A sedimentation tank construction method for desilting water diversion box culvert based on hydraulic parameter reduction

Abstract

The present invention discloses a method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction. The method is based on the conventional water diversion box culvert construction, and analyzes the sediment evolution law along the box culvert based on hydraulic calculation, and reduces the designed sediment carrying capacity of each section until the most likely sediment accumulation position in the box culvert is calculated, and the sediment accumulation amount in the box culvert is calculated in combination with the sediment entrainment of the river at the canal mouth. During the casting of the box culvert, referring to the calculated possible sediment accumulation position and sediment accumulation amount of the box culvert, holes of corresponding sizes are excavated and reserved at the bottom of the corresponding position of the box culvert to cast the sedimentation well, and openings are reserved at the top of the front and rear sections of the box culvert sedimentation well to set up an inspection shaft, and the construction of the desilting sedimentation well for the water diversion box culvert is completed, so as to realize the cleaning and removal of the sediment accumulated during the operation of the water diversion channel box culvert.

Description

Technical Field

[0001] The invention relates to the field of water conservancy and hydropower engineering construction, and in particular to a sedimentation pond construction method for desilting a water diversion box culvert based on hydraulic parameter reduction. Background Art

[0002] Box culverts are small water conveyance structures commonly found in irrigation water diversion projects. They are widely used in water conservancy projects because of their convenient construction, low cost, and strong adaptability to geological conditions. Since the structure of box culverts is relatively simple, most of the existing box culvert designs are linear structure designs based on standard drawings, usually only considering the elevation and slope of the box culvert. The slope is determined according to the actual project. In the case of no reverse slope, the critical slope is usually selected, which can reduce the amount of excavation work while ensuring the flood discharge or water-passing capacity of the box culvert.

[0003] However, in actual projects, especially in large irrigation projects, due to the long water transmission lines and the diverse structures of water transmission buildings, including box culverts, open channels, aqueducts, inverted siphons, etc., in the open channel connecting the box culvert section, when the channel slope support conditions of the open channel section at the box culvert mouth are not ideal, the silt eroded from the side walls of the channel slope is transported into the box culvert by the channel water flow. At this time, the hydraulic conditions in the box culvert no longer meet the original design and calculation conditions, which is easy to cause silt accumulation in the box culvert, and even blockage, seriously affecting the water transmission capacity and operation safety of the box culvert, causing huge economic losses. In addition, if the box culvert tunnel is small, long, and buried deep, dredging is very difficult and unsafe. Therefore, in order to meet the normal operation requirements of the water diversion project, it is very urgent to facilitate dredging and ensure its smooth water transmission.

[0004] To this end, this technology proposes a sedimentation tank construction method for desilting water diversion box culverts based on the reduction of sediment carrying capacity. This method is based on the conventional water diversion box culvert construction, and analyzes the sediment evolution law along the box culvert based on hydraulic calculation, and reduces the designed sediment carrying capacity of each section until the most likely sediment accumulation position in the box culvert is calculated, and the sediment accumulation amount in the box culvert is calculated in combination with the sediment carrying situation of the river at the canal mouth. During the casting process of the box culvert, referring to the calculated possible sediment accumulation position and sediment accumulation amount of the box culvert, holes of corresponding sizes are excavated at the bottom of the corresponding position of the box culvert to cast sedimentation wells, so as to realize the cleaning and removal of sediment accumulation during the operation of the water diversion channel box culvert.

[0005] For this sedimentation well construction method, calculating the location and amount of sedimentation and determining the location of the sedimentation well is the most critical link. Referring to the strength reduction theory for calculating slope stability, an innovative calculation method for reducing the sediment carrying capacity is proposed. The sediment carrying capacity of each section is calculated and used. This method can conveniently and accurately provide the construction and design plan of the water diversion box culvert sedimentation well. Summary of the invention

[0006] The present invention is conducted to solve the above-mentioned problem, and aims to provide a construction method for desilting a water diversion channel box culvert, which is suitable for long-distance water diversion projects with small burial depth and small diameter. The method is based on hydraulic parameter reduction, and determines the position and amount of possible silt accumulation in the box culvert by calculation, and excavates holes of corresponding sizes at the bottom of the box culvert at the corresponding position to cast sedimentation wells, so as to realize the cleaning and removal of silt accumulation during the operation of the water diversion channel box culvert. The method can optimize the construction plan, improve the construction accuracy, and save construction costs while ensuring the water delivery safety of the water diversion project.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The present invention provides a method for constructing a siltation pond for desilting a water diversion box culvert based on hydraulic parameter reduction, the method comprising the following steps:

