Protective device for improving local scouring of pier

Abstract

The utility model provides a protection device for improving local scouring of a pier, which is suitable for the pier and comprises a first protection part and a second protection part, the first protection part is located on the upstream face of the bridge pier to force water flow to be divided towards the two sides of the bridge pier, and the divided water flow flows downstream along the second protection part located on the downstream face to prevent downward jet flow and weaken horseshoe-shaped vortexes and tail vortexes. A flow field in the incident flow direction of the pier scours the first protection part located on the upstream face, and the first protection part on the upstream face changes the form of the upstream face of the pier so as to prevent scouring energy of downward jet flow to a pier foundation, inhibit generation of reverse pressure gradient, weaken energy of horseshoe vortexes and force water flow to be distributed to the two sides of the pier. The divided water flow flows to the downstream along the second protection part located on the downstream face, and the second protection part on the downstream face can restrain boundary layer separation, reduce the turbulent flow intensity of the tail of the pier, weaken tail vortex erosion and achieve the protection effect.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of bridge pier protection, and particularly relates to a protection device for improving local scouring of a bridge pier. BACKGROUND

[0002] Pier foundation scouring is one of the main factors causing bridge damage. Scouring reduces the buried depth of the pier foundation and the bearing capacity of the pile foundation, and finally leads to the water damage and collapse of the bridge.

[0003] The flow field near the pier can be divided into four categories: 1, front-pier backwater, mainly referring to the upward flow generated after the incoming flow hits the pier; 2, downward jet, mainly referring to the downward flow generated after the incoming flow hits the pier, which will scour the pier bottom; 3, horseshoe vortex, mainly referring to the horseshoe-shaped vortex generated at the pier bottom due to the reverse pressure gradient of the boundary layer flow blocked by the pier, which will scour the two sides of the pier bottom; 4, tail vortex, mainly referring to the vortex formed at the tail of the pier after the flow around the pier separates from the boundary layer, which will scour the tail of the pier.

[0004] The common scouring protection measures in the current engineering can be divided into two categories according to their mechanism: (1) active protection, which reduces the power of scouring flow for protection, such as sacrificial piles in front of the pier; (2) passive protection, which improves the riverbed's resistance to scouring for protection, such as riprap protection, for example, the utility model patent CN103243639A, the utility model name is a ring-wing type pier with anti-scouring effect, which blocks the downward flow by setting a ring-wing type anti-scouring plate for protection. Obviously, these protection methods are one-sided and cannot achieve all-around protection, which has certain limitations. UTILITY MODEL CONTENTS

[0005] The utility model aims to provide a protection device for improving local scouring of a bridge pier to overcome the above technical defects.

[0006] To solve the above technical problems, the utility model provides a protection device for improving local scouring of a bridge pier, which is suitable for a pier and includes a first protection part and a second protection part.

[0007] The first protection part is located on the water-facing surface of the pier to force the water flow to the two sides of the pier, and the water flow after the diversion flows downstream along the second protection part on the leeward surface to prevent the downward jet, weaken the horseshoe vortex, and weaken the tail vortex.

[0008] The first protection part is a streamlined anti-scouring sheath installed on the water-facing surface of the pier to prevent the downward jet and weaken the horseshoe vortex.

[0009] The streamlined anti-scouring sheath is a half-elliptic sheath which is rotated 180 degrees around the height direction of the pier.

[0010] The streamlined anti-scouring sheath is a half-elliptic sheath which is rotated 180 degrees around the height direction of the pier.

[0011] The short axis of the half-elliptic sheath and the central axis of the pier are overlapped.

[0012] The center of the plane where the half-elliptic sheath is located is inwardly recessed to form a half-hoop type recess for embedding the pier.

[0013] The streamlined anti-scouring sheath and the pier body are integrally formed or assembled and installed.

[0014] The second protection part is a flow guide block which is installed on the backwater surface of the pier to weaken the tail vortex.

[0015] The flow guide block is a three-dimensional structure which is stretched along the height direction of the pier.

[0016] The triangle is an isosceles triangle.

[0017] The contact surface of the flow guide block and the pier is a plane or a curved surface.

[0018] The protection device provided by the utility model realizes the combination of active protection and passive protection, and the protection device comprises a streamlined anti-scouring sheath and a flow guide block.

[0019] In order to make the above content of the utility model more obvious and easy to understand, the following preferred embodiments are taken, and the detailed description is as follows in combination with the drawings. DRAWINGS

[0020] Figure 1 It is a structural schematic view of the protection device.

