Calculation method for river erosion and protection structure
The calculation of river shear stress through momentum conservation and turbulence theory, combined with the unique riparian protection structure design, solve the problem of riparian stability caused by river erosion, reduce the risk of riparian collapse and improve safety.
Patent Information
- Application Number
- CN202411393088.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2025-01-10
AI Technical Summary
River erosion leads to an increase in the vertical height of the river bank, increasing the risk of river bank collapse and posing a threat to the safety of coastal buildings. It is difficult for the existing technology to effectively analyze river bank stability and provide effective protection.
Based on the conservation equation of momentum and Prandtl turbulence theory, a river bank protection structure is proposed, including the 'L'-shaped foot structure and the 'Γ'-shaped top structure, combined with the shore guard stone to reduce the slope of the river bank It also increases the anti-slip force, and the structure can be replaced independently.
Through theoretical analysis and structural design, the assessment and protection of the degree of riparian erosion is provided, which reduces the risk of riparian collapse, improves the stability and safety of riparian banks, and reduces replacement costs.
Smart Images
Figure CN119293913A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of ecological environment protection, and more specifically, to a calculation method and a protective structure for river erosion. Background Art
[0002] When a river is flowing, it will scour the riverbed and riverbank under the action of its own weight and the resistance of the side walls. Excessive scouring of the riverbed will increase the vertical height of the riverbank and increase the risk of riverbank collapse. Excessive scouring of the riverbank will also cause riverbank collapse, affecting the safety of buildings along the river.
[0003] Based on the momentum conservation equation, the present invention considers the influence of river bends and depth on flow velocity, proposes an expression for the shear stress of the river on the river channel, and analyzes the stability of the river bank. In addition, a river bank protection device is proposed according to the scouring damage of the river on the river channel. Summary of the invention
[0004] In order to overcome the deficiencies in the prior art, a calculation method and a protective structure for river erosion are provided.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A computational method for river erosion, including: S1. Calculate river shear stress: According to Newton's second law of motion and the momentum conservation formula, we can get: (1); Where: ρ is the water density, u is the average flow velocity of the water, t is time, m is mass, a is acceleration, ∆x is the length of the water, and ∆y is the height difference of the water; The pressure of water is: (2); Where: g is the acceleration due to gravity, then equation (1) can be transformed into: (3); Ignoring the depth change, equation (3) can be simplified to (4); In an open channel, the slope of the riverbed is very small. At this time, the horizontal length of the river is close to the actual length of the river surface. Therefore, equation (4) can be transformed into (5); Where, J is the hydraulic gradient; but: (6); S2. Calculate flow rate at different depths: The Prandtl mixing theory defines the turbulent mixing length as the distance that the water mass maintains its original characteristics. The expression of turbulent shear stress is: (7); Where: τ is the turbulent shear stress; τ0 is the bottom shear stress; l is the turbulent mixing length; u* is the friction velocity; y is the vertical position from the bottom of the water upward; (8); Where κ is the Karman constant; the bottom boundary is: (9); The flow gradient formula is: (10); The velocity distribution at different depths can be obtained by integration: (11); In the formula, u m is the surface velocity; S3. Calculate the flow velocity in the bend: Based on Prandtl turbulent shear stress, the formula for the circulation generated by the bend is as follows: (12) Where: r is the radius of curvature of the curve; u y is the flow velocity at a certain depth, which is solved by equation (11); S4. Compare river shear stress with riverbank shear strength: The shear strength is given below: (14) Where: σ is the normal stress acting on the shear surface, here is the deadweight load acting on the upper part of the soil, φ' is the effective internal friction angle, and c' is the effective cohesion.
[0006] Furthermore, as the river bank continues to erode, the river bank slope increases, increasing the risk of river bank collapse. The stability of the river bank is determined by the slope stability parameter calculation method, as shown in formula (15): (15) Where: W is the deadweight load of the soil on the sliding surface, α is the angle between the sliding surface and the horizontal plane, and L is the length of the sliding surface. The sliding surface position is from the toe of the river bank slope to the slope surface, the position is the N point position on the shore, N is the set of distances, and the distances are 0.1m, 0.2m...n from the slope shoulder, respectively. The angle formed by the line connecting the n point position and the toe of the slope and the horizontal plane is 30°.
