Construction method for reducing silt in urban river channel

Abstract

The application discloses a kind of for urban river channel silt reduction construction method, adopt rubber dam and store pit combination, store pit reduces water flow velocity, changes vertical distribution of silt, and makes silt particles concentrate downward, rubber dam adopts arch design, while weakening the impact of water flow on rubber dam, the silt in the silt source of upstream river channel is intercepted, so that it is accumulated to selected section convenient for mechanical dredging;Then, using the way of mechanical dredging, the sludge accumulated is removed for treatment after processing.The application has the advantages of simple and fast design, and the designer only needs to record the data such as river width, normal water level height, water flow velocity and model scale test, so as to carry out the design calculation of actual engineering.The method improves the dredging efficiency, reduces the silt accumulation of urban internal river channel, reduces the traffic pressure of urban internal river channel, and saves manpower and material resources.

Description

Technical Field

[0001] This invention relates to the field of river engineering technology, and in particular to a construction method for silt reduction structures in urban inland rivers. Background Technology

[0002] Many urban rivers in my country suffer from continuous siltation due to high sediment content in their upstream water sources. This siltation raises the riverbeds, lowers the safety standards for urban river design, and significantly reduces their flood control, drainage, and water storage capacity. As a result, numerous urban flooding disasters have occurred in recent years, seriously endangering people's lives and property. Furthermore, the silt contains large amounts of organic matter, which readily produces harmful substances, severely impacting aquatic life and affecting the urban environment.

[0003] Currently, river dredging mainly relies on mechanical dredging equipment. This method easily leads to the spread of pollutants in the riverbed sediment, making it unsuitable for cleaning rivers near residential areas. Furthermore, the dredged silt requires extensive transportation to designated locations for processing, impacting urban traffic. Dredging is costly, requires significant investment of manpower and resources, and is extremely inefficient. Therefore, there is an urgent need for a simple, environmentally friendly, and effective method to address urban river siltation.

[0004] Furthermore, existing urban river dredging methods, such as the method disclosed in CN103669281A, which uses rubber dams to assist in the targeted dredging of black and odorous rivers, involve constructing rubber dams after deep pits and building silt storage ponds on the banks for centralized silt treatment. This technology specifies the volume of the silt storage ponds. CN104452656A discloses a segmented river dredging construction method, which involves constructing flexible dams, excavating silt trenches in front of the dams, and treating the silt in silt treatment ponds, and also specifies the volume of the silt treatment ponds. Neither of these methods considers the problem of silt accumulation in the middle of the river, which makes subsequent mechanical dredging operations difficult. Moreover, neither method provides suitable technical construction parameters and calculation methods for silt treatment that do not affect fish activity in the river.

[0005] In summary, existing urban river channel planning and design of dams, such as rubber dams and overflow dams, are only used for water storage or containment projects, without considering the siltation effect and the impact on aquatic life. This has led to serious disruptions to fish migration and silt accumulation at the dam base, causing river blockages and severely compromising the structural safety of the dam. Especially after prolonged use, siltation frequently occurs in front of the dam, with large and irregular siltation areas making dredging difficult. Therefore, when designing dredging projects, it is crucial to consider the habits of fish in the river and the technical challenges of siltation during the construction of river channel silt reduction structures. Summary of the Invention