[0009] S1: According to the design data of the water diversion box culvert, determine the cross-sectional shape, size, cross-sectional area, wetted perimeter, design water depth, average water depth, hydraulic radius, bottom slope, and box culvert roughness parameters of the water diversion box culvert construction;

[0010] S2: Based on the hydrological data, determine the river water diversion conditions at the head of the box culvert, including the water diversion volume, sediment diversion volume, sedimentation volume, average sediment settling velocity, and designed sediment carrying capacity in each typical year;

[0011] S3: Calculate the water flow sediment carrying capacity of each section along the box culvert according to the design parameters. The calculation formula of the water flow sediment carrying capacity is determined according to the hydraulic conditions at the project site;

[0012] For example, the Yellow River region can adopt:

[0013]

[0014] Where: S i is the sediment-carrying capacity of the water flow in the i-th section, kg / m 3 ; V i is the water flow velocity of the i-th section, m / s; B i is the water surface width of the ith section, m; H i is the average water depth of the ith section, m; R i is the hydraulic radius of the ith section, m; g is the gravitational acceleration, m / s 2 , is the weighted average of sediment settling velocity, cm / s;

[0015] The Yangtze River region can also be calculated using the following formula:

[0016]

[0017] In the formula, k and m are the sand-carrying force coefficient and index, which can be obtained by consulting the calculation manual or experience;

[0018] S4: The calculated box culvert flow sediment carrying capacity S i , let it be equal to the designed sand content

[0019]

[0020] By reverse calculation, the non-silting flow velocity of each section of the box culvert under the designed sediment content is obtained.

[0021]

[0022] or

[0023]

[0024] S5: The flow velocity of the box culvert is calculated according to the average flow velocity of the constant uniform pipe flow through the water section, and the average flow velocity V of each section is calculated. i :

[0025]

[0026] C is the Xiecai coefficient of the i-th section, in m 1 / 2 / s, J is the hydraulic gradient of the i-th section

[0027]

[0028] Where n i is the roughness of the i-th section;

[0029] when Sometimes, sediment will accumulate at the cross section;

[0030] S6: In actual projects, different sections have different flow rates according to the site conditions. and the average flow velocity V i For example, in large irrigation projects, due to the long water supply lines and the diverse structures of water supply buildings, when the channel slope support conditions of the open channel section at the box culvert are not ideal, the silt eroded from the channel slope wall is transported into the box culvert by the channel water flow. At this time, the sand-carrying capacity of the water flow in the box culvert decreases, and the non-silting flow rate In addition, the roughness, hydraulic radius and hydraulic gradient of different sections will also change with the increase of sediment content in the water flow. The changes in roughness, hydraulic radius and hydraulic gradient will also affect the flow velocity of the box culvert. Therefore, combined with the actual situation of the project, the calculation parameters are reduced according to the following formula:

[0031] ηi j =η i j-1 -Δη

[0032] η i j is the value of the parameter that needs to be reduced in the i-th section at the j-th calculation; Δη is the amount of reduction of parameter η before each calculation, which is selected based on engineering experience; the hydraulic parameters η that need to be reduced include roughness, hydraulic radius, hydraulic gradient, average water depth and water surface width;

[0033] After reducing the parameters, the non-silting flow velocity V of each section of the box culvert is iteratively recalculated. i and the average flow velocity V i , and compare the non-silting flow velocity of the i-th section after each iteration and the average flow velocity V i , when the two are equal

[0034]

[0035] That is, the i-th section is the section where sediment deposition is most likely to occur along the box culvert;

[0036] S7: After determining the location of the section i where sediment deposition is most likely to occur, the sediment carrying capacity S is calculated by referring to the water diversion and sediment diversion of the river channel or box culvert outlet in the hydrological data and the parameters η after reduction. i , and combined with the box culvert section size and water depth, the cross-section sedimentation volume Q can be obtained through conventional sedimentation calculation y and sediment thickness H y , and fully consider the volume of sediment deposited in a dredging cycle, and finally determine the length L of the sedimentation tank c , Width W c and depth H c ;

