Yellow River silt slurry filling reclamation anti-clogging geotechnical cloth sand blocking and drainage method

Abstract

The invention provides a Yellow River silt slurry filling reclamation anti-clogging geotechnical cloth sand blocking and drainage method, and relates to the technical field of mine land reclamation and ecological restoration. The method comprises the following steps: mounting geotechnical cloth at a drainage section of Yellow River silt slurry filling reclamation; in the Yellow River silt slurry filling reclamation drainage process, vibration is applied to the geotechnical cloth, fine-particle silt remaining in pores of the geotechnical cloth is subjected to inertial separation, and therefore the fine-particle silt is prevented from blocking a drainage channel, and interception and smooth drainage of the fine-particle silt are achieved. According to the method, the geotextile is vibrated, the drainage speed can be stabilized while suspended silt is intercepted, and the drainage efficiency of the system is improved. The invention provides a practical and effective solution, and further promotes the development of the Yellow River sediment filling reclamation technology.

Description

Technical Field

[0001] The invention belongs to the technical field of mine land reclamation and ecological restoration, and particularly relates to a method for blocking and draining sand using a geotextile for filling and reclamation of Yellow River sediment slurry. Background Art

[0002] The impact of coal mining on land resources, especially arable land resources, is becoming increasingly serious, and the management of coal mining subsidence has become an urgent problem to be solved. Traditional management methods, such as filling with materials such as fly ash and coal gangue, can restore the surface morphology and land function to a certain extent, but the limited quantity of these materials and the potential risk of environmental pollution limit their wider application. In this context, the use of Yellow River silt for filling and reclamation has become an attractive alternative. Compared with traditional materials, Yellow River silt has the characteristics of fine particles and no pollution, especially the rich silt resources on the main canal, and its accumulation often causes blockage of the river. By using these silts to fill coal mining subsidence, not only can the problems of river siltation and silt accumulation occupying land be effectively solved, but also the reclamation of land damaged by coal mining can be achieved, which has significant dual benefits.

[0003] However, despite the potential of this method, it still faces many technical challenges in actual operation. The filled sediment contains a lot of water, and it is necessary to reduce the moisture content through reasonable drainage methods in order to further construct and reclaim it into arable land. If the drainage is directly carried out by excavating a drainage outlet on the end dike of the reclamation strip, although the drainage can be rapid, it will also cause the nutrient-rich fine-grained part of the sediment to be lost with the water, thereby affecting the permeability, water retention and fertilizer retention of the filled sediment layer. In addition, this direct drainage method is also prone to siltation of drainage ditches. What is more difficult is that due to the obstruction of the end dike, the water in the supersaturated sediment can only be discharged vertically, resulting in low drainage efficiency, prolonged reclamation period, and affecting the reclamation effect. Therefore, it is urgent to develop new technical methods that can not only effectively solve the problem of sediment loss, but also improve drainage efficiency and shorten the reclamation period, thereby promoting the large-scale application of the Yellow River sediment filling reclamation technology.

[0004] Previous studies have shown (Hu Zhenqi and Wang Peijun, 2018) (CN201610692862.4) that needle-punched non-woven geotextiles have certain potential in the Yellow River sediment filling and reclamation project, especially in controlling the loss of fine particles and promoting lateral drainage. However, practical applications have revealed that geotextiles are prone to clogging, which not only requires that the geotextile material must have a good balance between soil retention and water permeability, but also requires full consideration of the anti-clogging characteristics under dynamic soil and water pressure conditions during design. Although existing standards provide a basis for selection, such as ensuring the appropriate range of equivalent pore size, permeability coefficient and gradient ratio, in actual operation, the performance degradation and clogging of geotextiles under high soil and water pressure have become a technical bottleneck. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the present invention provides a method for intercepting and draining sand using geotextiles to prevent blockage in the reclamation of Yellow River sediment slurry. The geotextile is installed at the drainage section and vibration is applied to the geotextile to achieve stable drainage of the entire section of the geotextile side. The method of the present invention can stabilize the drainage speed while intercepting suspended sediment, thereby improving the drainage efficiency of the system. The method is particularly suitable for the Yellow River sediment filling and reclamation area in the coal mining subsidence area in the Yellow River basin.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a Yellow River sediment slurry filling reclamation anti-clogging geotextile sand interception and drainage method, comprising the following steps:

[0009] Install geotextiles at the drainage section of the Yellow River silt slurry filling and reclamation;

[0010] During the Yellow River sediment slurry filling and reclamation drainage process, the geotextile is vibrated to separate the fine sediment particles remaining in the pores of the geotextile by inertia, thereby preventing the fine sediment particles from blocking the drainage channel and achieving interception of the fine sediment particles and smooth drainage.

