CN110771291B - Covering layer partitioning method for improving leaching and salt discharging efficiency - Google Patents
Covering layer partitioning method for improving leaching and salt discharging efficiency Download PDFInfo
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- 150000003839 salts Chemical class 0.000 title claims abstract description 75
- 238000002386 leaching Methods 0.000 title claims abstract description 46
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000000638 solvent extraction Methods 0.000 title claims abstract description 12
- 238000007599 discharging Methods 0.000 title claims description 8
- 239000002689 soil Substances 0.000 claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
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- 239000003513 alkali Substances 0.000 claims abstract description 19
- 238000011049 filling Methods 0.000 claims abstract description 17
- 239000012466 permeate Substances 0.000 claims description 20
- 238000011033 desalting Methods 0.000 claims description 12
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
- A01B79/00—Methods for working soil
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
- A01B77/00—Machines for lifting and treating soil
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- Processing Of Solid Wastes (AREA)
Abstract
本发明公开了一种提高淋洗排盐效率的覆盖层分区方法，包括：(1)测量目标脱盐地块盐碱土渗透系数K；(2)根据渗透系数K，调配n种渗透系数不同的改性渗透介质；(3)根据排盐系统间距，在目标地块表面横向布设覆盖层网格，所述覆盖层网格分为n块渗透介质填充区，向填充区中填充改性渗透介质，根据填充区与暗管距离的增加，渗透介质的渗透系数依次增大；(4)对目标脱盐地块盐碱土进行排水淋洗；(5)脱盐完成后，回收覆盖层进行二次利用。本发明一方面使土壤表面入渗强度均衡分布，缩短淋洗脱盐周期和减少淋洗总水量；另一方面脱盐过程中不必渐进式淋洗，淋洗周期内始终保持淋洗场地完全淹没，方便淋洗措施的实施。
The invention discloses a covering layer partitioning method for improving the efficiency of leaching and salt removal, comprising: (1) measuring the permeability coefficient K of the saline-alkali soil of a target desalination block; (3) According to the distance between the salt discharge system, an overburden grid is arranged laterally on the surface of the target plot, and the overburden grid is divided into n permeable medium filling areas, and the modified permeable medium is filled into the filling area, According to the increase of the distance between the filling area and the hidden pipe, the permeability coefficient of the permeable medium increases sequentially; (4) Drainage and leaching the saline-alkali soil of the target desalination block; (5) After the desalination is completed, the covering layer is recovered for secondary use. On the one hand, the invention makes the infiltration intensity of the soil surface evenly distributed, shortens the leaching and demineralization period and reduces the total amount of leaching water; Facilitate the implementation of rinsing measures.
Description
Technical Field
The invention relates to a method for improving leaching and salt-removing efficiency, in particular to a covering layer partitioning method for improving leaching and salt-removing efficiency.
Background
Soil degradation is a potential threat to human survival, and soil salinization is a common soil degradation mode. According to the data in 2003, the total area of the saline-alkali soil in the world is 955 km2And accounts for about 10% of the total land area worldwide. The salinization problem of cultivated land in China is particularly serious, and the total area of the saline-alkali land in China is counted to be about 3.6 hundred million mu, which occupies 1/5 of the arable land area in China. Excessive salt accumulation on the surface of soil particles can change the physicochemical properties of soil, affect crop growth and ecological balance, and cause serious environmental and economic risks.
Flood irrigation drainage leaching systems (either underdrains or open channels) are an improved method of salt-alkali soil in widespread use throughout the world. In the soil leaching process, fresh water or reclaimed water is delivered to the soil surface in a flood irrigation mode, so that the soil surface is submerged to a certain degree. Under the action of the downward water flow, the saline water is mixed with the water flow and is washed towards the deep soil, and finally is discharged along with the water flow through the concealed pipe or the open channel. In fact, the rate of salt leaching is largely dependent on the soil surface infiltration intensity, without considering soil salt retention. The higher the infiltration strength, the faster the elution rate. However, according to the water quantity required by the unit area of the field for leaching, leaching efficiency is represented, and researches show that spatial differences exist in the distribution of field infiltration strength in the process of flood irrigation and leaching, namely the infiltration strength is higher at a position closer to a salt discharge system, and is lower at a position farther from the salt discharge system, and the difference of the infiltration strength is usually up to 1-2 orders of magnitude, so that the area near the salt discharge system is excessively leached, the area far from the salt discharge system is not sufficiently leached, the flood irrigation and leaching efficiency is reduced, and the consumption of fresh water resources is increased.
