A control system and method for secondary salinization of soil in irrigation areas

Abstract

The embodiment of the present invention discloses a control system and method for secondary salinization of soil in irrigation areas. The system includes: a groundwater seepage interception structure and a drainage structure located between the area where secondary salinization of soil in the irrigation area occurs and the area where it does not occur, and a groundwater forced drainage device located in the area where it occurs; the groundwater seepage interception structure extends along the boundary line direction between the area where it occurs and the area where it does not occur; the elevation of the area where it does not occur is greater than the elevation of the area where it occurs, and the groundwater seepage interception structure is used to intercept the groundwater in the area where it does not occur from infiltrating into the area where it occurs; the groundwater forced drainage device is used to discharge the groundwater in the area where it occurs to the drainage structure; the drainage structure is used to drain the groundwater discharged from the area where it occurs and the area where it does not occur into the drainage structure. This embodiment can improve the phenomenon of secondary salinization of soil in irrigation areas.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of soil secondary salinization prevention and control, and in particular, to a control system and method for soil secondary salinization in irrigation areas. Background Art

[0002] The tank area in the arid and semi-arid zone has little rainfall, strong evaporation, strong winds and lots of sand, and a very fragile ecological environment. The irrigation area has a long history of farming, and the irrigation and drainage system is basically complete, but the terrain is low, the drainage is poor, and the groundwater level is high, resulting in the increasingly prominent and worsening soil salinization problem, which has seriously restricted the stability of the ecosystem and the sustainable development of agriculture in the region.

[0003] Taking the Ningxia Yanghuang Irrigation Area as an example, its main soil parent materials are alluvial deposits and flood-alluvial deposits, with obvious sedimentary layers and the soil texture mainly composed of medium loam and heavy loam. There was no salinization problem before development. Due to unreasonable irrigation, complex terrain, complex soil structure, and especially multi-layer heavy clay soil in different parts, irrigation-type soil salinization occurred, seriously affecting crop growth, the ecological environment and houses in some villages. Summary of the invention

[0004] The embodiment of the present invention provides a control system and method for controlling secondary salinization of soil in an irrigation area to solve the above-mentioned problem.

[0005] In a first aspect, an embodiment of the present invention provides a control system for secondary salinization of soil in an irrigation area, comprising:

[0006] Groundwater interception and drainage structures located between the area where secondary salinization of the soil occurs and the area where it does not occur in the irrigation area, and groundwater forced drainage devices located in the area where it occurs;

[0007] The groundwater seepage cut-off structure is lower than the ground surface and extends along the boundary between the occurrence area and the non-occurrence area; the elevation of the non-occurrence area is greater than the elevation of the occurrence area, and the groundwater seepage cut-off structure is used to intercept the groundwater in the non-occurrence area from penetrating into the occurrence area;

[0008] The groundwater forced drainage device is installed underground in the occurrence area, and is used to discharge the groundwater in the occurrence area to the drainage structure;

[0009] The drainage structure is below the ground surface and is used to drain groundwater discharged from the occurrence area and the non-occurrence area into the drainage structure.

[0010] In a second aspect, an embodiment of the present invention provides a method for controlling secondary salinization of soil in an irrigation area, comprising:

[0011] Between the area where secondary salinization of the soil occurs and the area where it does not occur in the irrigation area, a groundwater seepage interception structure and a drainage structure are constructed; the groundwater seepage interception structure is lower than the ground surface and extends along the boundary line between the area where secondary salinization occurs and the area where it does not occur; the elevation of the area where secondary salinization does not occur is greater than the elevation of the area where secondary salinization occurs, and the groundwater seepage interception structure is used to intercept the groundwater in the area where secondary salinization does not occur from penetrating into the area where secondary salinization occurs;

[0012] A groundwater forced drainage device is installed in the occurrence area; the groundwater forced drainage device is installed underground in the occurrence area, and the groundwater forced drainage device is used to discharge the groundwater in the occurrence area to the drainage structure;

[0013] The drainage structure is below the ground surface and is used to drain groundwater discharged from the occurrence area and the non-occurrence area into the drainage structure.

[0014] The present invention provides a control system and method for secondary salinization of soil in an irrigation area. Through the interception and drainage method, a groundwater interception structure and a drainage structure are added between the area where secondary salinization occurs strongly and the area where it has not occurred in the irrigation area, so as to effectively intercept the underground runoff inflow from the upstream of the irrigation area, and solve the problems of excessively high groundwater level and severe soil salinization. At the same time, in conjunction with the groundwater forced drainage structure in the area where secondary salinization occurs strongly, the groundwater in the salinized land is forced to be discharged to the drainage structure for export, so as to further reduce the groundwater level and soil salinity in the salinized land. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 is a schematic diagram of a seepage interception structure and a drainage structure provided by an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of an underground runoff interception culvert drainage pipeline design provided by an embodiment of the present invention;

[0018] Figure 3 It is a schematic diagram of a three-dimensional geological structure model provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0021] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Over the years, with the development of land and irrigation of upstream farmland, the groundwater level in the irrigation area has risen year by year. Taking the Ningxia Yanghuang Irrigation Area as an example, the groundwater depth has risen from 8 to 12 meters to less than 1 meter. The special soil structure leads to slow vertical discharge of groundwater and rising water levels. Under strong evaporation, groundwater is mainly discharged by vertical evaporation, and the salt brought in by soil and irrigation accumulates on the surface, forming severe salinization.

