A flexible box-type grid ecological bridge pier bottom protection structure

Abstract

The present invention discloses a flexible box-type grid ecological bridge pier bottom protection structure, comprising a bridge pier, a cap disposed under the bridge pier, and a plurality of pile foundations for supporting the cap. An annular permeable grid box corresponding to the shape of the bridge pier is disposed on the outside of the bridge pier, and the inner size of the permeable grid box corresponds to the outer size of the bridge pier. The permeable grid box is disposed on the cap, and the top surface of the permeable grid box is flush with the riverbed of the corresponding river; the permeable grid box is filled with stones, and a plurality of fish nest bricks are embedded and fixed in the grids formed by the top surface and the outer side grid of the permeable grid box at intervals, and the outer surfaces of all the fish nest bricks are lower than the corresponding surface of the permeable grid box, thereby forming a plurality of pits on the top surface and the side of the permeable grid box. The bottom protection structure can effectively slow down the flow velocity of water near the bridge pier, reduce scouring, and avoid the bridge body from being scoured by the bottom of the bridge pier by the descending water flow and the vortex system, which causes the bridge body to be unstable. At the same time, it can also provide spawning grounds and predation grounds for benthic organisms and fish, and compensate for the negative impact of the bridge pier construction on the ecological environment of the water system.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to a flexible box-type grid ecological bridge pier bottom protection structure. Background Art

[0002] Domestic and foreign data show that the construction of large bridge piers will cause a sudden change in the local water flow boundary in the river channel, resulting in a sharp detour around the piers. The original straight-flowing water flow is blocked by the piers to form waterlogging, thereby generating a vertical spiral flow, which generates a strong downward shear force on the riverbed surface around the piers, and gradually forms scour pits. For the piers, due to the water blocking of the piers, the cross-sectional area of ​​the water flow is reduced, the flow velocity around the piers increases and a complex vortex structure is formed, the shear stress of the riverbed increases, and the riverbed sediments around the piers are transported by the water flow, resulting in a gradual decrease in the elevation of the riverbed surface, and scour pits are generated at high flow rates. The burial depth of the pier foundation is reduced, the abutment and pile foundation are exposed, and the bearing capacity of the bridge is reduced. In severe cases, the bridge will collapse, causing loss of life and property, and posing a great threat to public safety.

[0003] At present, according to the protection principle, there are two main types of scour protection at home and abroad: energy dissipation and bottom protection. Among them, one of the measures of the former is to set up a group of protective piles upstream and downstream of the foundation, which can effectively reduce the flow velocity of the water around the pier and move the scour pit forward, thereby reducing the scour depth within the foundation. However, due to the rapid flow of water at the main pier, the impact on the protective piles is very large, and the local scour of the protective piles themselves is also very serious, making it difficult to maintain their own stability. In addition, such settings also have a great impact on the flood and navigation conditions of the river. The latter uses structures such as riprap, sand pillows, sand bags, and soft rows to protect the pier foundation and its surroundings to resist the bottom downward vortex generated by the impact of the water flow in front of the pier, so as to achieve the effect of reducing the maximum scour depth. However, such methods have serious damage to the ecosystem and functions of the river, directly affecting the survival of fish and benthic organisms, and causing a sharp decline in biodiversity. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a flexible box-type grid ecological pier bottom protection structure, which can effectively slow down the water flow velocity near the piers, reduce scouring, and avoid the piers being washed by the descending water flow and the vortex system to cause the bridge body to become unstable. At the same time, it can also provide spawning and feeding grounds for benthic organisms and fish, thereby compensating for the negative impact of pier construction on the ecological environment of the water system.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A flexible box-type grid ecological pier bottom protection structure comprises a pier, a pedestal arranged under the pier and a plurality of pile foundations for supporting the pedestal, an annular permeable grid box corresponding to the shape of the pier is arranged on the outside of the pier, and the inner size of the permeable grid box corresponds to the outer size of the pier, the permeable grid box is arranged on the pedestal and the top surface of the permeable grid box is flush with the riverbed of the corresponding river; the permeable grid box is filled with stones, and a plurality of fish nest bricks are embedded and fixed at intervals in the squares formed by the top surface and the outer side grids of the permeable grid box, the fish nest bricks are arranged one by one in correspondence with the squares, and the outer surfaces of all the fish nest bricks are lower than the corresponding surfaces of the permeable grid box, thereby forming a plurality of pits on the top surface and the side of the permeable grid box.

[0007] Furthermore, the permeable grid box is composed of a plurality of permeable grid box units, and the permeable grid box units are at least one of an arc-shaped grid box or a rectangular grid box.

