15cm, and the porosity is ≤20% when manually stacked.

[0018] Furthermore, the internal and external double connection is as follows: the internal connection uses Φ10mm steel wire rope wrapped around the top and bottom and interlaced with mesh reinforcement ≥5 times; the external connection uses Φ6mm twisted edge steel wire wrapped alternately in single / double loops with a spacing of 10~15cm; the middle cage is reinforced by fully wrapping steel wire rope around the top and bottom.

[0019] Furthermore, the double-barrier section includes a first barrier downstream, a second barrier upstream, and a 1.0m wide connecting section between the two barriers; both barriers are single-row 2.0m high steel gabions tightly assembled, arranged at the same height, parallel, and along the entire length.

[0020] Furthermore, the precise casting is carried out during the dry season one year before the damming, and the deviation of the casting position is controlled within 20-30cm.

[0021] Furthermore, the closure of the dragon's mouth adopts the continuous high-intensity throwing of large stones and steel gabions, combined with the full-section advancement method and the protruding upstream corner method for advancement.

[0022] The present invention also provides an integrally assembled double-sill bottom protection structure, which is composed of a bottom protection section and a double-sill section rigidly connected along the water flow direction; the bottom protection section is composed of multiple rows of bottom protection steel gabions tightly assembled, and the double-sill section is composed of two parallel sills of equal height and the connecting section between the sills, and the whole is a continuous plate-type integrated structure.

[0023] Furthermore, the bottom protection section is 0.5~1.0m thick, the rock retaining wall is 2.0m high, and a 1.0m wide connecting section is provided between the retaining walls. The whole structure is arranged along the entire length perpendicular to the direction of water flow.

[0024] Furthermore, this bottom protection structure is suitable for the protection of river closure gaps in areas with high flow velocities, thick overburden layers, and poor riverbed erosion resistance. It can be deployed as a whole during the dry season one year before the closure and remains stable for many years.

[0025] The beneficial effects of this invention are:

[0026] 1. The reinforced gabion is double-connected inside and out to form a whole, and its impact resistance is far superior to that of scattered materials, which can remain stable for many years without loss.

[0027] 2. The double-layered stone retaining walls work together to significantly improve the stability of the embankment and virtually eliminate the possibility of collapse.

[0028] 3. Construction can be carried out during the dry season of the previous year before the closure. There is ample time for bottom protection construction before the closure, allowing sufficient time to conduct throwing tests, analyze the measured flow velocity and stroke distance curves, provide real-time feedback on underwater throwing retest results and adjust the throwing position, effectively ensuring the quality of bottom protection construction. The guarantee rate of riverbed protection before the closure is high, and the impact on flood discharge, diversion and navigation is small.

[0029] 4. The bottom-opening barge is assembled as a whole, and GPS and casting tests are coordinated, resulting in small underwater positioning deviation and a regular bottom protection shape.

[0030] 5. High impact resistance can be formed by filling the steel cage with readily available natural small and medium-sized stones on site. It has significant advantages in areas lacking large stones, and has good permeability and strong adaptability.

[0031] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments 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.

[0033] Figure 1 This is a plan view of the overall assembled double-sill bottom protection structure;

[0034] Figure 2 This is a cross-sectional view of the integrally assembled double-sill bottom protection structure;

[0035] Figure 3 This is a schematic diagram of a single steel cage structure and its overall assembly and connection method. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The specific embodiments of the present invention are as follows:

[0038] Example 1: Integrated double-sill bottom protection structure

[0039] Overall structural composition:

[0040] The integrally assembled double-sill bottom protection structure is an integrated underwater protection structure. It consists of two main parts rigidly connected from front to back along the water flow direction: the bottom protection section and the double-sill section. The whole structure is a continuous plate with a certain degree of flexibility and deformation adaptability.

[0041] Core component: reinforced gabion

[0042] Both the bottom protection and the rock retaining wall are assembled from standardized steel gabions, which are the basic structural units.

[0043] 1. Framework Creation

[0044] 1) Main frame: A cubic skeleton is welded with Φ20mm HRB400 steel bars and arranged along 12 edges; cross-shaped main steel bars are added to the center of each face to improve the rigidity of the cage.

[0045] 2) Mesh: Φ14mm HRB400 steel bars are welded into a 10cm×10cm mesh, with all intersections fully welded, without any missing welds or incomplete welds.

[0046] 2. Filling with stones and sealing

[0047] 1) Filler: Select hard stones with saturated compressive strength > 40MPa, softening coefficient > 0.8, freeze-thaw loss rate < 1%, and particle size ≥ 15cm; manually stack them, with large stones as the skeleton and small stones as the filler, porosity ≤ 20%, and leave 2.5cm for settlement superelevation.

[0048] 2) Covering: After the cage is full, cover it and tie it securely with wire. Set up special lifting points at the four corners.

[0049] 3. Standard Size

[0050] 1) Bottom-protecting reinforced gabion: 1.0m×1.0m×0.5m or 1.0m×1.0m×1.0m.