[0007] A protective structure against river erosion, comprising a foot structure, a top structure and revetment stones, wherein the foot structure is in an "L" shape, the bottom of the revetment stones is arranged at the corner of the foot structure, the top structure is in a "Γ" shape, a cavity is arranged at the upper end of the top structure, a protrusion connected to the upper end of the revetment stones is arranged at the lower end of the top structure, and a circular hole for fixing is arranged on the end face of the top structure.
[0008] Furthermore, the bank protection stones are concrete materials or large pieces of stone.
[0009] Furthermore, the foot structure includes a long side and a bottom plate that are vertically connected, and the length of the bottom plate is shorter than the length of the long side.
[0010] Furthermore, a side of the bottom plate away from the long side is fixedly connected with a short side.
[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention analyzes the degree of river bank erosion under different hydraulic parameters and forms, and provides theoretical support for the life safety of people on the river bank and in the surrounding areas.
[0012] 2. The present invention takes sediment movement into consideration and sets up a foot structure, thereby reducing the river bank slope and increasing the river bank's anti-slip force; the foot structure and the stone are not an integral whole, and when erosion occurs at the bottom, the stone will not be broken due to its own weight; since the long side of the foot structure is close to the water body, when erosion causes the bottom to be suspended and the foot structure to sink, the river bank soil will not be completely exposed to the water body, causing the river bank to be eroded.
[0013] 3. The protective structure of the present invention is composed of three unconnected entities. When a part is damaged, it can be replaced. The operation is convenient and the replacement cost is reduced. It has certain economic value. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0015] Figure 1 It is a schematic diagram of the overall structure of the second embodiment; Figure 2 This is a schematic diagram of the revetment stone structure; Figure 3 It is a schematic diagram of the top structure; Figure 4 A schematic diagram of the foot structure.
[0016] In the figure: 1-foot structure, 11-long side, 12-bottom plate, 13-short side, 2-top structure, 21-cavity, 22-protrusion, 23-round hole, 3-bank protection stone. DETAILED DESCRIPTION
[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0018] Embodiment 1: A computational method for river erosion, including: S1. Calculate river shear stress: According to Newton's second law of motion and the momentum conservation formula, we can get: (1); Where: ρ is the water density, u is the average flow velocity of the water, t is time, m is mass, a is acceleration, ∆x is the length of the water, and ∆y is the height difference of the water; The pressure of water is: (2); Where: g is the acceleration due to gravity, then equation (1) can be transformed into: (3); Ignoring the depth change, equation (3) can be simplified to (4); In an open channel, the slope of the riverbed is very small. At this time, the horizontal length of the river is close to the actual length of the river surface. Therefore, equation (4) can be transformed into (5); Where, J is the hydraulic gradient; but: (6).
[0019] The velocity of water is affected by the plane shape and cross-sectional shape. The magnitude of water velocity varies with different depths and plane shapes. Only when the velocity magnitude is determined can the shear stress be solved. Therefore, it is also necessary to calculate the flow velocity at different depths and the flow velocity in the bend. Specifically: S2. Calculate flow rate at different depths: The Prandtl mixing theory defines the turbulent mixing length as the distance that the water mass maintains its original characteristics. The expression of turbulent shear stress is: (7); Where: τ is the turbulent shear stress; τ0 is the bottom shear stress; l is the turbulent mixing length; u* is the friction velocity; y is the vertical position from the bottom of the water upward; (8); Where κ is the Karman constant; the bottom boundary is: (9); The flow gradient formula is: (10); The velocity distribution at different depths can be obtained by integration: (11); In the formula, u m is the surface velocity.