In order to increase the washing efficiency of the salt discharge system, a progressive washing method was proposed since the last 50 th century. The gradual leaching is to leach an area far away from the salt discharge system, and then gradually enlarge the leaching range until the soil surface is completely submerged. From the analysis and calculation perspective, Yongsi and the like in the early century of this century quantitatively discuss the rationality and effectiveness of the progressive leaching method. However, the progressive washing method is complex to implement, and needs to change the soil submerging range in the washing process, so that the automation degree is low, and the large-scale integrated operation is not facilitated.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a covering layer partitioning method which has uniform infiltration, short leaching period and improved leaching efficiency of a salt discharge system.
The technical scheme is as follows: the invention relates to a covering layer partitioning method for improving leaching and salt discharging efficiency, which comprises the following steps:
(1) measuring the permeability coefficient K of the saline-alkali soil of the target desalting land block;
(2) according to the permeability coefficient K, n kinds of modified permeation media with different permeability coefficients are prepared, and the permeability coefficients are respectively K1、K2、K3……Kn，n≥3；
(3) According to the distance between the salt removal systems, covering layer grids are transversely arranged on the surface of the target land, the covering layer grids are divided into n penetrating medium filling areas, n kinds of modified penetrating media in the step (2) are filled into the filling areas, and according to the increase of the distance between the filling areas and the salt removal systems, the penetrating coefficients of the penetrating media are sequentially increased;
(4) draining and leaching the saline-alkali soil of the target desalting land block;
(5) and after the desalting is finished, recovering the covering layer for secondary utilization.
The salt discharge system is a concealed conduit salt discharge system or an open channel salt discharge system. When the salt discharge system is an open channel salt discharge system, the permeable medium filling area is arranged between adjacent open channels, and the edge of the permeable medium filling area is provided with a water retaining weir.
Preferably, the following steps are carried out before (1): and (3) selecting a target desalting land, burying a plurality of salt discharging and salt discharging systems (concealed pipes or open channels) at equal intervals, and directly entering (1) if the salt discharging systems exist in the field.
Preferably, the following steps are carried out before (1): and ploughing, loosening and leveling the surface soil according to the target depth of desalination.
Preferably, in the step (1), the diameter of the hidden pipe can be 10-20cm, the burial depth D of the hidden pipe can be 0.6-2.0 m, and the gradient of the hidden pipe can be 1-2.5%.
Preferably, in the step (1), the excavation depth of the open channel is 1m-2.5m, the slope of the side slope of the open channel is 45% -30%, and the slope of the bottom of the open channel can be 1% -2.5%.
Preferably, in the step (1), the distance L between the concealed conduit salt elimination systems is selected according to specific topographic and geological conditions or a reference specification part 2 of technical specification for improving saline-alkali soil by a salt elimination system: the empirical formula in planning design and implementation is as follows: l ═ gamma · KsD/100, wherein KsIs the saturated permeability coefficient, cm/d; d is the buried depth of the salt removing system, cm; gamma is empirical coefficient, clay is 40, loam is 30, sand is 20.
Preferably, in the step (1), the distance L between the open channel salt discharge system and the open channel salt discharge system is selected according to specific topographic and geological conditions, wherein the selectable range of clay foundations is 40-100 m, the selectable range of loam foundations is 100-150 m, and the selectable range of sandy soil foundations is 150-300 m
In (1), the permeability coefficient K of the saline-alkali soil is an average value of a plurality of sampling points which are equidistantly distributed in the horizontal direction and the vertical direction.
The filling areas are symmetrically arranged left and right by taking a single concealed pipe or an open channel of the salt discharging system as a center.
Preferably, in (2), the permeation is modifiedLog of ratio of permeability coefficient of medium to permeability coefficient of saline-alkali soil10(KnThe value range of/K) is as follows: -3 to 4.
Preferably, different logs10(Knand/K) equally dividing the value range according to the number of the partitions.