[0011] In some embodiments, the specific steps of installing the geotextile include:

[0012] A fixing pile is set at intervals of 1.5 to 2 meters along the drainage direction perpendicular to the drainage direction at the drainage section, and the geotextile is laid flatly on one side of the wire mesh used to support the geotextile, and the wire mesh is located on the drainage side of the geotextile. The geotextile and the wire mesh are fixed to the fixing piles by pressure strips and rivets to complete the installation of the geotextile.

[0013] In some embodiments, the mesh has an aperture of 2 cm to 5 cm.

[0014] In some embodiments, vibration is applied to the geotextile in any of the following two ways:

[0015] Method 1: Install an automatic beating device according to site conditions, and use the beating components of the automatic beating device to beat the surface of the geotextile, with the beating direction being consistent with the normal direction of the geotextile;

[0016] Method 2: manually use a handheld beating component to beat the surface of the geotextile, and the beating direction is consistent with the normal direction of the geotextile.

[0017] In some embodiments, the hammering component is a mallet, and the number of the mallets can be determined according to the spacing between the fixed piles; the weight of a single mallet is controlled at 0.5kg to 5kg, the amplitude is controlled at 20mm to 100mm, and the hammering frequency is controlled at (1,30] times / minute.

[0018] In some embodiments, the sand-trapping and drainage method further includes screening the geotextile according to the particle size of the Yellow River silt filled before installing the geotextile, and the specific steps are as follows:

[0019] An evaluation index system is constructed based on the permeability, soil retention and anti-clogging properties of geotextiles, each performance includes at least one evaluation index, and multiple geotextiles to be screened are measured to obtain the original values ​​of each evaluation index of each geotextile to be screened;

[0020] Standardizing the obtained original values ​​of the evaluation indicators to eliminate the dimensional differences between different evaluation indicators;

[0021] The entropy weight method is used to determine the weight of each evaluation index;

[0022] The comprehensive performance scores of various geotextiles are calculated according to the weights of the evaluation indicators and the standardized processing results, and the geotextile with the highest comprehensive performance score is selected for the Yellow River silt slurry filling, reclamation and drainage project.

[0023] In some embodiments, the permeability evaluation index is the permeability coefficient of the geotextile and the change in the permeability coefficient under the maximum vertical pressure borne by the geotextile during drainage;

[0024] The soil retention evaluation index is the equivalent pore size of the geotextile;

[0025] The evaluation indexes of the anti-blocking property are the gradient ratio of the geotextile and the sediment retention rate of the geotextile. The sediment retention rate is defined as the percentage of the volume of the pores of the geotextile filled with sediment particles to the total volume of the pores of the geotextile.

[0026] In some embodiments, the permeability coefficient is set as a positive indicator, the permeability coefficient change, gradient ratio and sediment retention rate are set as negative indicators, and the equivalent pore size is set as an intermediate indicator; the formula used for standardizing each evaluation indicator is:

[0027]

[0028] In the formula, x ijis the original value of the jth evaluation index of the i-th geotextile to be screened, j = 1, 2, ..., n, n is the number of evaluation indicators, n = 5, j is 1, 2, 3, 4, 5, which correspond to the permeability coefficient, the change of permeability coefficient under the maximum vertical pressure of the geotextile during drainage, the equivalent pore size, the gradient ratio and the sediment retention rate, i = 1, 2, ..., m, m is the total number of geotextiles to be screened; x' ij is the standardized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened; a is the reference value, which is taken as the characteristic particle size d of the Yellow River sediment 85 , that is, the maximum particle size with a cumulative distribution of 85% in the sediment particle size distribution curve;

[0029] In some embodiments, the weight of each evaluation index is calculated as follows:

[0030]

[0031] In the formula, w j is the weight corresponding to the jth evaluation index; e j is the entropy value corresponding to the jth evaluation index; p ij is the probability of the normalized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened; ij is the original value of the jth evaluation index of the i-th geotextile to be screened, j = 1, 2, ..., n, n is the number of evaluation indicators, n = 5, j is 1, 2, 3, 4, 5, which correspond to the permeability coefficient, the change of permeability coefficient under the maximum vertical pressure of the geotextile during drainage, the equivalent pore size, the gradient ratio and the sediment retention rate, i = 1, 2, ..., m, m is the total number of geotextiles to be screened; x' ij It is the standardized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened.