[0020] S3. Calculate the flow velocity in the bend: Based on Prandtl turbulent shear stress, the formula for the circulation generated by the bend is as follows: (12) Where: r is the radius of curvature of the curve; u y is the flow velocity at a certain depth, which can be solved by equation (11).
[0021] S4. Determine scour damage: When the shear stress of the water flow is greater than the shear strength of the river bank soil, the river bank will erode. The shear strength is as follows: (14) Where: σ is the normal stress acting on the shear surface, here is the deadweight load acting on the upper part of the soil, φ' is the effective internal friction angle, and c' is the effective cohesion.
[0022] The extent of riverbank erosion under the ratio of shear stress to shear strength can be determined through on-site testing and experiments, and the location of maximum erosion can be analyzed.
[0023] Determining the risk of riverbank collapse: As the river bank continues to erode, the river bank slope increases, increasing the risk of river bank collapse. The stability of the river bank is determined by the slope stability parameter calculation method, as shown in Formula 15: (15) Where: W is the deadweight load of the soil on the sliding surface, α is the angle between the sliding surface and the horizontal plane, and L is the length of the sliding surface. The sliding surface position is from the toe of the river bank slope to the slope surface, the position is the N point position on the shore, N is the set of distances, and the distances are 0.1m, 0.2m...n from the slope shoulder, respectively. The angle formed by the line connecting the n point position and the toe of the slope and the horizontal plane is 30°.
[0024] The computational model is used to identify the areas with the greatest erosion and then protect them.
[0025] Embodiment 2: A protective structure against river erosion is used to protect the maximum erosion position found by the calculation model in the first embodiment.
[0026] Specifically, Figures 1 to 4 The structure comprises a foot structure 1, a top structure 2 and a revetment stone 3. The foot structure 1 is in an "L" shape, the bottom of the revetment stone 3 is arranged at the corner of the foot structure 1, and the top structure 2 is arranged on the upper part of the revetment stone 3. The revetment stone 3 is directly laid on the river bank, and can be made of concrete material, large stone or other waterproof material, which is required to have high strength.
[0027] The foot structure 1 comprises a vertically connected long side 11 and a bottom plate 12, the bottom plate 12 is shorter than the long side 11, and a short side 13 is fixedly connected to one side of the bottom plate 12 away from the long side 11. The short side is mainly used to squeeze the stone and fix the stone on the river bank.
[0028] The design of the foot structure can effectively fix the stone and ensure the stability of the riverbank structure. The structure also has the ability to receive river silt, allowing the silt to adhere to the upper part of the stone, thereby reducing the slope of the riverbank. More importantly, the deposition of silt increases the deadweight of the riverbank, which significantly improves the overall stability of the riverbank. The foot structure and the stone are not formed in one piece. When facing bottom erosion, even if the bottom is eroded, due to the independence of the structure, the stone will not break due to its own weight, thus ensuring the integrity of the riverbank structure. In addition, considering that the long side of the foot structure is close to the water body, even if the bottom is suspended and the structure settles due to erosion, the riverbank soil will not be completely exposed to the water body, thus effectively avoiding the risk of damage to the riverbank due to scouring.
[0029] The top structure 2 is in the shape of "Γ", and a cavity 21 is provided at the upper end of the top structure 2. Planting soil is added to the cavity 21 to plant green plants to improve the greening beauty. A protrusion 22 connected to the upper end of the revetment stone 3 is provided at the lower end of the top structure 2, and a circular hole 23 is provided on one side of the top structure 2. The revetment stone 3 is fixed by soil nails passing through the circular hole 23.
[0030] How to do it: Step 1: First place the foot structure 1, with the short side 13 of the foot structure 1 facing the river bank and the long side 11 facing the water body. The short side 13 should be buried in the river bank soil, leaving a part of the bottom plate 12 to place the revetment stone 3.
[0031] Step 2: The bottom of the revetment stone 3 is first placed on the foot structure 1, and then the whole is close to the river bank. The different revetment stone 3 plates should be spliced tightly to minimize the impact of the river on the river bank.