[0023] In view of this, an embodiment of the present invention provides a control system for secondary salinization of soil in an irrigation area. In view of the characteristics of secondary salinization in the irrigation area after many years of surface irrigation, a groundwater interception structure and a drainage structure are added between the area where secondary salinization occurs strongly and the area where secondary salinization has not occurred in the irrigation area through engineering management methods, so as to effectively intercept the underground runoff in the upstream of the irrigation area and solve the problems of excessively high groundwater level and severe soil salinization. At the same time, the groundwater forced drainage structure in the area where secondary salinization occurs strongly is used to force the groundwater to be discharged to the drainage structure, so as to further reduce the groundwater level and soil salinity, and effectively solve the problems of secondary soil salinization and salt-alkali erosion in some villages.

[0024] Specifically, the groundwater seepage interception structure and drainage mechanism are below the ground surface and extend along the boundary line between the occurrence area and the non-occurrence area. They can include ditch seepage interception and drainage and culvert seepage interception and drainage, and can be implemented either way according to the land properties and regional topography. Figure 1 Schematic diagram of a seepage interception structure and a drainage structure provided by an embodiment of the present invention, wherein the drainage structure is a culvert and the seepage interception structure is a geotextile, corresponding to the culvert seepage interception drainage mode. Figure 1 The right area in the figure is the area where secondary soil salinization has not occurred, and the left area is the area where secondary soil salinization has occurred. Usually, the elevation of the non-occurring area is greater than the elevation of the occurring area. Irrigation water will infiltrate downstream, causing the groundwater level to rise and salt to flow back to form saline-alkali land. In this embodiment, a ditch extending along the dividing line is excavated at the boundary between the two areas, and a drainage culvert is installed at the bottom of the ditch. A geotextile substantially perpendicular to the ground is installed on the side of the culvert close to the non-occurring area to prevent the groundwater in the non-occurring area from infiltrating into the occurring area, prevent the water level in the occurring area from continuing to rise, and avoid further aggravation of secondary soil salinization. As time goes by, the moisture in the soil of the two sides will also infiltrate into the culvert and be discharged, further lowering the groundwater level in the two sides.

[0025] In addition, a groundwater forced drainage device is installed in the occurrence area, which may include a precipitation well leading from the ground to the underground, a photovoltaic drainage pump is installed in the precipitation well, and a water outlet pipe is connected between the photovoltaic drainage pump and the drainage structure. When irrigating the irrigation area, the photovoltaic drainage pump collects groundwater in the occurrence area and discharges the groundwater into the culvert through the water outlet pipe.

[0026] Under the channel interception drainage method, Figure 1 There are no culverts or geotextiles in the system, and the ditch serves as both a groundwater interception and drainage structure. Water from upstream areas where secondary salinization has not occurred cannot penetrate into downstream areas where secondary salinization has occurred due to ditch interception, and is discharged along the ditch at the same time, achieving ditch interception and drainage.

[0027] Based on the same inventive concept, an embodiment of the present invention also provides a method for controlling secondary salinization of soil in an irrigation area, comprising: constructing a groundwater seepage cutoff structure and a drainage structure between an area where secondary salinization of soil in an irrigation area occurs and an area where it does not occur; the groundwater seepage cutoff structure is below the ground surface and extends along the boundary line between the area where secondary salinization of soil occurs and the area where it does not occur; the elevation of the area where secondary salinization does not occur is greater than the elevation of the area where it occurs, and the groundwater seepage cutoff structure is used to intercept the groundwater in the area where it does not occur from infiltrating into the area where it occurs; a groundwater forced drainage device is installed in the area where secondary salinization of soil occurs; the groundwater forced drainage device is installed underground in the area where secondary salinization occurs, and the groundwater forced drainage device is used to discharge the groundwater in the area where secondary salinization occurs to the drainage structure; the drainage structure is below the ground surface, and the drainage structure is used to drain the groundwater discharged from the area where secondary salinization occurs and the area where it does not occur into the drainage structure.

[0028] The above control system and method are described in detail below through a specific implementation. Figure 1 Taking a village in the Yanghuang Irrigation District of Ningxia as an example, the approximate dividing line between the area where secondary salinization of the soil in the irrigation area occurs and the area where it does not occur is first determined, and then a ditch with a length of 1000m is excavated along the extension direction of the dividing line. The ditch is dug 5.2m deep, the ditch side slope is 1:1.25, and the ditch bottom slope is 1 / 500. Since the area is located in silt sand and sandy loam, it is prone to sand flow and sudden surges, which affect the stability of the foundation pit. Therefore, precipitation and water isolation measures should be taken during the excavation construction. In this embodiment, precipitation wells are reasonably arranged according to the permeability of different soil layers to reduce the water level of the subsurface soil layer of the foundation pit. During the excavation of the foundation trench, the construction site personnel always pay attention to the changes in the groundwater level and monitor the stability of the slope. If any problems are found, the construction will be stopped and reported in time.

[0029] Optionally, 100 sandless concrete dewatering wells with a depth of 10m and an inner diameter of Φ35cm can be constructed, with a dewatering shift of 9,000 shifts. Dewatering construction can reinforce the soil at the bottom of the foundation pit and improve the strength of the soil at the bottom of the pit, thereby reducing the uplift of the pit bottom and the deformation of the surrounding structure, and preventing excessive surface settlement outside the pit; at the same time, it is conducive to slope stability and landslide prevention. Dewatering wells can be set outside the foundation pit to facilitate excavators and workers to work in the pit.