[0032] In some embodiments, the comprehensive performance score of the geotextile is calculated according to the following formula:

[0033]

[0034] In the formula, w j is the weight of the jth evaluation index; γ i is the comprehensive performance score of the i-th geotextile to be screened.

[0035] Features and beneficial effects of the present invention:

[0036] The present invention can intercept suspended sediment and stabilize the drainage rate by applying vibration to the geotextile, thereby improving the drainage efficiency of the system. By applying existing engineering equipment or simple manual intervention, the accumulation of sediment on the surface of the geotextile is successfully prevented, ensuring the smooth flow of the drainage system. In addition, the method of the present invention also screens the geotextile according to the particle size of the filled Yellow River sediment, selects the geotextile with the best comprehensive performance, and further ensures the drainage efficiency. This method effectively improves the efficiency of the Yellow River sediment slurry filling and reclamation, and is suitable for a wide range of reclamation engineering scenarios, especially under conditions of limited equipment, and can still provide significant technical advantages. Under the existing equipment and technical conditions, the present invention provides a practical and effective solution, which further promotes the development of the Yellow River sediment filling and reclamation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of installing a geotextile at a drainage section and beating it with a mallet in the sand-trapping and drainage method provided by an embodiment of the present invention;

[0038] Figure 2 (a) and (b) are schematic diagrams of the installation of the drainage device and geotextile used in the indoor simulation of the drainage process of the Yellow River silt slurry filling and reclamation of coal mining subsidence land by the sand retention and drainage method provided in the embodiment of the present invention.

[0039] Figure 3 This is a diagram to verify the effect of the sand retaining and drainage method of the present invention provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] On the contrary, the present application covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present application as defined by the claims. Further, in order to make the public have a better understanding of the present application, some specific details are described in detail in the detailed description of the present application below. Those skilled in the art can fully understand the present application without the description of these details.

[0042] A method for retaining and draining Yellow River sediment slurry for reclamation and anti-clogging geotextiles includes the following steps:

[0043] Install geotextiles at the drainage section of the Yellow River silt slurry filling and reclamation;

[0044] During the Yellow River sediment slurry filling and reclamation drainage process, the geotextile is vibrated to separate the fine sediment particles remaining in the pores of the geotextile by inertia, thereby preventing the fine sediment particles from blocking the drainage channel and achieving interception of the fine sediment particles and smooth drainage.

[0045] In some embodiments, see Figure 1 , which is a schematic diagram of installing geotextile at the drainage section of the Yellow River silt filling and reclamation. First, according to the drainage section of the cofferdam earth embankment 6 filled and reclaimed by the Yellow River silt filling and reclamation, a geotextile 3 of appropriate size and a wire mesh 2 for supporting the geotextile 3 are cut. The aperture of the wire mesh 2 is preferably [2,5], unit: cm. Then, at the drainage section, a fixing pile 4 is set at intervals of 1.5 meters to 2 meters perpendicular to the drainage direction. The geotextile 3 is flatly laid on the inner side of the wire mesh 2, that is, the wire mesh 2 is located on the drainage side of the geotextile 3, and the geotextile 3 and the wire mesh 2 are fixed to the fixing pile 4 by the pressure strip 4 and the rivet 1 to realize the installation of the geotextile 3 and prevent the displacement of the geotextile 3 in subsequent operations.

