An improved sewer design method

Abstract

The application belongs to the technical field of municipal drainage pipeline design, and particularly relates to an improved drainage pipeline design method. First, sewage pipeline preliminary design is carried out according to a conventional design process, and relevant design parameters of each drainage pipe section in the design range are determined; second, water flow shearing capacity in the pipe network is analyzed; third, anti-scouring shearing force after accumulation of particulate matters in sewage is analyzed; fourth, scouring characteristic analysis is carried out, and whether the design parameters meet the particulate matter scouring condition is identified; finally, the original design parameters are optimized until the particulate matter non-silting condition is met. The application can consider the non-silting conditions of different types of particulate pollutants at different times in the process of drainage pipeline design, and fundamentally improves the present situation of a large number of drainage pipeline silting.

Description

Technical Field

[0001] This invention relates to the field of municipal drainage network design technology, specifically an improved drainage pipeline design method. Background Technology

[0002] The "Outdoor Drainage Design Standard" (GB50014-2021) stipulates that the minimum design flow velocity for sewage pipes under full design capacity should be 0.6 m / s, and for rainwater pipes and combined sewer pipes under full flow capacity, it should be 0.75 m / s. When the design flow velocity cannot meet the minimum design flow velocity, anti-sludge measures should be added. However, during the initial design phase, it was assumed that no particulate matter existed in the drainage pipes. With the gradual elimination of septic tanks in urban areas and the widespread use of household food waste disposers, a large amount of more easily settled food residue has entered the drainage pipes. A significant portion of these particles will inevitably settle within the pipes at some point during transport. Studies have found that when pipe sediment occupies the pipe network capacity, it simultaneously increases the roughness of the pipe walls. If the sediment thickness reaches 5% of the pipe diameter, the increase in bottom roughness coefficient alone (i.e., leading to a decrease in flow velocity) can cause a reduction in transport capacity of approximately 20%. Therefore, sediment accumulation can easily create a vicious cycle in pipe operation, and relying solely on the original minimum design flow velocity standard is no longer sufficient to prevent sedimentation within the pipes.

[0003] Therefore, we seek to develop a method for designing pipeline-related parameters and measures based on the non-sludge-free conditions of different types of particulate pollutants in pipelines. Summary of the Invention

[0004] The purpose of this invention is to provide an improved drainage pipe design method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An improved drainage pipe design method includes:

[0007] Step 1: Preliminary design based on standard design procedures:

[0008] Based on the existing drainage network design process, determine the relevant design parameters for each drainage pipe section within the design scope, specifically including the amount of sewage Q received by the m-th drainage pipe section over time t. sm (t), groundwater infiltration rate Q gm The magnitude of (t), and the length of each pipe segment l m Pipe diameter D m Slope i m Flow velocity v m and fill level (h / D) m ;

[0009] Step 2, water flow shear capacity analysis:

[0010] Based on the hydraulic parameters of the m-th drainage pipe segment, the variation τ of the average shear force of the water flow in the m-th drainage pipe segment with time t is calculated. bm (t);

[0011] Step 3: Analysis of erosion shear force after accumulation of particulate matter in wastewater:

[0012] Within the design scope, potential drainage users for the proposed drainage pipeline are selected, and wastewater samples are collected. Particulate matter in the wastewater samples collected at multiple times is accumulated, and the accumulated particulate matter is subjected to an erosion shear force τ. c The determination of (k), where k is the number of times the collected sewage is collected;

[0013] Step 4, scour characteristic analysis:

[0014] The τ bm The value of τ changes dynamically with time t throughout the day, and this dynamic change has s peaks and u troughs, that is, the day is divided into s+u stages. Within each stage, τ bm The value of τ changes dynamically with time t, representing the τ within each of the aforementioned stages. bm The (t) value and the erosion shear force τ of the particulate matter collected near the time point. c (k) Subtract, i.e., e = τ bm (t)-τ c (k) When the proportion of e≥0 in each drainage pipe segment of each stage exceeds the preset proportion, it is considered that the currently selected relevant design parameters can achieve the condition that the drainage pipe does not accumulate sediment.