[0030] Furthermore, the layout of the dewatering wells in the pit can be determined according to the effective pumping area of ​​a single well (the empirical value is) based on the area of ​​the foundation pit, and the empirical value is determined based on the characteristics of the site's phreatic aquifer and the plane shape of the foundation pit, usually within 100m 2 ~150m 2 Optionally, the effective pumping area of ​​a single well in the formation in this area is about 130m 2The drainage pipe well is arranged at 1.0m from the outer edge. The specific depth of the well can be determined according to the excavation depth of the foundation pit in the corresponding area. The drainage work should be closely coordinated with the excavation construction, and the number of drainage wells should be adjusted in time according to the excavation sequence and progress.

[0031] The number of tube wells in the pit can be calculated according to the following formula:

[0032] n=A / a

[0033] Where: n is the number of wells; A is the dewatering area of ​​the foundation pit (m 2 ); a—effective pumping area of ​​a single well (m 2 ).

[0034] Finally, it was determined that a total of 100 drainage wells were arranged around the foundation pit. The well depth is 10 meters, and the well mouth should be 0.50m above the ground to prevent surface sewage from seeping into the well. Generally, high-quality clay or cement slurry is used to seal it, and its depth is 10m. The well wall pipe uses sand-free concrete pipe. Note that during the construction of the pipe well, the depth of the well point is all controlled by the elevation of the bottom of the well. If the site elevation fluctuates, the well wall pipe should be increased or decreased accordingly at the top section of the pipe well. The location of the well is 1.0 on the south side of the foundation pit and 7.0m away from the axis.

[0035] After the trench is excavated, a 1000-meter Φ60-cm sandless concrete drainage culvert is installed at the bottom of the trench. Specifically, a culvert gravel cushion layer is laid in a dry environment. The cushion layer is 0.2 meters thick and 1.0 meters wide. A 1000-meter Φ60-cm sandless concrete drainage culvert is installed at the bottom of the trench on the cushion layer. The culvert is backfilled with gravel filter material around it, with a thickness of not less than 20 cm. Figure 2 The design diagram of the cross section of the underground runoff interception culvert drainage pipe is shown in Table 1, and the longitudinal section data of the culvert drainage pipe are shown in Table 1. At the same time, geotextile is laid in a substantially vertical direction on the downstream side of the sandless concrete pipe as a seepage interception wall. The bottom slope of the drainage culvert is 1 / 800, and the culvert pipe interface adopts welding technology. One inspection well is designed every 100 meters.

[0036] Table 1 Cut-off culvert longitudinal section data

[0037]

[0038]

[0039] Optionally, if the culvert crosses a farmland road, excavations can be carried out on both sides of the road, and then the culvert pipe can be pushed into the soil under the farmland road by pipe jacking to avoid damaging the farmland road.

[0040] Furthermore, the radius of the culvert drainage pipe must meet the maximum drainage flow rate. Specifically, the maximum drainage flow rate required for the drainage culvert is 374m3 / h, the designed concealed pipe is a sandless concrete pipe, the pipe slope is 1 / 800, the roughness x=0.018, and the pipe drainage is a pressureless free flow. Then the maximum flow rate of the pipe is Q=S×V, where S represents the cross-sectional area of ​​the concealed pipe and V represents the maximum flow rate.

[0041] When the inner diameter of the concealed pipe is φ=30cm, S=3.14159×0.15×0.15=0.07m 2 , hydraulic radius R = 0.5 × 0.15 = 0.075m, pipeline slope J = 1 / 800, maximum flow rate = R 2 / 3 J 1 / 2 / x=0.65m / s, then the maximum flow rate Q=0.65×0.07=0.0455m 3 / s=163.8m 3 / h.

[0042] When the inner diameter of the concealed pipe is φ = 40 cm: S = 3.14159 × 0.2 × 0.2 = 0.1256 m 2 , hydraulic radius R = 0.5 × 0.20 = 0.1m, pipeline slope J = 1 / 800, maximum flow rate = R 2 / 3 J 1 / 2 / x=0.85m / s,maximum flow rate Q=0.85×0.1256=0.10676m 3 / s=384.3m 3 / h. Therefore, when the drainage pipe uses a concealed pipe with an inner diameter of φ30cm, the maximum drainage flow rate can reach 163.8m 3 / h drainage flow rate cannot meet the drainage requirements; when using a concealed pipe with an inner diameter greater than φ40cm, the maximum drainage flow rate can reach 384.3m 3 / h drainage flow, meeting the maximum pipeline flow of 374m 3 Preferably, the present embodiment uses a drainage concealed pipe with an inner diameter of 60 cm to fully ensure the drainage capacity.

[0043] While constructing the groundwater seepage interception structure and the drainage structure, this embodiment also installs a groundwater forced drainage device in the occurrence area, through which the groundwater in the occurrence area is discharged to the culvert, further lowering the groundwater level in the occurrence area and reducing the degree of soil salinization. Optionally, the groundwater forced drainage device can use solar well equipment, including a precipitation well and a photovoltaic drainage pump installed in the well; an outlet pipe is connected between the photovoltaic drainage pump and the drainage structure, and the groundwater collected by the photovoltaic drainage pump is discharged to the culvert through the outlet pipe.