[0046] In some embodiments, see Figure 1 During the Yellow River silt filling process, vibration is applied to the surface of the geotextile in either of the following two ways:

[0047] Method 1: Automatic beating method: Determine the appropriate installation position of the automatic beating device according to the site conditions to ensure that it can effectively apply vibration to the geotextile area; then, fix the automatic beating device firmly at the selected position, and use bolts or other methods to prevent the beating device from moving or shaking during operation; then, correctly connect the power supply according to the requirements of the beating device to ensure that the power supply is stable and meets the voltage and current requirements; then, use the beating component 5 of the automatic beating device to beat the surface of the geotextile 3, and the beating direction is consistent with the normal direction of the geotextile 3 (see Figure 1 The surface of the geotextile 3 is beaten with the beating component 5 in the direction of the arrow shown in the figure, that is, in a direction perpendicular to the paper surface) to improve the sediment drainage efficiency; before formal use, testing and debugging are carried out to check the operation of the automatic beating equipment and the vibration effect; finally, after the installation is completed, a safety inspection is carried out to ensure that the automatic beating equipment is firmly installed and there are no safety hazards. At the same time, the surrounding environment is checked and protective measures are taken if necessary.

[0048] Method 2: Manual beating method: Manually hold the beating component 5 to beat the surface of the geotextile 3, and the requirements for the beating direction are the same as those in method 1.

[0049] Furthermore, the hammering components 5 used in the automatic hammering method and the manual hammering method are both mallets, and the number of mallets can be determined according to the spacing between the fixed piles 4; the weight of a single mallet is preferably [0.5, 5] kg, the amplitude is controlled at [20, 100] mm, and the hammering frequency is controlled at (1, 30] times / minute.

[0050] Both of the above methods can achieve the effect of applying vibration to the geotextile, so that the fine particles of sediment adjacent to the upstream side of the geotextile 3 are inertially separated, preventing the fine particles of sediment from accumulating on the surface of the geotextile 3, thereby preventing the fine particles of sediment from remaining in the pores of the geotextile 3 and blocking the drainage channel.

[0051] In some embodiments, the sand-trapping and drainage method provided by the embodiments of the present invention further includes screening the geotextile according to the particle size of the filled Yellow River silt before installing the geotextile, and the specific steps are as follows:

[0052] Firstly, an evaluation index system was constructed. According to the three basic criteria of permeability, soil retention and anti-blocking, a multi-level evaluation index system was established. Among them, the evaluation index of permeability is the permeability coefficient of geotextile (which can be obtained by referring to the standard ASTM D 5493:2023 (Standard Test Method for Permittivity of Geotextiles Under Load)) and the change of permeability coefficient under the maximum vertical pressure of geotextile during drainage (which can be obtained by referring to the standard ASTM D 5493:2023); the evaluation index of soil retention is the equivalent pore size of geotextile (which can be obtained by referring to the standard ASTM D4751-12 (Standard Test Method for Determining A pparent Opening Size of a Geotextile)); the evaluation index of anti-blocking is the gradient ratio of geotextile (which can be obtained by referring to the standard, ASTM D 5101-12 (Standard Test Method for Measuring the Filtration Compatibility of Soil-Geotextile Systems)) and the sediment retention rate of geotextile. Assume that the sediment retention rate of geotextile is T p , which is defined as the volume of the pores of the geotextile filled with sediment particles (V s ) accounts for the total pore volume of geotextile (V v ), that is:

[0053]

[0054] Secondly, in order to eliminate the dimensional differences between different evaluation indicators, the data of each evaluation indicator are standardized, and the standardized formula is used to convert the original evaluation indicator value into a dimensionless evaluation indicator value; among them, the permeability coefficient is a positive indicator, and the larger the value, the better; the permeability coefficient change, gradient ratio and sediment retention rate of the geotextile under the maximum vertical pressure are negative indicators, and the smaller the value, the better; the equivalent aperture is an intermediate indicator, and the closer the value is to the reference value, the better; the standardized processing formulas for each evaluation indicator are as follows:

[0055]

[0056] In the formula, x ij is the original value of the jth evaluation index of the i-th geotextile to be screened, j = 1, 2, ..., n, n is the number of evaluation indicators, in this embodiment n = 5, j = 1, 2, 3, 4, 5 correspond to the permeability coefficient, the change of the permeability coefficient under the maximum vertical pressure of the geotextile during drainage, the equivalent pore size, the gradient ratio and the sediment retention rate, i = 1, 2, ..., m, m is the total number of geotextiles to be screened; x' ij is the normalized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened; a is the reference value. Since only the equivalent pore size of the geotextile is selected as the intermediate index in this embodiment, the reference value a can be taken as the characteristic particle size d of the Yellow River sediment. 85 , that is, the maximum particle size with a cumulative distribution of 85% in the sediment particle size distribution curve;

[0057] Next, the weight of each evaluation index is constructed, and the entropy weight method is used to objectively determine the weight of each evaluation index according to the amount of data information;

[0058]

[0059] In the formula, w j is the weight corresponding to the jth evaluation index; e j is the entropy value corresponding to the jth evaluation index; p ij is the probability of the normalized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened.

