A numerical simulation method and device for drainage and salt removal from concealed pipes under different inlet resistance conditions

Abstract

The present invention provides a method and apparatus for numerically simulating underground pipe drainage and salt removal under different inlet resistance conditions, comprising: step 1. collecting basic data of the study area; step 2. establishing a mathematical model of groundwater movement and solute transport based on the collected basic data; step 3. establishing a numerical model of groundwater movement and solute transport based on the established mathematical model, discretizing the model in time and space, defining the model boundaries, and inputting the initial groundwater level and salinity, geological parameters, and upper boundary sources and sinks; step 4. calibrating and verifying the model to obtain correction factors under different actual underground pipe inlet resistance conditions; step 5. setting multiple different underground pipe inlet resistance conditions and different underground pipe layout parameters to perform numerical simulations of drainage and salt removal; step 6. outputting drainage and salt removal amounts and determining the layout parameters of underground pipes with different inlet resistances based on design objectives. The present invention is capable of analyzing underground pipe drainage and salt removal under different inlet resistance conditions and guiding the layout design of actual underground pipe projects.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural drainage and salt removal simulation concealed pipe layout, and particularly relates to a method and device for numerical simulation of concealed pipe drainage and salt removal considering different inlet resistance conditions. Background Art

[0002] Soil salinization is a global agricultural problem and one of the main causes of arable land shortages and ecological degradation. Concealed pipes are an effective method for draining and removing salt from farmland. They avoid the large footprint and proneness of drainage ditches, offer advantages such as a long service life, and facilitate agricultural intensification and mechanization. However, to effectively drain and remove salt, a rational pipe layout must be established, primarily focusing on pipe depth, spacing, and diameter.

[0003] Currently, the methods commonly used to study concealed pipe layouts are mainly divided into field trials and numerical simulations. Field trials involve setting up different concealed pipe layouts in the field, measuring the drainage and salt discharge under different layouts, and conducting comparative analysis. However, this method is time-consuming and labor-intensive, inevitably subject to experimental errors, and the resulting recommended concealed pipe layouts are often only applicable under experimental conditions. Current numerical simulation models and software often have limited applicability and fail to account for the impact of varying concealed pipe inlet resistance on drainage and salt discharge.

[0004] In order to simulate and analyze the amount of concealed pipe drainage and salt removal under different concealed pipe inlet resistance conditions and determine the appropriate concealed pipe layout parameters to ensure the concealed pipe drainage and salt removal effect and drainage and salt removal needs, it is necessary to develop a numerical simulation method for concealed pipe drainage and salt removal that can consider the influence of different concealed pipe inlet resistances. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for numerical simulation of concealed pipe drainage and salt removal under different inlet resistance conditions, which can be used for numerical simulation of concealed pipe drainage and salt removal under the influence of different concealed pipe inlet resistances, so as to determine appropriate concealed pipe layout parameters to ensure the concealed pipe drainage and salt removal effect and drainage and salt removal requirements.

[0006] In order to achieve the above object, the present invention adopts the following scheme:

[0007] <Method>

[0008] A numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions, characterized by comprising the following steps:

[0009] Step 1. Collect basic data of the study area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing underground pipe layout parameters;

[0010] Step 2. Based on the collected basic data of the study area, a mathematical model of groundwater movement and solute transport in the study area is established, as shown in the following equations (1) and (2):

[0011]

[0012] Where i represents the x, y, and z axis directions; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ;S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s1, s2 are the simulation boundaries; is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1 ;

[0013]

[0014] Where θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i is the average seepage velocity along the i-axis, LT -1 ;q s is the aquifer flow per unit volume from external sources and sinks, representing sources (positive values) and sinks (negative values), T -1 ; C s is the concentration of solute dissolved in the source and sink terms, ML -3 ;∑R n is the chemical reaction term, ML -3 T -1 ;

[0015] Step 3. Based on the established mathematical model, a numerical model of groundwater movement and solute transport in the study area is established, time and space discretization is performed, model boundaries are defined, and initial groundwater level and salinity, geological parameters, and source and sink terms are input;

[0016] Step 4. Based on the measured underground pipe drainage and salt removal data, calibrate the aquifer parameters, simulate the underground pipe drainage and salt removal under different actual underground pipe inlet resistance conditions, and fit the measured values ​​to obtain the correction factor C under different actual underground pipe inlet resistance conditions. sdr value;

[0017] Step 5. Set different concealed pipe inlet resistance conditions and different concealed pipe layout parameters to perform numerical simulation of water and salt removal;

[0018] Step 6. Output the drainage and salt discharge amount, and determine the appropriate layout parameters of the concealed pipes with different inlet resistances based on the design objectives.