[0051] 2) Reinforced gabion for rock retaining wall: 2.0m×2.0m×2.0m.

[0052] integral connection process between cages

[0053] The sections are assembled on the bottom-opening platform, using internal and external double connections to form a whole:

[0054] 1. Internal connection (steel wire rope wrapped around top and bottom)

[0055] Pre-lay Φ10mm steel wire rope;

[0056] The top and bottom of adjacent cages are wrapped with steel wire ropes once, and the exposed mesh steel bars are inserted ≥5 times, and then twisted and tightened.

[0057] 2. External connection (twisted edge fastening)

[0058] Using Φ6mm twisted steel wire, a flanging machine is used to alternately wind single or double turns on the main frame of adjacent cages, with a spacing of 10~15cm, to achieve rigid fastening.

[0059] 3. Reinforcement of the intermediate cage

[0060] For the internal cage that cannot be twisted on the outside, steel wire rope is fully wrapped around the top and bottom to ensure overall force transmission.

[0061] Bottom protection section structure and connection

[0062] 1) Location: Located on the upstream side of the entire bottom protection structure, directly covering the easily eroded riverbed at Longkou.

[0063] 2) Structure: It is composed of multiple rows of reinforced gabions arranged closely together and assembled as a whole, with a thickness of 0.5~1.0m.

[0064] (3) Connection relationship: The downstream edge of the bottom protection section is rigidly connected to the upstream face of the second sill of the rock retaining wall, forming a continuous whole.

[0065] Double-channel rock retaining wall structure and connection

[0066] 1) Location: Located on the downstream side of the bottom protection structure, it undertakes the main functions of rockfall prevention, erosion resistance and toe protection.

[0067] 2) Composition: The double-threshold system consists of three parts: the first threshold, the second threshold, and the connecting section between the thresholds.

[0068] 3) First barrier: On the downstream side, a single row of 2.0m high reinforced gabions is tightly assembled.

[0069] 4) The second barrier: on the upstream side, it is connected to the bottom protection and is a single-row 2.0m high stone retaining wall with tightly assembled steel gabions.

[0070] 5) Inter-sill connection section: Between the two sills, multiple rows of 0.5~1.0m high steel gabions are assembled to form a 1.0m wide integral connection section to ensure that the two sills share the load.

[0071] 6) Overall characteristics: The two embankments are of equal height, parallel and of equal length, and are arranged along the entire length of the vertical water flow direction, forming an inseparable whole with the bottom protection section.

[0072] Example 2 Implementation Steps

[0073] S1. Calculation of bottom protection structure dimensions

[0074] The dimensions of the bottom protection structure should meet the requirements for structural stability. The stability calculation of the bottom protection structure at the dam opening mainly includes particle size calculation and pouring distance calculation. The particle size of the blocks should meet the stability requirements for dumping in flowing water during the non-flood season one year before the damming, and should also meet the requirement of not being eroded during the flood season before and during the damming period.

[0075] 1) Particle size calculation

[0076] The critical stable particle size of the projectile is calculated using the formula for calculating the particle size and mass of the projectile based on the flat-block throwing test. d The minimum mass of the thrown object is given by formulas (1) and (2).

[0077] Critical stable particle size of the projectile: (1)

[0078] The mass of the thrown object should not be less than: (2)

[0079] In the formula: d —Critical stable particle size of the projectile, converted to the diameter of a sphere (m). v —Average flow velocity at the inlet (m / s);k —Comprehensive stability coefficient, dynamic water throwing (steel cage is taken as 1.2); g —Acceleration due to gravity, taken as 9.8 m / s² 2 ; ρ m —Density of the projectile (t / m³) 3 ); ρ —Water density (t / m³) 3 ); W —Mass of the intercepted and thrown object (t).

[0080] 2) Stroke distance calculation

[0081] The calculated throw distance determines the point of entry into the water. The throw distance is the distance between the stable point of the rock on the riverbed and the point of entry into the water; it is related to flow parameters and riverbed roughness, and is estimated using empirical formulas.

[0082] (3)

[0083] In the formula: L — Stroke distance (m); v —Average flow velocity at the inlet (m / s); H —Water depth (m); d —The diameter of the projectile (m) is converted into the diameter of a sphere using the equal volume method, and is the result calculated by formula (1).

[0084] S2. Determining the scope of the bottom protection

[0085] The protection zone is divided into the length along the embankment axis (width of the opening) and the length along the water flow direction.

[0086] 1) The length of the embankment along the axis is determined by the width of the opening corresponding to the flow velocity at the opening exceeding the scour resistance velocity of the overburden layer.

