Optimization method and system for layout parameters and leaching quota of subsurface pipes in the field of arid areas

Abstract

The present invention provides a method and a system for optimizing the layout parameters of subsurface pipes and leaching quota in arid areas. The method provided includes: Step 1. Collect basic data of the construction area, natural condition data, the space of variables to be solved, and the target desalination rate; Step 2. Based on the basic data collected in Step 1, construct a semi-theoretical and semi-empirical formula for calculating the cumulative drainage volume and cumulative salt drainage volume of subsurface pipes under fully drained conditions; Step 3. Determine the correction coefficient γ considering the non-fully drained subsurface pipes based on the soil texture parameters partially input in Step 1, and obtain the corrected calculation formula for the drainage and salt drainage volume of subsurface pipes considering non-fully drained conditions; Step 4. Discretize and optimize the space of variables to be solved, discretize the leaching quota I, the subsurface pipe burial depth Z<subgt;D< / subgt;, and the subsurface pipe spacing L to be solved in the solution range, and use the formula in Step 3 to solve the reasonable leaching quota and subsurface pipe layout parameters. The present invention aims to optimize the layout parameters of subsurface pipes and the supporting leaching quota for different field conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural drainage and desalination simulation subsurface pipe layout, and particularly relates to an optimization method and system for subsurface pipe layout parameters and leaching quota in the fields of salinized areas. Background Art

[0002] Soil salinization is an important factor affecting agricultural development in arid regions. In order to improve salinized soil, subsurface pipes are widely used in arid regions. The main function of subsurface pipes in arid regions is to cooperate with leaching to remove salts in the soil during the non-growing period, so as to achieve the effect of accelerating soil desalination. To improve the salt drainage efficiency of subsurface pipes and save water resources, the optimization of subsurface pipe layout parameters such as pipe burial depth and spacing, and leaching quota is the key technology and main task in the design of subsurface pipe drainage and desalination systems.

[0003] At present, there are two methods for determining subsurface pipe layout and leaching quota: field experiments and computer simulations. Field experiments are to set different subsurface pipe layouts and leaching quotas in the field, and determine the subsurface pipe layout method by measuring specific indicators such as drainage and salt discharge volume, crop yield and quality, etc. However, this method is only applicable to specific situations, such as fixed crops and specific soil conditions, and the test period is long, the cost is high, and the indicator measurement is complex. And computer simulation programs require more input parameters, are complex to use and operate, and are not friendly and convenient for front-line engineering personnel.

[0004] In order to determine appropriate subsurface pipe layout parameters (spacing and burial depth), as well as the supporting leaching quota, and promote the popularization of subsurface pipes under the conditions of water saving and salt inhibition in arid agricultural areas, it is necessary to develop a more convenient and accurate optimization method for subsurface pipe layout and leaching quota. Summary of the Invention

[0005] The purpose of the present invention is to provide a semi-theoretical and semi-empirical formula for determining the drainage and salt discharge volume of subsurface pipes in the field in view of the deficiencies of existing methods, so as to optimize the subsurface pipe layout parameters (burial depth, spacing) and supporting leaching quota for different field conditions.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] An optimization method for subsurface pipe layout and leaching quota in arid areas fields includes the following steps:

[0008] Step 1. Collect basic data of the construction area, natural condition data, the space of variables to be solved, and the target salt drainage rate;

[0009] Step 2. Based on the basic data collected in Step 1, construct a semi-theoretical and semi-empirical formula for calculating the cumulative drainage volume and cumulative salt discharge volume of subsurface pipes under fully drained conditions:

[0010] Step 3. Based on the soil texture parameters input in part of Step 1, determine the correction coefficient γ considering the insufficient drainage of the buried pipes, and obtain the calculation formula for the drainage and salt removal amount of the buried pipes after correction considering insufficient drainage as follows:

[0011]

[0012]

[0013] Where: γ is the correction coefficient considering the insufficient drainage of the buried pipes, [-], which is mainly related to the soil texture and the spacing of the buried pipes, and the value range is generally 0 to 1;

[0014] Step 4. Discretize and optimize the space of the variables to be solved. Discretize the leaching quota I, the buried depth Z D and the spacing L of the buried pipes in the solution range to obtain an array of options, which are represented by I[i], Z D [j], L[k] respectively. The buried depth of the buried pipes is arranged from large to small, and the rest are arranged from small to large; use the formula in Step 3 to solve the reasonable leaching quota and the layout parameters of the buried pipes. The optimization logic is: preferentially select the solution with a smaller leaching quota. Under the same leaching quota, for the two qualified solutions of large buried depth and large spacing and small buried depth and small spacing, preferentially select the latter.

[0015] Preferably, the natural condition data in Step S1 includes soil texture parameters, soil moisture content, salt content, groundwater depth, and salinity; the space of the variables to be solved includes the ranges and discretization steps of the spacing, buried depth, and leaching quota of the buried pipes.