[0006] This invention provides a construction method for silt reduction structures in urban inland rivers. Its purpose is to solve the technical problem of ensuring siltation in selected sections of the river after a rubber dam intercepts sediment from upstream sources, allowing the sediment to accumulate away from the dam base. This reduces dredging difficulty while ensuring dam safety and minimizing the impact of the project on river fish activity. The method combines a rubber dam with a sediment storage pit, effectively reducing the height of the rubber dam without compromising silt interception, thus minimizing the impact on river fish activity. The method uses model tests consistent with actual engineering projects to determine parameters, applying different parameters to different projects for specialized treatment. Then, mechanical dredging is used to remove and process the accumulated silt, improving dredging efficiency, reducing urban traffic congestion, and saving manpower and resources.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A construction method for silt reduction structures in urban inland rivers includes a silt storage pit 3, a rubber dam 1, and supports 2, a rubber dam base 4, a silt storage pit base 5, and anchoring devices arranged sequentially along the water flow direction on the river channel. The supports are symmetrically distributed on both banks of the river channel. The supports are connected to the rubber dam base 4, which is located at the bottom of the riverbed, by concrete pouring. The silt storage pit base 5 at the bottom of the silt storage pit 3 is connected to the riverbed bottom and the rubber dam base 4, along with the front and rear ends along the water flow direction, by a concrete-poured slope. The rubber dam is located on the rubber dam base 4 between two supports. Anchoring devices are used to connect the rubber dam to the supports and to the rubber dam base 4.

[0009] The rubber dam is constructed in an arched shape on the horizontal plane, with both ends curving towards the direction of water flow, forming a streamlined water-retaining dam body. This structure allows sediment to be concentrated and deposited on the bank for later mechanical dredging. The sediment storage pit 3 is constructed in an arched shape around the rubber dam. The diameter of the rubber dam body is smaller than the depth of the river channel, allowing shallow, clear water with a low sediment content to overflow from the top of the rubber dam body to the downstream. The rubber dam includes the following design parameters:

[0010] The vertical distance L from the top of the central axis of the rubber dam to the middle of the dam body;

[0011] The distance between the two ends of the dam body is D;

[0012] Dam height H1;

[0013] The rise-span ratio μ is the ratio of the vertical distance L at the middle of the dam body to the distance D at both ends, L / D. The value of the rise-span ratio μ ranges from 1 / 4 to 1 / 6.

[0014] λ — The ratio of dam height H1 to river channel depth H at normal water level, H1 / H;

[0015] γ—The ratio of the depth at which the cumulative sediment content at the bottom reaches 98% to the total depth in a scaled-down test of a normal flow channel model.

[0016] First, a scaled-down test of a normal flow channel model was conducted to measure sediment distribution. Based on the sediment distribution curve with depth, the parameter γ was calculated. The dam body parameters of the rubber dam were calculated using the following formula:

[0017] λ = 1 - 2γ (Formula 1)

[0018] H1=λH Formula 2

[0019]

[0020] L=Dμ Formula 4

[0021] Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel.

[0022] The method wherein the sludge storage pit includes the following design parameters:

[0023] The slope of the mud storage pit is 1:1.

[0024] The depth of the mud storage pit is H2;

[0025] The bottom length of the cross-section of the mud storage pit is L1;

[0026] The bottom width of the mud storage pit is B1.

[0027] And calculate according to the following formula:

[0028] H2 = H Formula 5

[0029] L1 = 3H Formula 6

[0030] B1 = B - 2H (Formula 7)

[0031] Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel.

[0032] The method wherein the abutment is embedded in the riverbank soil, the horizontal cross-section of the abutment is square, the side length of the abutment is L4, one apex of the square facing the dam body is chamfered, a vertical support surface 6 on the chamfered corner is perpendicularly connected to the dam body, the distance L3 between the outer end of the support surface and the riverbank line is 0.1m, the length of the support surface is L5, and the abutment includes the following design parameters:

[0033] The side length of the support is L4;

[0034] The distance L3 between the outer end of the support surface and the riverbank is 0.1m.

[0035] The length of the support surface is L5.

[0036] Calculate using the following formula:

[0037]

[0038] L5 = H Formula 9

[0039] Where H represents the normal water level depth of the river channel.

[0040] The method involves determining the vertical distribution pattern of river sediment through a constant-flow river model test. The model test material is sampled from riverbed sediment, and the test parameters, such as flow velocity and flow depth, are the same as the river flow velocity and constant-flow depth. The model width is reduced to decrease the test scale, and γ is calculated based on the vertical distribution curve of river sediment obtained from the model test.