[0021] Explanation of the reference signs:

[0022] 100. protection device; 110. streamlined anti-scouring sheath; 120. flow guide block;

[0023] 200. bridge pier DETAILED DESCRIPTION

[0024] The other advantages and effects of the present application can be easily understood by those skilled in the art from the content disclosed in the present specification.

[0025] It should be noted that in the present application, the up, down, left and right in the figures are considered as the up, down, left and right of the protection device for improving local scouring of the bridge pier described in the present specification.

[0026] Exemplary embodiments of the present application will now be described with reference to the accompanying drawings. The present application can, however, be carried out in many different ways, and is not limited to the embodiments described herein, which are provided for the purpose of fully and completely disclosing the present application and to convey the full scope of the present application to those skilled in the art. The terminology used herein is not intended to limit the present application. In the drawings, like reference numerals refer to like elements throughout.

[0027] Unless otherwise defined, the terms (including technical terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it is to be understood that the terms defined by dictionaries and the like are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art, and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0028] The present application provides a protection device for improving local scouring of a bridge pier, which is suitable for a bridge pier 200. The protection device 100 is arranged on the pier body of the bridge pier 200. Please refer to Figure 1 The protection device 100 comprises a first protection part and a second protection part, and the specific structure is as follows:

[0029] The first protection part is located on the water-facing surface of the bridge pier 200 to force the water flow to be divided into two parts on both sides of the bridge pier 200. The water flow after being divided flows along the second protection part located on the backwater surface to the downstream to prevent downward jet flow, weaken horseshoe vortex and tail vortex.

[0030] Please continue to refer to Figure 1 The protection device 100 located on the water-facing surface is scoured by the flow field in the direction of the incoming flow of the bridge pier. The first protection part on the water-facing surface forces the water flow to be divided into two parts on both sides of the bridge pier 200. The water flow after being divided flows along the second protection part located on the backwater surface to the downstream to prevent downward jet flow, weaken horseshoe vortex and tail vortex.

[0031] The flow field is a concept commonly used in fluid mechanics to describe the spatial distribution characteristics of fluid motion. The flow field causing bridge scour mainly includes three parts: downward jet, horseshoe vortex and wake vortex. The following will specifically explain how the protection device protects the pier 200.

[0032] The protection device 100 includes a streamlined scour protection sheath 110 and a flow guide block 120. The streamlined scour protection sheath 110 is installed on the water-facing side of the pier 200 to prevent downward jet and weaken the horseshoe vortex, i.e., the first protection part is the streamlined scour protection sheath 110; the flow guide block 120 is installed on the water-leaving side of the pier to weaken the wake vortex, i.e., the second protection part is the flow guide block 120.

[0033] When the water flow in front of the pier rushes to the pier 200, the water flow will first scour the streamlined scour protection sheath 110. Due to the streamlined design of the streamlined scour protection sheath 110, the water flow is changed in direction and forced to flow to both sides of the pier 200, thereby reducing the scouring energy of the downward jet on the pier foundation; in addition, the streamlined scour protection sheath 110 can suppress the generation of adverse pressure gradient and weaken the energy of the horseshoe vortex; at the same time, the streamlined scour protection sheath 110 has a certain sand-fixing capacity and can prevent the sand below the sheath from being washed away, which has a similar effect to riprap protection.

[0034] After the water flow is divided, it flows downstream along the flow guide block 120 located on the water-leaving side. The flow guide block 120 can suppress boundary layer separation, reduce the turbulence intensity at the tail of the pier 200, and weaken the tail vortex erosion, thereby playing a protective role.

[0035] Regarding the shape of the pier 200, there is no limitation in actual application, but the present embodiment selects a cylindrical pier 200 as shown in Figure 1 for the convenience of explaining the protection device 100. Please refer to Figure 1 , it can be seen that the streamlined scour protection sheath 110 perpendicular to the water flow direction is arranged on the bottom of the cylindrical pier 200 in the water-facing direction, and the flow guide block 120 perpendicular to the water flow direction is arranged on the bottom of the cylindrical pier 200 in the water-leaving direction.

[0036] Please refer to Figure 1 , the streamlined scour protection sheath 110 includes:

[0037] a semi-elliptical rotating ellipsoid formed by rotating a semi-ellipse by 180° along the height direction of the pier, and the control equation of the shape is:

[0038]

[0039] wherein a and b are the major and minor semi-axes of the semi-ellipse, a≥b>0, and x≥0, wherein x, y and z are the x-axis, y-axis and z-axis in the coordinate system.