[0016] Preferably, the semi-theoretical and semi-empirical formulas for calculating the cumulative drainage volume and the cumulative salt removal amount of the buried pipes under the condition of sufficient drainage are as follows:

[0017]

[0018]

[0019] In the formula, θ r and θ s are the residual soil moisture content and the saturated soil moisture content respectively, [-]; α is a parameter related to the average size of the soil pores, [L -1 ; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n; W0 and W1 are the profile water storage at the start and end of the buried pipe drainage respectively, [L 2 ; I is the leaching water volume, [L 2 ; Z D and Z GW are the z coordinate values of the center of the cross-section of the buried pipe and the position of the initial groundwater level respectively, [L]; CGW is the solute concentration of groundwater, [ML -2 .

[0020] Preferably, the salt drainage volume of the subsurface pipe drainage is calculated based on the following assumptions:

[0021] (1) The subsurface pipe can drain water sufficiently. That is, after the subsurface pipe drainage ends, the soil water potential h and the soil height z satisfy That is and the groundwater level is consistent with the depth where the subsurface pipe is located, that is, the soil water potential at the depth where the subsurface pipe is located is 0;

[0022] (2) Assume that after the subsurface pipe drainage ends, the profile water content θ also varies linearly with depth, and the soil surface depth is calculated through the water head;

[0023] (3) Assume that the water volume in the aquifer is much larger than the water volume in the soil profile, that is, the leaching water entering the groundwater from the unsaturated zone will not significantly change the groundwater concentration. Therefore, it can be considered that the drainage concentration of the subsurface pipe is consistent with the initial groundwater concentration.

[0024] Preferably, in step 3, the correction coefficient γ takes into account the insufficient drainage and salt removal caused by too large subsurface pipe spacing and poor soil hydraulic conductivity. It is obtained by using the variable-saturated soil water and solute model to simulate the salt drainage volume of the subsurface pipe, namely Q w and Q s under different soil textures, different subsurface pipe spacings and depths, leaching quotas and initial groundwater levels, and the ratio of the cumulative drainage volume and cumulative salt removal volume calculated by the constructed semi-theoretical and semi-empirical formula. A corresponding table of the correction coefficient γ and the subsurface pipe spacing is constructed.

[0025] Preferably, step 4 is specifically as follows:

[0026] Construct the following optimized objective function and control conditions:

[0027]

[0028] where Q sT is the target salt removal rate, R represents the subsurface pipe operation risk function. Compared with the subsurface pipe layout with large depth and large spacing, the small depth and small spacing correspond to less risk because the latter means more subsurface pipes per unit area, which is beneficial to reducing the operation risk caused by subsurface pipe blockage during the long-term operation of the subsurface pipe; in addition, the solution with a smaller leaching quota is preferably selected in the formula.

[0029] Preferably, the steps to solve the leaching quota I, the subsurface pipe depth Z D and the subsurface pipe spacing L are as follows:

[0030] Step1. The leaching quota I and the subsurface pipe depth Z to be solvedD The space between the blind pipes and the spacing L are discretized in the solution range to obtain an array of options, which are represented by I[i], Z D [j], and L[k] respectively. The depth of the blind pipes is arranged from large to small, and the rest are arranged from small to large;

[0031] Step2. Calculate the maximum depth of the blind pipe Z and the cumulative salt drainage volume using the semi-theoretical and semi-empirical formula, and the salt drainage volume corresponding to the minimum leaching quota I[0] under the maximum depth of the blind pipe Z D [0]; gradually increase the leaching quota until the calculated salt drainage volume is greater than the target salt drainage volume Q . Then, take the minimum leaching quota at this time as the recommended optimal leaching quota I sT ; op

[0032] Step3. Calculate the optimal leaching quota I and the maximum depth of the blind pipe Z using the semi-theoretical and semi-empirical formula, and the salt drainage volume corresponding to the optimal leaching quota I op and the maximum depth of the blind pipe Z D [0]; gradually decrease the depth of the blind pipe until the calculated salt drainage volume is less than the target salt drainage volume Q . Then, take the minimum depth of the blind pipe in the previous step as the recommended optimal depth of the blind pipe Z sT ; Dop

[0033] Step4. Calculate the optimal leaching quota I , the optimal depth of the blind pipe Z , and the corrected salt drainage volume Q op under the minimum spacing L[0] of the blind pipe, using the semi-theoretical and semi-empirical formula. Gradually increase the spacing of the blind pipes until the calculated corrected salt drainage volume Q Dop is less than the target salt drainage volume Q s . Then, take the maximum spacing of the blind pipes in the previous step as the recommended optimal spacing L s of the blind pipe; sT op ;

[0034] Step5. The above I op , Z Dop and L op are the recommended optimal blind pipe layout and the supporting leaching quota.