[0087] Intercepting the flow of water from the dam. Q g Calculate according to formula (4):

[0088] (4)

[0089] In the formula: Q g —The flow rate of the diversion dam is (m³) 3 / s); σ n —Inundation coefficient, the value of which is related to the inundation limit: 1.0 for non-inundated flow and 0.9 for inundated flow; g —Acceleration due to gravity, taken as 9.8 m / s² 2 ; m —The flow coefficient, which takes into account the effect of contraction, is generally taken as 0.30 (triangular) to 0.32 (trapezoidal). hu The water depth upstream of Longkou (m); h d —Water depth downstream of Longkou (m); h k —Critical water depth at Longkou (m); B cp —Average water surface width at Longkou (m), when the submergence flow ( h d / h u When ≥0.7) B cp = S × h d + b When the floodwaters ( h d / h u When ≥0.7) B cp = S × h k + b ; S —The slope ratio of the embankment is taken as 1.5; b —Width of the bottom of the dragon's mouth (m).

[0090] Longkou average flow velocity v Calculate according to formula (5):

[0091] (5)

[0092] In the formula: v —Average flow velocity at Longkou (m / s); h p —Depth of the water at Longkou (m), when the floodwaters ( h d / h u When ≥0.7) h p = h d non-submerged flow h p = h k ; h d —Water depth downstream of Longkou (m); h k —Critical water depth at Longkou (m).

[0093] In the calculation parameters of formulas (4) and (5), except for the critical water depth at Longkou... h k Trial calculations are required; all other parameters are known.

[0094] Critical water depth h k The critical water depth can be calculated using formula (6):

[0095] (6)

[0096] In the formula: Q g —The flow rate of the diversion dam is (m³) 3 / s); g —Acceleration due to gravity, taken as 9.8 m / s² 2 ; B k —Critical water depth h k The corresponding width of the water passage section at the time (m); h k —Critical water depth at Longkou (m); S —The slope ratio of the embankment is taken as 1.5.

[0097] 2) Length in the direction of water flow L The calculation should extend beyond the toe of the embankment slope, and should be performed separately for the portion above and below the embankment axis. The calculation formula is as follows:

[0098] Above the embankment axis:

[0099] Below the axis of the embankment:

[0100] Length in the direction of water flow:

[0101] S3. Reinforcing cage fabrication

[0102] The production steps are as follows: fabricate steel cages on the shore → weld the mesh → manually fill with stones → seal and tie the cage → set up four corner lifting points.

[0103] The dimensions of the gabion cube with reinforcing steel reinforcement are: 1.0m×1.0m×0.5m or 1.0m×1.0m×1.0m.

[0104] The dimensions of the reinforced gabion cube for the rock retaining wall are 2.0m × 2.0m × 2.0m.

[0105] The reinforced gabion is constructed with a main frame made of 20mm diameter steel bars welded together. These main frame bars are distributed along the 12 edges of the cube. Additionally, cross-shaped main frame bars are added at the center of each of the six faces to increase the cage's stability. A 10cm x 10cm grid is made using 14mm steel bars, with welded connections at the intersections. The fabricated reinforced gabion is filled with boulders and sealed. The completed reinforced gabion is hoisted onto the working platform of a bottom-opening barge (a boat with an open bottom), and the double-sill bottom protection structure is assembled in sections. The section dimensions are determined by calculations of the bottom protection dimensions and the dimensions of the bottom-opening barge platform. The assembly sequence and principle are as follows: starting from one end and working from the outside in, assembling each section sequentially. The cage assembly includes two parts: the internal cage wire rope top and bottom winding connection and the external cage wire rope twisting connection. Beforehand, lay 10mm diameter steel wire ropes on the steel gabion assembly position. After the steel gabions are hoisted into place, wrap the top and bottom of each pair of adjacent cages with a steel wire rope. When wrapping, the exposed mesh reinforcement on the outer surface needs to be interlaced and wrapped more than 5 times. After wrapping, twist and tighten the steel wire rope to complete the connection of the inner cages. For the outer cage edge connection, use a flanging machine to wrap 6mm diameter edge steel wires on the frame reinforcement of the adjacent cages in an alternating "single loop-double loop" pattern with an interval of 10~15cm.

[0106] S4. Transport and unloading

[0107] The prepared reinforced gabions are lifted by 50t (for hoisting the sand retaining sill reinforced gabions) and 16t (for hoisting the bottom reinforced gabions) cranes, transported to the dock by dump trucks, and then unloaded onto the bottom barge working platform by 50t and 16t cranes and neatly arranged.

[0108] S5. Platform assembly

[0109] On the working platform of the bottom-opening barge, the barge is assembled in groups according to the width of the bottom-opening barge compartment (2 rows of stone barriers + several rows of bottom protection), and the inner and outer double connections are completed. Steel wire ropes are used to connect and fasten the adjacent outer cages. When the middle cage cannot be twisted, steel wire ropes are used to wrap around the top and bottom of the cage to form an integral piece.

[0110] S6. Underwater Measurement and Positioning

[0111] Underwater surveys were conducted on the riverbed topography within 100m upstream and downstream of the levee axis, and control points along the levee axis, as well as a certain number of elevation and horizontal control points, were established.