[0015] Step 5, optimize design parameters:

[0016] If the proportion of e≥0 in each drainage pipe segment of each stage fails to exceed the preset proportion, the relevant design parameters in step one need to be reselected, and the verification is carried out again according to steps one to five until the requirement in step four is that the proportion of e≥0 in each drainage pipe segment of each stage exceeds the preset proportion.

[0017] In a preferred embodiment, step two, the analysis of the water flow shear capacity, specifically includes the following steps:

[0018] Based on the hydraulic parameters of the m-th drainage pipe segment, and according to formulas (1), (2), and (3), the variation value τ of the average shear force of the water flow in the m-th drainage pipe segment with time t is calculated. bm (t);

[0019] τ bm (t)=ρ·g·Rh ·J (1)

[0020]

[0021]

[0022] Where J is the energy gradient, v is the flow velocity, K is the pressure loss coefficient, I is the hydraulic gradient, n is the Manning roughness coefficient, ρ represents the density of water, and R... h Let represent the hydraulic radius, and t represent time t.

[0023] In a preferred embodiment, in step three, the sewage collection frequency can be evenly distributed according to time t0, where 6h≥t0≥1h, then the daily collection frequency is 24 / t0.

[0024] In a preferred embodiment, in step three, the particulate matter in the wastewater can be collected by static sedimentation and then the τ can be measured. c (k).

[0025] In a preferred embodiment, in step three, the τ c (k) can be measured by pipe-type hydraulic flushing devices, annular trough hydraulic devices, and jet shear force measuring equipment.

[0026] In a preferred embodiment, in steps four and five, the preset ratio is 30%.

[0027] In a preferred embodiment, the improved drainage pipe design method described above is applicable to sewage pipes, combined sewer pipes, or rainwater pipes.

[0028] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0029] The improved drainage pipeline design method described in this invention fully considers the shear resistance characteristics of particulate matter in sewage in different regions and at different times, as well as the changes in hydraulic conditions under the periodic drainage characteristics of the drainage pipeline. It also avoids the influence of the spatial and temporal specificities of the drainage pipeline on particulate matter erosion. In summary, this method has wide applicability, is comprehensive, and is relatively simple. Attached Figure Description

[0030] The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a flowchart of the entire invention;

[0032] Figure 2This is a schematic diagram of the drainage pipe in the embodiment.

[0033] Legend:

[0034] Figure 2 In Chinese: A, Design Scope; SW, Sewage Pipeline; F1, Manhole; S1-2, Pipe Section; F2, Manhole; S2-3, Pipe Section; F3, Manhole; S3-4, Pipe Section; F4, Manhole. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the terms "side", "upper", "lower", "top", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0037] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] Figure 1 This is a flowchart of the entire invention.

[0039] like Figure 1 As shown, an improved drainage pipe design method includes:

[0040] Step 1: Preliminary design based on standard design procedures:

[0041] Based on the existing drainage network design process, determine the relevant design parameters for each drainage pipe section within the design scope, specifically including the amount of sewage Q received by the m-th drainage pipe section over time t. sm (t), groundwater infiltration rate Q gm The magnitude of (t), and the length of each pipe segment l m Pipe diameter D mSlope i m Flow velocity v m and fill level (h / D) m .

[0042] Step 2: Analysis of water flow shear capacity:

[0043] Based on the hydraulic parameters of the m-th drainage pipe segment, and according to formulas (1), (2), and (3), the variation value τ of the average shear force of the water flow in the m-th drainage pipe segment with time t is calculated. bm (t).

[0044] τ bm (t)=ρ·g·R h ·J (1)

[0045]

[0046]

[0047] Where J is the energy gradient, v is the flow velocity, K is the pressure loss coefficient, I is the hydraulic gradient, n is the Manning roughness coefficient, ρ represents the density of water, and R... h Let represent the hydraulic radius, and t represent time t.

[0048] Step 3: Analysis of erosion shear force after accumulation of particulate matter in wastewater:

[0049] Within the design scope, potential drainage users for the planned drainage pipeline are selected, and wastewater samples are collected. The wastewater collection frequency can be uniformly distributed according to time t0, where 6h ≥ t0 ≥ 1h, then the daily collection frequency is 24 / t0. Particulate matter in the wastewater collected at each time point is accumulated, and the accumulated particulate matter is subjected to erosion shear force τ. c The determination of (k), where k is the number of times the collected sewage is collected.