[0019] Furthermore, in step 6, the calculation formula for the concealed pipe drainage under different inlet resistance conditions is as follows:

[0020]

[0021]

[0022]

[0023]

[0024] Where Q d The drainage volume of each concealed pipe grid, L 3 T -1 ;q d is the drainage volume per unit area in the dark drainage control area, LT -1 ; m is the number of concealed pipes; f is the length of the concealed pipe, L; L is the distance between concealed pipes, L; K is the saturated hydraulic conductivity, LT -1 ;d e is the equivalent depth, L; h is the vertical distance from the groundwater level at the center of the line connecting the two concealed pipes to the elevation of the concealed pipe, L; C sdr The effective radius is r e,f The correction coefficient of the hydraulic conductivity correction factor of the concealed pipe with an effective radius of r can reflect the size of the concealed pipe inlet resistance. It takes a value between 0 and 1. The smaller the value, the greater the concealed pipe inlet resistance. It is dimensionless. d is the distance from the center of the concealed pipe to the impermeable layer, L; r is the radius of the concealed pipe, L.

[0025] Furthermore, in step 6, the correction coefficient C sdr The calculation formula is as follows:

[0026]

[0027]

[0028] ρ d =D / 2r e,f

[0029]

[0030]

[0031]

[0032] Where C dis the hydraulic conductivity correction factor for concealed pipe drainage, which is used to consider the effect of the surrounding material of the actual concealed pipe being significantly more permeable than the soil. It is dimensionless; D is the side length of the grid surrounding the concealed pipe where the saturated permeability coefficient needs to be adjusted, L; r e,f is the effective radius of the concealed pipe, L; ρ d It is the ratio of the mesh side length of the area around the concealed pipe where the saturated permeability coefficient needs to be adjusted to the effective diameter of the concealed pipe. It is dimensionless.

[0033] Furthermore, in step 6, the calculation formula for the salt discharge amount of the concealed pipe is as follows:

[0034] S d =C g Q d (10)

[0035] Where S d The salt discharge capacity of each blind pipe grid, MT -1 ; C g is the groundwater concentration of the concealed pipe grid, ML -3 .

[0036] <Device>

[0037] A numerical simulation device for drainage and salt removal from concealed pipes under different inlet resistance conditions, characterized by comprising:

[0038] The basic data acquisition department collects basic data of the research area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing underground pipe layout parameters;

[0039] The modeling department is connected to the basic data acquisition department in communication. Based on the basic data collected by the basic data acquisition department, the mathematical models of groundwater movement and solute transport in the study area are established as shown in formula (1) and formula (2) respectively. Then, based on the established mathematical models, the numerical models of groundwater movement and solute transport in the study area are established, time and space discretization is performed, the model boundary is defined, and the initial groundwater level and salinity, geological parameters and source and sink terms are input;

[0040]

[0041] Where i represents the x, y, and z axis directions; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ;S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s1, s2 are the simulation boundaries; is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1.

[0042]

[0043] Where θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i is the average seepage velocity along the i-axis, LT -1 ;q s is the aquifer flow per unit volume from external sources and sinks, representing sources (positive values) and sinks (negative values), T -1 ; C s is the concentration of solute dissolved in the source and sink terms, ML -3 ;∑R n is the chemical reaction term, ML -3 T -1 ;

[0044] The layout department is connected to the basic data acquisition department and the modeling department, and inputs the concealed pipe distribution and layout parameter data into the model, including the spatial location distribution of the concealed pipes and the buried depth, spacing, and radius of the concealed pipes;

[0045] The calibration and verification department is connected to the basic data acquisition department, modeling department and layout department. It calibrates and verifies the model based on the collected underground pipe drainage data. Based on the collected measured underground pipe drainage and salt discharge data, it simulates the underground pipe drainage and salt discharge under different actual underground pipe inlet resistance conditions and fits the measured values ​​to obtain the correction factor C under different actual underground pipe inlet resistance conditions. sdr ;

[0046] The simulation department is connected to the calibration and verification department and the layout department to simulate the drainage and salt discharge under different concealed pipe inlet resistance, concealed pipe burial depth, and spacing, and output the results;

[0047] The control unit is connected to the basic data acquisition unit, modeling unit, layout unit, calibration and verification unit, and simulation unit to control their operations.