[0112] S7. Throwing Test

[0113] Before the actual deployment, several deployment tests were conducted using a bottom-opening barge at different flow velocities. The bottom-opening barge was positioned 20-30m downstream of the bottom protection area, and double rows of steel gabion strings were simultaneously submerged to the bottom of the water to conduct underwater measurements. The flow velocity-stroke distance relationship curve was measured to guide precise deployment.

[0114] S8. Construction Positioning

[0115] Based on the results of the throwing test and the measured average flow velocity, the standard throwing strips were divided upstream according to the width of the opening size of the bottom-opening barge's movable compartment, shifting the stroke distance corresponding to the measured flow velocity. A fixed floating object was set up within the designated throwing strip area. After the bottom-opening barge traveled to the designated area, its installed GPS positioning system compared the positioning floating object with the actual throwing position in real time to control the throwing location.

[0116] S9. Precision Throw

[0117] The project was carried out during the dry season of the year preceding the river closure, when the riverbed flow was low and the water level was low, which was conducive to construction. Bottom-opening barges were used for placement, with real-time monitoring of the flow velocity and adjusting the barge position accordingly based on the velocity-distance relationship curve. A GPS positioning system installed on the barges compared the placement position with the positioning float in real time to ensure precise placement. Real-time feedback of underwater placement retest results allowed for timely adjustments to the placement position, effectively controlling the placement deviation within 20-30cm to guarantee the quality of the riverbed protection construction.

[0118] S10. Pre-occupation of the diversion embankment

[0119] Following the completion of the bottom protection construction, the pre-entry construction of the dike will proceed normally during the dry season of the following year. The general construction steps are: transporting materials onto the dike → unloading materials at the dike head → centralized pushing and throwing or unloading and pounding → forming the dam head. The pre-entry materials can be selected from gravel or boulders, depending on the available material resources in the construction area.

[0120] S11. Closing the Dragon's Mouth

[0121] The closure of the dam was achieved through continuous, high-intensity dumping of large stones and reinforced gabions (or precast concrete blocks), employing a combination of full-section advancing and protruding upstream corner methods. The general construction steps are: material transportation → unloading → concentrated pushing and dumping or unloading and impact dumping → closure.

[0122] The first specific application of this embodiment is as follows:

[0123] The method for closure of the dike based on the integrally assembled double-sill bottom protection structure specifically includes the following steps:

[0124] S1. The dimensions of the bottom protection structure meet the requirements for structural stability.

[0125] 1) Particle size calculation

[0126] The particle size calculation is based on the previous calculation. The retaining wall is placed in the flowing water during the non-flood season one year before the closure. The retaining wall structure must safely pass through the flood season of the year before the closure in the Longkou Riverbed. The retaining wall structure must ensure stability during the closure process. The flow velocity at the inlet is different for each time period, as detailed in Table 1. The maximum value of 1.0 m is taken as the calculation result.

[0127] Table 1

[0128]

[0129] (2) Stroke distance calculation

[0130] The distance calculation is based on the previous calculation. The bottom protection is thrown into the flowing water during the non-flood season one year before the closure, as detailed in Table 2.

[0131] Table 2

[0132]

[0133] S2. Determining the scope of the bottom protection

[0134] 1) Length of the dike along its axis

[0135] The width of the inlet along the spur dike axis that corresponds to a flow velocity exceeding the scour resistance velocity of the overburden layer by 3.4 m / s is 40~60 m, as detailed in Table 3.

[0136] Table 3

[0137]

[0138] 2) Length in the direction of water flow

[0139] The water depth and the length along the flow direction vary depending on the width of the dam opening during different periods of dam closure. The maximum value is taken, as detailed in Table 4.

[0140] Table 4

[0141]

[0142] 3) Model test verification

[0143] The calculation results were verified through model experiments:

[0144] 1) The bottom protection thickness is 1.0m, and the individual dimensions of a steel gabion are 1.0m × 1.0m × 1.0m (length × width × height). The gabions are spliced ​​together and arranged closely. The length along the axis of the spur dike is 40~60m, and the length along the direction of water flow extends beyond the toe of the spur dike. The length above the axis of the spur dike is 10~20m, and the length below the axis of the spur dike is 20~30m, for a total of 30~50m.

[0145] 2) The gabion retaining wall is located downstream, with each individual reinforced gabion measuring 2.0m × 2.0m × 2.0m (length × width × height). Experimental studies were conducted on three arrangements of the reinforced gabions: single-row dispersed arrangement, double-row dispersed arrangement, and double-row closely arranged arrangement. When the gap width was greater than 40m, none of the three types of retaining walls were washed away by the water flow and remained stable. When the gap width was 40m, the reinforced gabions in the single-row dispersed arrangement were washed away in the main flow zone; the reinforced gabions in the double-row dispersed arrangement shifted slightly downwards in the main flow zone but were not washed away; and the double-row closely arranged arrangement remained stable under all flow rates in the difficult section. Based on the analysis of the model test results, it is considered to install two reinforced gabion retaining walls, with a length of 30-50m perpendicular to the water flow direction and equal to the bottom protection.