[0037] S8 refers to the calculated length of the sedimentation tank L c , Width W c and depth H c , carry out box culvert construction, dig out a sedimentation pond under the section where silt accumulation is most likely to occur, set up a formwork and pour concrete, embed it into the box culvert, and cast it as a whole;

[0038] S9: According to the length and burial depth of the box culvert, determine whether it is necessary to reserve holes at the top when pouring the box culvert. After covering and backfilling the box culvert, reserve a ladder passage at the top of the vertical shaft to facilitate personnel to go down for dredging and maintenance;

[0039] S10: If it is necessary to add a sedimentation pond to an existing box culvert under special circumstances, it is necessary to evaluate the actual situation and dig a sedimentation pond in the existing box culvert.

[0040] Optionally, common shapes of the water-passing cross-section in S1 include rectangle and circle, and the dimensions include the length, width, height and diameter of each cross-section. Some cross-section dimensions remain unchanged or change along the way, and the hydraulic radius needs to be obtained by calculating the shape, size and wetted perimeter of the water-passing cross-section.

[0041] Optionally, the water diversion box culvert in S1 should have a certain length and a small diameter. If the box culvert is very short or has a large diameter, there is no need to set up a siltation tank. Because the box culvert is short or has a large diameter, even if silt accumulates, it will not cause any major problems, and personnel can also easily enter the box culvert directly from the culvert mouth to directly dredge and desilt.

[0042] Optionally, the length of the selected intervals of each section along the box culvert in S3, in addition to selecting sections at certain intervals, should also be based on whether there are significant changes in the hydraulic conditions of the box culvert, such as changes in the box culvert mouth, bottom slope gradient, gradual changes in section size, forks, bends, etc., where additional calculation sections should be added.

[0043] Optionally, S5 determines whether silt is deposited in the box culvert by calculation. In addition to obtaining the relationship between the average flow velocity and the non-silting flow velocity by direct calculation, it can also be analyzed by numerical simulation to improve the calculation efficiency.

[0044] Optionally, the hydraulic parameter η to be reduced in S6 generally includes roughness, hydraulic radius, hydraulic gradient, average water depth and water surface width. The reduction rate of these parameters should be adjusted according to the actual situation of the project and the focus of attention. For example, if the project pays more attention to the siltation caused by the change in roughness, other parameters can be kept unchanged, and only the location where the siltation first occurs can be analyzed by reducing the roughness. Δη is the amount of reduction of the parameter η before each calculation. It is selected according to engineering experience and can be as small as possible to increase the incremental step of the calculation iteration and improve the calculation accuracy.

[0045] Optionally, the structure of the S8 sedimentation tank should be dug into a rectangular groove. If the calculated depth of the sedimentation tank is less than the thickness of the box culvert, it is also possible to form a groove by pouring a small amount of concrete without digging. In addition to making an open sedimentation tank, a metal cover with holes can be added to the sedimentation tank to improve the flow capacity, which is conducive to locking the silt in the sedimentation tank and facilitating cleaning. In addition, the bottom of the sedimentation tank can be made into a small slope reverse slope against the direction of the water flow, which is also conducive to the sedimentation of silt in the sedimentation tank.

[0046] Optionally, holes are reserved at the top of the box culvert in S9, and the steel bars of the box culvert should be arranged to avoid the holes. The steel bars near the holes should meet the structural strength and construction requirements if designed to be replaced. Attention should be paid to the structural strength of the openings. If necessary, transverse and longitudinal beams and columns should be arranged near the openings.

[0047] Optionally, in S9, it is determined whether it is necessary to reserve holes on the top of the box culvert when casting the box culvert according to the length and burial depth of the box culvert. The box culvert is short and there is no need to set up a separate vertical shaft, and silt can be directly entered from the culvert mouth to the sedimentation tank for dredging. The box culvert is buried deep, and it is not suitable to reserve holes on the top of the box culvert because the cost of construction and support is high and it is more dangerous for personnel to operate.