[0048] Furthermore, it also includes:

[0049] The input and display unit is connected to the basic data acquisition unit, modeling unit, layout unit, calibration and verification unit, simulation unit and control unit for allowing users to input operation instructions and display corresponding information.

[0050] Furthermore, it also includes:

[0051] The image generation unit is in communication with the layout unit, the simulation unit, the input and display unit, and the control unit. It generates a corresponding concealed pipe layout diagram based on the concealed pipe drainage system arranged by the layout unit, and generates a corresponding water and salt discharge change chart based on the drainage and salt discharge simulated by the simulation unit.

[0052] The input display unit displays the image generated by the image generating unit.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The present invention relates to a method and device for numerically simulating the drainage and salt removal of underground pipes under different inlet resistance conditions. It can simulate the dynamic situation of drainage and salt removal of underground pipes only according to the buried depth, spacing, and radius of the underground pipes, and can determine the drainage and salt removal effect of the underground pipe system in the entire area. At the same time, it also makes up for the deficiency of existing numerical simulation models and software for drainage and salt removal of underground pipes that cannot consider the influence of different underground pipe inlet resistances on the drainage and salt removal amount of underground pipes, and provides a new way to simulate drainage and salt removal of underground pipes under different inlet resistance conditions, and provides a method for determining the layout design of underground pipe drainage systems under different inlet resistance conditions. Furthermore, based on the method and device for numerically simulating the drainage and salt removal of underground pipes under different inlet resistance conditions of the present invention, a regional underground pipe layout diagram that meets the corresponding drainage and salt removal targets can be generated, providing more intuitive technical support for the actual underground pipe construction layout. Construction according to the regional underground pipe layout diagram can effectively ensure the drainage and salt removal effect of the underground pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Flow chart of the numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions provided by the present invention;

[0056] Figure 2 The geographical location of the test area and the layout of the concealed pipes (a) and the evaporation data diagram (b) involved in the embodiments of the present invention;

[0057] Figure 3 Graph showing the comparison between the simulated and measured values ​​of the single-width drainage volume of concealed pipes in the test areas S(a), A1(b), A2(c), A3(d), and A4(e) in the embodiments of the present invention;

[0058] Figure 4 Schematic diagram of the layout of the trench pipes in the simulation area after expansion in an embodiment of the present invention;

[0059] Figure 5 The different C values ​​when the distance between hidden pipes in the simulation area is 10m in the embodiment of the present invention are shown in FIG. sdr The drainage volume (a) and drainage volume (b) of the concealed pipe under the buried depth, and the different C when the concealed pipe spacing is 100m sdr and the amount of drainage (c) and salt discharge (d) of the concealed pipes under the buried depth of the concealed pipes;

[0060] Figure 6 These are the 13 recommended schemes involved in the embodiments of the present invention and the spatial distribution of groundwater depth in the simulation area under the condition of no concealed drainage pipes. DETAILED DESCRIPTION

[0061] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0062] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0063] <Example>

[0064] like Figure 1 As shown, the numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions provided in this embodiment includes the following steps:

[0065] 1. Collect basic data of the study area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing underground pipe layout parameters;

[0066] The underground pipe drainage test was carried out in a certain field. The geographical location of the test area, the layout of underground pipes and the conditions of the outsourcing materials are as follows: Figure 2 As shown, the test area is 150m long and 82m wide. It is divided into five 82m×30m areas according to the different materials and thickness of the outer covering of the concealed pipe. The five areas only have different resistance conditions for the entrance of the concealed pipe, and other conditions are the same. Three corrugated pipes are arranged in each area, of which the concealed pipe in the middle is a monitoring concealed pipe, and the concealed pipes on both sides serve to avoid the influence of the concealed pipes in adjacent areas. The concealed pipe is 82m long, the buried depth is 1.4m, and the spacing is 10m. The test area is small, with a surface elevation of about 986.5m. The terrain is relatively flat, the strata are mainly Quaternary sediments, the rock type is mainly sandy loam, and the groundwater distribution is in the form of upper phreatic water-lower multi-layer confined water, and the phreatic layer is relatively thick. The leaching test started on October 25, 2018 and ended on November 14. The leaching quota was 570mm. There was no precipitation during the test. The evaporation was based on the daily evaporation data of Yanqi Station, as shown in the figure. Figure 2 shown.