[0040] According toFigure 1 As shown, the outer shape of the streamlined scour protection jacket 110 is streamlined, which aims to reduce friction and guide the water flow along the streamline direction, thereby reducing the scour of the water flow on the pier 200.

[0041] Specifically, the streamlined scour protection jacket 110 is a half-rotated ellipsoid formed by rotating a semi-ellipse by 180° around the height direction of the pier. Specifically, it refers to a semi-ellipse cut along the major axis, and the semi-ellipse is coplanar with the central axis of the pier. That is, the maximum thickness of the streamlined scour protection jacket 110 is at the short half-axis of the semi-ellipse, and the thickness gradually decreases along the long half-axis, thereby forming a streamlined shape.

[0042] The streamlined scour protection jacket 110 can change the shape of the pier's water-facing surface to prevent downward jet flow. In order to change the size and direction of the water flow through the streamlined scour protection jacket 110 and force it to flow to both sides of the pier 200, in some embodiments, the short axis of the semi-ellipse overlaps with the central axis of the pier 200. That is, the central axis of the pier 200 passes through the origin of the semi-ellipse of the streamlined scour protection jacket 110. For details, please refer to Figure 1 .

[0043] The center of the plane where the semi-ellipse of the streamlined scour protection jacket 110 is located is recessed inward to form a half-hoop-shaped recess for embedding the pier 200. That is, the streamlined scour protection jacket 110 has at least a bottom surface that can be parallel to the radial plane of the pier 200, and the edge of the bottom surface extends upward to form a wrapping curved surface. When viewed from above, the streamlined scour protection jacket 110 appears as a semicircle, and when viewed from the side, the center of the plane where the semi-ellipse is located is actually a half-hoop-shaped recess. The purpose is to increase the contact area between the streamlined scour protection jacket 110 and the pier 200 and ensure the stability when being scoured.

[0044] The streamlined scour protection jacket 110 and the pier body are integrally formed or assembled and installed.

[0045] In some embodiments, the streamlined scour protection jacket 110 is a solid structure.

[0046] Continuing to refer to Figure 1 , the flow guide block 120 is a three-dimensional structure formed by stretching a triangle along the height direction of the pier 200, and the vertex of the triangle points downstream of the water flow. That is, the flow guide block 120 is similar to a wedge, and the stretching height is consistent with the maximum thickness of the streamlined scour protection jacket 110.

[0047] In some embodiments, the triangle of the flow guide block 120 is an isosceles triangle, and at this time, the several bottom edges of the flow guide block 120 form a rectangle fixedly connected with the pier body of the pier 200, or the flow guide block 120 is integrally formed with the pier 200.

[0048] In some embodiments, the flow guide block 120 is in the shape of a triangular prism, i.e., has five faces, which are upper and lower parallel and opposite isosceles triangles, and three rectangles surrounding the two isosceles triangles, wherein the rectangles sharing edges with the base of the isosceles triangles are fixed to the pier body 200.

[0049] When the streamlined scour protection sleeve 110 changes the size and direction of the water flow to force it to flow to both sides of the pier 200, the water flow will flow along the two rectangles (not fixed to the pier 200) of the flow guide block 120 and converge downstream.

[0050] The contact surface between the flow guide block 120 and the pier 200 is a plane or a curved surface. Whether it is a plane or a curved surface, the connection between the flow guide block 120 and the pier 200 is a reliable and stable connection, and the flow guide block 120 can suppress the separation of the boundary layer behind the pier, reduce the turbulence intensity of the pier tail, and weaken the tail vortex erosion, thereby playing a protective role.

[0051] In order to fully exert the sand-fixing ability of the streamlined scour protection sleeve 110, based on the scour pit data obtained from the water channel test and CFD simulation, the distance from the bottom outer edge of the streamlined scour protection sleeve 110 to the center of the pier (i.e., a in the shape control equation) should not be less than 2.5 times the diameter of the pier.

[0052] Based on the Melville water channel test data, a numerical model was established to carry out three-dimensional numerical calculation. The test water channel is 19m long, 0.456m wide, 0.15m deep, the average flow velocity is 0.25m / s, the median particle size of the sediment is 0.385mm, and the sediment rest angle is 32°. A cylinder with a diameter of 5.08cm is placed in the center of the water channel as a pier model. According to the water channel test arrangement and numerical simulation requirements, the calculation domain is 25cm high, of which the sediment thickness is 5cm, the water depth is 15cm, and the air above is 5cm. The width is set to the actual water channel width of 45.6cm. In order to make the upstream flow and downstream wake fully developed, the center of the pier is 15d (d is the diameter of the cylindrical pier, 15d=0.762m) away from the inlet and outlet. In order to ensure the smoothness of the flow, 5d of fixed bed is arranged at the upstream and downstream.

