Spur dike rigid bottom protection structure suitable for strong tidal bore environment

Abstract

According to the spur dike rigid bottom protection structure suitable for the strong tidal bore environment, grading block stones are thrown and filled on the coating face around an original spur dike, and permeable frame reinforced concrete regular tetrahedrons are regularly and densely arranged on the upper portions of the grading block stones, so that a protection system is formed; the dumping and filling range of the graded block stones is 15-20 meters above and below the dam body and 20 meters around the dam head, the graded block stones are dumped and filled from a bed surface below-1.5--6.5 meters, and the thickness of a tidying and polishing surface layer of the graded block stones is 1-2 meters; 1-2 layers of permeable frame reinforced concrete regular tetrahedrons are thrown and filled. The spur dike has the advantages that the water flow scouring strength is reduced, the stability of the beach face around the spur dike is enhanced, the change of water flow is smoother and softer, and scouring of the water flow to the coating face can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of groyne bottom protection technology, specifically to a rigid groyne bottom protection structure that protects vertical pile foundations or groyne structures in a river channel by covering and protecting the silty sand foundation and reducing the flow velocity in a strong tidal environment, so as to prevent the strong tidal and reciprocating flow from scouring the groyne and pile foundation. Background Technology

[0002] The Zhejiang Provincial Institute of Estuarine and Coastal Research has conducted multiple tidal bore observations along the Qiantang River, finding that the propagation speed of estuarine tidal bores can reach 4-6.5 m / s.

[0003] There are three main interacting flow structures at the head of a groyne: concentrated flow around the head, subsurface flow, and vertical vortex behind the head. The combined effect of these three factors is the main driving force behind localized scouring of the groyne and subsequent water damage. In the Qiantang River, the flow around the head of a groyne is even more complex due to the influence of tidal bores.

[0004] In the practice of groyne scour control engineering, various measures are taken to control the development of local scour pits at the groyne head. These measures may weaken the dynamics of the water flow near the groyne, such as by rationally setting the length, height, spacing, and angle of the groyne to smooth the water flow at the groyne head as much as possible; or improve the scour resistance of the bed surface near the groyne head, such as by using riprap, irregularly shaped blocks, or concrete hinged decking as a bedding layer for bottom protection at the groyne head.

[0005] The tetrahedral permeable frame gradually reduces the scouring energy of the water flow along its path through the turbulence effect of its members, thereby protecting the bed surface. Compared to solid protective materials (such as solid concrete tetrahedrons), its advantage lies in transforming the abrupt disturbance of solid materials on the water flow into a gradual disturbance along the path of the permeable material, and changing the overall disturbance of solid materials on the water flow into local disturbances of individual members, thus making the change in water flow smoother and gentler. Comparative practice has shown that the permeable tetrahedron is more effective than the solid concrete tetrahedron in reducing velocity and preventing scouring.

[0006] In current engineering applications, tetrahedral permeable frames are mostly prefabricated using reinforced concrete members with a length of 1.0m and a cross-sectional size of 0.1m × 0.1m. This frame structure is mostly used for erosion prevention of the Yangtze River embankment and has also been used in the Feiyun River, but it has not been implemented in the Qiantang River area with strong tidal surges and high flow velocities. Summary of the Invention

[0007] The purpose of this invention is to provide a rigid bottom protection structure for groynes suitable for strong tidal environments, which reduces the intensity of water flow scouring, enhances the stability of the beach surface around the groynes, promotes smoother and gentler changes in water flow, and effectively reduces the scouring effect of water flow on the surface.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: A rigid bottom protection structure for groynes suitable for strong tidal bore environments involves filling the surface around the original groyne with graded rubble to protect the sandy soil foundation of the river channel under strong tidal bores, while simultaneously preventing scouring of the bottom sand by the tidal flow. Above the graded rubble, a series of regularly arranged, densely packed, precast, medium-to-large-sized, permeable reinforced concrete tetrahedrons form a protective system for the beach surface, thus mitigating the scouring energy and intensity of the water flow and making the beach surface around the groyne more stable. The graded rubble is placed within a 15-20 meter range upstream and downstream of the groyne and within a 20-meter radius around the groyne head. The graded rubble is placed from a depth of -1.5 to -6.5 meters below the bed surface, with a rubble layer thickness of 1-2 meters. One to two layers of the permeable reinforced concrete tetrahedrons are then placed.