[0067] 2. Based on the collected basic data of the study area, a mathematical model of groundwater movement and solute transport in the study area is established, as shown in the following equations (1) and (2):

[0068]

[0069] Where i represents the x, y, and z axis directions; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ;S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s1, s2 are the simulation boundaries; is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1 .

[0070]

[0071] Where θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i is the average seepage velocity along the i-axis, LT -1 ;q s is the aquifer flow per unit volume from external sources and sinks, representing sources (positive values) and sinks (negative values), T -1 ; C s is the solute dissolved concentration in the source and sink terms, ML -3 ;∑R n is the chemical reaction term, ML -3 T -1 ;

[0072] 3. Based on the established mathematical model, the control range of the underground pipe in the middle of the five districts was taken as the research object. The numerical models of groundwater movement and solute migration were established respectively. The time and space were discretized, the model boundaries were defined, and the initial groundwater level and mineralization, geological parameters and source and sink terms were input. The above conditions were set in the same way for each model.

[0073] Temporal and spatial discretization: The model was horizontally divided into 830 grid cells (83 rows × 10 columns) with a grid size of 1 m × 1 m. The vertical simulation depth was 20 m, divided into two numerical layers, representing shallow and deep diving, respectively. The thickness of the first layer was set to 5 m, and the thickness of the second layer was set to 15 m. The probabilistic period was from October 25, 2018, to November 14, 2018, with a stress period and time step of 1 day.

[0074] Define the model boundary: The boundary of the plot is relatively clear. The drainage ditch is on the east side, which is set as the drainage boundary. Since leaching also occurred outside other boundaries during the experiment, the lateral recharge of groundwater was not significant, so the other side boundaries were generalized as water-isolating boundaries.

[0075] Geological parameters: The geological parameters required for the water flow model include water supply and permeability. The first layer has a water supply of 0.03 and a permeability of 0.9 m / d, while the second layer has a water supply of 0.06 and a permeability of 4 m / d. The geological parameters required for the solute model include diffusivity and effective porosity. The longitudinal diffusivity for both the first and second layers is 0.01 m, the horizontal and vertical diffusivities are 0.1 and 0.01 times the longitudinal diffusivity, respectively, and the effective porosity is 0.3.

[0076] Initial groundwater depth and groundwater mineralization: both are given based on the collected data. The initial groundwater depth is 2m and the initial groundwater mineralization is 15g / L.

[0077] Source and sink treatment: Irrigation infiltration recharge is calculated by formula (3),

[0078] q irri =Q irri a i (3)

[0079] Among them, q irri They are respectively the irrigation infiltration recharge, L; Q irri is the irrigation amount, L; α i is the irrigation infiltration recharge coefficient.

[0080] Phreatic evaporation is calculated by equations (4) and (5):

[0081]

[0082] E0=ηE pan (5)

[0083] Where E is the diving evaporation rate, LT -1 ; E0 is the evaporation rate of water surface, LT -1 ;h s is the surface elevation, L; ξ is the phreatic evaporation coefficient, dimensionless; h e is the limit evaporation depth, L; η is the evaporation dish conversion coefficient, dimensionless; E pan is the measured evaporation rate of the evaporating dish, LT -1 .

[0084] 4. Calibrate the model aquifer parameters based on the collected measured underground pipe discharge data. Figure 3The simulation values ​​of the single-width drainage of the concealed pipes in the five districts are compared with the measured values. The RMSE of the single-width drainage of the concealed pipes in the five districts (S, A1, A2, A3, and A4) are 0.057m 2 、0.017m 2 , 0.005m 2 、0.024m 2 , 0.012m 2 , MRE are 7.39%, 3.82%, 1.87%, 5.75% and 2.80% respectively. The simulated values ​​of the single width drainage of the concealed pipe are very close to the measured values. e,f They are 40.0mm, 37.0mm, 42.3mm, and 41.5mm respectively, and the corresponding parameters are C sdr They are 0.0168, 0.0106, 0.0302, and 0.0236 respectively. The simulation results show that the correction coefficient C sdr It can accurately reflect the impact of different concealed pipe inlet resistance conditions on concealed pipe drainage. In addition, if the simulated value differs significantly from the measured value, the simulation accuracy can be improved by adjusting the hydrogeological parameters and the coefficients of the source and sink terms, mainly including the permeability coefficient, water supply degree, and irrigation infiltration recharge coefficient.