[0035] The present invention also provides an optimization system for the blind pipe layout and leaching quota in the field of arid areas, including:

[0036] ​​​The data input section is for the user to input the basic data of the area to be constructed, including soil texture parameters, initial soil moisture content and salt content, groundwater depth and salinity, the optimization range and discretization step length of the variable to be solved, and the target salt drainage rate;

[0037] The correction coefficient storage and call section stores the correction coefficient γ values corresponding to different buried pipe spacings for different soil textures and is communicatively connected to the basic data input section. Based on the soil texture parameters input by the basic data input section, it calls the correction coefficient γ;

[0038] The modeling section is communicatively connected to the basic data input section and the correction coefficient storage and call section. Based on the soil texture parameters of the basic data input section and the correction coefficient γ of the correction coefficient storage and call section, it establishes the following corrected calculation formula for the salt drainage volume of the buried pipe drainage in the area to be constructed;

[0039]

[0040] Q s =γQ s C GW

[0041] In the formula, θ r and θ s are the residual soil moisture content and the saturated soil moisture content respectively, [-]; α is a parameter related to the average size of soil pores, [L -1 ; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n; W0 and W1 are the profile water storages at the start and end of the buried pipe drainage respectively, [L 2 ; I is the leaching water volume, [L 2 ; Z D and Z GW are the z - coordinate values of the center of the buried pipe cross - section and the position of the initial groundwater table respectively, [L]; C GW is the groundwater solute concentration, [ML -2 ;

[0042] The optimization section is communicatively connected to the data input section and the modeling section. Based on the optimization range and discretization step length of the variable to be solved input by the input section, it obtains the alternative arrays I[i], Z D [j], L[k], and calculates the optimal buried pipe layout and leaching quota combination that meet the target salt drainage volume within the alternative array space based on the buried pipe salt drainage volume calculation formula provided by the modeling section.

[0043] Preferably, it further includes:

[0044] The correction parameter generation unit is communicatively connected to the basic data input unit and the correction coefficient storage and call unit. For users with a strong professional background, this unit can be selected. According to the soil parameter information of the basic data input unit, it calls the variable-saturated soil water and solute model to simulate the drainage and salt removal amounts of the subsurface drainage pipes under different pipe spacings, burial depths, leaching quotas, and initial groundwater levels, and customizes the correction coefficient values for the given soil parameters. At the same time, the soil information and the corresponding soil parameter correction values will be transmitted to the correction coefficient storage and call unit for storage and can be called by all users.

[0045] Preferably, it further includes:

[0046] The image generation unit is communicatively connected to the optimization unit. According to the subsurface drainage pipe layout parameters and leaching quota provided by the optimization unit, it generates a schematic diagram showing the final soil water storage, salt storage, subsurface drainage pipe drainage volume, and salt removal volume.

[0047] Preferably, it further includes:

[0048] The economic analysis unit is communicatively connected to the optimization unit. According to the subsurface drainage pipe layout parameters and leaching quota provided by the optimization unit, it analyzes and calculates the construction cost of the subsurface drainage pipes and the annual supporting leaching cost.

[0049] Compared with the prior art, the present application has the following beneficial effects:

[0050] The optimization system for the subsurface drainage pipe layout and leaching quota in the arid area involved in the present invention can calculate the cumulative drainage and salt removal amounts of the subsurface drainage pipes only according to natural conditions such as soil texture parameters, initial soil moisture content and salt content, groundwater depth and salinity. Combining the optimization range and discrete step length of the variables to be solved provided by the user and the target salt removal rate, the optimal combination of subsurface drainage pipe layout and leaching quota that meets the target salt removal rate can be obtained. The principle of this method is simple, the required input variables are few, and it is convenient to operate and use, making up for the disadvantages of poor universality, long test period, and high cost of field tests. At the same time, compared with computer simulation programs, it is more user-friendly and convenient for front-line engineering personnel. Further, the optimization system for the subsurface drainage pipe layout and leaching quota in the arid area based on the present invention can also analyze and calculate the construction cost of the subsurface drainage pipes and the annual supporting leaching cost, which is beneficial to promoting the popularization of subsurface drainage pipes under the conditions of water saving and salt inhibition in arid agricultural areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0052] Figure 1Explanation diagram for the assumptions used in constructing the semi-theoretical and semi-empirical formula under fully drained conditions for the present invention;

[0053] Figure 2 Logic diagram for the optimization unit of the present invention to solve the optimal combination of subsurface pipe layout and leaching quota;

[0054] Figure 3 Schematic diagram of non-matching grids used in the unsaturated soil water solute model called by the correction coefficient generation unit of the present invention;

[0055] Figure 4 Schematic diagram of the system flow and communication connections of each part for the optimization of subsurface pipe layout and leaching quota in the field in arid areas provided by the present invention. Detailed implementation mode

[0056] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0058] The present invention will be described in detail below with reference to the accompanying drawings. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0059] Embodiment:

[0060] The optimization method for subsurface pipe layout and leaching quota in the field in arid areas provided in this embodiment includes the following steps:

[0061] 1. Input the basic data of the research area, including soil texture, initial soil moisture content and salt content, groundwater depth and salinity, the space of variables to be solved (the range and step length of subsurface pipe spacing, burial depth, and leaching quota), and the target salt drainage rate;

[0062] Among them, the soil texture parameters include the main parameters in the van Genuchten model. The van Genuchten model is as follows:

[0063]

[0064] In the formula, θ r and θ sare the residual soil moisture content and the saturated soil moisture content, [-]; α is a parameter related to the average size of soil pores, [L -1 ; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n.