[0050] The particulate matter in the wastewater can be collected by static sedimentation and then the τ value can be measured. c (k).

[0051] The τ c (k) can be measured by pipe-type hydraulic flushing devices, annular trough hydraulic devices, and jet shear force measuring equipment.

[0052] Step 4: Scour Characteristic Analysis:

[0053] The τ bm The value of τ changes dynamically with time t throughout the day, and this dynamic change has s peaks and u troughs, that is, the day is divided into s+u stages. Within each stage, τ bm The value of τ changes dynamically with time t. The τ value within each of the aforementioned stages...bm The (t) value and the erosion shear force τ of the particulate matter collected near the time point. c (k) Subtract, i.e., e = τ bm (t)-τ c (k). When the proportion of e≥0 in each drainage pipe segment of each stage exceeds 30%, it can be considered that the currently selected relevant design parameters can achieve the condition that the drainage pipe does not accumulate sediment.

[0054] Step 5: Optimize design parameters:

[0055] If the proportion of e≥0 in each drainage pipe segment of each stage fails to exceed 30%, the relevant design parameters in step one need to be reselected, and the verification is carried out again according to steps one to five until the requirement in step four that the proportion of e≥0 in each drainage pipe segment of each stage exceeds 30% is met.

[0056] Example:

[0057] Figure 2 This is a schematic diagram of the drainage pipe in the embodiment.

[0058] like Figure 2 As shown, this invention is an improved drainage pipe design method based on the analysis of particulate matter scour performance. The specific implementation steps are as follows:

[0059] The following calculation steps are all based on sewage pipes.

[0060] (1) Determine the layout of the sewage pipeline (this example only considers the design of the main pipeline): such as Figure 2 As shown, within the design scope A, a sewage pipeline SW is arranged, which includes pipe segments S1-2, S2-3, S3-4, manholes F1, F2, F3, and F4.

[0061] (2) Preliminary data confirmation of the design flow of the sewage pipeline SW: The sewage volume received by each pipe section within the design range A is shown in Table 1.

[0062] (3) Hydraulic calculation of the sewage pipeline SW: Determine the length and ground slope of the pipe section S1-2, pipe section S2-3, and pipe section S3-4; determine the inner bottom elevation of the inspection wells F1, F2, F3, and F4; according to the provisions of the "Outdoor Drainage Design Standard" (GB50014-2021) and the current data, the parameters of each pipe section of the sewage pipeline SW are initially set as detailed in Table 1.

[0063] Table 1, Preliminary Hydraulic Calculation Table

[0064]

[0065] (4) Flushing characteristic analysis, taking the pipe section S2-3 as an example, the pipe section S2-3 receives a concentrated upstream flow of 25 L / s, and the peak value of the sewage Q1' generated in the receiving area of ​​the pipe section S2-3 is 13.09 L / s. During the entire dry day, Q1' has three trough periods and two peak periods. The Q1' of the three trough periods is less than 3 L / s, so the flow rate Q of the three trough periods is not higher than 28 L / s. Based on the design flow rate Q = 28 L / s and the filling degree h / D = 0.5, and based on equation (1), it can be seen that τ bm (t) This stage is 0.89 N / m 2 .

[0066] Within the design scope A, potential wastewater dischargers for the proposed wastewater pipeline were selected, and wastewater samples were collected every 3 hours, with 30L collected each time, for a total of 8 collections per day, totaling 240L. Particulate matter in the wastewater collected at each time point was accumulated, and the accumulated particulate matter was subjected to erosion shear force τ. c (k) was determined. The determination was performed using a pipe-and-channel hydraulic flushing device. The τ values ​​of the four samples corresponding to the three trough periods were... c (k) is 0.94 N / m 2 0.92 N / m 2 0.82 N / m 2 0.90 N / m 2 At this point, it is clear that at least two of the three trough periods cannot satisfy e≥0, with the proportion exceeding 30% (which is 0 in both cases).