[0044] Furthermore, in a specific implementation, a drainage well can be arranged at each intersection of lanes in the village. The drainage well adopts a reinforced concrete structure, with a diameter of 1m and a depth of 10m. There are 18 drainage wells in total. Submersible pumps are installed in the wells to collect groundwater during both irrigation and non-irrigation periods, and discharge it into underground pipes through a forced drainage pump station. The flow rate of the drainage pump is determined according to the designed runoff depth, drainage area and drainage duration generated by the rainstorm:

[0045] Q1=Rω / 79.2T

[0046] Where: Q1——designed drainage flow of the pump station (m 3 / s); R——design runoff depth generated by design rainstorm, using 20mm rainstorm per day; ω——drainage area; T——drainage duration (days);

[0047] Total head of the pump: H = H net + h loss, h loss = h edge loss + h local loss, where:

[0048] 1) Along the way loss: h Along the way loss = 10.28Ln2Q2 / D*5.33

[0049] Where: h is the loss along the way; m is the water quota; n is the pipe roughness coefficient, which is 0.012 for steel pipe; D is the inner diameter of the pipe (m); Q is the flow rate in the pipe (m 3 / s);

[0050] 2) Local loss: h local loss = 0.083∑ζQ2 / D4

[0051] Where: h local loss - local resistance loss; ∑ζ - the sum of local resistance coefficients, which can be found in the "Electrical and Mechanical Drainage and Irrigation Design Manual"; D - pipe inner diameter (m); Q - flow rate in the pipe (m 3 / s).

[0052] Based on the measured data, the elevation of the ditch bottom in front of the pump station inlet pool, the normal water level elevation, the inlet pool water level elevation, the pool bottom elevation, the pump station outlet pool water level elevation, the outlet pool pipe center elevation, etc. are analyzed to obtain the net head and the total head of the pump station.

[0053] Based on the above parameters, the selection of water pump model is as follows:

[0054] serial number <![CDATA[Flow rate (m 3 / h)]]> Lift(m) Solar inverter pump model Power(kw) 1 20 26 150QJ(R)20-26 / 4 3

[0055] A suitable open space can be selected to arrange the pump station, and a 2m high plastic steel fence is used for protection. The distribution box is made of fiberglass with a size of 0.8×0.8m. A new DN1000 pipe well with a depth of 10m is built at the end of the forced drainage water collection pipe. The water outlet pipe of the water pump is made of steel pipe with a diameter of 80mm and a wall thickness of 6mm.

[0056] The detailed parameters of the photovoltaic pump station are shown in Table 2:

[0057] Table 2

[0058]

[0059] After the secondary salinization of the soil in the irrigation area was controlled by the above-mentioned system equipment, the changes in the groundwater level and soil salinity in the secondary saline land are shown in Table 3. It can be seen that the groundwater depth in the secondary saline land increased exponentially before and after the construction, that is, the groundwater level was greatly reduced, which effectively prevented the return of soil salt and improved soil salinization.

[0060] Table 3

[0061]

[0062] Optionally, in another specific implementation, before actual construction, the culvert depth and the number and location of the precipitation wells in the occurrence area (i.e., the location of the photovoltaic drainage pump) can be determined by numerical simulation of groundwater movement, so as to maximize the utilization rate of equipment and reduce the cost of treatment while ensuring the anti-salinization effect. The specific determination process is as follows:

[0063] Step 1: Construct a three-dimensional geological structure model of the irrigation area. Specifically, according to the drilling data of the irrigation area, indoor experiments can be conducted on the soil samples obtained from each borehole to measure the basic physical and mechanical parameters such as porosity, permeability, and water supply degree, and the aquifer medium information in the three-dimensional space of the irrigation area can be calculated. Combined with the geological characteristics such as the stratum lithology and geological structure of the irrigation area in the survey report, a three-dimensional hydrogeological structure model can be established using Rockworks software and Modflow software as the basis for numerical simulation of groundwater movement. The specific modeling process is the existing technology, Figure 3 Taking the permeability coefficient as an example, the morphology of the three-dimensional model of some areas is displayed.

[0064] Step 2: Determine the value range of the culvert depth [h min ,h max ] and the number of precipitation wells in the occurrence area [N min ,N max ], and the culvert depth and N maxThe positions of the precipitation wells are initialized to generate multiple groups of initial solutions. This embodiment will determine a set of appropriate parameter values ​​for the culvert depth, the number and location of precipitation wells through genetic algorithms and numerical simulations of groundwater movement. This step first completes the parameter initialization. Specifically, first determine the value ranges of the number of precipitation wells and the culvert depth. These ranges can be set manually based on experience, or they can be preliminarily estimated based on the irrigation volume and the law of groundwater movement. Optionally, the amount of groundwater that needs to be discharged each day can be preliminarily determined based on the annual irrigation volume and / or rainfall in the occurrence area, and then the minimum number of water pumps required to discharge the groundwater is determined according to the state of the water pump working 24 hours a day at the designed drainage flow rate. The number of water pumps at this time is the minimum number N of precipitation wells. min ; Then determine a maximum number N based on the construction cost max When determining the range of the culvert depth h (h ≥ 0), numerical simulation can be used to determine at what depth the groundwater will not return to the surface without irrigation and drainage measures, thereby determining the minimum value of the culvert depth h. min This is because the geotextile has no interception effect on the water below the culvert. Such a depth can ensure to a certain extent that the water below the culvert will not return to the ground after infiltrating into the occurrence area. Then, according to the construction cost of the culvert and the geotextile, the maximum value of the culvert depth h is determined. max , similarly, this value can be set manually. Then, when using genetic algorithms to find the optimal solution, [N min ,N max ]、[h min ,h max ] and the location range of the occurrence area limit the solution space. When the parameters are initialized, the culvert depth and N can be randomly generated in the solution space. max The initial positions of the wells are determined, and the initial positions of the wells are kept different from each other. A pseudo-random sequence, a Halton sequence or other methods may be used for generation, and this embodiment does not impose any specific limitation.