[0065] The salt drainage rate R D is defined as follows:

[0066]

[0067] In the formula, S0 is the total initial salt mass in the soil profile within a certain depth, [M], which is calculated from the initial salt content.

[0068] The parameter values in the van Genuthen model for a certain sandy loam soil are shown in Table 1:

[0069] Table 1 Various soil parameter tables for virtual scenarios

[0070]

[0071] 2. For this sandy loam soil, establish a semi-theoretical and semi-empirical formula for calculating the salt drainage volume of subsurface pipe drainage under fully drained conditions:

[0072] According to the water balance, the salt drainage volume of subsurface pipe drainage can be calculated using the following formula:

[0073]

[0074]

[0075] Where: W0 and W1 are the profile water storages at the start and end of subsurface pipe drainage, respectively, [L 2 ; I is the leaching water volume, [L 2 ; and are the subsurface pipe drainage volume and the subsurface pipe salt drainage volume under fully drained conditions, respectively, with the dimensions [L 2 and [ML -1 ; C D is the subsurface pipe drainage concentration, [ML -2 .

[0076] To calculate the subsurface pipe salt drainage volume using formula (3), we make the following assumptions and simplifications:

[0077] (1) The subsurface pipe can drain water fully, that is, after the subsurface pipe drainage ends, the soil water potential h and the soil height z satisfy That is and the groundwater level is the same as the depth of the subsurface pipe, that is, the soil water potential at the depth of the subsurface pipe is 0, as shown in Figure 1 (b);

[0078] (2) We assume that after the subsurface drainage is completed, the profile water content θ also varies linearly with depth, and the soil surface depth is calculated through the water head, as shown in Figure 1 (a). Such an assumption will overestimate the total water volume in the soil profile after subsurface drainage, but it is convenient for calculating the total water volume in the soil profile after subsurface drainage;

[0079] (3) Assume that the water volume in the aquifer is much larger than the water volume in the soil profile, that is, the leaching water entering the groundwater in the unsaturated zone will not significantly change the groundwater concentration. Therefore, it can be considered that the drainage concentration is consistent with the initial groundwater concentration.

[0080] Based on assumption (1), after the subsurface drainage is completed, the soil water potential at the depth of the subsurface drain and the soil surface are 0 and -Z respectively D , and combined with Equation (2), the volumetric water content at the depth of the subsurface drain and the volumetric water content θ0 at the soil surface are respectively:

[0081]

[0082]

[0083] where: Z D is the value of the z - coordinate of the center of the cross - section of the subsurface drain, [L]; the other parameters are the parameters in the van Genuthen model.

[0084] Since the initial groundwater level is Z GW below which the soil water content is saturated before and after subsurface drainage. Therefore, for W0 and W1 in Equation (1), only the soil water storage above Z GW needs to be concerned. In actual situations, W0 is generally a known quantity, and according to assumption (2), W1 can be calculated as follows

[0085]

[0086] Substituting Equation (5) into (3a) gives And based on assumption (3), we can get That is

[0087]

[0088]

[0089] where, θ r and θ s are the residual water content and saturated water content of the soil respectively, [-]; α is a parameter related to the average size of soil pores, [L -1; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n; W0 and W1 are the profile water storages at the start and end of the subsurface drainage, respectively, [L 2 ; I is the leaching water volume, [L 2 ; Z D and Z GW are the z - coordinate values of the center of the cross - section of the subsurface drain and the position of the initial groundwater table, respectively, [L]; C GW is the groundwater solute concentration, [ML -2 .

[0090] So far, an empirical formula for the salt drainage volume of subsurface drainage under fully drained conditions has been constructed. In this formula, the subsurface drainage volume is related to the initial groundwater depth, leaching water volume, subsurface drain depth, and soil texture. In addition to the above factors, the subsurface salt drainage volume is also related to the groundwater solute concentration.

[0091] 3. In actual situations, within a specified time, the subsurface drain often cannot drain fully, especially in cases where the soil hydraulic conductivity is poor or the subsurface drain spacing is large. Based on the soil texture parameters input in part 1, a correction coefficient γ considering the non - full drainage of the subsurface drain is determined, and the corrected calculation formula for the subsurface drainage and salt drainage volume considering non - full drainage is as follows:

[0092]

[0093]

[0094] Among them: γ is the correction coefficient considering the non - full drainage of the subsurface drain, [-], which is mainly related to the soil texture and the subsurface drain spacing, and its value range is generally 0 - 1;

[0095] Combined with the basic data, the variable - saturated soil water and solute model VCFVM is called to simulate the subsurface drainage volume under different subsurface drain spacings and depths, leaching quotas, and initial groundwater levels, and the correction coefficient value γ for the given soil parameters is customized.