[0060] Finally, the weights obtained by the entropy weight method are combined to calculate the comprehensive performance score of each geotextile to be screened, and the geotextile with the highest comprehensive score is selected for the Yellow River silt slurry filling reclamation and drainage project. The higher the comprehensive score, the better the comprehensive performance of the geotextile, and the more suitable it is for the Yellow River silt slurry filling reclamation and drainage project. The comprehensive performance score of the geotextile is calculated according to the following formula:

[0061]

[0062] In the formula, w jis the weight of the jth evaluation index; γ i is the comprehensive performance score of the i-th geotextile to be screened.

[0063] In order to verify the effectiveness of the method of the present invention, the drainage process of the Yellow River sediment slurry filling and reclamation of coal mining subsidence land was simulated indoors.

[0064] See also Figure 2 (a) and (b) are schematic diagrams of the installation of drainage devices and geotextiles. Cut wire mesh of 60×80 (width×height) and RN250 and RN200 (hot-melt bonded non-woven geotextiles 250g / m 2 , 200g / m 2 ) geotextile was tested in a PP plastic water tank with indoor specifications of 120×60×80cm (length×width×height). The geotextile and wire mesh were flattened on the drainage section with a flange and fixed with screws to prevent displacement in subsequent operations.

[0065] Weigh 100 kg of air-dried Yellow River silt and pour it into a bucket with a diameter of 80 cm and a height of 120 cm, and mix it into 300 kg / m 3 The mud and sand slurry is continuously stirred and transported to the PP plastic water tank through a sludge pump to simulate the filling and drainage of collapsed land.

[0066] During the filling process of the slurry, the surface of the geotextile was beaten with an external mallet to achieve a vibration effect. The vibration frequency was adjusted within the range of (1,30) times / min with a 1 kg mallet and an amplitude of 20 mm to keep the silt particles suspended and prevent them from settling on the geotextile.

[0067] refer to Figure 3 , which is the experimental data of two geotextiles RN250 and RN200 in the sand retention and drainage method of the present invention provided in the embodiments of the present disclosure. During the drainage process, the geotextile was hit with a mallet to achieve vibration. The results show that after the water is quickly discharged, after a period of time, without the effect of vibration, the drainage flow rate tends to be stable and maintained at 15 to 20 g·s -1 . With the increase of vibration frequency, the drainage flow rate gradually increased, but after reaching 20 times / minute, the drainage flow rate did not increase significantly, and the significance parameter p>0.05, and no significant difference was found. This shows that in the case of residual soil particles in the later stage, the geotextile treatment can improve the drainage efficiency through stable vibration, and with the increase of the number of hits, the drainage speed also increases.

[0068] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0069] Although examples of the present invention have been shown and described above, it is to be understood that the above examples are illustrative and are not to be construed as limitations of the present invention, and that a person skilled in the art may make changes, modifications, substitutions and variations to the above examples within the scope of the present invention.

Claims

1. A method for blocking and draining the Yellow River sediment slurry for reclamation and anti-clogging geotextiles, characterized in that: The following steps are involved: Install geotextiles at the drainage section of the Yellow River silt slurry filling and reclamation; During the Yellow River sediment slurry filling and reclamation drainage process, the geotextile is vibrated to separate the fine sediment particles remaining in the pores of the geotextile by inertia, thereby preventing the fine sediment particles from blocking the drainage channel and achieving interception of the fine sediment particles and smooth drainage.