[0065] Step 3: Encode each group of initial solutions into a binary sequence or a real number sequence as the current population in the genetic algorithm. Optionally, taking the binary sequence as an example, each solution sequence includes two parts: the culvert depth part and the precipitation well location part, where the precipitation well location part is composed of N max The positions of N precipitation wells are arranged in sequence. maxBy counting the locations of precipitation wells, the actual number of precipitation wells can be obtained. For example, when the locations of two wells are the same or very close, they are considered to be the same well. When encoding each parameter separately, the maximum value in the parameter value range corresponds to a sequence of all 1s, and the minimum value corresponds to a sequence of all 0s. For the intermediate value, the parameter value range can be divided into equal steps with the required data accuracy as the step size. Each interval obtained by the division is mapped to a solution in the parameter space, corresponding to a binary sequence. This ensures that each individual in the binary code is within the value range of each parameter. Exemplarily, the structure of the encoded binary sequence can be [binary sequence of culvert depth][binary sequence of the x coordinate of the first precipitation well][binary sequence of the y coordinate of the first precipitation well]…[binary sequence of the Nth max Binary sequence of x-coordinates of precipitation wells] [Nth max A binary sequence of the y coordinates of the precipitation wells], where x and y can be longitude and latitude, or can be custom ground coordinate system coordinates. After dividing the x-coordinate and y-coordinate value ranges with a set distance as the step size, it is equivalent to dividing the occurrence area into multiple two-dimensional grids, each grid is a solution of the position space, corresponding to its own x and y coordinates.

[0066] Step 4: Input the parameter combinations corresponding to each individual in the current population into the three-dimensional geological structure model, and dynamically simulate the groundwater movement under a certain irrigation strategy. Optionally, first decode the binary sequence in the current individual into the specific value of each parameter, and add the models of the culvert, geotextile and precipitation well to the three-dimensional geological structure model of the irrigation area according to the specific culvert depth and precipitation well location. Optionally, the culvert model and precipitation well model can be added according to the design parameters in the previous embodiment. The culvert model meets the size design parameters of the culvert, and the precipitation well model meets the design drainage flow of the pump station; if there are at least two wells with the same or very close positions, they are considered to be the same precipitation well, and only one well is modeled; at the same time, the relevant parameters at the geotextile position can be set to complete the geotextile modeling to ensure the impermeability of the geotextile, for example, the porosity and / or permeability coefficient at the geotextile position is set to 0. In addition, channel modeling can also be performed in the vertical space from the ground to the culvert, with the channel wall replacing the geotextile to intercept the upstream water, and the channel bottom replacing the culvert to drain the water, thereby eliminating the steps of geotextile modeling and culvert modeling; accordingly, the entire numerical simulation method is also applicable to the channel seepage interception and drainage method, and can ultimately assist in determining a reasonable channel depth, as well as the number and location of precipitation wells in the occurrence area. After each model is added, the current groundwater level distribution of the irrigation area can be obtained by interpolating the borehole data, and the water level data can be imported into the three-dimensional geological structure model as the simulation starting point, and the groundwater movement simulation of the future set time period is performed according to the set irrigation strategy. Of course, the initial water level at different spatial locations is usually different. The set irrigation strategy can follow the current irrigation strategy or adopt the irrigation strategy planned in the future, or other irrigation strategies that are consistent with the actual situation. This embodiment does not make any special restrictions. In particular, in this embodiment, the groundwater level at each spatial position is regularly detected during the simulation process. If the groundwater level at all spatial positions in the influence area of ​​a certain precipitation well is lower than the set threshold and maintained for a period of time, the precipitation well is stopped; when the groundwater level in the area is higher than the set threshold again and maintained for a period of time, the precipitation well is restarted. The influence area can be determined according to the effective pumping area or influence radius of a single well, or an empirical value can be taken.

[0067] Step 5. Determine whether the simulation results of each individual meet the optimal goal. If not, use a genetic algorithm to optimize the current population to obtain a new current population, return to step 4, and enter the next cycle. Repeat this iterative cycle until the final simulation result meets the optimal goal. Among them, the optimal goal can be that the final groundwater level at each spatial position in the simulation result is less than the set threshold, or the number of iterations is greater than the set number, or the total duration of the iterative calculation is greater than the set duration, etc. If all individuals in the current population do not meet the optimal goal, a genetic algorithm is used to generate the next generation population. Specifically, first construct the following fitness function for all individuals in the current population:

[0068]

[0069]

[0070] Among them, h represents the hidden depth in the current individual, within the specified value range [h min ,h max ], the smaller the culvert depth, the lower the construction difficulty and cost. N represents the number of precipitation wells in the current individual, within the specified value range [N min ,N max ], the fewer the number of precipitation wells, the lower the construction cost and difficulty. i It represents the total drainage volume of the ith precipitation well in the current individual during the simulation process, which can be obtained by multiplying the drainage flow rate of the precipitation well and the working time; x represents the standard deviation of the total drainage volume of each precipitation well; the smaller x is, the more balanced the utilization rate of each precipitation well and its equipment is; Represents the normalized x. The normalized range can be all individuals in the current population. Optional. Among them, x min and x max Respectively represent the maximum and minimum values ​​in x of all individuals. w1, w2 and w3 represent three weights respectively, w1+w2+w3=1. It can be seen that the smaller the culvert depth h, the fewer the number of precipitation wells, the more balanced the utilization rate of the precipitation wells and their equipment (total drainage), the larger the value of the fitness function, and the better the current individual. It should be noted that formula (1) (2) is only a function form for realizing the fitness evaluation method, and other fitness functions that can realize the evaluation also belong to the protection scope of the present invention.