[0085] 5. Set different concealed pipe inlet resistance conditions and different concealed pipe layout parameters (including concealed pipe burial depth and spacing) to perform numerical simulation of drainage and salt removal.

[0086] Based on the calibrated model parameters, the simulation area is expanded to a simulation area of ​​200m×600m (e.g. Figure 4 The simulation simulates the drainage and salt discharge of underground pipes under different inlet resistances, underground pipe depths, and spacings. The initial conditions and source and sink settings remain unchanged, and all boundaries are set as water-blocking boundaries. The drainage ditch is located in the middle of the simulation area and is 600m long. Its parameter settings also remain unchanged. The simulation lasts 20 days. 11 underground pipe depths of 1.0 to 2.0m, 10 underground pipe spacings of 10 to 100m, and 14 C sdr The amount of drainage and salt discharged from underground pipes under 1540 combination scenarios were analyzed.

[0087] 6. Output the amount of drainage and salt discharge, and determine the appropriate layout parameters of concealed pipes with different inlet resistances based on the design objectives.

[0088] The calculation formula for the drainage volume of concealed pipes under different inlet resistance conditions is as follows:

[0089]

[0090]

[0091]

[0092]

[0093] Where Q d The drainage volume of each concealed pipe grid, L 3 T -1 ;q d is the drainage volume per unit area in the dark drainage control area, LT -1 ; m is the number of concealed pipes; f is the length of the concealed pipe, L; L is the distance between concealed pipes, L; K is the saturated hydraulic conductivity, LT -1 ;d e is the equivalent depth, L; h is the vertical distance from the groundwater level at the center of the line connecting the two concealed pipes to the elevation of the concealed pipe, L; C sdr The effective radius is r e,f The correction coefficient of the hydraulic conductivity correction factor of the concealed pipe with an effective radius of r can reflect the size of the concealed pipe inlet resistance. It takes a value between 0 and 1. The smaller the value, the greater the concealed pipe inlet resistance. It is dimensionless. d is the distance from the center of the concealed pipe to the impermeable layer, L; r is the radius of the concealed pipe, L.

[0094] Wherein, in step 6, the correction coefficient C sdr The calculation formula is as follows:

[0095]

[0096]

[0097] ρ d =D / 2r e,f

[0098]

[0099]

[0100]

[0101] Where C d is the hydraulic conductivity correction factor for concealed pipe drainage, which is used to consider the effect that the permeability of the wrapping material around the actual concealed pipe is significantly greater than the permeability of the soil. It is dimensionless; D is the side length of the grid containing the area around the concealed pipe where the saturated permeability coefficient needs to be adjusted, L; r e,f is the effective radius of the concealed pipe, L; ρ d is the ratio of the mesh side length of the area around the blind pipe where the saturated permeability coefficient needs to be adjusted to the effective diameter of the blind pipe. It is dimensionless. In step 6, the formula for calculating the salt discharge amount of the blind pipe is as follows:

[0102] S d =C g Q d (10)

[0103] Where S d The salt discharge capacity of each blind pipe grid, MT -1 ; C g is the groundwater concentration of the concealed pipe grid, ML -3 .

[0104] In this example, the design goal was to achieve the average drainage volume per unit area of ​​the concealed pipes in the test area (including five plots, S, A1, A2, A3, and A4). Appropriate concealed pipe burial depths and spacing schemes under different inlet resistance conditions were screened. Due to the large leaching quota and the presence of open ditch drainage, both the saturated and unsaturated zones were in a salt discharge state during the simulation under each scheme. Therefore, no design goal was set from the perspective of salt discharge level.