[0009] Furthermore, the graded rubble layer for bottom protection should be implemented when the tidal current velocity is low during neap tides and floods to prevent water erosion; after reaching the designed thickness, the permeable frame reinforced concrete tetrahedrons should be evenly placed in 1-2 layers using a hoisting method.

[0010] Furthermore, the open frame is a reinforced concrete tetrahedron with a central open structure, forming a cavity through the side reinforced concrete frame. The frame is reinforced with side lengths of 2.5 to 3 meters, and the frame columns are triangular prisms with rounded arcs. The frame thickness is 45 to 50 centimeters.

[0011] Furthermore, four rows of graded rubble are filled upstream and downstream of the dam body, with two layers of regularly arranged, densely packed, permeable reinforced concrete tetrahedrons on the upper part; eight rows of graded rubble are filled around the dam head, with two layers of regularly arranged, densely packed, permeable reinforced concrete tetrahedrons on the upper part.

[0012] Furthermore, the regularly arranged, densely packed, perforated reinforced concrete frame on all four sides of the dam body and dam head weighs 4 to 5 tons.

[0013] Furthermore, the graded rubble is provided with the following proportions: 70% of the rubble weighs 30-50 kg and 30% weighs 50-100 kg. This is beneficial for rubble density and bottom compaction, as well as for construction operations. The selected rubble should be fresh and unweathered. The saturated compressive strength of the graded rubble layer is not less than 40 MPa and the softening coefficient is not less than 0.75.

[0014] Compared with the prior art, the present invention has the following advantages: A rigid bottom protection structure for groynes suitable for strong tidal environments is proposed. This structure uses well-graded riprap with a thickness of at least 2m to protect the sandy soil foundation of a tidal river channel. A permeable frame reinforced concrete tetrahedron, through the flow-dissipating effect of its members, gradually reduces the scouring energy of the water flow along the bottom, thereby reducing the intensity of the scouring and protecting the bed surface. This enhances the stability of the surrounding beach. Not only does it reduce the weight of the tetrahedron, but more importantly, compared to solid protective materials (such as solid concrete tetrahedrons), the permeable frame tetrahedron transforms the abrupt disturbance of solid materials on the water flow into a gradual disturbance along the flow path, turning the overall disturbance of solid materials into local disturbance of the frame. This results in a smoother and gentler water flow, effectively reducing the scouring effect on the surface. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the planar layout of the present invention.

[0016] Figure 2 This is a schematic diagram of the cross-sectional arrangement of the present invention.

[0017] Figure 3 This is a schematic diagram of the open frame reinforced concrete tetrahedral two-layer stacked structure of the present invention.

[0018] Figure 4 This is a schematic diagram of the external structure of the hollow frame reinforced concrete tetrahedron of the present invention.

[0019] Reference numerals: 1. Openwork frame reinforced concrete tetrahedron; 2. Graded rubble; 3. Groynes structure. Detailed Implementation

[0020] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0021] A rigid bottom protection structure for groynes suitable for strong tidal bore environments, such as Figure 1 , 2 As shown, graded rubble 2 is placed upstream and downstream of the dam body and around the dam head of the groyne structure 3. The placement is carried out from a bed depth of -1.5 to -6.5 meters. Four rows of graded rubble 2 are placed upstream and downstream of the dam body, and eight rows of graded rubble 2 are placed within 20 meters around the dam head, forming a 2-meter-thick graded rubble surface. Then, two layers of perforated frame reinforced concrete tetrahedrons 1 are regularly and densely arranged on the graded rubble surface, as shown in the diagram. Figure 3 As shown, a hollow frame structure with a thickness of 45 cm and a weight of 4 tons is formed.