[0071] According to the fitness calculated by the above formula, multiple individuals can be selected as parent individuals, and multiple offspring individuals can be obtained by crossover and mutation of the parent individuals. The specific selection, crossover and mutation strategies are mature methods in genetic algorithms and can be flexibly selected according to actual conditions. In general, the better the individual, the higher the probability of being selected as the parent individual. When generating offspring individuals, since the coding fragments of each parameter in the parent individual are independently crossed and mutated, it is possible that the positions of two precipitation wells in the offspring individuals are the same. In this case, the two precipitation wells can be considered to be the same precipitation well. Accordingly, after obtaining the offspring individuals, first determine whether the number of precipitation wells is less than N. min , if so, discard the individual. For the remaining offspring individuals, the following fitness function can be constructed:

[0072]

[0073]

[0074] in, is the adaptation factor between the current individual precipitation well distribution and the distribution of the amount of water to be discharged, The smaller it is, the higher the degree of match between the two. ρ,i represents the precipitation well density ρ at the i-th precipitation well position under the current individual i The maximum value of the precipitation well density at all spatial locations in the occurrence area ρ max The ratio, r d,i represents the amount of water to be discharged at the location of the i-th precipitation well under the current individual d i The maximum value d of the amount of water to be discharged at all spatial locations in the occurrence area max The ratio of the two ratios, the absolute value of the difference between the two ratios | r ρ,i -r d,i The smaller | is, the more the distribution of precipitation wells matches the distribution of the amount of water to be discharged, that is, the more groundwater there is to be discharged, the more precipitation wells there are. Such a distribution of well locations is more reasonable, and the total pumping volume (i.e., total drainage volume) of each precipitation well is easier to balance in actual operation. It can be seen that the smaller the culvert depth h is, the fewer the number of precipitation wells is, the more the distribution of precipitation wells matches the distribution of the amount of water to be discharged, the larger the value of the fitness function is, and the better the current individual is. Similarly, formulas (3) and (4) are only a function form for realizing the fitness evaluation method. Other fitness functions that can realize the evaluation also fall within the scope of protection of the present invention. Several specific examples are given below:

[0075] Optionally, in addition to formula (4), the adaptation factor can also be calculated by the above two ratios at all spatial positions in the occurrence area:

[0076]

[0077] Among them, N a represents the total number of spatial locations within the occurrence area, j = 1, 2, ..., N a , r ρ,j represents the precipitation well density ρ at the jth spatial position under the current individual j The maximum value of the precipitation well density at all spatial locations in the occurrence area ρ max The ratio, r d,j Indicates the amount of water to be discharged at the jth spatial position under the current individual d j The maximum value d of the amount of water to be discharged at all spatial locations in the occurrence area max The ratio of ρ,i and r d,i (i=1,2,…,N) are r ρ,j and r d,j (j=1,2,…,N a) is the value at the location of the precipitation well. Formula (4) pays more attention to the matching degree at the location of the precipitation well, and maintains a reasonable distribution of drainage between local areas where precipitation wells are deployed; Formula (5) pays more attention to the matching degree of the entire occurrence area, and maintains a reasonable distribution of drainage in the entire area.

[0078] Optionally, the adaptation factor can be calculated by softmax normalization method. That is, the softmax function is used to calculate the precipitation well density ρ at all spatial locations in the occurrence area j and the amount of water to be discharged d j Normalize them separately:

[0079]

[0080]

[0081] in, and are the normalized ρ j and d j This normalization method can convert the density of precipitation wells and the amount of water to be discharged into a number between [0-1], and to a certain extent avoid the concentrated distribution of values, and can also be used as a calculation Basis:

[0082]

[0083] or

[0084] In practical applications, one of the formulas (4), (5), (8), and (9) can be selected and combined with formula (3) according to the specific situation to form the fitness function of the offspring individuals to ensure the simulation effect. This embodiment does not impose any specific restrictions.

[0085] Furthermore, the amount of water to be discharged can be reflected by the initial water level at the beginning of the simulation, that is, d i or j The value is the initial water level at the corresponding position. The initial water level represents the current water accumulation situation and is a comprehensive reflection of the historical irrigation volume, soil geological conditions, etc. Especially when the irrigation strategy remains unchanged, it can well reflect the amount of water to be discharged at each position; it can also reflect the amount of water to be discharged according to the location of the irrigation equipment. The closer a certain spatial position is to the irrigation equipment, the more irrigation equipment covers the position, and the greater the amount of water to be discharged. The density of precipitation wells at a certain spatial position can be solved in the following way: gradually expand the circular area or square area outward with the position as the center. When the circular or square area includes a set number of precipitation wells for the first time, divide the set number by the area of ​​the circular or square area at this time to obtain the density of the precipitation wells at this position.

[0086] The fitness of the remaining offspring individuals can be calculated by the above method, and the parent individuals and these offspring individuals are merged into a new individual set. According to the fitness of each individual, multiple optimal individuals are selected from the set to form a new current population, and return to step 4 to enter the next cycle. Iterate in this way until the final simulation result meets the optimal goal. It is worth mentioning that in order to retain the excellent genes of the parent individuals and offspring individuals in the current population, this embodiment constructs a fitness function with similar structure for the parent individuals and offspring individuals respectively to measure the advantages and disadvantages of each individual in terms of construction cost, construction difficulty, and equipment utilization. For the parent individuals, the more balanced the total drainage of each precipitation well during the simulation process, the more reasonable the location distribution of the precipitation well is; while the offspring individuals have not yet been numerically simulated, and the equipment utilization cannot be measured by the drainage during the simulation process. Therefore, the rationality of the location distribution is measured according to the matching degree between the precipitation well distribution and the drainage distribution. Although the data used in the two are different, the representation meanings are comparable, so the fitness of the two generations of individuals can be compared together, and the best individual in the entire set is selected without paying special attention to the ratio of the parent generation individuals to the offspring individuals in the best individuals; of course, it is also possible to compare the individuals of the same generation separately, select some best individuals from the parent generation and the offspring respectively, and maintain the ratio of the parent generation individuals to the offspring individuals in the current population, which is not specifically limited in this embodiment.