[0096] In actual engineering applications, γ is obtained by querying the γ table provided in this method according to the soil texture of the construction area. The γ table provided in this method is obtained by pre - simulating the subsurface drainage and salt drainage volumes (Q w and Q s ) under different soil textures, different subsurface drain spacings and depths, leaching quotas, and initial groundwater levels using the variable - saturated soil water and solute model, and then back - calculating the γ value in combination with formulas (3) and (7), and finally obtaining the relationship table between γ and the subsurface drain spacing under a given soil texture.

[0097] In step 2 of the optimization method for the layout of subsurface pipes and leaching quota in the arid area provided by the present invention, the variable-saturated soil water and solute model adopted is a node-based finite volume method model (VCFVM). This model is suitable for non-matching locally refined grids, as shown in Figure 3 . This model is conducive to saving computational costs and quickly generating correction coefficients for unsaturated drainage under different pipe spacings, burial depths, leaching quotas, and initial groundwater levels.

[0098] In this embodiment, to fully consider the γ values in various scenarios, 5 pipe spacing levels (10, 20, 30, 40, 50 m), 2 pipe burial depth levels (1.4, 1.8 m), 6 leaching quota levels (20, 25, 30, 35, 40, 45 cm), and 3 initial groundwater level levels (2.1, 2.8, 3.6 m) are set. Each level of each variable generates each scenario in a fully combined manner (accumulating 180 scenarios).

[0099] The initial soil moisture content of each treatment in the 0 - 2.0 m soil layer is shown in Table 2. It should be noted that for different leaching quotas, the single-day infiltration amount remains unchanged, and different leaching quotas are achieved by adjusting the single-day infiltration amount; for different initial groundwater levels, they are achieved by setting the initial soil moisture content. For example, for an initial groundwater depth of 3.6 m, the initial soil moisture content of the soil below 3.6 m is all set to the saturated moisture content.

[0100] Table 2 Initial soil moisture content and initial solute concentration of each virtual scenario

[0101]

[0102] The VCFVM spatial simulation domain Ω is [0, L] × [0, 500] cm (L is the pipe spacing), and the time simulation domain is [0, 24] d. The VCFVM models for soil water and solute are shown in Eqs. (8a) and (8b) respectively:

[0103]

[0104]

[0105] Where: K is the soil hydraulic conductivity, [LT -1 ; h is related to the soil water potential, [L]; θ is the soil volumetric water content, [-]; C is the water capacity, related to the water potential h, [L -1 ; D is the hydrodynamic dispersion coefficient, [L 2 T -1 ; c is the solute concentration, [ML -2 ; f w and f s are the source-sink terms of soil water and solute respectively, and the dimensions are [L2 T -1 and [MT -1 .

[0106] Finally, the correction coefficient γ values for different buried pipe spacings of the sandy loam soil are obtained, and the errors of the corrected salt drainage and salt removal amounts of the buried pipes, RRMSE, are shown in Table 3.

[0107] Table 3 Initial soil moisture content and initial solute concentration of each virtual scenario

[0108]

[0109] It can be seen that the average error of the calculated value of the salt drainage and salt removal amount of the buried pipe corrected by the correction coefficient is about 10% relative to the array model. Considering the actual engineering use, it is considered that this accuracy meets the requirements, and the γ values in Table 3 are the correction coefficient values corresponding to different buried pipe spacings of the sandy loam soil.

[0110] 4. Step 4 is specifically as follows:

[0111] Construct the following optimized objective function and control conditions:

[0112]

[0113] Among them, Q sT represents the target salt removal amount calculated according to the actual crop requirements, etc.; R represents the buried pipe operation risk function. Compared with the buried pipe layout with large burial depth and large spacing, the small burial depth and small spacing correspond to less risk because the latter means more buried pipes per unit area, which is beneficial to reducing the operation risk caused by buried pipe blockage during the long-term operation of the buried pipes; in addition, in the formula, the solution with a smaller leaching quota is preferably selected.