[0008] Furthermore, the permeable grid box is composed of multiple layers of permeable grid box units in the longitudinal direction, and the permeable grid box units of two adjacent layers are connected correspondingly.

[0009] Furthermore, the permeable grid box is composed of multiple layers of permeable grid box units in the transverse direction, and the permeable grid box units of two adjacent layers are correspondingly connected.

[0010] Furthermore, the arc grille box and the rectangular grille box are both cast by reinforced concrete, and a number of connection holes are reserved on the six sides of the arc grille box and the rectangular grille box, so that adjacent permeable grille box units can be connected through connectors to form a whole.

[0011] Furthermore, the central angle of each arc-shaped grille box is 30 to 60 degrees.

[0012] Furthermore, the median particle size D 50 Calculated by the following formula:

[0013]

[0014] Where: U—flow velocity in front of the pier, m / s;

[0015] y 0 —Deepness of water travel, m.

[0016] Furthermore, the width of the permeable grid box is 2 to 4 m, and the height is 2 to 4 m.

[0017] Furthermore, a plurality of grids are arranged in the permeable grid box, and the distance between two adjacent grids is 0.2 to 0.5 m.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention provides a permeable grid box on the foundation, and the stones filled in the permeable grid box are not easily dispersed, which can effectively ensure the integrity of the permeable grid box and the stones, and can effectively increase the local roughness near the pier, thereby effectively slowing down the flow rate of water near the pier and reducing scouring. At the same time, it can avoid scouring damage directly caused by expanding the pier foundation.

[0020] In addition, fish nest bricks are embedded in the grilles on the top and sides of the permeable grille box at intervals, and the outer surface of the fish nest bricks is lower than the corresponding surface of the permeable grille box, thereby forming a concave and convex structure on the top and sides of the permeable grille box, which is beneficial to increase the length of the water flow streamline and reduce the scouring caused by high flow velocity during floods. At the same time, it can form a terrain with alternating rapids and slow currents, and coexistence of deep pools and shallows, thereby providing adaptive habitats for rapids and slow current biological communities, and spawning grounds for fish migration.

[0021] 2. The permeable grid box of the present invention is composed of a detachable arc-shaped grid box and a rectangular grid box, and has a certain flexibility. It can produce adaptive deformation as the bottom sediment is washed away, thereby preventing and reducing continuous scouring around the river channel, reducing the problems of reduced buried depth of bridge pier foundations and reduced bearing capacity caused by continuous scouring, and can also effectively reduce construction costs.

[0022] 3. The permeable grid box of the present invention is a detachable structure, which is convenient to assemble, repair and replace. When a certain arc-shaped grid box or rectangular grid box is damaged, it can be replaced in time, which is beneficial to extend the service life of the permeable grid box and reduce engineering costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 - Side view of the invention.

[0024] Figure 2 - Top view of the invention.

[0025] Figure 3 -Curved grille box.

[0026] Figure 4 -Rectangular grille box.

[0027] Among them: 1-bridge pier; 2-permeable grille box; 2a rectangular grille box; 2b arc grille box; 3-stone; 4-fish nest brick; 5-capping platform; 6-pile foundation. DETAILED DESCRIPTION

[0028] See also Figure 1 to Figure 4A flexible box-type grid ecological pier bottom protection structure comprises a pier 1, a cap 5 arranged under the pier 1 and a plurality of pile foundations 6 for supporting the cap 5. An annular permeable grid box 2 corresponding to the shape of the pier 1 is arranged on the outside of the pier 1, and the inner size of the permeable grid box 2 corresponds to the outer size of the pier 1. The permeable grid box 2 is arranged on the cap 5 and the top surface of the permeable grid box 2 is flush with the riverbed of the corresponding river; the permeable grid box 2 is filled with stone 3, and a plurality of fish nest bricks 4 are embedded and fixed at intervals in the squares formed by the top surface and the outer side grid of the permeable grid box 2. The fish nest bricks 4 are arranged one by one in correspondence with the squares, and the outer surfaces of all the fish nest bricks 4 are lower than the corresponding surfaces of the permeable grid box 2, thereby forming a plurality of pits on the top surface and the side of the permeable grid box 2.

[0029] The stones are filled in the permeable grille box. The stones and the permeable grille box have good integrity. Compared with riprap protection, the protection effect will not be weakened due to the internal filling stones being washed away. At the same time, it can effectively increase the local roughness near the bridge piers, thereby effectively slowing down the flow rate of water near the bridge piers and reducing scouring. At the same time, it can avoid scouring damage directly caused by expanding the bridge pier foundation.