[0146] S3. Reinforcing cage fabrication

[0147] The dimensions of a single reinforced gabion for the bottom protection are 1.0m × 1.0m × 1.0m (length × width × height), and the dimensions of a single reinforced gabion for the retaining wall are 2.0m × 2.0m × 2.0m (length × width × height). The main frame reinforcement uses 20mm diameter HRB400 steel bars, with a 10cm × 10cm mesh made of 14mm diameter HRB400 steel bars. Intersections are welded, and the bending of the steel bars meets the specifications. The lap length of the lap welds meets the requirements of 10d on one side and 5d on both sides. Every intersection is welded in place, and incomplete welds are strictly prohibited. The reinforcement cage processing site is located at the left bank spoil heap. Processed reinforcement cages are filled with riprap nearby, covered, and stacked as a whole. The filling stone is hard, not easily weathered, not easily hydrolyzed, and not easily broken, with a saturated compressive strength > 40Mpa, a softening coefficient > 0.8, and a freeze-thaw loss rate < 1%. The size of the boulders should not be less than 15cm. Stone filling requires manual stacking, using large stones as the framework and smaller stones for filling the gaps. The filling must be tight, with a porosity not exceeding 20%. Considering stone settlement, a 2.5cm margin should be allowed during filling. After filling, cover the gabion and secure it firmly with wire. The gabion should have four lifting points. The gabion should be hoisted onto flat ground near the bank at the processing site, and on-site testing should be conducted to identify and address any problems promptly.

[0148] S4. Transport and unloading

[0149] The prepared reinforced gabions were lifted using 50t cranes (for lifting gabions for sand retaining walls) and 16t cranes (for lifting gabions for lifting bottom protection walls). One gabion was lifted at a time and transported to the temporary dock in 25t or 32t dump trucks, with 2-3 gabions laid flat on each truck. The 50t cranes (for lifting gabions for sand retaining walls) and 16t cranes (for lifting gabions for lifting bottom protection walls) were then used to unload the gabions at a depth of 1000m. 3 The bottom-opening barge work platform is arranged in a row along the axis of the dike for easy assembly.

[0150] S5. Platform assembly

[0151] The bottom protection structure is assembled on the bottom-opening barge platform. (Based on a 1000m...) 3 The opening dimensions and width of the bottom-opening movable silo are determined. The number of rows of steel cages assembled in the first batch is 2 rows of stone retaining walls + 8 rows of bottom protection, and thereafter 12 rows of bottom protection. Adjacent outer cages are connected and secured with steel wire ropes. When the middle cage cannot be connected with steel wire ropes, steel wire ropes are wrapped around the top and bottom of the cage to assemble the steel gabion into a whole.

[0152] S6. Underwater Measurement and Positioning

[0153] Underwater surveying was conducted to obtain a riverbed topographic map within 100m upstream and downstream of the levee axis, and control points for the levee axis, as well as a certain number of elevation control points and horizontal control points, were established.

[0154] S7. Throwing Test

[0155] Before the actual deployment, several deployment tests were conducted using a bottom-opening barge at different flow velocities. The bottom-opening barge was positioned 20-30m downstream of the bottom protection area, and double rows of reinforced gabion strings were simultaneously submerged to the bottom of the water to conduct underwater measurements. The relationship curve between flow velocity and displacement was measured to guide precise deployment.

[0156] S8. Construction Positioning

[0157] Based on the results of the throwing test and the measured average flow velocity, after shifting upstream by approximately 50m, then according to 1000m... 3 The opening width of the bottom-opening barge's movable compartment is divided into standard throwing strips in the direction of water flow, with each strip being 12m wide. A fixed floating object positioning throwing strip is set up within the designated area. After the bottom-opening barge travels to the designated area, its installed GPS positioning system compares the positioning floating object with the actual throwing position in real time to control the throwing location.

[0158] S9. Precision Throw

[0159] The project was carried out during the dry season of the year preceding the river closure, when the riverbed flow was low and the water level was low, which was conducive to construction. Bottom-opening barge placement was employed, with real-time monitoring of flow velocity during construction and adjustments to the barge position based on the velocity-distance relationship curve. (From 1000m) 3 The GPS positioning system installed on the bottom-opening barge compares the positioning with the floating object in real time to control the casting position, achieving precise casting. It provides real-time feedback on underwater casting retest results, allowing for timely adjustments to the casting position. The effective casting position deviation is controlled within 20-30cm, ensuring the quality of the bottom protection construction. Steps 3-9 are repeated, with the bottom-opening barge making four round trips to the shore to complete the bottom protection casting task.

[0160] S10. Pre-occupation of the diversion embankment

[0161] Following the completion of the bottom protection construction, the pre-entry construction of the diversion embankment will proceed normally during the dry season of the following year, with a diversion flow of 2430 m³. 3 / s. The construction steps are as follows: 0.1~0.3m stone and rubble mixture is dumped and transported to the embankment → unloading at the embankment head → centralized pushing and dumping → when encountering steep riverbed changes and difficult sections to occupy, 0.3~0.7m mixed rubble is used to occupy the sections → forming the embankment head.