The proportion of each component in the modified osmotic medium mixed material is changed according to the osmotic coefficient.
Preferably, in (3), the overlay layer grid is divided into n permeable medium filled areas, and the width of each permeable medium filled area is L/2n, wherein L is the distance between two adjacent salt discharge systems.
And the covering layer grid walls of the adjacent permeable medium filling areas are made of permeable materials.
And a screen is arranged at the bottom of the covering layer grid.
Preferably, in the step (4), the depth of the submerged water on the surface of the desalted land can be selected from 5cm to 10cm, and the mineralization degree of the leaching water is not more than 2 mg/g.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
(1) the subarea covering layer adopted by the invention inhibits the area with high infiltration strength of the field surface, strengthens the area with low infiltration strength, ensures that the infiltration strength of the soil surface is uniformly distributed, is favorable for uniformly leaching salt in the whole desalting field range, improves the utilization rate of fresh water or reclaimed water, and has water-saving efficiency of about 70-80%;
(2) the zonal covering layer adopted by the invention increases the infiltration strength of the soil surface in the area far away from the salt discharge system, accelerates the leaching period of the salt discharge system, and has the period reduction rate of 65-75%;
(3) the invention can ensure that the surface of the desalted soil can be completely submerged and leached at one time in the leaching process of the salt discharge system, and the soil submerging range is not required to be changed by extra measures, thereby facilitating the implementation of leaching measures;
(4) when the leaching process is temporarily stopped (such as extreme evaporation weather conditions, blockage of a water pipeline and completion of desalination), the partitioned covering layer on the soil surface can effectively reduce the evaporation of water on the soil surface, slow down the formation process of a non-saturated zone on the soil surface and effectively inhibit the phenomenon of capillary negative pressure salt return;
(5) the partition covering layer can be paved and recovered through machinery, large-scale integrated operation is facilitated, and subsequent agricultural planting and natural drainage processes are not affected.
Drawings
FIG. 1 is a schematic diagram of the seepage of a concealed conduit salt discharge system without a zoned cover layer;
FIG. 2 is a schematic diagram of the seepage of an open channel salt rejection system without a zoned cover;
FIG. 3 is a cross-sectional seepage diagram of example 1;
FIG. 4 is a cross-sectional seepage diagram of example 2;
FIG. 5 is a graph showing the variation of the infiltration amount per unit area of the soil surface in example 1;
fig. 6 is a simulation of total water infiltration distribution in example 1.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
Example 1
FIG. 1 shows a desalination plot without zone cover, in this embodiment the salt rejection system is a closed conduit salt rejection system, which includes a closed conduit 10 and a desalination plot 12, where the groundwater flow line 13 of the salt rejection system is in the shape shown in the figure.
FIG. 3 shows the desalted land after the formation of zone cover, where n is 4. Including concealed conduits 10, desalination plots 13, screens 112, zonal covers, ground water flow lines (with no zonal covers) 141, and ground water flow lines (with zonal covers) 142. The partitioned overlay comprises an overlay mesh 111, K1Permeable Medium filled regions 121, K2Permeate media fill zones 122, K3Permeate media fill regions 123, K4The infiltration medium fills region layer 124.
The method for partitioning the cover layer to improve the salt leaching efficiency is further described with reference to fig. 3:
firstly, a modified saline-alkali soil 13 is selected, and a plurality of salt drainage concealed pipes 10 with equal intervals are buried. Particularly, the diameter of the hidden pipe can be 8-20 cm, and the hidden pipe is buriedThe depth D can be 0.6-2.0 m, and the gradient of the concealed pipe can be 1-2.5%; the interval L of the concealed conduits is selected according to specific topographic and geological conditions or a reference specification, part 2 of technical rules for concealed conduit improvement of saline-alkali soil: the empirical formula in planning design and implementation is as follows: l ═ gamma · KsD/100, wherein KsIs the saturated permeability coefficient, cm/d; d is the buried depth of the concealed pipe, cm; gamma is empirical coefficient, clay is 40, loam is 30, sand is 20.