[0030] Fish nest bricks are embedded in the grilles on the top and sides of the permeable grille box at intervals, and the outer surface of the fish nest bricks is lower than the corresponding surface of the permeable grille box, so that a concave and convex structure is formed on the top and sides of the permeable grille box, which is beneficial to increase the length of the water flow streamline and reduce the scouring caused by the high flow rate during the flood period. At the same time, it can form a terrain with alternating rapids and slow currents, and coexistence of deep pools and shallows, thereby providing adaptive habitats for rapids and slow current biological communities, and spawning grounds for fish migration.

[0031] In a specific implementation, the permeable grid box 2 is composed of a plurality of permeable grid box units, and the permeable grid box unit is at least one of an arc-shaped grid box 2b and a rectangular grid box 2a.

[0032] The structure of the curved grille box is as follows: Figure 3 As shown, the structure of the rectangular grid box is as follows Figure 4 As shown in the figure, if the bridge pier is a cylindrical pier, the corresponding permeable grille box is composed of several arc-shaped grille boxes; if the bridge pier is a rectangular pier, the corresponding permeable grille box is composed of several rectangular grille boxes; if the bridge pier is a round pier, such as Figure 1 and Figure 2 As shown, the corresponding permeable grid box is composed of a plurality of arc-shaped grid boxes and a plurality of rectangular grid boxes.

[0033] In this way, the layout can be adjusted according to needs to better adapt to water flow conditions and complex riverbed terrain. At the same time, the assembled permeable grille box has a certain flexibility and can produce adaptive deformation as the bottom sediment is washed away, thereby preventing and reducing continuous scouring around the river channel, reducing the problems of reduced buried depth of bridge pier foundations and reduced bearing capacity caused by continuous scouring, and effectively reducing construction costs.

[0034] In specific implementation, the permeable grid box 2 is composed of multiple layers of permeable grid box units in the longitudinal direction, and the permeable grid box units of two adjacent layers are connected correspondingly.

[0035] In a specific implementation, the permeable grid box is composed of multiple layers of permeable grid box units in the transverse direction, and the permeable grid box units of two adjacent layers are connected correspondingly.

[0036] Multiple layers of permeable grid box units may be arranged in the longitudinal and / or transverse directions according to the scouring range and scouring depth.

[0037] In specific implementation, the arc grille box 2b and the rectangular grille box 2a are both cast by reinforced concrete, and a number of connection holes are reserved on the six sides of the arc grille box 2b and the rectangular grille box 2a, so that adjacent permeable grille box units can be connected through the connecting piece 7 to form a whole.

[0038] The connecting member 7 is a connecting buckle or / and a polymer bolt. The reinforced concrete casting is adopted to effectively ensure the strength of the permeable grid box.

[0039] In a specific implementation, the central angle of each arc-shaped grille box 2b is 30-60°.

[0040] In specific implementation, the median particle size D of the stone 3 50 Calculated by the following formula:

[0041]

[0042] Where: U—flow velocity in front of the pier, m / s;

[0043] y 0 —Deepness of water travel, m.

[0044] In a specific implementation, the width of the water-permeable grid box 2 is 2 to 4 m, and the height is 2 to 4 m.

[0045] In specific implementation, a plurality of grids are arranged in the permeable grid box 2, and the distance between two adjacent grids is 0.2-0.5 m.

[0046] Before making the permeable grille box unit, first place the stones and fish nest bricks in the permeable grille box unit, then use reinforced concrete to cast the permeable grille box unit, and then transport the permeable grille box unit filled with stones and fish nest bricks to the construction site and assemble it.

[0047] The present invention is further described in detail below in conjunction with specific implementation modes.

[0048] The engineering overviews of Example 1, Comparative Example 1 and Comparative Example 2 are as follows:

[0049] The total length of the bridge over a river in a mountainous area in the southwest is 3.82km, the main span is 1.24km, the round-head piers have a round head radius of 5m, and the rectangular part is 20m long. The water depth in front of the river piers during the flood season is 4m, and the flow velocity of the river during the flood season is 10.14m / s.

[0050] For the above project, different bottom protection measures were set on the bridge piers according to Example 1 and Comparative Example 1 and Comparative Example 2, and experimental research was carried out on the scouring range and scouring depth, the number of biological communities near the piers, and the fish density.