[0162] S11. Closing the Dragon's Mouth

[0163] The closure construction steps were as follows: material transportation → unloading → alternating use of centralized pushing and throwing with unloading, ramming, and throwing → closure. Large stones over 0.7m in diameter and 2.0m × 2.0m × 2.0m (length × width × height) reinforced gabion cages were continuously and intensely thrown during the construction. A combined approach of full-section advancing and protruding upstream corner method was used, and the closure was completed in 56 hours with rapid river closure.

[0164] In this embodiment: the interception flow rate is 2430 m³ / h 3 The flow rate is 100m wide at the mouth, with an average flow velocity of 2.87~3.92m / s. A single-spur dike is used for entry. Model tests show that large-scale material erosion and collapse frequently occur at the dike head, endangering construction safety and delaying the entry speed. Through theoretical discussion and experimental research, a pre-installed double-spur dike bottom protection structure is deployed during the dry season one year before the dike closure. The bottom protection is 40~60m long along the water flow direction and 30~50m long perpendicular to the water flow direction. Through deployment tests and real-time flow velocity monitoring, the bottom opening and positioning are adjusted in a timely manner to achieve precise deployment. A 1000m... 3 The bottom-opening barge made six round trips to the bank to complete the bottom protection placement task. Underwater re-measurement after construction showed that the deviation between the bottom protection position and the preset position was controlled within 20cm. The construction was precise, rapid, and reliable, requiring no dry-land conditions and without time-limited constraints. During the formal closure, the collapse of the spur dike head was virtually eliminated, effectively increasing the riverbed roughness in the Longkou section, improving the stability boundary conditions of the placed material, effectively intercepting the placed material, increasing the stability of the downstream slope toe of the spur dike, reducing material loss, and lowering the placement intensity, achieving a safe and rapid closure within 56 hours.

[0165] The second specific application of this embodiment is as follows:

[0166] The method for closure of the dike based on the integrally assembled double-sill bottom protection structure specifically includes the following steps:

[0167] S1. The dimensions of the bottom protection structure meet the requirements for structural stability.

[0168] 1) Particle size calculation

[0169] The particle size calculation is based on the previous calculation. The retaining wall is placed in the flowing water during the non-flood season one year before the closure. The retaining wall structure must safely pass through the flood season of the year before the closure in the Longkou Riverbed. The retaining wall structure must ensure stability during the closure process. The flow velocity at the inlet is different for each time period, as detailed in Table 1. The maximum value of 0.5m is taken as the calculation result.

[0170] Table 1

[0171]

[0172] 2) Stroke distance calculation

[0173] The distance calculation is based on the previous calculation. The bottom protection is thrown into the flowing water during the non-flood season one year before the closure, as detailed in Table 2.

[0174] Table 2

[0175]

[0176] S2. Determining the scope of the bottom protection

[0177] 1) Length of the dike along its axis

[0178] The width of the inlet along the spur dike axis that corresponds to a flow velocity exceeding the scour resistance velocity of the overburden layer by 3.2 m / s is 30-40 m, as detailed in Table 3.

[0179] Table 3

[0180]

[0181] 2) Length in the direction of water flow

[0182] The water depth and the length along the flow direction vary depending on the width of the dam opening during different periods of dam closure. The maximum value is taken, as detailed in Table 4.

[0183] Table 4

[0184]

[0185] 3) Model test verification

[0186] The calculation results were verified through model experiments:

[0187] 1) The bottom protection thickness is 0.5m, and the individual dimensions of a steel gabion are 1.0m × 1.0m × 0.5m (length × width × height). The gabions are spliced ​​together and arranged closely. The length along the axis of the spur dike is 30~40m, and the length along the direction of water flow extends beyond the toe of the spur dike. The length above the axis of the spur dike is 5~10m, and the length below the axis of the spur dike is 10~20m, for a total of 15~30m.

[0188] 2) The gabion retaining wall is located downstream, with each reinforced gabion measuring 2.0m × 2.0m × 2.0m (length × width × height). Two reinforced gabion retaining walls are installed, with a length of 15~30m perpendicular to the water flow direction and equal to that of the bottom protection.