[0053] On this basis, the protective device of the present embodiment is added, and according to the design of the present embodiment, the parameter a of the streamlined scour protection sleeve is set to 2.5 times the diameter of the pier, the distance from the end point of the triangular flow guide block to the center of the pier is set to 1.5 times the diameter of the pier, and the height b of the sleeve is set to 3 kinds, which are D, 0.6D, and 0.5D. The present embodiment simulates 4 groups of working conditions, and the specific working condition arrangement and numerical calculation results are shown in the following table:

[0054]

[0055] D in the table is the diameter of the pier, and the influence coefficient is the percentage of the decrease of the protection working condition compared with the non-protection working condition. It can be seen from the table that the embodiment can effectively reduce the riverbed shear stress and flow velocity, and further reduce the local scour pit depth, and has good scour protection effect; among the protection devices corresponding to the three different sheath heights, the linear design of the protection device is best and the anti-scour effect is best when the sheath height is 0.5D.

[0056] The sheath height b refers to the maximum thickness of the flow line type anti-scour sheath 110.

[0057] The protection device for improving local scour of the pier provided by the embodiment realizes the combination of active protection and passive protection through the flow line type anti-scour sheath and the triangular flow guide block, and solves the problem of insufficient comprehensive effect of the conventional protection. The flow line type anti-scour sheath changes the shape of the pier water surface to prevent downward jet flow, changes the size and direction of the downward jet flow to force it to flow to both sides of the pier, and further reduces the scouring energy of the downward jet flow on the pier foundation. In addition, the flow line type anti-scour sheath can inhibit the generation of adverse pressure gradient and weaken the energy of the horseshoe vortex. At the same time, the flow line type anti-scour sheath has a certain sand fixation capacity and can prevent the sand below the sheath from being washed away, which has an effect similar to that of riprap protection. The triangular flow guide block can inhibit boundary layer separation, reduce the turbulence intensity at the tail of the pier, and weaken the tail vortex erosion, thereby playing a protection role.

[0058] Those skilled in the art can understand that the above embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. A protection device for improving local scour around a bridge pier, adapted to a bridge pier (200), characterized in that, The first protection part is a streamlined protection jacket (110), and the second protection part is a flow guide block (120); The first protection part is located on the water-facing surface of the pier (200) to force the water flow to be divided into two parts, and the divided water flows along the second protection part located on the water-leaving surface to the downstream to prevent downward jet flow, weaken horseshoe vortex and tail vortex.

2. The device for ameliorating localized scour of a bridge pier according to claim 1, wherein The streamlined protection jacket (110) is installed on the water-facing surface of the pier (200) to prevent downward jet flow and weaken horseshoe vortex.

3. The device for ameliorating localized scour of a bridge pier according to claim 2, wherein The streamlined protection jacket (110) is a half-rotated ellipsoid formed by rotating a half-ellipse around the height direction of the pier by 180°.

4. The device for ameliorating localized scour of a bridge pier according to claim 3, wherein The streamlined protection jacket (110) is a half-rotated ellipsoid formed by rotating a half-ellipse around the height direction of the pier by 180°, specifically, a half-ellipse cut along the major axis, and the half-ellipse is coplanar with the central axis of the pier. The short axis of the half-ellipse overlaps with the central axis of the pier.

5. The device for ameliorating local scour around a bridge pier according to claim 4, wherein The center of the plane where the half-ellipse of the streamlined protection jacket (110) is located is recessed inward to form a half-hoop type groove for embedding the pier (200). The streamlined protection jacket (110) and the pier body are integrally formed or assembled and installed.

6. The device for ameliorating localized scour around a bridge pier according to claim 2, wherein The flow guide block (120) is installed on the water-leaving surface of the pier (200) to weaken the tail vortex. The flow guide block (120) is a three-dimensional structure formed by stretching a triangle along the height direction of the pier, and the vertex of the triangle points to the downstream of the water flow.

7. The device for ameliorating local scour around a bridge pier according to claim 6, wherein The triangle is an isosceles triangle.

8. A device for ameliorating local scour of a bridge pier according to claim 6 or 7, wherein The contact surface between the flow guide block (120) and the pier (200) is a plane or a curved surface.

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