[0051] Example 1

[0052] This embodiment adopts a flexible box-type grid ecological bridge pier bottom protection structure, and its structure is as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the box-type grid structure is connected around the bridge piers through prefabricated screw holes, with two layers arranged horizontally and two layers arranged vertically, and the upper part is flush with the riverbed surface. According to the structural requirements, the arc section (connected by an arc-shaped grid box) in the present invention has an inner radius of 5m, a corresponding central angle of 60o, an outer radius of 12m, and a width of 3m; the straight section (connected by a rectangular grid box) is 5m long and 3m wide, and the height of the arc-shaped grid box and the rectangular grid box are both 2m. Each grid box is provided with 2 layers of grids, the width between the grids is 40cm, the thickness of each layer of grids is 25cm, and each layer is evenly distributed in the box. The median particle size D of the stone 50 According to the above formula, take 0.50m. As shown in the figure, 50*50cm embedded square fish nest bricks are arranged on the top and outer side of the grille box.

[0053] Experimental observation results: Under the above-mentioned flexible box-type grid pier bottom protection arrangement, the pier structure was not affected by the scouring according to the river flow rate during the flood season, and the water flow rate around the bridge body slowed down. The bottom protection structure in front of the pier did not change, and the riverbed surface in front of the bottom protection was scoured, forming a maximum scouring pit depth of 3.40m; the bottom protection structure behind the pier did not change, and there were traces of scouring on the riverbed surface behind the pier, forming a maximum scouring pit depth of 0.71m.

[0054] Comparative Example 1

[0055] This comparative example does not take any protective measures. Due to the lack of box-type grid pier bottom protection, the roughness around the pier is reduced, so the scouring marks are obvious, and the farthest distance of the scouring pit is 150m from the pier; the maximum flow rate is 0.19m / s higher than that of the example, and the scouring pit range is 35.7% larger. Due to the scouring effect of the horseshoe vortex in front of the pier and the wake vortex behind the pier, the maximum scouring depth of the scouring pit is 6.40m, and the pier loses its bearing capacity.

[0056] Comparative Example 2

[0057] This comparative example adopts traditional riprap protection, and the riprap range is three times the pier radius, that is, the farthest distance of the riprap from the pier is b = 3R 桥墩 =15m, height h=4m, median particle size of riprap D 50 Take 0.50m, and its top elevation is flush with the riverbed.

[0058] Experimental observation results: Affected by the scouring of water flow during the flood season, riprap protection can play a certain protective role in the initial stage. However, as time goes by, some stones are dispersed by the water flow, and the original riprap range and height change. The presence of irregularly distributed riprap with large particle size increases the pressure gradient trend of the riverbed side pressure pipe, which in turn enhances the scouring effect of the water flow on the pier. The maximum scouring pit depth on the front side of the riprap area is 8.6m; the maximum scouring pit depth on the front side of the bridge pier is 4.2m. This protection method lacks integrity under the scouring of water flow. The riprap structure reset after the scouring of water flow enhances the scouring capacity of the water flow, posing a threat to the safety of the bridge, and also increases the risk of accidents for navigable ships.

[0059] The fish density near the pier in Example 1 was measured to be 3.2 fish / m 3 , the fish density near the pier in comparison with Example 1 reached 0.3 fish / m 3 , the fish density near the pier in comparison with Example 2 reached 0.8 fish / m 3 The velocity of the flow field around the pier in Example 1 is affected by the surface structure of the pier, forming a habitat of alternating rapids and slow flows. The portable transistor biome meter measured that the average number of rapid and slow flow biomes was 13.3 times the average number of biomes in Comparative Example 1 and 10.1 times the average number of biomes in Comparative Example 2.

[0060] The engineering overview of Example 2 and Comparative Example 3 is as follows: The total length of the river-crossing bridge on a mountain river in the southwest is 2.56 km, the main span is 1.14 km, the cylindrical bridge piers have a cylindrical radius of 4 m, the water depth in front of the river piers during the flood season is 4 m, and the maximum river flow velocity during the flood season is 7.8 m / s.

[0061] For the above project, different pier bottom protections were set on the bridge piers according to Example 2 and Comparative Example 3, and experimental studies on the scouring depth, the number of biological communities near the piers, and the fish density were carried out.

[0062] Example 2

[0063] This embodiment adopts a flexible box-type grid ecological bridge pier bottom protection structure, and its structure is as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the box-type grid structure is connected around the pier through prefabricated screw holes, with two layers arranged horizontally and two layers arranged vertically, and the upper elevation is level with the bed surface. According to the structural requirements, the arc segment (formed by arc-shaped grid box connection) in the present invention has an inner radius of 4m and an outer radius of 6m, corresponding to a central angle of 45o, and a bottom protection single-layer box height of 2m. The grid box is provided with two layers of grids, with a width of 20cm between grids and a thickness of 25cm for each layer, and each layer is evenly distributed in the box. The median particle size D of the stone 50 According to the above formula, take 0.30m. Arrange 50*50cm embedded square fish nest bricks on the top and sides of the grille box.