[0087] After the iteration, for at least one individual that meets the optimal goal, the best several can be selected as the final parameter values ​​according to the fitness to enter the construction stage or other subsequent stages. It is worth mentioning that after the construction according to the above parameters, the groundwater level can also be regularly observed during actual use. When the groundwater level within the influence range of a precipitation well is higher than the set threshold and maintained for a period of time, the equipment in the well is turned on. When the groundwater level drops and maintains for a period of time, the equipment in the well is temporarily turned off to minimize energy consumption and equipment loss. Of course, in the simulation, if the working time of each precipitation well is not particularly concerned, such as when the simulation time in the future is short, or when simulating specific periods such as irrigation period or rainstorm period that require continuous drainage, each precipitation well can also be set to be in working state all the time. Correspondingly, when selecting the parent individual and the child individual, the same fitness function as the above child individual can be used (a combination of any one of formulas (3) and (4)(5)(8)(9), especially with (8) or (9)), which can also improve the matching degree between the well location distribution and the amount of water to be discharged, and obtain a better well location distribution.

[0088] In summary, the present embodiment provides a control system and method for secondary salinization of soil in irrigation areas. Through the interception and drainage method, groundwater interception structures and drainage structures are added between the areas where secondary salinization occurs strongly and the areas where it has not occurred in the irrigation areas, effectively intercepting the underground runoff in the upstream of the irrigation area, and solving the problems of excessively high groundwater levels and heavy soil salinization. At the same time, in conjunction with the groundwater forced drainage structure in the areas where secondary salinization occurs strongly, the groundwater in the salinized land is forced to be discharged to the drainage structure for export, further reducing the groundwater level and soil salinity in the salinized land, which is particularly suitable for the management and control of salinized land in irrigation areas, especially the soil management in pumping irrigation areas. At the same time, considering that the construction area is located in silt sand and sandy loam, which is prone to sand flow and sudden surges, the present embodiment performs precipitation construction during the excavation construction process to ensure slope stability and construction safety, and prevents channel excavation from damaging channels and farmland roads.

[0089] In addition, the embodiment of the present invention also provides a method for determining construction parameters through numerical simulation, and optimizes the culvert depth (or channel depth), and the number and location of precipitation wells in salinized areas. In the optimization process, the principles of reducing the culvert depth h (h ≥ 0), reducing the number of precipitation wells, and improving the rationality of the distribution of precipitation wells are adopted. For the parent and child individuals, the fitness evaluation is performed by the balance of the drainage volume of each well during the simulation process, and the matching degree between the well density and the drainage volume to be discharged, which is conducive to determining reasonable construction parameters, while ensuring the improvement effect of salinization, and maximizing the utilization rate of equipment and reducing the cost of governance.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A control system for secondary salinization of soil in irrigation areas, characterized in that: include: Groundwater interception and drainage structures located between the area where secondary salinization of the soil occurs and the area where it does not occur in the irrigation area, and groundwater forced drainage devices located in the area where it occurs; The groundwater seepage cut-off structure is lower than the ground surface and extends along the boundary between the occurrence area and the non-occurrence area; the elevation of the non-occurrence area is greater than the elevation of the occurrence area, and the groundwater seepage cut-off structure is used to intercept the groundwater in the non-occurrence area from penetrating into the occurrence area; The groundwater forced drainage device is installed underground in the occurrence area, and is used to discharge the groundwater in the occurrence area to the drainage structure; The drainage structure is lower than the ground surface, and is used to drain the groundwater discharged from the occurrence area and the non-occurrence area into the drainage structure; The groundwater seepage interception structure is a geotextile, the drainage structure is a culvert, and the groundwater forced drainage device includes a plurality of precipitation wells from the ground to the underground, each precipitation well is equipped with a photovoltaic drainage pump; the culvert depth, and the number and location of the precipitation wells are determined by the following method: Determine the value range of culvert depth [h min ,h max ] and the number of precipitation wells in the occurrence area [N min ,N max ], and the culvert depth and N max Initialize the positions of the precipitation wells to generate the current population of the genetic algorithm; import each individual in the current population into the three-dimensional geological structure model of the irrigation area, and dynamically simulate the groundwater movement under a certain irrigation strategy; when at least two precipitation wells are at the same position, only one well is modeled; during the simulation process, the groundwater level at each spatial position is regularly detected, and if the groundwater level in the influence area of ​​a certain precipitation well is lower than the set threshold, the precipitation well is stopped; when the groundwater level in the area is higher than the set threshold again, the precipitation well is restarted; Determine whether the simulation results of each individual meet the optimal goal. If not, The function selects multiple individuals as parent individuals and mutates multiple offspring individuals; merges each parent individual and each offspring individual into a new individual set, selects multiple optimal individuals from the set as the new current population according to the fitness of each individual, and re-substitutes them into the structural model to perform groundwater dynamic simulation until the simulation result meets the optimal goal; wherein the optimal goal is that the future groundwater level at each spatial position is less than the set threshold; the fitness function for the parent individual is: Where h represents the culvert depth, N represents the number of precipitation wells; x i represents the total drainage of the ith precipitation well, which is obtained by multiplying the drainage flow of the precipitation well by the working time; x represents the standard deviation of the total drainage of each precipitation well, represents the normalized x; w1, w2 and w3 represent three weights respectively, w1+w2+w3=1; The fitness function for offspring individuals is: or in, is the adaptation factor between the distribution of precipitation wells and the distribution of drainage volume, The smaller it is, the better the match between the two. and Respectively represent the normalized precipitation well density and the amount of water to be discharged at the location of the ith precipitation well, N a represents the total number of spatial locations within the occurrence region, and They respectively represent the normalized precipitation well density and the amount of water to be discharged at the j-th spatial position, and the normalization method is maximum normalization or softmax normalization; the precipitation well density is solved in the following way: gradually expand the symmetrical area outward with a spatial position as the center, and when the symmetrical area includes a set number of precipitation wells for the first time, divide the set number by the area of ​​the symmetrical area at this time to obtain the precipitation well density at the spatial position.