[0114] Preferably, as Figure 2 shown, the steps to solve the leaching quota I, the buried depth ZD of the buried pipe, and the buried pipe spacing L are as follows:

[0115] Step1. Discretize the leaching quota I, the buried depth Z D of the buried pipe, and the buried pipe spacing L in the solution range to obtain an array of options, which are represented by I[i], Z D [j], L[k] respectively. The buried depth of the buried pipe is arranged from large to small, and the rest are arranged from small to large;;

[0116] Step2. Calculate the maximum buried depth Z of the buried pipe and the salt removal amount corresponding to the minimum leaching quota I[0] according to the semi-theoretical and semi-empirical formula of the cumulative drainage volume and the cumulative salt removal amount D of the buried pipe. Increase the leaching quota in turn until the calculated salt removal amount is greater than the target salt removal amount Q ​sT , then the minimum leaching quota at this time is taken as the recommended optimal leaching quota I op ;

[0117] Step3. Calculate the optimal leaching quota I and the maximum buried depth Z of the blind drain according to the semi-theoretical and semi-empirical formula of the cumulative drainage volume and the cumulative salt drainage volume op of the blind drain D [0], and the corresponding salt drainage volume Reduce the buried depth of the blind drain in turn until the calculated salt drainage volume is less than the target salt drainage volume Q sT , then the minimum buried depth of the blind drain in the previous step is taken as the recommended optimal buried depth Z of the blind drain Dop ;

[0118] Step4. Calculate the optimal leaching quota I and the optimal buried depth Z of the blind drain according to the semi-theoretical and semi-empirical formula of the cumulative drainage volume and the cumulative salt drainage volume op of the blind drain Dop , the corrected salt drainage volume Q under the minimum blind drain spacing L[0], s Increase the blind drain spacing in turn until the calculated corrected salt drainage volume Q s is less than the target salt drainage volume Q sT , then the maximum blind drain spacing at this time is taken as the recommended optimal blind drain spacing L op ;

[0119] Step5. The above I op , Z Dop and L op are the recommended optimal blind drain layout and the supporting leaching quota.

[0120] In this embodiment, based on the optimization range and the discrete step length of the input variables to be solved, the discrete leaching quota, the buried depth of the blind drain and the blind drain spacing are obtained as follows.

[0121] I = {20, 25, 30, 35, 40, 45, 50} cm;

[0122] Z D = {1.8, 1.6, 1.4, 1.2, 1.0} m;

[0123] L = {10, 20, 30, 40, 50} m;

[0124] We respectively take 30%, 40%, 50% as the target salt drainage rate (that is, the target salt drainage volumes are 0.23, 0.31, 0.39 g / cm2), and optimize the reasonable leaching quota and the blind drain layout of the sandy loam soil under different initial groundwater levels. The specific results are shown in Table 4.

[0125] Table 4 Reasonable leaching quota and buried pipe layout parameters under different soil textures, initial groundwater levels, and target salt drainage rates

[0126]

[0127] As Figure 4 shown, in this embodiment, an optimization system for buried pipe layout and leaching quota in arid areas that can automatically implement the above method is also provided, including: a data input unit, a correction coefficient storage and call unit, a correction coefficient generation unit, a modeling unit, an optimization unit, and an economic analysis unit.

[0128] The data input unit is used to read the data input by the user, including natural condition data (soil texture parameters, soil moisture content and salt content, groundwater depth and salinity), the space of variables to be solved (the range and step length of buried pipe spacing, depth, and leaching quota), and the target salt drainage rate.

[0129] The correction coefficient storage and call unit is used to store the correction coefficient γ values corresponding to different soil textures and different buried pipe spacings, and is communicatively connected to the basic data input unit. Based on the soil texture parameters input by the basic data input unit, the correction coefficient γ is called.

[0130] The correction parameter generation unit is communicatively connected to the basic data input unit and the correction coefficient storage and call unit. According to the soil parameter information of the basic data input unit, the variable-saturated soil water and solute model is called to simulate the salt drainage amount of buried pipes under different buried pipe spacings, depths, leaching quotas, and initial groundwater levels, and the correction coefficient values for the given soil parameters are customized. At the same time, the soil information and the corresponding soil parameter correction values will be transmitted to the correction coefficient storage and call unit for storage and available for all users to call.

[0131] The modeling unit is communicatively connected to the basic data input unit and the correction coefficient storage and call unit. Based on the soil texture parameters of the basic data input unit and the correction coefficient γ of the correction coefficient storage and call unit, the calculation formula for the salt drainage amount of buried pipes in the area to be constructed as shown in Equation (6) above is established.

[0132] The optimization unit is communicatively connected to the basic data input unit and the modeling unit. Based on the optimization range and step length of the variables to be solved input by the input unit, the available arrays I[i], Z D [j], L[k] are obtained, and the optimal combination of buried pipe layout and leaching quota that meets the target salt drainage amount is calculated within the available array space based on the buried pipe salt drainage amount calculation formula provided by the modeling unit.

[0133] The image generation unit is communicatively connected to the optimization unit. According to the buried pipe layout parameters and leaching quota provided by the optimization unit, a schematic diagram showing the final soil water storage, salt storage, buried pipe drainage volume, and salt drainage volume is generated.

[0134] The Economic Analysis Department, which is communicatively connected to the Optimization Department, analyzes and calculates the construction cost of the buried pipes and the annual supporting flushing cost according to the buried pipe layout parameters and flushing quota provided by the Optimization Department.