[0105] During the 20-day period, the average drainage volume per unit area of ​​the underground pipes in the test area was about 0.197 m3, so the designed drainage volume of the underground pipes should be at least 23640 m3. 3 Taking the case where the distance between concealed pipes is 10m and 100m respectively, different C sdr The amount of drainage and salt discharged from underground pipes at different buried depths is as follows Figure 5 When the distance between concealed pipes is 10m, different C sdr The drainage volume of underground pipes changes with the buried depth of underground pipes. Figure 5 As shown in (a), the drainage volume of the underground pipe increases with the increase of the buried depth of the underground pipe. When C sdr When C is equal to 0.01, all buried pipes cannot meet the design drainage requirements. sdr When C is equal to 0.03, the buried depth of the concealed pipe must be at least 1.8m to meet the design drainage requirements. sdr When C is equal to 0.05, the buried depth of the concealed pipe is more than 1.2m to meet the design drainage requirements. sdr When the value is not less than 0.07, the buried pipes with a depth of more than 1.0m can meet the design drainage requirements. When the distance between the buried pipes is 100m, different C sdr The drainage volume of underground pipes changes with the buried depth of underground pipes. Figure 5 As shown in (c), when C sdr When it is not greater than 0.70, the buried pipes at all depths cannot meet the design drainage requirements. sdr When C is equal to 0.90, the buried depth of the concealed pipe must be at least 1.8m to meet the design drainage requirements. sdr When it is equal to 1.00, the buried depth of the concealed pipe must be more than 1.6m to meet the design drainage requirements. Figure 5 (c) with Figure 5(a) By comparison, it can be found that the drainage volume of the concealed pipes when the distance between the concealed pipes is 100m is significantly reduced compared with that when the distance between the concealed pipes is 10m. In order to achieve the same design drainage requirements, a deeper buried depth of the concealed pipes is required. Under this condition, C sdr Smaller concealed pipes (i.e. concealed pipes with greater inlet resistance) cannot meet the design drainage requirements. Therefore, under this condition, the actual concealed pipe project should consider arranging concealed pipes more densely.

[0106] Based on the simulation and analysis results, different C sdr The recommended schemes with the best buried pipe depth and spacing under the value of 23.6×10 3 ~28.6×10 3 m 3 The salt discharge volume of underground pipes is between 309 and 368 tons, and the average groundwater depth in the area is between 1.03 and 1.29 meters. The spatial distribution of groundwater depth in the simulation area under each recommended scheme and without underground pipe drainage is as follows: Figure 6 As shown. Figure 6 As shown in (a), when there is no underground drainage, the groundwater depth in the simulation area is between 0.2 and 1.4 m, and the groundwater depth in most areas is less than 0.8 m. The spatial distribution of groundwater depth is mainly affected by the drainage ditch. The groundwater depth has a maximum value near the drainage ditch. The farther away from the drainage ditch, the shallower the groundwater depth. Figure 6 As shown in (b)-(n), when there is concealed drainage, the groundwater depth in the simulation area is between 0.5 and 1.5 m, which is significantly deeper than when there is no concealed drainage. In addition, it can be found that the groundwater depth is significantly deeper near the concealed drainage, indicating that the concealed drainage and lowering of the groundwater level are effective.

[0107] Table 1. Concealed drainage and salt discharge volume and regional average groundwater depth under 13 recommended schemes

[0108]

[0109] Furthermore, this embodiment also provides a numerical simulation device for concealed pipe drainage and salt removal under different inlet resistance conditions that can automatically implement the above method, including: a basic data acquisition unit, a modeling unit, a layout unit, a calibration and verification unit, a simulation unit, an image generation unit, an input and display unit, and a control unit.

[0110] The basic data acquisition department is used to obtain basic data of the study area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing concealed pipe layout parameters.

[0111] The modeling department is connected to the basic data acquisition department in communication. Based on the basic data collected by the basic data acquisition department, the mathematical models of groundwater movement and solute transport in the study area are established as shown in formula (1) and formula (2) respectively. Then, based on the established mathematical models, the numerical models of groundwater movement and solute transport in the study area are established, time and space discretization is performed, the model boundary is defined, and the initial groundwater level and salinity, geological parameters and source and sink terms are input;

[0112]

[0113] Where i represents the x, y, and z axis directions; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ;S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s1, s2 are the simulation boundaries; is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1 .

[0114]

[0115] Where θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i is the average seepage velocity along the i-axis, LT -1 ;q s is the aquifer flow per unit volume from external sources and sinks, representing sources (positive values) and sinks (negative values), T -1 ; C s is the solute dissolved concentration in the source and sink terms, ML -3 ;∑R n is the chemical reaction term, ML -3 T -1 ;

[0116] The layout department is connected to the basic data acquisition department and the modeling department, and inputs the concealed pipe distribution and layout parameter data into the model, including the spatial location distribution of the concealed pipes and the buried depth, spacing, and radius of the concealed pipes.

[0117] The calibration and verification department is connected to the basic data acquisition department, modeling department and layout department. It calibrates and verifies the model based on the collected underground pipe drainage data. Based on the collected measured underground pipe drainage and salt discharge data, it simulates the underground pipe drainage and salt discharge under different actual underground pipe inlet resistance conditions and fits the measured values ​​to obtain the correction factor C under different actual underground pipe inlet resistance conditions. sdr .