[0032] Step 3: Place the top structure 2, with the raised portion of the top structure 2 close to the revetment stone 3.
[0033] Step 4: Use soil nails to pass through the circular holes 23 and enter the river bank, increase the extrusion of the protrusions 22 on the revetment stones 3, and use friction to fix the stones.
[0034] Step 5: Plant green plants in the cavity 21 of the top structure 2 for beautification.
[0035] Only the preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the protection scope of the present invention.
Claims
1. A calculation method for river erosion, characterized in that: include: S1. Calculate river shear stress: According to Newton's second law of motion and the momentum conservation formula, we can get: （1）； Where: ρ is the water density, u is the average flow velocity of the water, t is time, m is mass, a is acceleration, ∆x is the length of the water, and ∆y is the height difference of the water; The pressure of water is: （2）； Where: g is the acceleration due to gravity, then equation (1) can be transformed into: （3）； Ignoring the depth change, equation (3) can be simplified to （4）； In an open channel, the slope of the riverbed is very small. At this time, the horizontal length of the river is close to the actual length of the river surface. Therefore, equation (4) can be transformed into （5）； Where, J is the hydraulic gradient; but: (6); S2. Calculate flow rate at different depths: The Prandtl mixing theory defines the turbulent mixing length as the distance that the water mass maintains its original characteristics. The expression of turbulent shear stress is: （7）； Where: τ is the turbulent shear stress; τ0 is the bottom shear stress; l is the turbulent mixing length; u* is the friction velocity; y is the vertical position from the bottom of the water upward; （8）； Where κ is the Karman constant; the bottom boundary is: （9）； The flow gradient formula is: （10）； The velocity distribution at different depths can be obtained by integration: （11）； In the formula, u m is the surface velocity; S3. Calculate the flow velocity in the bend: Based on Prandtl turbulent shear stress, the formula for the circulation generated by the bend is as follows: （12） Where: r is the radius of curvature of the curve; u y is the flow velocity at a certain depth, which is solved by equation (11); S4. Compare river shear stress with riverbank shear strength: The shear strength is given below: （14） Where: σ is the normal stress acting on the shear surface, here is the deadweight load acting on the upper part of the soil, φ' is the effective internal friction angle, and c' is the effective cohesion.
2. The method for calculating river erosion according to claim 1, characterized in that: As the river bank continues to erode, the river bank slope increases, increasing the risk of river bank collapse. The stability of the river bank is determined by the slope stability parameter calculation method, as shown in formula (15): （15） Where: W is the deadweight load of the soil on the sliding surface, α is the angle between the sliding surface and the horizontal plane, and L is the length of the sliding surface. The sliding surface position is from the toe of the river bank slope to the slope surface, the position is the N point position on the shore, N is the set of distances, and the distances are 0.1m, 0.2m...n from the slope shoulder, respectively. The angle formed by the line connecting the n point position and the toe of the slope and the horizontal plane is 30°.
3. A protective structure against river erosion, characterized in that: The invention comprises a foot structure (1), a top structure (2) and a revetment stone (3), wherein the foot structure (1) is in an "L" shape, the bottom of the revetment stone (3) is arranged at the corner of the foot structure (1), the top structure (2) is in a "Γ" shape, a cavity (21) is arranged at the upper end of the top structure (2), a protrusion (22) connected to the upper end of the revetment stone (3) is arranged at the lower end of the top structure (2), and a circular hole (23) for fixing is arranged at the end surface of the top structure (2).
4. A protective structure against river erosion according to claim 3, characterized in that: The revetment stone (3) is a concrete material or a large piece of stone.
5. The protective structure against river erosion according to claim 3, characterized in that: The foot structure (1) comprises a long side (11) and a bottom plate (12) which are vertically connected, and the length of the bottom plate (12) is shorter than the length of the long side (11).
6. A protective structure against river erosion according to claim 5, characterized in that: A side of the bottom plate (12) away from the long side (11) is fixedly connected to a short side (13).