[0048] Optionally, in addition to determining the location of the sedimentation tank by hydraulic calculation in advance, the box culvert in S10 may reveal problems due to different geological conditions, changes in hydraulic conditions at the box culvert mouth, changes in rainfall conditions, and the influence of rotation, which may cause the calculated location of the sedimentation tank to be inconsistent with the actual silt deposition location. It is also possible to add a sedimentation tank at a later stage by excavating at the bottom of the built box culvert, but while ensuring the stability and safety of the box culvert, try to avoid damaging the box culvert structure.

[0049] Beneficial effects of the present invention:

[0050] 1. The desilting tank construction method of the present invention calculates the possible silting position and siltation amount of the water diversion box culvert to guide the construction of the desilting well of the box culvert, so as to realize the cleaning and removal of the silted sand during the operation of the water diversion channel box culvert. The mechanical model is clear, the construction is simple and the cost is low.

[0051] 2. The method for constructing a siltation pond for desilting a water diversion box culvert based on hydraulic parameter reduction of the present invention is simple and accurate in calculation, and can calculate the possible siltation position and siltation amount of the water diversion box culvert. The flow velocity of each section is calculated by hydraulic parameter reduction method, and the section most prone to siltation is obtained through continuous reduction and iteration. This method can conveniently and accurately provide the construction and design scheme of the water diversion box culvert siltation well. DETAILED DESCRIPTION

[0052] The following will be combined with 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.

[0053] Example

[0054] The present invention provides a method for constructing a siltation pond for desilting a water diversion box culvert based on hydraulic parameter reduction, the method comprising the following steps:

[0055] S1: According to the design data of the water diversion box culvert, determine the cross-sectional shape, size, cross-sectional area, wetted perimeter, design water depth, average water depth, hydraulic radius, bottom slope, and box culvert roughness parameters of the water diversion box culvert construction;

[0056] S2: Based on the hydrological data, determine the river water diversion conditions at the head of the box culvert, including the water diversion volume, sediment diversion volume, sedimentation volume, average sediment settling velocity, and designed sediment carrying capacity in each typical year;

[0057] S3: Calculate the water flow sediment carrying capacity of each section along the box culvert according to the design parameters. The calculation formula of the water flow sediment carrying capacity is determined according to the hydraulic conditions at the project site;

[0058] For example, the Yellow River region can adopt:

[0059]

[0060] Where: S i is the sediment-carrying capacity of the water flow in the i-th section, kg / m 3 ; V i is the water flow velocity of the i-th section, m / s; B i is the water surface width of the ith section, m; H i is the average water depth of the ith section, m; R i is the hydraulic radius of the ith section, m; g is the gravitational acceleration, m / s 2 , is the weighted average of sediment settling velocity, cm / s;

[0061] The Yangtze River region can also be calculated using the following formula:

[0062]

[0063] In the formula, k and m are the coefficient and index of the sand-carrying force, which can be obtained by consulting the calculation manual or experience;

[0064] S4: The calculated box culvert flow sediment carrying capacity S i , let it be equal to the designed sand content

[0065]

[0066] By reverse calculation, the non-silting flow velocity of each section of the box culvert under the designed sediment content is obtained.

[0067]

[0068] or

[0069]

[0070] S5: The flow velocity of the box culvert is calculated according to the average flow velocity of the constant uniform pipe flow through the water section, and the average flow velocity V of each section is calculated. i :

[0071]

[0072] C is the Xiecai coefficient of the i-th section, in m 1 / 2 / s, J is the hydraulic gradient of the i-th section

[0073]

[0074] Where n i is the roughness of the i-th section;

[0075] when Sometimes, sediment will accumulate at the cross section;

[0076] S6: In actual projects, different sections have different flow rates according to the site conditions. and the average flow velocity V i For example, in large irrigation projects, due to the long water supply lines and the diverse structures of water supply buildings, when the channel slope support conditions of the open channel section at the box culvert are not ideal, the silt eroded from the channel slope wall is transported into the box culvert by the channel water flow. At this time, the sand-carrying capacity of the water flow in the box culvert decreases, and the non-silting flow rate In addition, the roughness, hydraulic radius and hydraulic gradient of different sections will also change with the increase of sediment content in the water flow. The changes in roughness, hydraulic radius and hydraulic gradient will also affect the flow velocity of the box culvert. Therefore, combined with the actual situation of the project, the calculation parameters are reduced according to the following formula:

[0077] η i j =η i j-1 -Δη

[0078] η i j is the value of the parameter that needs to be reduced in the i-th section at the j-th calculation; Δη is the amount of reduction of parameter η before each calculation, which is selected based on engineering experience; parameter η is the hydraulic parameter that needs to be reduced, which is taken as roughness, hydraulic radius, and hydraulic gradient;

[0079] After reducing the parameters, the non-silting flow velocity of each section of the box culvert is iteratively recalculated. and the average flow velocity V i , and compare the non-silting flow velocity of the i-th section after each iteration and the average flow velocity V i , when the two are equal

[0080]

[0081] That is, the i-th section is the section where sediment deposition is most likely to occur along the box culvert;

[0082] S7: After determining the location of the section i where sediment deposition is most likely to occur, the sediment carrying capacity S is calculated by referring to the water diversion and sediment diversion of the river channel or box culvert outlet in the hydrological data and the parameters η after reduction. i , and combined with the box culvert section size and water depth, the cross-section sedimentation volume Q can be obtained through conventional sedimentation calculation y and sediment thickness H y , and fully consider the volume of sediment deposited in a dredging cycle, and finally determine the length L of the sedimentation tank c , Width W c and depth H c ;

[0083] S8 refers to the calculated length of the sedimentation tank L c , Width W c and depth H c , carry out box culvert construction, dig out a sedimentation pond under the section where silt accumulation is most likely to occur, set up a formwork and pour concrete, embed it into the box culvert, and cast it as a whole;

[0084] S9: According to the length and burial depth of the box culvert, determine whether it is necessary to reserve holes at the top when pouring the box culvert. After covering and backfilling the box culvert, reserve a ladder passage at the top of the vertical shaft to facilitate personnel to go down for dredging and maintenance;

[0085] S10: If it is necessary to add a sedimentation pond to an existing box culvert under special circumstances, it is necessary to evaluate the actual situation and dig a sedimentation pond in the existing box culvert.

[0086] Specifically, in this embodiment, a reservoir irrigation project is taken as an example. The project is a large-scale water diversion project, which includes various water conveyance structures such as open channels, tunnels, box culverts, inverted siphons, and aqueducts. During the excavation process, a section of the open channel with a length of nearly 500 m collapsed due to the slope collapse on the left bank, and it was difficult to cut the slope. Therefore, the open channel was changed to a box culvert. The box culvert is a rectangular culvert. Since the culvert mouth is an open channel connected to the box culvert, and the open channel slope is an unsupported excavated slope, it is considered that the silt eroded from the side wall of the channel slope will be transported into the box culvert by the channel water flow in the future, which is easy to cause siltation in the box culvert, affecting the water conveyance capacity and operation safety of the box culvert. Therefore, this method is used to construct a sedimentation well in the box culvert to meet the normal operation requirements of the water diversion project and facilitate the silt removal of the box culvert.

[0087] The above embodiment includes the following steps in the specific implementation process:

[0088] S1: According to the design data of the water diversion box culvert, the water-passing section of the water diversion box culvert is determined to be a rectangle, the length of the rectangular section is a, the width is b, the cross-sectional area is A, the wetted perimeter is X, the design water depth is H, the average water depth is H, the hydraulic radius is R, the bottom slope is i, and the box culvert roughness is n.

[0089] S2: Based on the hydrological data, determine the river water diversion situation at the head of the box culvert, including the water diversion volume Q in each typical year. w , Sediment intake Q s , average sediment settling velocity Designed sand-carrying capacity

[0090] S3: Calculate the water flow sediment carrying capacity of each section along the box culvert according to the design parameters. Since the project location of this embodiment belongs to the Yangtze River Basin, the calculation formula for the water flow sediment carrying capacity is:

[0091]

[0092] Where k and m are the sand-carrying coefficient and index; S i is the sediment-carrying capacity of the water flow in the i-th section, kg / m 3 ; V i is the water flow velocity of the i-th section, m / s; B i is the water surface width of the ith section, m; H i is the average water depth of the ith section, m; R i is the hydraulic radius of the ith section, m; g is the gravitational acceleration, m / s 2 , is the weighted average of sediment settling velocity, cm / s.

[0093] Record in the table below.