[0118] The simulation department is connected to the calibration and verification department and the layout department to simulate the drainage and salt discharge under different concealed pipe inlet resistance, concealed pipe burial depth, and spacing and output them.

[0119] The image generation unit is communicatively connected with the layout unit, simulation unit and control unit. It generates a corresponding concealed pipe layout diagram according to the concealed pipe drainage system arranged by the layout unit, and generates a corresponding water and salt discharge change chart according to the drainage and salt discharge simulated by the simulation unit.

[0120] The input display unit is communicatively connected with the basic data acquisition unit, the modeling unit, the layout unit, the calibration and verification unit, the simulation unit, the control unit and the image generation unit, and is used to allow the user to input operation instructions and display corresponding information. For example, the input display unit can display the basic data acquired by the basic data acquisition unit in a list form, display the groundwater flow, solute mathematical model and numerical model constructed by the modeling unit, and display the calibration and verification status of the calibration and verification unit, display all the concealed pipe drainage system plans laid out by the layout unit, and can also display the images generated by the image generation unit.

[0121] The control unit is connected to the basic data acquisition unit, modeling unit, layout unit, calibration and verification unit, simulation unit, image generation unit, and input and display unit to control their operations.

[0122] The above embodiments are merely illustrative of the technical solutions of the present invention. The method and apparatus for numerically simulating concealed pipe drainage and salt removal under varying inlet resistance conditions, as described herein, are not limited solely to those described in the above embodiments but are subject to the scope defined by the claims. Any modifications, supplements, or equivalent substitutions made by persons skilled in the art based on these embodiments are within the scope of protection claimed by the claims.

Claims

1. A numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions, characterized in that: The steps include: Step 1. Collect basic data of the study area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing underground pipe layout parameters; Step 2. Based on the collected basic data of the study area, a mathematical model of groundwater movement and solute transport in the study area is established, as shown in the following equations (1) and (2): （1） Where, i express x,y,z Axis direction; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ; S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s 1 , s 2 is the simulation boundary; φ is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1 ; （2） Where, θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i For the i Axial average seepage velocity, LT -1 ; q s is the aquifer flow per unit volume of the external source and sink terms, representing positive values ​​for sources and negative values ​​for sinks, T -1 ; C s is the solute dissolved concentration in the source and sink terms, ML -3 ;∑ R n is the chemical reaction term, ML - 3 T -1 ; Step 3. Based on the established mathematical model, a numerical model of groundwater movement and solute transport in the study area is established. Time and space discretization is performed, the model boundary is defined, and the initial groundwater level and salinity, geological parameters, and source and sink terms are input. Step 4. Based on the collected measured blind pipe drainage and salt removal data, simulate the blind pipe drainage and salt removal under different actual blind pipe inlet resistance conditions and fit the measured values ​​to obtain the correction factor under different actual blind pipe inlet resistance conditions. C sdr value; Step 5. Set different concealed pipe inlet resistance conditions and different concealed pipe layout parameters to perform numerical simulation of water and salt removal; Step 6. Output the drainage and salt discharge amount, and determine the appropriate layout parameters of the concealed pipes with different inlet resistances according to the design objectives; correction coefficient C sdr The calculation formula is as follows: （7） （8） （9） Where, C d is the hydraulic conductivity correction factor for concealed pipe drainage, which is used to take into account the effect that the permeability of the wrapping material around the actual concealed pipe is significantly greater than the permeability of the soil. It is dimensionless. D The mesh side length, L, needs to be adjusted to include the area around the blind pipe where the saturated permeability coefficient needs to be adjusted. r e,f is the effective radius of the concealed pipe, L; ρ d It is the ratio of the mesh side length of the area around the concealed pipe where the saturated permeability coefficient needs to be adjusted to the effective diameter of the concealed pipe. It is dimensionless.

2. The numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions according to claim 1 is characterized by: In step 6, the formula for calculating the drainage volume of the concealed pipe under different inlet resistance conditions is as follows: （3） （4） （5） （6） Where, Q d The drainage volume of each concealed pipe grid, L 3 T -1 ; q d is the drainage volume per unit area in the dark drainage control area, LT -1 ; m is the number of concealed pipes; f is the length of the concealed pipe, L; L is the concealed pipe spacing, L; K is the saturated hydraulic conductivity, LT -1 ; d e is the equivalent depth, L; h L is the vertical distance from the groundwater level at the center of the line connecting the two concealed pipes to the elevation of the concealed pipes; C sdr The effective radius is r e,f Compared with the effective radius of the hidden pipe r The correction coefficient of the hydraulic conductivity correction factor of the concealed pipe can reflect the size of the concealed pipe inlet resistance. The value is between 0 and 1. The smaller the value, the greater the concealed pipe inlet resistance. It is dimensionless. D d is the distance from the center of the concealed pipe to the impermeable layer, L; r is the radius of the hidden pipe, L.