[0189] S3. Reinforcing cage fabrication

[0190] The dimensions of a single reinforced gabion for the bottom protection are 1.0m × 1.0m × 0.5m (length × width × height), and the dimensions of a single reinforced gabion for the retaining wall are 2.0m × 2.0m × 2.0m (length × width × height). The main frame reinforcement uses 20mm diameter HRB400 steel bars, with a 10cm × 10cm mesh made of 14mm diameter HRB400 steel bars. Intersections are welded, and the bending of the steel bars meets the specifications. The lap length of the lap welds meets the requirements of 10d on one side and 5d on both sides. Every intersection is welded in place, and incomplete welds are strictly prohibited. The reinforcement cage processing site is located at the left bank spoil heap. Processed reinforcement cages are filled with riprap nearby, covered, and stacked as a whole. The filling stone is hard, not easily weathered, not easily hydrolyzed, and not easily broken, with a saturated compressive strength > 40Mpa, a softening coefficient > 0.8, and a freeze-thaw loss rate < 1%. The size of the boulders should not be less than 15cm. Stone filling requires manual stacking, using large stones as the framework and smaller stones for filling the gaps. The filling must be tight, with a porosity not exceeding 20%. Considering stone settlement, a 2.5cm margin should be allowed during filling. After filling, cover the gabion and secure it firmly with wire. The gabion should have four lifting points. The gabion should be hoisted onto flat ground near the bank at the processing site, and on-site testing should be conducted to identify and address any problems promptly.

[0191] S4. Transport and unloading

[0192] The prepared reinforced gabions were lifted using 50t cranes (for lifting gabions for sand retaining walls) and 16t cranes (for lifting gabions for lifting bottom protection walls). One gabion was lifted at a time and transported to the temporary dock in 25t or 32t dump trucks, with 2-3 gabions laid flat on each truck. The 50t cranes (for lifting gabions for sand retaining walls) and 16t cranes (for lifting gabions for lifting bottom protection walls) were then used to unload the gabions at a depth of 500m. 3 The bottom-opening barge work platform is arranged in a row along the axis of the dike for easy assembly.

[0193] S5. Platform assembly

[0194] The bottom protection structure is assembled on the bottom-opening barge platform. (Based on a 500m...) 3 The opening dimensions and width of the bottom-opening movable silo are determined. The number of rows of steel cages assembled in the first batch is 2 rows of stone retaining walls + 4 rows of bottom protection, and thereafter 8 rows of bottom protection. Adjacent outer cages are connected and secured with steel wire ropes. When the middle cage cannot be connected with steel wire ropes, steel wire ropes are wrapped around the top and bottom of the cage to assemble the steel gabion into a whole.

[0195] S6. Underwater Measurement and Positioning

[0196] Underwater surveying was conducted to obtain a riverbed topographic map within 100m upstream and downstream of the levee axis, and control points for the levee axis, as well as a certain number of elevation control points and horizontal control points, were established.

[0197] S7. Throwing Test

[0198] Before the actual deployment, several deployment tests were conducted using a bottom-opening barge at different flow velocities. The bottom-opening barge was positioned 20-30m downstream of the bottom protection area, and double rows of reinforced gabion strings were simultaneously submerged to the bottom of the water to conduct underwater measurements. The relationship curve between flow velocity and displacement was measured to guide precise deployment.

[0199] S8. Construction Positioning

[0200] Based on the results of the throwing test and the measured average flow velocity, after shifting upstream by approximately 50m, then by 500m... 3 The opening width of the bottom-opening barge's movable compartment is divided into standard throwing strips in the direction of water flow, with each strip being 8 meters wide. A fixed floating object positioning throwing strip is set up within the designated area. After the bottom-opening barge travels to the designated area, its installed GPS positioning system compares the positioning with the floating object in real time to control the throwing position.

[0201] S9. Precision Throw

[0202] The project was carried out during the dry season of the year preceding the river closure, when the riverbed flow was low and the water level was low, which was conducive to construction. A bottom-opening barge was used for placement, and the flow velocity was monitored in real time during construction. The position of the bottom-opening barge was adjusted appropriately based on the flow velocity-distance relationship curve. (From 500m) 3 The GPS positioning system installed on the bottom-opening barge compares the positioning with the floating object in real time to control the casting position, achieving precise casting. It provides real-time feedback on underwater casting retest results, allowing for timely adjustments to the casting position. The effective casting position deviation is controlled within 20-30cm, ensuring the quality of the bottom protection construction. Steps 3-9 are repeated, with the bottom-opening barge making four round trips to the shore to complete the bottom protection casting task.

[0203] S10. Pre-occupation of the diversion embankment

[0204] Following the completion of the bottom protection construction, the pre-occupancy construction of the diversion embankment will proceed normally during the dry season of the following year, with a diversion flow of 2380 m³ / h. 3 / s. The construction steps are as follows: 0.1~0.3m stone and rubble mixture is dumped and transported to the embankment → unloading at the embankment head → centralized pushing and dumping → when encountering steep riverbed changes and difficult sections to occupy, 0.3~0.7m mixed rubble is used to occupy the sections → forming the embankment head.

[0205] S11. Closing the Dragon's Mouth

[0206] The closure construction steps were as follows: material transportation → unloading → alternating use of centralized pushing and throwing with unloading, ramming, and throwing → closure. Large stones over 0.7m in diameter and 2.0m × 2.0m × 2.0m (length × width × height) reinforced gabion cages were continuously and intensely thrown during construction. A combined approach of full-section advancing and protruding upstream corner method was used, and the closure was completed in 30 hours with rapid river closure.