[0094] Section number i 1 2 3 ……………… i Water flow sand carrying capacity <![CDATA[S1]]> <![CDATA[S2]]> <![CDATA[S3]]> <![CDATA[S i ]]>

[0095] S4: The calculated box culvert flow sediment carrying capacity S i , let it be equal to the designed sand content

[0096]

[0097] By reverse calculation, the non-silting flow velocity of each section of the box culvert under the designed sediment content is obtained.

[0098] S5: The flow velocity of the box culvert is calculated according to the average flow velocity of the constant uniform pipe flow through the water section, and the average flow velocity V of each section is calculated. i :

[0099]

[0100] C is the Xiecai coefficient of the i-th section, in m 1 / 2 / s, J is the hydraulic gradient of the i-th section

[0101]

[0102]

[0103] Where n i is the roughness of the i-th section, and K is the flow modulus of the i-th section.

[0104] The non-silting flow velocity of each section and the average flow velocity V i Record in the table below.

[0105]

[0106] S6: In this large irrigation project, due to the long water supply line and the diverse structures of water supply buildings, in the open channel connecting the box culvert, the channel slope of the open channel section at the box culvert entrance is only an excavated unsupported slope. The channel slope and wall are prone to erosion of sediment into the box culvert under long-term operation. At this time, the sediment carrying capacity of the water flow in the box culvert decreases, and the non-silting flow velocity V i Also decreased.

[0107] In addition, the roughness, hydraulic radius and hydraulic gradient of different sections will also change with the increase of sediment content in the water flow, and the changes in roughness, hydraulic radius and hydraulic gradient will also affect the flow velocity of the box culvert. Therefore, based on the actual situation of the project, the roughness, hydraulic radius and hydraulic gradient are reduced:

[0108] n i j =n i j-1 -Δn

[0109] R i j =R i j-1 -ΔR

[0110] J i j =J i j-1 -ΔJ

[0111] η i j is the value of the parameter that needs to be reduced for the i-th section at the j-th calculation; Δη is the amount of reduction of the parameter η before each calculation.

[0112] The roughness, hydraulic radius, and hydraulic gradient are iterated j times to recalculate the non-silting flow velocity V of each section of the box culvert. i and the average flow velocity V i , and compare the non-silting flow velocity V of the i-th section after each iteration i and the average flow velocity V i Record in the table below.

[0113]

[0114] Record after the jth reduction At this time, the recorded section i is the section location where siltation is most likely to occur along the box culvert.

[0115] S7: After determining the location of the section i where sediment deposition is most likely to occur, the water diversion volume of the river channel or box culvert outlet in the reference hydrological data is Q w , Sediment intake Q s , average sediment settling velocity Designed sand-carrying capacity And the sediment carrying capacity S calculated after reducing each parameter η i , and combined with the box culvert section size and water depth, the cross-section sedimentation volume Q can be calculated y and sediment thickness H y , and fully consider the volume of silt deposited in a dredging cycle, and finally determine the length L of the sedimentation tank c , Width W c and depth H c .

[0116] S8 refers to the calculated length of the sedimentation tank L c , Width W c and depth H c , carry out box culvert construction, dig a sedimentation pond under the section where silt accumulation is most likely to occur, erect a mold and pour concrete, embed it into the box culvert, and cast it as a whole.

[0117] S9: As the box culvert is long and not buried deep, holes are reserved on the top when casting the box culvert. After covering and backfilling the box culvert, a vertical shaft ladder passage is added on the top to facilitate personnel to go down for dredging and maintenance.

[0118] The present invention provides a construction method for desilting a water diversion channel box culvert, which is suitable for long-distance water diversion projects with small burial depth and small diameter. The method is based on hydraulic parameter reduction, and determines the possible silt accumulation position and silt accumulation amount of the box culvert by calculation, and excavates holes of corresponding sizes at the bottom of the box culvert at the corresponding position to pour a sedimentation well, so as to realize the cleaning and removal of silt accumulation during the operation of the water diversion channel box culvert, and optimizes the construction plan, improves the construction accuracy, and saves the construction cost while ensuring the water delivery safety of the water diversion project.