[0041] The method wherein the span-to-span ratio μ is 1 / 5.

[0042] The mud storage pit 3 is surrounded by a 1:1 slope.

[0043] The beneficial effects of this invention are:

[0044] This method combines a rubber dam with a sediment storage pit, effectively reducing the height of the rubber dam without affecting the sediment interception effect and minimizing the impact of the project on fish activity in the river. The rubber dam intercepts sediment from upstream sources, while the sediment storage pit allows it to accumulate in selected sections, keeping the accumulated sediment away from the dam base. This reduces the difficulty of dredging while ensuring the safety of the dam structure. Parameters are determined using model tests consistent with actual engineering projects, allowing for customized treatment of different projects.

[0045] Rubber dams are simple to construct, and their height can be determined based on the water volume. The dam height controls the overflow rate and overflow layer at the dam crest, preventing sediment from flowing downstream and reducing the sediment content in urban rivers without affecting fish activity. This invention reduces sediment flow into urban rivers while allowing it to accumulate at designated locations. The accumulated sediment can then be removed mechanically without impacting the urban environment or traffic, making it an effective method for solving urban river siltation. Attached Figure Description

[0046] Figure 1 A schematic diagram of the overall structure of the present invention;

[0047] Figure 2 A schematic diagram of the overall structure of the present invention arranged in a cross-section along the direction of water flow;

[0048] Figure 3A schematic cross-sectional view of the support on the horizontal plane of the present invention;

[0049] Figure 4 The flowchart of the calculation design method of this invention;

[0050] Figure 5 Vertical cumulative sediment content distribution curve of a scaled-down model test according to an embodiment of the present invention;

[0051] Figure 6 The siltation distribution diagram after arranging the silt storage pit and rubber dam in an embodiment of the present invention.

[0052] Explanation of the attached drawing numbers: 1—Rubber dam; 2—Abutment; 3—Sediment storage pit; 4—Rubber dam bottom slab; 5—Sediment storage pit bottom slab; 6—Support surface; Detailed Implementation

[0053] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are merely illustrative of the technical features and concepts of the present invention and should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made based on the essence of the present invention should be covered within the scope of protection of the present invention.

[0054] See Figures 1-4 As shown, the present invention provides a construction method for silt reduction structures in urban inland rivers, comprising a silt storage pit 3, a rubber dam 1, and supports 2, a rubber dam base 4, a silt storage pit base 5, and anchoring devices arranged sequentially along the water flow direction on the river channel. The supports are symmetrically distributed on both banks of the river channel. The supports are connected to the rubber dam base 4, which is located at the bottom of the riverbed, by concrete pouring. The silt storage pit base 5 at the bottom of the silt storage pit 3 is connected to the bottom of the riverbed and the rubber dam base 4 by concrete pouring along the front and rear ends of the silt storage pit 3. The rubber dam is located on the rubber dam base 4 between the two supports. Anchoring devices are used to connect the rubber dam to the supports and to the rubber dam base 4. The anchoring devices adopt a traditional structure and will not be described in detail.

[0055] The rubber dam 1 is set in an arched structure on the horizontal plane, see Figure 1 The rubber dam is curved at both ends towards the direction of water flow, forming a streamlined water-retaining dam body. The silt storage pit 3 is an arched structure surrounding the rubber dam. The curvature of the dam body reduces the force of the flowing water on the dam body, while simultaneously allowing the accumulated silt to collect in the bank area, facilitating mechanical dredging. The diameter of the rubber dam body is smaller than the depth of the river channel, allowing shallow, clear water with a lower sediment content to overflow from the top of the rubber dam body to the downstream, thus making it easier for silt to accumulate in this area. The rubber dam includes the following design parameters:

[0056] The vertical distance L from the top of the central axis of the rubber dam to the middle of the dam body;

[0057] The distance between the two ends of the dam body is D;

[0058] Dam height H1;

[0059] The sag-to-span ratio μ is the ratio of the vertical distance L of the dam body to the distance D between its two ends, L / D. The value of the sag-to-span ratio μ ranges from 1 / 4 to 1 / 6.