Then, the following steps are carried out:
(1) according to the target depth of desalination, turning, loosening and leveling the surface soil to ensure the uniformity of surface soil particles and remove pore dead zones, increase the porosity and reduce capillary negative pressure; particularly, the permeability coefficient K of the saline-alkali soil is the average value of a plurality of sampling points, wherein the distance between the horizontal sampling points is L/16cm, and the range is the target desalting plot; the distance between the vertical sampling points is 20 cm-40 cm, and the range is 0 cm-500 cm from the ground surface.
(2) Preparing four modified permeation media according to the permeability coefficient K of the saline-alkali soil, wherein the permeability coefficient of each permeation medium is K1、K2、K3And K4(ii) a Particularly, the value ranges of the corresponding permeability coefficients of the four modified permeation media are log respectively10(K1/K)＝-3～2,log10(K2/K)＝-1.5～0.5,log10(K3(ii) 1-0 and log ═ K-10(K4and/K) 1-4, wherein the modified permeation medium is river sand, clay, loam, fly ash, gypsum powder and other materials which are mixed according to a certain proportion, and the proportion of each component can be changed according to the permeability coefficient.
(3) The prefabricated overlay mesh 111 is laid according to the interval of the concealed pipes, wherein the bottom of the overlay mesh 111 is provided with a screen 112 to prevent the mixing of the packing materials and facilitate the recycling of the packing materials. Modified osmotic medium K by using construction machinery1、K2、K3And K4Sequentially filled to K1Permeate medium filled region 121, K2Permeate medium fill zone 122, K3Permeate media fill region 123, K4Permeate medium fill region 124.
(4) Using oresAnd water with the degree of dissolution not more than 2mg/g is used as a rinsing water source to submerge the surface of the desalted land block to 5cm-10 cm. In the drain rinsing process, the partition is covered with a layer K1The permeable medium filled region 121 is filled with a porous medium having a lower permeability coefficient, thereby reducing the surface infiltration strength of the region, while the porous medium having a higher permeability coefficient is disposed away from the concealed conduit region, resulting in the convergence of the surface water flow of the lateral blanket to the higher permeability filled region, increasing the surface infiltration strength of these regions. On the other hand, K1The infiltration medium filled area 121 is decreased in infiltration amount, resulting from K2Permeate medium fill zone 122, K3Permeate media fill region 123, K4The subsurface flow line 142 of the permeate filled region 124 may flow laterally to the closed conduit. Compared with the underground water flow line 141, the zonal coverage enhances the cross flow effect, and the cross flow reduces the water flow seepage path and accelerates the discharge of salt into the concealed conduit. In addition, when the leaching process is temporarily stopped (such as extreme evaporation weather conditions, blockage of a water pipeline and completion of desalination), the partitioned covering layer on the soil surface can effectively reduce the evaporation of water on the soil surface, slow down the formation process of a soil surface unsaturated zone and effectively inhibit the phenomenon of capillary negative pressure salt return.
(5) And after the desalting is finished, recovering the partitioned covering layer for secondary utilization.
In order to show that the partitioned covering layer designed by the invention can improve the leaching desalination efficiency of the concealed conduit salt discharge system, the surface infiltration amount, the leaching period and the total leaching water amount under the two conditions of setting and not setting the partitioned covering layer are compared by using a numerical simulation mode.
Example 2
Fig. 2 shows a desalination plot without zone cover, in this embodiment the salt discharge system is an open channel salt discharge system, which includes an open channel 20, a desalination plot 14 and a weir 11, and the groundwater flow line 15 of the salt discharge system is in the shape shown in the figure.
Fig. 4 shows the desalted land after the formation of the partitioned cover layer, where n is 4. Including screen 212, zoned overlay. The partitioned overlay includes an overlay mesh 211, K1Permeate medium fill regions 221, K2Permeate media fill region 222, K3Permeate media filled zone223、K4The infiltration medium fills region layer 224. The groundwater flow line 16 of the salt discharge system now takes the shape of the figure.
Firstly, the improved saline-alkali land 14 is selected, the salt-draining open channel 20 is excavated or the existing channel is reconstructed, and the open channel drainage system is arranged. The open channel excavation depth is 1m-2.5m, and the slope of the open channel side slope is 45% -30%. The distance L between the two open channels is selected according to specific topographic and geological conditions, the clay foundation can be selected within the range of 40m-100m, the loam foundation can be selected within the range of 100m-150m, and the sandy soil foundation can be selected within the range of 150m-300 m. And arranging a water retaining weir at the position of the covering layer to be paved at the edge of the open channel.