[0207] In this embodiment: the interception flow rate is 2380 m³ / h. 3 The dam has a width of 800m and an average flow velocity of 2.96~3.80m / s. Enclosure construction utilizes a single-spur dike with a thick overburden layer and poor erosion resistance. Model tests show that large-scale material erosion and collapse frequently occur at the dike head, jeopardizing construction safety and delaying the closure process. Through theoretical discussion and experimental research, a pre-installed double-spur dike bottom protection structure was deployed during the dry season one year prior to the damming. The bottom protection structure is 30~40m long along the flow direction and 15~30m long perpendicular to the flow direction. By conducting deployment tests and real-time flow velocity monitoring, the positioning of the bottom opening was adjusted in a timely manner to achieve precise deployment. A 500m... 3 The bottom-opening barge made four round trips to the bank to complete the bottom protection placement task. Underwater re-measurement after construction showed that the deviation between the bottom protection position and the preset position was controlled within 20cm. The construction was precise, rapid, and reliable, requiring no dry-land conditions and without time-limited constraints. During the formal closure, the collapse of the spur dike head was virtually eliminated, effectively increasing the riverbed roughness in the Longkou section, improving the stability boundary conditions of the placed material, effectively intercepting the placed material, increasing the stability of the downstream slope toe of the spur dike, reducing material loss, and lowering the placement intensity. This resulted in a safe and rapid closure within 30 hours, approximately one month ahead of schedule.

[0208] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for closing a dike with an integrally assembled double-sill bottom protection structure, characterized in that, Includes the following steps: 1) During the dry season one year before the closure, a prefabricated, integrally assembled double-sill embankment bottom protection structure is constructed. The bottom protection structure is composed of a bottom protection section and a double-sill embankment section rigidly connected in sequence along the water flow direction. Standardized steel gabions are assembled into a whole through double internal and external connections. 2) The bottom protection structure is assembled in sections using a bottom-opening barge platform. The relationship between current velocity and distance is determined through throwing tests. GPS and floating objects are used for joint positioning to carry out precise underwater throwing. 3) After the bottom protection structure is completed, the dike will be pre-entered during the dry season of the following year to form the head of the dam; 4) Large stones and reinforced gabions were continuously thrown in, and the full-section advancement method and the protruding upstream corner method were combined to advance and complete the closure of the sluice gate.

2. The method according to claim 1, characterized in that, The core component of the overall assembled double-slope bottom protection structure is a reinforced gabion; the bottom protection reinforced gabion has a size of 1.0m×1.0m×0.5m or 1.0m×1.0m×1.0m, and the retaining gabion has a size of 2.0m×2.0m×2.0m.

3. The method according to claim 1, characterized in that, The reinforced gabion frame is welded with Φ20mm HRB400 steel bars, and the mesh is welded with Φ14mm HRB400 steel bars into a 10cm×10cm grid. The filling stone is hard stone with saturated compressive strength >40MPa, softening coefficient >0.8, freeze-thaw loss rate <1%, and particle size ≥15cm. The porosity is ≤20% when manually stacked.

4. The method according to claim 1, characterized in that, The internal and external double connection is as follows: the internal connection uses Φ10mm steel wire rope wrapped around the top and bottom and interlaced with mesh steel bars ≥5 times; the external connection uses Φ6mm twisted steel wire wrapped alternately in single / double loops with a spacing of 10~15cm; the middle cage is reinforced by fully wrapping steel wire rope around the top and bottom.

5. The method according to claim 1, characterized in that, The double-barrier section includes a first barrier downstream, a second barrier upstream, and a 1.0m wide connecting section between the two barriers; both barriers are single-row, 2.0m high reinforced gabions tightly assembled, arranged at the same height, parallel, and along the entire length.

6. The method according to claim 1, characterized in that, The precise casting is carried out during the dry season one year before the river is dammed, and the deviation of the casting position is controlled within 20-30cm.

7. The method according to claim 1, characterized in that, The closure of the dragon mouth adopts the continuous high-intensity throwing of large stones and steel gabions, combined with the full-section advancement method and the protruding upstream corner method.

8. A fully assembled double-sill bottom protection structure, characterized in that, Along the direction of water flow, it consists of a bottom protection section and a double-barrier section rigidly connected together; the bottom protection section is made of multiple rows of reinforced gabions tightly assembled, and the double-barrier section is made of two parallel barrier sections of equal height and the connecting section between the barriers. The whole is a continuous plate-type integrated structure.

9. The bottom protection structure according to claim 8, characterized in that, The bottom protection section is 0.5~1.0m thick, the rock retaining wall is 2.0m high, and a 1.0m wide connecting section is set between the retaining walls. The whole structure is arranged along the entire length perpendicular to the direction of water flow.

10. The bottom protection structure according to claim 8, characterized in that, This bottom protection structure is suitable for the protection of river closure gaps in areas with high flow velocity, thick overburden, and poor riverbed erosion resistance. It can be deployed as a whole during the dry season one year before the closure and remains stable for many years.

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