[0060] λ — The ratio of dam height H1 to river channel depth H at normal water level, H1 / H;

[0061] γ—The ratio of the depth at which the cumulative sediment content at the bottom reaches 98% to the total depth in a scaled-down test of a normal flow channel model.

[0062] First, a scaled-down test of a normal flow channel model was conducted to measure sediment distribution. Based on the sediment distribution curve with depth, the parameter γ was calculated. The dam body parameters of the rubber dam were calculated using the following formula:

[0063] λ = 1 - 2γ (Formula 1)

[0064] H1=λH Formula 2

[0065]

[0066] L=Dμ Formula 4

[0067] Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel.

[0068] The method described herein, wherein the sediment storage pit is used to reduce water flow velocity and promote sediment deposition; the present invention, while achieving the same sediment interception effect, reduces the height of the rubber dam, promotes fish migration in the river channel, and avoids the accumulation of floating debris on the river surface; the sediment storage pit includes the following design parameters:

[0069] The slope of the mud storage pit is 1:1.

[0070] The depth of the mud storage pit is H2;

[0071] The bottom length of the cross-section of the mud storage pit is L1;

[0072] The bottom width of the mud storage pit is B1.

[0073] And calculate according to the following formula:

[0074] H2 = H Formula 5

[0075] L1 = 3H Formula 6

[0076] B1 = B - 2H (Formula 7)

[0077] Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel.

[0078] The method involves a rubber dam base plate made of cast concrete, with anchoring devices used to fix the dam body to the base plate to prevent movement and wear caused by water flow. The rubber dam is supported at both ends by supports embedded in the riverbank soil. Each support has a square cross-section with a side length L4. One corner of the square facing the dam body is chamfered, and a vertical support surface 6 on the chamfer is perpendicularly connected to the dam body to prevent relative displacement between the top of the rubber dam and the support surface. The distance L3 between the outer end of the support surface and the riverbank is 0.1m to increase the stability of the support surface. The length of the support surface is L5. The support includes the following design parameters:

[0079] The side length of the support is L4;

[0080] The distance L3 between the outer end of the support surface and the riverbank is 0.1m.

[0081] Support face length L5;

[0082] Calculate using the following formula:

[0083]

[0084] L5 = H Formula 9

[0085] Where H represents the normal water level depth of the river channel.

[0086] The method involves determining the vertical distribution pattern of river sediment through a constant-flow river model test. The model test material is sampled from riverbed sediment, and the test parameters, such as flow velocity and flow depth, are the same as the river flow velocity and constant-flow depth. The model width is reduced to decrease the test scale, and γ is calculated based on the vertical distribution curve of river sediment obtained from the model test.

[0087] The method wherein the span-to-span ratio μ is preferably 1 / 5.

[0088] Preferably, the mud storage pit (3) is surrounded by a 1:1 slope.

[0089] The rubber dam described in this invention is arched, with both ends curved towards the direction of water flow. This curvature reduces the force of the flowing water on the dam body, while simultaneously allowing silt to collect at the riverbank, facilitating mechanical dredging. The dam's diameter is smaller than the river's depth, causing shallower, less sediment-laden water to overflow to the lower sections, thus increasing siltation in those areas. The silt storage pit reduces water flow velocity, promoting siltation. This invention achieves the same silt interception effect while reducing the dam's height, promoting fish migration in the river and preventing the accumulation of floating debris on the surface. The silt storage pit has a 1:1 slope and a depth H2, the same as the normal water level, ensuring its effectiveness in reducing water flow velocity. The dam's base is constructed of concrete cast into the riverbed, and anchoring devices secure the dam body to the base, preventing movement and wear caused by water flow. The rubber dam is supported by piers at both ends, with the pier support surfaces perpendicular to the rubber dam to prevent relative displacement between the rubber dam and the pier support surfaces.