[0067] (5) Optimize design parameters:

[0068] At this point, the diameter of pipe section S2-3 can be reduced or other design parameters can be changed to improve the performance of pipes during the trough period. bm (t), until the proportion of e≥0 in each drainage pipe segment of each stage exceeds the requirement of 30%.

[0069] It should be noted that the steps of the above-mentioned improved drainage pipe design method are not only applicable to sewage pipes, but also to combined sewer and stormwater pipes, which can be designed with reference to this method and will not be repeated here.

[0070] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. An improved drainage pipe design method, characterized in that, include: Step 1: Preliminary design based on standard design procedures: Based on the existing drainage network design process, determine the relevant design parameters for each drainage pipe section within the design scope, specifically including the first... m Section of drainage pipe over time t Wastewater volume received Q sm (t) Groundwater infiltration Q gm (t) Size, length of each pipe section l m Pipe diameter D m ,slope i m Flow rate v m and fullness ( h / D) m ; Step 2, water flow shear capacity analysis: According to the above-mentioned first m The hydraulic parameters of the drainage pipe section were calculated to obtain the first section. m The average shear force of water flow in a section of drainage pipe over time t Change value τ bm (t) ; Step 3: Analysis of erosion shear force after accumulation of particulate matter in wastewater: Within the design scope, potential drainage users for the proposed drainage pipeline are selected, and wastewater samples are collected. Particulate matter in the wastewater samples collected at multiple times is accumulated, and the accumulated particulate matter is subjected to erosion shear stress testing. τ c (k) The determination, among which k This refers to the th time that the collected sewage was collected; Step 4, scour characteristic analysis: The τ bm (t) Value per day over time t And dynamic change, the dynamic change has s Each peak and u Each trough, dividing a single day into... s + u Each stage, within each of the aforementioned stages τ bm (t) Value over time t The dynamic changes will affect each of the aforementioned stages. τ bm (t) The value and the erosion shear force of the particles collected at near the time point τ c (k) Subtract them, i.e., e = τ bm (t)- τ c (k) When the proportion of e≥0 in each drainage pipe segment of each stage exceeds the preset proportion, it is considered that the currently selected relevant design parameters achieve the condition that the drainage pipe does not accumulate sediment. Step 5, optimize design parameters: If the proportion of e≥0 in each drainage pipe segment of each stage fails to exceed the preset proportion, the relevant design parameters in step one need to be reselected, and the verification is carried out again according to steps one to five until the requirement in step four is that the proportion of e≥0 in each drainage pipe segment of each stage exceeds the preset proportion.

2. The improved drainage pipe design method according to claim 1, characterized in that, Step two, the analysis of the water flow shear capacity, specifically includes the following steps: According to the above-mentioned first m The hydraulic parameters of the drainage pipe section are calculated according to formulas (1), (2), and (3) to obtain the first section. m The average shear force of water flow in a section of drainage pipe over time t Change value τ bm (t) ; (1) (2) (3) in, J It's the energy gradient. v It's the flow rate. K It is the pressure loss coefficient. I It is the hydraulic gradient. n It is the Manning roughness coefficient. ρ This indicates the density of water. R h Indicates the hydraulic radius. t express t time.

3. The improved drainage pipe design method according to claim 1, characterized in that, In step three, the frequency of wastewater collection can be based on time. t 0 Uniform distribution, 6h ≥ t 0 If the time is ≥ 1 hour, then the daily data collection frequency is 24. / t 0 .

4. The improved drainage pipe design method according to claim 1, characterized in that, In step three, the particulate matter in the wastewater is collected and measured after static sedimentation. τ c (k) .

5. An improved drainage pipe design method according to claim 1, characterized in that, In step three, the aforementioned τ c (k) The measurements were taken using a pipe-type hydraulic flushing device, an annular trough hydraulic device, and a jet-type shear force measuring device.

6. The improved drainage pipe design method according to claim 1, characterized in that, In steps four and five, the preset ratio is 30%.

7. An improved drainage pipe design method according to claim 1, characterized in that, The improved drainage pipe design method described above is applicable to sewage pipes, combined sewer pipes, or rainwater pipes.

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