[0022] like Figure 4 As shown, the open frame reinforced concrete tetrahedron 1 has an open center, forming a cavity through the side reinforced concrete frame. The frame is reinforced with side lengths of 2.5 to 3 meters, and the frame columns are triangular prisms with rounded arcs.

[0023] Related research defines porosity as the degree of voidness and throwing density within a unit volume of porous tetrahedral group: ; Where: V 群 V represents the total volume of space occupied by the open tetrahedron group; 单 N is the volume of water displaced by a single open tetrahedron; N is the number of tetrahedrons in the open tetrahedron group.

[0024] When the permeability per unit volume is low, the water-blocking performance of the permeable tetrahedron group is relatively strong, resulting in weak water permeability. Water flow into the permeable tetrahedron group is restricted, and the energy dissipation effect is relatively low. As the permeability increases, the porosity inside the permeable tetrahedron group increases, enhancing its permeability. Sufficient water flow is allowed inside, and the water-blocking and energy dissipation performance of the members within the permeable tetrahedron group is fully utilized, with the deceleration rate gradually increasing, reaching its maximum when the permeability reaches approximately 5. When the permeability increases further, the water permeability improves rapidly, but because there are no members with a sufficient volume ratio to block and dissipate the water flow, the water-blocking performance of the permeable tetrahedron group weakens significantly, resulting in a decrease in energy dissipation efficiency and a rapid decrease in the deceleration rate.

[0025] The above structure is laid out, considering an 80% bottom porosity, per 100m 2 If approximately 47 perforated reinforced concrete tetrahedrons can be thrown into the second floor, the perforation rate is 5.2%, which is consistent with relevant research results.

[0026] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept 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 rigid bottom protection structure for groynes suitable for strong tidal bore environments, characterized in that: Graded rubble is filled on the surface around the original groynes. The top layer of the graded rubble consists of regularly arranged, densely packed, perforated reinforced concrete tetrahedrons, forming a protective system. The graded rubble is filled within 15-20 meters upstream and downstream of the dam body and within 20 meters around the dam head. The graded rubble is filled from a depth of -1.5 to -6.5 meters below the bed surface, and the thickness of the graded rubble surface layer is 1-2 meters. The perforated reinforced concrete tetrahedrons are filled in 1-2 layers.

2. The rigid bottom protection structure of a groyne suitable for strong tidal bore environments according to claim 1, characterized in that: The side length of the open frame reinforced concrete tetrahedron is 2.5 to 3 meters, the frame columns are rounded triangular prisms, and the frame thickness is 45 to 50 centimeters.

3. A rigid bottom protection structure for groynes suitable for strong tidal bore environments according to claim 1 or 2, characterized in that: The dam body is filled with four rows of graded rubble upstream and downstream, and the upper part is filled with two layers of regular, densely arranged, perforated reinforced concrete tetrahedrons; the dam head is filled with eight rows of graded rubble, and the upper part is filled with two layers of regular, densely arranged, perforated reinforced concrete tetrahedrons.

4. A rigid bottom protection structure for groynes suitable for strong tidal bore environments according to claim 3, characterized in that: The regularly arranged, densely packed, perforated reinforced concrete frame on the four sides of the dam body and dam head weighs 4 to 5 tons.

5. A rigid bottom protection structure for groynes suitable for strong tidal bore environments as described in claim 1 or 4, characterized in that: The graded rubble is provided with the following proportions: 70% of the rubble weighs 30-50 kg and 30% of the rubble weighs 50-100 kg; the saturated compressive strength of the graded rubble layer is not less than 40 MPa and the softening coefficient is not less than 0.75.

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