[0119] The sedimentation tank construction method of the present invention calculates the possible sedimentation position and sedimentation amount of the water diversion box culvert to guide the construction of the sedimentation well of the box culvert, so as to realize the cleaning and removal of the sedimentation during the operation of the water diversion channel box culvert. The mechanical model is clear, the construction is simple and the cost is low.

[0120] The method for constructing a siltation tank for desilting a water diversion box culvert based on hydraulic parameter reduction of the present invention is simple and accurate in calculation, and can calculate the possible siltation position and siltation amount of the water diversion box culvert. The flow velocity of each section is calculated by hydraulic parameter reduction method, and the section most prone to siltation is obtained through continuous reduction and iteration. This method can conveniently and accurately provide the construction and design scheme of the siltation well of the water diversion box culvert.

[0121] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction, characterized in that: The method comprises the following steps: S1: According to the design data of the water diversion box culvert, determine the cross-sectional shape, size, cross-sectional area, wetted perimeter, design water depth, average water depth, hydraulic radius, bottom slope, and box culvert roughness parameters of the water diversion box culvert construction; S2: Based on the hydrological data, determine the river water diversion conditions at the head of the box culvert, including the water diversion volume, sediment diversion volume, sedimentation volume, average sediment settling velocity, and designed sediment carrying capacity in each typical year; S3: Calculate the water flow sediment carrying capacity of each section along the box culvert according to the design parameters. The calculation formula of water flow sediment carrying capacity is determined according to the hydraulic conditions at the project site; The Yellow River region can adopt: Where: S i is the sediment-carrying capacity of the water flow in the i-th section, kg / m 3 ; is the water flow velocity of the ith section, m / s; B i is the water surface width of the ith section, m; H i is the average water depth of the ith section, m; R i is the hydraulic radius of the ith section, m; g is the gravitational acceleration, m / s 2 , is the weighted average of sediment settling velocity, cm / s; The Yangtze River region is calculated using the following formula: In the formula, k and m is the sand-carrying force coefficient and index; S4: The calculated sediment carrying capacity of the box culvert flow S i , let it be equal to the designed sand content By reverse calculation, the non-silting flow velocity of each section of the box culvert under the designed sediment content is obtained. ; or ； S5: The flow velocity of the box culvert is calculated according to the average flow velocity of the constant uniform pipe flow through the water section, and the average flow velocity of each section is calculated. : is the Xie Cai coefficient of the ith section, in m 1 / 2 / s, is the hydraulic gradient of the i-th section in n i is the roughness of the i-th section; when Sometimes, sediment will accumulate at the cross section; S6: In actual projects, different sections have different flow rates according to the site conditions. and average flow rate In large irrigation projects, due to the long water supply lines and the diverse structures of water supply buildings, when the channel slope support conditions of the open channel section at the box culvert are not ideal, the silt eroded from the channel slope wall is transported into the box culvert by the channel water flow. At this time, the sand-carrying capacity of the water flow in the box culvert decreases, and the non-silting flow rate In addition, the roughness, hydraulic radius and hydraulic gradient of different sections will also change with the increase of sediment content in the water flow. The changes in roughness, hydraulic radius and hydraulic gradient will also affect the flow velocity of the box culvert. Therefore, combined with the actual situation of the project, the calculation parameters are reduced according to the following formula: is the value of the parameter that needs to be reduced for the i-th section at the j-th calculation; For parameters The amount of reduction before each calculation is selected based on engineering experience; the hydraulic parameters to be reduced Including roughness, hydraulic radius, hydraulic gradient, average water depth and water surface width; After reducing the parameters, the non-silting flow velocity of each section of the box culvert is iteratively recalculated. and average flow rate , and compare the non-silting flow velocity of the i-th section after each iteration and average flow rate , when the two are equal That is, the i-th section is the section where sediment deposition is most likely to occur along the box culvert; S7: After determining the location of the section i where sediment deposition is most likely to occur, refer to the water diversion volume, sediment diversion volume and various parameters of the river channel or box culvert outlet in the hydrological data. Sediment carrying capacity calculated after reduction S i , and combined with the box culvert section size and water depth, the cross-section sedimentation volume Q can be obtained through conventional sedimentation calculation y and sediment thickness H y , and fully consider the volume of sediment deposited in a dredging cycle, and finally determine the length L of the sedimentation tank c , Width W c and depth H c ; S8 refers to the calculated length of the sedimentation tank L c , Width W c and depth H c , carry out box culvert construction, dig out a sedimentation pond under the section where silt accumulation is most likely to occur, set up a formwork and pour concrete, embed it into the box culvert, and cast it as a whole; S9: According to the length and burial depth of the box culvert, determine whether it is necessary to reserve holes at the top when pouring the box culvert. After covering and backfilling the box culvert, reserve a ladder passage at the top of the vertical shaft to facilitate personnel to go down for dredging and maintenance; S10: If it is necessary to add a sedimentation pond to an existing box culvert under special circumstances, it is necessary to evaluate the actual situation and dig a sedimentation pond in the existing box culvert.

2. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: The common shapes of water-passing sections in S1 are rectangle and circle, and the dimensions include the length, width, height and diameter of each section. Some of the cross-sectional dimensions remain unchanged or change along the way. The hydraulic radius needs to be calculated through the shape, size and wetted perimeter of the water-passing section.

3. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: The water diversion box culvert in S1 should be of a certain length and have a small diameter. If the box culvert is very short or has a large diameter, there is no need to set up a sedimentation tank. Because the box culvert is short or has a large diameter, even if silt accumulates, it will not cause any major problems, and personnel can also easily enter the box culvert directly from the culvert mouth to dredge and remove silt.

4. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: The selection of each section along the box culvert in S3 needs to consider the length of the section interval. In addition to selecting sections at certain intervals, it should also be based on whether the hydraulic conditions of the box culvert change. Additional calculation sections should be added at the box culvert mouth, where the bottom slope changes, where the section size changes gradually, and at branch roads and bends.

5. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: S5 determines whether silt is silting up in the box culvert by calculation. In addition to obtaining the relationship between the average flow velocity and the non-silting flow velocity through direct calculation, it also uses numerical simulation to improve calculation efficiency.

6. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: Hydraulic parameters to be reduced in S6 Including roughness, hydraulic radius, hydraulic gradient, average water depth and water surface width. The reduction rate of these parameters should be adjusted according to the actual situation of the project and the focus of attention. The project focuses on the siltation caused by the change of roughness, keeps other parameters unchanged, and only analyzes the location where siltation first occurs by reducing the roughness. For parameters The amount of reduction before each calculation is selected based on engineering experience and should be as small as possible to increase the incremental step of the calculation iteration and improve the calculation accuracy.

7. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: The structure of S8 sedimentation tank should be dug into a rectangular trough. If the calculated depth of the sedimentation tank is less than the thickness of the box culvert, there is no need to dig down, and a trough can be formed by pouring less concrete. In addition to making an open sedimentation tank, a metal cover with holes is added to the sedimentation tank to improve the flow capacity, which is conducive to locking the sediment in the sedimentation tank and facilitating cleaning. In addition, the bottom of the sedimentation tank is made into a small slope against the direction of the water flow, which is also conducive to the sedimentation of sediment in the sedimentation tank.

8. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: Holes are reserved on the top of the box culvert in S9. The steel bars of the box culvert should be arranged to avoid the holes. If the steel bars near the holes are replaced, they should meet the structural strength and construction requirements. Attention should be paid to the structural strength of the openings. If necessary, transverse and longitudinal beams and columns should be set near the openings.

9. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: In S9, it is determined whether it is necessary to reserve holes on the top of the box culvert when casting it based on the length and burial depth of the box culvert. The box culvert is short and does not require a separate vertical shaft, so silt can be directly removed from the culvert mouth into the siltation tank. The box culvert is buried deep and it is not suitable to reserve holes on the top of the box culvert because the construction and support costs are high and it is more dangerous for personnel to operate.

10. A method for constructing a sedimentation tank for desilting a water diversion box culvert based on hydraulic parameter reduction according to claim 1, characterized in that: In addition to determining the location of the sedimentation basin in advance through hydraulic calculations in the box culvert of S10, due to different problems caused by different geological conditions, changes in hydraulic conditions at the box culvert mouth, changes in rainfall conditions, and the influence of rotation, the calculated location of the sedimentation basin may be inconsistent with the actual silt deposition location. By adding a sedimentation basin at a later stage, excavation is carried out at the bottom of the built box culvert. However, the box culvert structure should be avoided as much as possible while ensuring its stability and safety.

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