[0090] Example

[0091] This invention provides a river channel silt reduction construction scheme, including a rubber dam 1, abutments 2, a silt storage pit 3, a rubber dam bottom slab 4, and a silt storage pit bottom slab 5.

[0092] This embodiment describes a method for urban river channel management, comprising the following steps:

[0093] Given that the river channel is 20m wide (B), 1.5m deep (H), and has a flow velocity of 0.5m / s.

[0094] Based on the above parameters, an indoor model test was designed. The model test parameters were: model width B' 0.5m, water depth H 1.5m, and model water flow velocity 0.5m / s. The test material was sampled from riverbed sediment. The test parameters, water flow velocity and depth, were the same as the river flow velocity and normal water level depth. The model width was reduced to decrease the test scale. The vertical distribution curve of cumulative sediment concentration in the riverbed obtained from the model test is shown below. Figure 5 .

[0095] Depend on Figure 5 It can be concluded that the depth from the bottom where the cumulative sand concentration reaches 98% is h = 0.25m, and H is the water depth of the scaled-down model test, H = 1.5m.

[0096] Based on the cumulative sediment concentration distribution curve with depth, the parameter γ = h / H = 0.25 / 1.5 = 1 / 6 is calculated for this test material. The parameter λ is calculated using Formula 1. Therefore, the parameters and specific steps of the actual silt reduction design scheme are as follows:

[0097] S1: Based on the selected site, level the ground, set up a water interception plan, treat the foundation according to the existing siltation, and remove the existing silt if necessary. Then level the site. According to Formula 1: λ=1-2γ, obtain the parameter λ=2 / 3. According to Formula 2: H1=λH, calculate the height of rubber dam 1.

[0098]

[0099] Calculate the distance D between the two ends of the dam body according to Formula 3:

[0100]

[0101] The span-to-span ratio μ is taken as 1 / 5. The vertical distance L from the top of the dam's central axis to the middle of the dam is calculated according to Formula 4:

[0102] L = Dμ = 17.78 * 0.2 = 3.54m

[0103] S2: Further, an excavator is used to excavate the mud storage pit 3. A 10cm thick rubber dam bottom plate 4 and mud storage pit bottom plate 5 are laid at the bottom of the mud storage pit 3 and the rubber dam 1. The mud storage pit 3 is surrounded by a 1:1 slope. The depth H2 of the mud storage pit 3 is calculated according to formula 5.

[0104] H2 = H = 1.5m

[0105] According to Formula 6, the bottom length of the cross-section of the mud storage pit 3 is calculated to be L1:

[0106] L1 = 3H = 4.5m

[0107] The bottom width B1 of the mud storage pit 3 is calculated according to Formula 7, using the following formula:

[0108] B1 = B - 2H = 17m

[0109] S3: Further, reinforced concrete is used to cast the support pier 2, and the side length L4 of the support pier is calculated according to formula 8:

[0110]

[0111] The length of the support face is calculated as L5 according to Formula 9, and then calculated using the following formula:

[0112] L5 = H = 1.5m

[0113] S4: Further fill the rubber dam 1 with water until the height of the rubber dam 1 is 1m and then stop filling the water. The rubber dam 1 is made of high-strength synthetic fiber as a traditional material and is anchored on the concrete base plate and the support pier 2.

[0114] S5: Further, remove the water interception devices around the site.