[0135] The above embodiments are merely illustrative examples of the technical solutions of the present invention. The optimization method and device for the buried pipe layout and flushing quota in the arid area fields involved in the present invention are not limited only to the content described in the above embodiments, but are subject to the scope defined by the claims. Any modification, supplement or equivalent replacement made by those skilled in the art of the present invention on the basis of this embodiment is within the scope protected by the claims of the present invention.

Claims

1. An optimization method for the layout of subsurface pipes and leaching quota in the field of arid areas, characterized in that, It includes the following steps: Step 1. Collect the basic data of the construction area, natural condition data, the space of variables to be determined, and the target desalination rate; Step 2. Based on the basic data collected in Step 1, construct a semi-theoretical and semi-empirical formula for calculating the cumulative drainage volume and cumulative salt drainage volume of the buried pipe under fully drained conditions and the cumulative salt drainage volume under fully drained conditions; the semi-theoretical and semi-empirical formula for calculating the cumulative drainage volume and the cumulative salt drainage volume under fully drained conditions is as follows: where θ r and θ s are the residual soil water content and the saturated soil water content, respectively, [-]; α is a parameter related to the average size of soil pores, [L -1 ; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n; W0 and W1 are the profile water storages at the start and end of subsurface drainage, respectively, [L 2 ; I is the leaching water volume, [L 2 ; Z D and Z GW are the values of the z coordinates of the center of the cross-section of the subsurface drain and the initial groundwater table location, respectively, [L]; C GW is the groundwater solute concentration, [ML -2 ; Step 3. Based on the soil texture parameters input in part of Step 1, determine the correction coefficient γ considering the insufficient drainage of the blind pipes, and obtain the corrected calculation formula for the desalination amount of blind pipe drainage considering insufficient drainage as follows: Where: γ is the correction coefficient considering the insufficient drainage of the blind pipes, [-], which is related to the soil texture and the blind pipe spacing, and the value range is 0 to 1; Step 4. Spatial discretization and optimization of the variables to be solved. Discretize the leaching quota I, the buried depth Z of the buried pipe D and the buried pipe spacing L in the solution range to obtain an array of options, denoted by I[i], Z D [j], L[k] respectively. The buried depth of the buried pipe is arranged from large to small, and the rest are arranged from small to large. Use the formula in Step 3 to solve the reasonable leaching quota and the buried pipe layout parameters. The optimization logic is as follows: preferentially select the solution with a smaller leaching quota. Under the same leaching quota, for the two solutions that meet the requirements, namely large buried depth and large spacing and small buried depth and small spacing, preferentially select the latter.

2. The optimization method for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 1, wherein: The natural condition data in Step S1 includes soil texture parameters, soil moisture content, salt content, groundwater depth, and salinity; the space of variables to be determined includes the range and step length of the blind pipe spacing, burial depth, and leaching quota.

3. The optimization method for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 1, wherein: In Step 2, the desalination amount of blind pipe drainage is calculated based on the following assumptions: (1) The blind drain can fully drain water. That is, after the blind drain drainage ends, the soil water potential h and the soil height z satisfy That is and the groundwater level is consistent with the depth where the blind drain is located. That is, the soil water potential at the depth where the blind drain is located is 0; (2) Assume that after the blind pipe drainage ends, the profile moisture content θ also changes linearly with depth, and the soil surface depth is calculated through the water head; (3) Assume that the water volume in the aquifer is much larger than the water volume in the soil profile, that is, the leaching water entering the groundwater in the unsaturated zone will not significantly change the groundwater concentration. Therefore, it can be considered that the blind pipe drainage concentration is consistent with the initial groundwater concentration.

4. The optimization method for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 1, characterized in that: In step 3, the correction coefficient γ takes into account the insufficient drainage and salt removal caused by the too large spacing of the blind pipes and the poor water conductivity of the soil. It is obtained by using the variable saturation soil water and solute model to simulate the blind pipe drainage and salt removal amounts, namely Q w and Q s under different soil textures in advance, with different blind pipe spacings, burial depths, leaching quotas and initial groundwater levels, and the cumulative drainage volume of the blind pipes and the cumulative salt removal amount calculated by the constructed semi-theoretical and semi-empirical formula. A corresponding table of the correction coefficient γ and the blind pipe spacing is constructed.

5. The optimization method for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 1, characterized in that: Step 4 is specifically as follows: Construct the optimized objective function and control conditions as follows: Among them, Q sT is the target desalination rate, and R represents the risk function of the subsurface pipe operation. Compared with the subsurface pipe layout with a large burial depth and large spacing, the small burial depth and small spacing correspond to less risk because the latter means more subsurface pipes per unit area, which is conducive to reducing the operation risk caused by pipe blockage during the long-term operation of the subsurface pipes. In addition, in the formula, the solution with a smaller leaching quota is preferably selected.