Then, the following steps are carried out:
(1) same as in example 1, step (1);
(2) preparing four modified permeation media according to the permeability coefficient K of the saline-alkali soil, wherein the permeability coefficient of each permeation medium is K1、K2、K3And K4(ii) a Particularly, the value ranges of the corresponding permeability coefficients of the four modified permeation media are log respectively10(K1/K)＝-2--1,log10(K2/K)＝-1-0,log10(K3K) ═ 0-1 and log10(K4The modified penetrating medium is river sand, clay, loam, fly ash, gypsum powder and other materials mixed in certain proportion, and the proportion of each component may be changed based on the penetrating coefficient.
(3) Steps (3) to (5) are the same as those in steps (3) to (5) of example 1.
The subarea covering layer adopted by the invention inhibits the area with high infiltration strength of the field surface, strengthens the area with low infiltration strength, ensures that the infiltration strength of the soil surface is uniformly distributed, is favorable for uniformly leaching salt in the whole desalting field range, improves the utilization rate of fresh water or reclaimed water, and has water-saving efficiency of about 70-80%; the zonal covering layer adopted by the invention increases the infiltration strength of the soil surface in the area far away from the salt discharge system, accelerates the leaching period of the salt discharge system, and has the period reduction rate of 65-75%; the invention can ensure that the surface of the desalted soil can be completely submerged and leached at one time in the leaching process of the salt discharge system, and the soil submerging range is not required to be changed by extra measures, thereby facilitating the implementation of leaching measures; when the leaching process is temporarily stopped (such as extreme evaporation weather conditions, blockage of a water pipeline and completion of desalination), the partitioned covering layer on the soil surface can effectively reduce the evaporation of water on the soil surface, slow down the formation process of a non-saturated zone on the soil surface and effectively inhibit the phenomenon of capillary negative pressure salt return; the partition covering layer can be paved and recovered through machinery, large-scale integrated operation is facilitated, and subsequent agricultural planting and natural drainage processes are not affected.
Taking example 1 as an example, numerical simulations were performed using groundwater seepage and solute transfer processes in the SUTRA software package.
According to the field survey data of the east region of the Chongming island, the permeability coefficient of the desalted land is 1m/D, the porosity is 0.3, and the longitudinal dispersion coefficient DL0.1m, transverse diffusion coefficient DT0.01m, and the initial concentration of groundwater in aquifer is 10kg/m3. The buried depth of the concealed pipes is 1m, the diameter of the concealed pipes is 8cm, the distance between the concealed pipes is 20m, the water-impermeable layer is-5 m, and the fixed water head on the soil surface is 5cm high. Since the groundwater flow is distributed symmetrically about the concealed pipe, half of the model was chosen for numerical simulation, the size of the model being 10m x 5 m. Numerical simulation 1 (hereinafter referred to as simulation 1) represents a case where the partition covering layer is not provided, and numerical simulation 2 (hereinafter referred to as simulation 2) represents a case where the partition covering layer is provided. Wherein each permeability coefficient of the covering layer of the numerical simulation subarea is K1＝0.01m/d，K2＝0.1m/d，K31m/d and K410m/d, i.e. log10(K1/K)＝-2,log10(K2/K)＝-1,log10(K3K) ═ 0 and log10(K4/K)＝1。
Fig. 5 is a graph showing the variation tendency of infiltration per unit area of soil surface, with the solid line representing simulation 1 and the dotted line representing simulation 2. As shown by the solid line, the unit infiltration intensity of the soil surface at the position near the concealed conduit is quite large, which indicates that the water flow velocity of the area is large, the salt scouring capability is strong, and the salt can be quickly washed into the concealed conduit. Along with the increase of the distance from the hidden pipe, the unit infiltration strength of the soil surface is sharply reduced by 1-2 orders of magnitude, which indicates that the flow velocity of infiltration water flow in the area far away from the hidden pipe is small, and the salt scouring energy is reducedInsufficient force resulted in a slow downward elution of salt in the region between the two closed tubes. The huge difference of the spatial distribution of the unit infiltration strength delays the leaching desalination period on one hand, and on the other hand, the high-strength infiltration is carried out in an area close to the concealed pipe for a long time, so that the salt scouring efficiency of unit water volume is reduced, and the utilization rate of water resources is reduced. As shown by the dotted line, at a position near the dark tube (e.g., K)1Osmotic agent filled region 121) had a sharp drop in unit infiltration strength compared to numerical simulation 1 in this region due to the inhibition of infiltration by the zoned coating. While the permeability coefficient of the permeable medium in each partition along the direction far away from the concealed conduit is distributed in a manner of increasing by one order of magnitude, resulting in the convergence of the water flow on the surface of the transverse covering layer to a higher permeability filling area, increasing K2Permeate medium fill zone 122, K3Permeate media fill region 123, K4The surface infiltration strength of the osmotic agent-filled zone 124, thereby shortening the leaching cycle.