3. The numerical simulation method for drainage and salt removal from concealed pipes under different inlet resistance conditions according to claim 1 is characterized by: in, In step 6, the formula for calculating the salt discharge amount of the concealed pipe is as follows: （10） Where, S d The salt discharge capacity of each blind pipe grid, MT -1 ; C g is the groundwater concentration of the concealed pipe grid, ML -3 .

4. A numerical simulation device for drainage and salt removal from concealed pipes under different inlet resistance conditions, characterized in that: include: The basic data acquisition department collects basic data of the research area, including spatial geographic data, meteorological data, hydrogeological data, water diversion and drainage data, and existing underground pipe layout parameters; The modeling department is connected to the basic data acquisition department in communication. Based on the basic data collected by the basic data acquisition department, the mathematical models of groundwater movement and solute transport in the study area are established as shown in Equations (1) and (2) respectively. Then, based on the established mathematical models, the numerical models of groundwater movement and solute transport in the study area are established, time and space discretization is performed, the model boundaries are defined, and the initial groundwater level and salinity, geological parameters and source and sink terms are input. （1） Where, i express x,y,z Axis direction; K ii is the saturated hydraulic conductivity tensor, LT -1 ; W is the external source and sink term, T -1 ; S s is the aquifer water storage rate, L -1 ; H is the water head, L; Ω is the simulation range, L; s 1 , s 2 is the simulation boundary; φ is the first type of boundary condition, L; ψ is the second type of boundary condition, L 2 T -1 ; （2） Where, θ is the porosity of the aquifer medium, L 3 L -3 ; C c is the solute concentration, ML -3 ; t is time, T; D ij is the hydrodynamic diffusion coefficient tensor; v i For the i Axial average seepage velocity, LT -1 ; q s is the aquifer flow per unit volume of the external source and sink terms, representing positive values ​​for sources and negative values ​​for sinks, T -1 ; C s is the solute dissolved concentration in the source and sink terms, ML -3 ;∑ R n is the chemical reaction term, ML - 3 T -1 ; The layout department is connected to the basic data acquisition department and the modeling department, and inputs the concealed pipe distribution and layout parameter data into the model, including the spatial location distribution of the concealed pipes and the buried depth, spacing, and radius of the concealed pipes; The calibration and verification department is connected to the basic data acquisition department, modeling department and layout department. It calibrates and verifies the model based on the collected underground pipe drainage data. Based on the collected measured underground pipe drainage and salt discharge data, it simulates the underground pipe drainage and salt discharge under different actual underground pipe inlet resistance conditions and fits the measured values ​​to obtain the correction factors under different actual underground pipe inlet resistance conditions. C sdr value; The simulation department is connected to the calibration and verification department and the layout department to simulate the drainage and salt discharge under different concealed pipe inlet resistance, concealed pipe burial depth, and spacing, and output the results; The control unit is connected to the basic data acquisition unit, modeling unit, layout unit, calibration and verification unit, and simulation unit to control their operations; The device for numerically simulating drainage and salt removal from concealed pipes under different inlet resistance conditions is used to execute the steps of the method for numerically simulating drainage and salt removal from concealed pipes under different inlet resistance conditions described in any one of claims 1-3.

5. The numerical simulation device for drainage and salt removal from concealed pipes under different inlet resistance conditions according to claim 4 is characterized in that: Also includes: The input and display unit is connected to the basic data acquisition unit, modeling unit, layout unit, calibration and verification unit, simulation unit and control unit for allowing users to input operation instructions and display corresponding information.

6. The numerical simulation device for drainage and salt removal from concealed pipes under different inlet resistance conditions according to claim 5 is characterized in that: Also includes: The image generation unit is in communication with the layout unit, the simulation unit, the input and display unit, and the control unit. It generates a corresponding concealed pipe layout diagram based on the concealed pipe drainage system arranged by the layout unit, and generates a corresponding water and salt discharge change chart based on the drainage and salt discharge simulated by the simulation unit. The input display unit displays the image generated by the image generating unit.

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