[0115] like Figure 6 The diagram shows the sediment distribution plan of the sediment storage pit 3 after implementation of this embodiment. The curves in the diagram are contour lines, and the numbers represent the elevation of the sediment at that location, in meters (m). It can be seen that the sediment elevation is high near the riverbank, indicating the main sediment deposition area, with sediment primarily deposited along the riverbank. The sediment elevation is low in the river center, with less sediment deposition. This phenomenon is mainly due to the arched structure of the rubber dam, which causes suspended sediment to move towards both sides of the riverbank, making it easier for sediment to deposit on both sides of the river. This deposition range ensures convenient mechanical dredging.

Claims

1. A construction method for silt reduction structures in urban inland rivers, comprising a silt storage pit (3), a rubber dam (1), and a rubber dam base plate (4), a support pier (2), and a silt storage pit base plate (5) arranged sequentially along the water flow direction on the river channel; characterized in that, The piers are symmetrically distributed on both sides of the river. The piers are connected to the rubber dam base plate (4) set at the bottom of the riverbed by concrete pouring. The bottom plate (5) of the mud storage pit (3) at the bottom of the mud storage pit is connected to the bottom of the riverbed and the rubber dam base plate by concrete pouring along the front and rear ends of the mud storage pit in the direction of water flow. The rubber dam is located on the rubber dam base plate between the two piers. The rubber dam and the piers, and the rubber dam and the rubber dam base plate are all connected by anchoring devices. The rubber dam is constructed in an arched shape on the horizontal plane, with both ends curving towards the direction of water flow, forming a streamlined dam body that impounds water. This structure allows sediment to be concentrated and deposited on the bank for later mechanical dredging. The sediment storage pit (3) is constructed in an arched shape around the rubber dam. The diameter of the rubber dam body is smaller than the depth of the river channel, allowing shallow, clear water with a low sediment content to overflow from the top of the rubber dam body to the downstream. The rubber dam includes the following design parameters: The vertical distance L from the top of the central axis of the rubber dam to the middle of the dam body; The distance between the two ends of the dam body is D; Dam height H1; Sagittal span ratio —The ratio of the vertical distance L of the dam body to the distance D between its two ends, L / D, is the rise-span ratio. The value ranges from 1 / 4 to 1 / 6; —The ratio of dam height H1 to river channel depth H at normal water level, H1 / H; —The ratio of the depth at which the cumulative sediment content at the bottom reaches 98% to the total depth in a scaled-down test of a normal flow channel model; First, a scaled-down test of a normal flow channel model was conducted to measure sediment distribution, and parameters were calculated based on the sediment distribution curve with depth. The parameters of the rubber dam are calculated using the following formula: Official 1 Official 2 Official 3 Official 4 Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel; The mud storage pit includes the following design parameters: The slope of the mud storage pit is 1:

1. The depth of the mud storage pit is H2; The bottom length of the cross-section of the mud storage pit is L1; The bottom width of the mud storage pit is B1; And calculate according to the following formula: Official 5 Official 6 Official 7 Where H is the normal water level depth of the river channel, and B is the distance between the two banks of the river channel.

2. The method according to claim 1, characterized in that, The abutment is embedded in the riverbank soil. The horizontal cross-section of the abutment is set as a square with a side length of L4. One apex of the square facing the dam body is set as a chamfer. The vertical support surface (6) on the chamfer is vertically connected to the dam body. The distance L3 between the outer end of the support surface and the riverbank line is 0.1m. The length of the support surface is L5. The abutment includes the following design parameters: The side length of the support is L4; The distance L3 between the outer end of the support surface and the riverbank is 0.1m. Support face length L5; Calculate using the following formula: Official 8 Official 9 Where H represents the normal water level depth of the river channel.

3. The method according to claim 1, characterized in that, The vertical distribution pattern of sediment in the river channel was determined through the normal flow river model test. The test material was sampled from the riverbed sediment, and the test parameters—flow velocity and depth—were the same as the normal flow velocity and depth of the river. The model width was reduced to decrease the test scale. The vertical sediment distribution curve obtained from the model test was then used to calculate... .

4. The method according to claim 1, characterized in that, The sag-span ratio It is 1 / 5.

Images