6. The optimization method of the layout of subsurface pipes and leaching quota in the field of arid areas according to claim 4, characterized in that: Steps for solving the leaching quota I, the buried depth Z of the buried pipe D and the spacing L of the buried pipes are as follows: Step1. Space-discretize the leaching quota I to be solved, the buried depth Z of the buried pipe D and the buried pipe spacing L within the solution range to obtain an array of options, represented by I[i], Z D [j], L[k] respectively. The buried depth of the buried pipe is arranged from large to small, and the rest are arranged from small to large; Step2. Calculate the maximum buried depth Z of the blind pipe according to the semi-theoretical and semi-empirical formula of the cumulative drainage volume of the blind pipe and the cumulative salt drainage volume and the corresponding salt drainage volume under the minimum leaching quota I[0] when the salt drainage volume D [0] and the minimum leaching quota I[0] are calculated Increase the leaching quota in sequence until the calculated salt drainage volume is greater than the target salt drainage volume Q sT , then take the minimum leaching quota at this time as the recommended optimal leaching quota I op ; Step 3.According to the accumulated drainage volume of the concealed pipe and cumulative salt discharge Calculation of optimal elution quota using a semi-theoretical and semi-empirical formula op and the maximum buried depth Z D [0] corresponds to the amount of salt discharged Reduce the buried depth of the concealed pipe gradually until the calculated salt discharge amount is reached. Less than the target salt discharge amount Q sT , then the minimum buried depth of the concealed pipe in the previous step is used as the recommended optimal buried depth Z Dop ; Step 4. Calculate the optimal leaching quota I and the cumulative salt drainage using a semi-theoretical and semi-empirical formula, and calculate the optimal buried depth Z of the blind pipe op , the corrected salt drainage Q under the minimum blind pipe spacing L[0] Dop . Increase the blind pipe spacing in sequence until the calculated corrected salt drainage Q s is less than the target salt drainage Q s . Then take the maximum blind pipe spacing in the previous step as the recommended optimal blind pipe spacing L sT ; op ​ Step5. The above-mentioned I op , Z Dop and L op are the recommended optimal blind pipe layouts and supporting flushing quotas.

7. An optimization system for the layout of subsurface pipes and leaching quota in the field in arid areas, characterized in that, It includes: Data input section, where the user inputs the basic data of the area to be constructed, including soil texture parameters, initial soil moisture content and salt content, groundwater depth and salinity, the optimization range and step length of variables to be determined, and the target desalination rate; Correction coefficient storage and call section, which stores the correction coefficient γ values corresponding to different soil textures and different blind pipe spacings, and is connected to the basic data input section in communication. Based on the soil texture parameters input by the basic data input section, it calls the correction coefficient γ; Modeling section, which is connected to the basic data input section and the correction coefficient storage and call section in communication. Based on the soil texture parameters of the basic data input section and the correction coefficient γ of the correction coefficient storage and call section, it establishes the corrected calculation formula for the desalination amount of blind pipe drainage in the area to be constructed as shown below; Q s = γQ s C GW where, θ r and θ s are the residual soil moisture content and the saturated soil moisture content, respectively, [-]; α is a parameter related to the average size of soil pores, [L -1 ; n is a parameter related to the soil pore size distribution, [-]; m and n satisfy m = 1 - 1 / n; W0 and W1 are the profile water storages at the start and end of subsurface drainage, respectively, [L 2 ; I is the leaching water volume, [L 2 ; Z D and Z GW are the z - coordinate values of the center of the cross - section of the subsurface drain and the position of the initial groundwater table, respectively, [L]; C GW is the groundwater solute concentration, [ML -2 ; The optimization department is communicatively connected to the data input department and the modeling department. Based on the optimization range and discrete step length of the variable to be solved input by the input department, it obtains the selectable arrays I[i], Z D [j], L[k], and calculates the optimal combination of subsurface pipe layout and leaching quota that meets the target salt drainage volume within the selectable array space based on the subsurface pipe salt drainage volume calculation formula provided by the modeling department.

8. The optimization system for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 7, characterized in that, It also includes: Correction parameter generation section, which is connected to the basic data input section and the correction coefficient storage and call section in communication. For users with a strong professional background, this section can be selected. According to the soil parameter information of the basic data input section, it calls the variable-saturated soil water and solute model to simulate the desalination amount of blind pipe drainage under different blind pipe spacings and burial depths, leaching quotas, and initial groundwater levels, and customizes the correction coefficient values for the given soil parameters. At the same time, the soil information and the corresponding soil parameter correction values will be transmitted to the correction coefficient storage and call section for storage and can be called by all users.

9. The optimization system for the layout of subsurface pipes and leaching quota in the field in arid areas according to claim 7, characterized in that It also includes: Image generation section, which is connected to the optimization section in communication. According to the blind pipe layout parameters and leaching quota provided by the optimization section, it generates a schematic diagram showing the final soil water storage, salt storage, blind pipe drainage volume, and desalination amount; Economic analysis section, which is connected to the optimization section in communication. According to the blind pipe layout parameters and leaching quota provided by the optimization section, it analyzes and calculates the blind pipe construction cost and the annual supporting leaching cost.

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