2. The system according to claim 1, characterized in that The culvert is buried between the occurrence area and the non-occurrence area, and extends along the boundary direction between the occurrence area and the non-occurrence area; The geotextile is installed on one side of the culvert close to the occurrence area, and extends upward from the bottom of the culvert to the ground.

3. According to the system of claim 2, the radius of the drainage pipe of the culvert must meet the required maximum drainage flow rate.

4. The system according to claim 1, characterized in that A water outlet pipe is connected between the photovoltaic drainage pump and the drainage structure; When the groundwater level in the occurrence area is higher than a set threshold, the photovoltaic drainage pump collects the groundwater and discharges the groundwater to the drainage structure through the outlet pipe.

5. The system according to claim 1, wherein the flow rate of the photovoltaic drainage pump is determined according to the designed runoff depth, drainage area and drainage duration generated by heavy rain.

6. The system according to claim 1, wherein the groundwater in the non-occurrence area is discharged to the drainage structure in an infiltration manner.

7. A method for controlling secondary salinization of soil in irrigation areas, characterized in that: include: Between the area where secondary salinization of the soil occurs and the area where it does not occur in the irrigation area, a groundwater seepage interception structure and a drainage structure are constructed; the groundwater seepage interception structure is lower than the ground surface and extends along the boundary line between the area where secondary salinization occurs and the area where it does not occur; the elevation of the area where secondary salinization does not occur is greater than the elevation of the area where secondary salinization occurs, and the groundwater seepage interception structure is used to intercept the groundwater in the area where secondary salinization does not occur from penetrating into the area where secondary salinization occurs; Install groundwater forced drainage devices in the occurrence area; The groundwater forced drainage device is installed underground in the occurrence area, and is used to discharge the groundwater in the occurrence area to the drainage structure; The drainage structure is lower than the ground surface, and is used to drain the groundwater discharged from the occurrence area and the non-occurrence area into the drainage structure; Wherein, the groundwater seepage interception structure is a geotextile, the drainage structure is a culvert, the groundwater forced drainage device includes a plurality of precipitation wells from the ground to the underground, and each precipitation well is installed with a photovoltaic drainage pump; before the construction of the groundwater seepage interception structure and the drainage structure, it also includes: Determine the value range of culvert depth [h min ,h max ] and the number of precipitation wells in the occurrence area [N min ,N max ], and the culvert depth and N max Initialize the positions of the precipitation wells to generate the current population of the genetic algorithm; import each individual in the current population into the three-dimensional geological structure model of the irrigation area, and dynamically simulate the groundwater movement under a certain irrigation strategy; when at least two precipitation wells are at the same position, only one well is modeled; during the simulation process, the groundwater level at each spatial position is regularly detected, and if the groundwater level in the influence area of ​​a certain precipitation well is lower than the set threshold, the precipitation well is stopped; when the groundwater level in the area is higher than the set threshold again, the precipitation well is restarted; Determine whether the simulation results of each individual meet the optimal goal. If not, select multiple individuals as parent individuals according to the fitness function, and mutate multiple offspring individuals; merge each parent individual and each offspring individual into a new individual set, select multiple optimal individuals from the set as the new current population according to the fitness of each individual, and re-substitute them into the structural model to perform groundwater dynamic simulation until the simulation results meet the optimal goal; wherein the optimal goal is that the future groundwater level at each spatial position is less than the set threshold; the fitness function for the parent individual is: Where h represents the culvert depth, N represents the number of precipitation wells; x i represents the total drainage of the ith precipitation well, which is obtained by multiplying the drainage flow of the precipitation well by the working time; x represents the standard deviation of the total drainage of each precipitation well, represents the normalized x; w1, w2 and w3 represent three weights respectively, w1+w2+w3=1; The fitness function for offspring individuals is: or in, is the adaptation factor between the distribution of precipitation wells and the distribution of drainage volume, The smaller it is, the better the match between the two. and Respectively represent the normalized precipitation well density and the amount of water to be discharged at the location of the ith precipitation well, N a represents the total number of spatial locations within the occurrence region, and They respectively represent the normalized precipitation well density and the amount of water to be discharged at the j-th spatial position, and the normalization method is maximum normalization or softmax normalization; the precipitation well density is solved in the following way: gradually expand the symmetrical area outward with a spatial position as the center, and when the symmetrical area includes a set number of precipitation wells for the first time, divide the set number by the area of ​​the symmetrical area at this time to obtain the precipitation well density at the spatial position.

8. The method according to claim 7, characterized in that The construction of groundwater interception and drainage structures between the area where secondary salinization of the soil occurs and the area where it does not occur in the irrigation area includes: Digging trenches between areas where secondary salinization of the irrigated soil occurs and areas where it does not occur; Install the culvert at the bottom of the channel, and vertically lay the geotextile on the downstream side of the culvert; After paving is completed, earth backfill is carried out above the culvert.

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