Fig. 6 shows the distribution of total water volume of four subareas during the whole desalting period in the two modes of simulation 1 and simulation 2. Simulation 1 at K1The total infiltration amount of the infiltration medium filling area 121 reaches approximately 8.3m3/m2Occupying 80% of the total infiltration of the soil surface, and K2Permeate medium fill zone 122, K3Permeate filled regions 123 and K4The total infiltration amount of the permeable medium filled region 124 is 1.3m3/m2,0.5m3/m2And 0.3m3/m2The distribution accounts for 12%, 5% and 3% of the total infiltration amount on the soil surface. And in simulation 2, K1Permeate medium filled region 121, K2Permeate medium fill zone 122, K3Permeate filled regions 123 and K4The total infiltration amount of the infiltration medium filling area 124 is 0.31m3/m2,0.83m3/m2,0.84m3/m2And 0.41m3/m2Which respectively account for 13%, 34%, 36% and 17% of the total infiltration amount of the soil surface. According to the data, the infiltration total amount of the simulation 2 is saved by 77% compared with that of the simulation 1, the distribution of the infiltration amount of each sub-filling area is more balanced, the salt is enabled to be uniformly leached downwards, and the leaching efficiency is improved.
Claims (10)
1. A covering layer partitioning method for improving the salt leaching and discharging efficiency is characterized by comprising the following steps:
(1) measuring the permeability coefficient K of the saline-alkali soil of the target desalting land block;
(2) according to the permeability coefficient K, n kinds of modified permeation media with different permeability coefficients are prepared, and the permeability coefficients are respectively K1、K2、K3……Kn，n≥3；
(3) According to the distance between the salt removal systems, covering layer grids are transversely arranged on the surface of the target land, the covering layer grids are divided into n penetrating medium filling areas, n kinds of modified penetrating media in the step (2) are filled into the filling areas, and according to the increase of the distance between the filling areas and the salt removal systems, the penetrating coefficients of the penetrating media are sequentially increased;
(4) draining and leaching the saline-alkali soil of the target desalting land block;
(5) and after the desalting is finished, recovering the covering layer for secondary utilization.
2. The overburden partitioning method for improving the efficiency of leaching salt rejection of claim 1, wherein said salt rejection system is a closed conduit salt rejection system.
3. The overburden partitioning method for improving stripping salt efficiency of claim 1 wherein said salt rejection system is an open channel salt rejection system.
4. The method of claim 3, wherein the permeate-filled region is disposed between two adjacent channels.
5. The method of claim 4, wherein the permeable media-filled region is provided with a water dam at the edge thereof.
6. The overburden partitioning method for improving the efficiency of leaching salt rejection of claim 1 wherein said salt rejection system is a combination concealed conduit and open channel salt rejection system.
7. The overburden partitioning method for improving the efficiency of leaching reject salts as recited in claim 1 wherein in (1) the permeability coefficient K of the saline alkali soil is an average of a plurality of sampling points that are equally spaced horizontally and vertically.
8. The method of claim 1, wherein the fill zones are arranged side-to-side symmetrically about a single closed conduit or open channel of the salt rejection system.
9. The method of claim 1, wherein the walls of the cells of the cover layer adjacent the packed region of permeable medium are permeable to water.
10. The method of claim 1, wherein a screen is placed on the bottom of the grid of the cover layer.
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