[0064] Experimental observation results: Under the above-mentioned flexible box-type grid pier bottom protection arrangement, after a certain period of scouring by the maximum flow velocity of the year, the riverbed surface in front and behind the bottom protection was scoured, with the maximum scouring pit depth of 1.79cm on the front side and 0.83m on the rear side. The pier structure was not affected, and the bottom protection structure in front and behind the pier did not change.

[0065] Comparative Example 3

[0066] The configuration of this comparative example is the same as that of the above-mentioned Example 2, except that fish nest bricks are not provided in this comparative example.

[0067] Experimental observation results: Under the structural arrangement of this comparative embodiment, after being scoured by the maximum flow rate of the year for a certain period of time, the riverbed surfaces in front and behind the bottom protection were affected by the scouring of the water flow, with the maximum scour pit depth of 1.82m on the front side and 0.82m on the rear side; the pier structure was stable, and there was no change in the bottom protection structure in front and behind the piers.

[0068] The fish density near the pier in Example 2 was measured to be 3.1 fish / m 3 , Comparative Example 3: Fish density near the pier is 0.9 fish / m 3 The velocity of the flow field around the pier in Example 2 is affected by the surface structure of the pier, forming a habitat of alternating rapids and slow flows. The portable transistor biome meter measured that the average number of rapid and slow flow biomes was 11.3 times that of Comparative Example 3.

[0069] Finally, it should be noted that the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A flexible box-type grid ecological bridge pier bottom protection structure, comprising a bridge pier, a cap disposed under the bridge pier, and a plurality of pile foundations for supporting the cap. It is characterized in that An annular permeable grille box corresponding to the shape of the pier is provided on the outside of the bridge pier, and the inner size of the permeable grille box corresponds to the outer size of the pier. The permeable grille box is arranged on the pedestal and the top surface of the permeable grille box is flush with the riverbed of the corresponding river; the permeable grille box is filled with stones, and a plurality of fish nest bricks are embedded and fixed in the squares formed by the top surface and the outer side grilles of the permeable grille box at intervals, and the fish nest bricks are arranged one by one in correspondence with the squares, and the outer surfaces of all the fish nest bricks are lower than the corresponding surface of the permeable grille box, so that a plurality of pits are formed on the top surface and the side surface of the permeable grille box, thereby forming a concave and convex structure on the top surface and the side surface of the permeable grille box, which is convenient for increasing the length of the water flow streamline and reducing the scouring caused by the high flow rate during the flood period, and at the same time forming a terrain with alternating rapids and slow flows, and coexistence of deep pools and shallows, providing a habitat for biological communities and a spawning ground for fish migration; The permeable grid box is composed of a plurality of permeable grid box units, and the permeable grid box units are at least one of an arc-shaped grid box or a rectangular grid box.

2. A flexible box-type grid ecological bridge pier bottom protection structure according to claim 1, It is characterized in that The permeable grid box is composed of multiple layers of permeable grid box units in the longitudinal direction, and the permeable grid box units of two adjacent layers are correspondingly connected.

3. According to claim 2, a flexible box-type grid ecological bridge pier bottom protection structure, It is characterized in that The permeable grid box is composed of multiple layers of permeable grid box units in the transverse direction, and the permeable grid box units of two adjacent layers are correspondingly connected.

4. According to claim 3, a flexible box-type grid ecological bridge pier bottom protection structure, It is characterized in that The arc grille box and the rectangular grille box are both cast by reinforced concrete, and a number of connection holes are reserved on the six sides of the arc grille box and the rectangular grille box, so that adjacent permeable grille box units can be connected through connectors to form a whole.

5. According to claim 1, a flexible box-type grid ecological bridge pier bottom protection structure, It is characterized in that The central angle of each arc grille box is 30 to 60 degrees.

6. The flexible box-type grid ecological bridge pier bottom protection structure according to claim 1, It is characterized in that Median particle size D of stone 50 Calculated by the following formula: Where: U—flow velocity in front of the pier, m / s; y 0 —Deepness of water travel, m.

7. The flexible box-type grid ecological bridge pier bottom protection structure according to claim 1, It is characterized in that The width of the permeable grille box is 2 to 4 m, and the height is 2 to 4 m.

8. The flexible box-type grid ecological bridge pier bottom protection structure according to claim 1, It is characterized in that There are several grilles in the permeable grille box, and the distance between two adjacent grilles is 0.2 to 0.5m.

Images