2. The method for retaining and draining sand according to claim 1, characterized in that: The specific steps of installing the geotextile include: A fixing pile is set at intervals of 1.5 to 2 meters along the drainage direction perpendicular to the drainage direction at the drainage section, and the geotextile is laid flatly on one side of the wire mesh used to support the geotextile, and the wire mesh is located on the drainage side of the geotextile. The geotextile and the wire mesh are fixed to the fixing piles by pressure strips and rivets to complete the installation of the geotextile.

3. The sand trapping and drainage method according to claim 2, characterized in that: The aperture of the wire mesh is 2 cm to 5 cm.

4. The sand trapping and drainage method according to claim 2, characterized in that: Vibration is applied to the geotextile in either of the following two ways: Method 1: Install an automatic beating device according to site conditions, and use the beating components of the automatic beating device to beat the surface of the geotextile, with the beating direction being consistent with the normal direction of the geotextile; Method 2: manually use a handheld beating component to beat the surface of the geotextile, and the beating direction is consistent with the normal direction of the geotextile.

5. The sand trapping and drainage method according to claim 4, characterized in that: The hammering component is a mallet, and the number of the mallets can be determined according to the spacing between the fixed piles; the weight of a single mallet is controlled at 0.5kg to 5kg, the amplitude is controlled at 20mm to 100mm, and the hammering frequency is controlled at (1,30] times / minute.

6. The method for retaining and draining sediment according to any one of claims 1 to 5, characterized in that: The sand interception and drainage method also includes screening the geotextile according to the particle size of the filled Yellow River silt before installing the geotextile, and the specific steps are as follows: An evaluation index system is constructed based on the permeability, soil retention and anti-clogging properties of geotextiles, each performance includes at least one evaluation index, and multiple geotextiles to be screened are measured to obtain the original values ​​of each evaluation index of each geotextile to be screened; Standardizing the obtained original values ​​of the evaluation indicators to eliminate the dimensional differences between different evaluation indicators; The entropy weight method is used to determine the weight of each evaluation index; The comprehensive performance scores of various geotextiles are calculated according to the weights of the evaluation indicators and the standardized processing results, and the geotextile with the highest comprehensive performance score is selected for the Yellow River silt slurry filling, reclamation and drainage project.

7. The sand trapping and drainage method according to claim 6, characterized in that: The permeability evaluation index is the permeability coefficient of the geotextile and the change in the permeability coefficient under the maximum vertical pressure borne by the geotextile during drainage; The soil retention evaluation index is the equivalent pore size of the geotextile; The evaluation indexes of the anti-blocking property are the gradient ratio of the geotextile and the sediment retention rate of the geotextile. The sediment retention rate is defined as the percentage of the volume of the pores of the geotextile filled with sediment particles to the total volume of the pores of the geotextile.

8. The method for retaining and draining sand according to claim 7 is characterized in that: The permeability coefficient is a positive indicator, the permeability coefficient change, gradient ratio and sediment retention rate are all negative indicators, and the equivalent aperture is an intermediate indicator; the formula used to standardize each evaluation index is: In the formula, x ij is the original value of the jth evaluation index of the i-th geotextile to be screened, j = 1, 2, ..., n, n is the number of evaluation indicators, n = 5, j is 1, 2, 3, 4, 5, which correspond to the permeability coefficient, the change of permeability coefficient under the maximum vertical pressure of the geotextile during drainage, the equivalent pore size, the gradient ratio and the sediment retention rate, i = 1, 2, ..., m, m is the total number of geotextiles to be screened; x' ij is the standardized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened; a is the reference value, which is taken as the characteristic particle size d of the Yellow River sediment 85 , that is, the maximum particle size with a cumulative distribution of 85% in the sediment particle size distribution curve.

9. The method for retaining and draining sand according to claim 7, characterized in that: The calculation formula of the weight of each evaluation index is as follows: In the formula, w j is the weight corresponding to the jth evaluation index; e j is the entropy value corresponding to the jth evaluation index; p ij is the probability of the normalized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened; ij is the original value of the jth evaluation index of the i-th geotextile to be screened, j = 1, 2, ..., n, n is the number of evaluation indicators, n = 5, j is 1, 2, 3, 4, 5, which correspond to the permeability coefficient, the change of permeability coefficient under the maximum vertical pressure of the geotextile during drainage, the equivalent pore size, the gradient ratio and the sediment retention rate, i = 1, 2, ..., m, m is the total number of geotextiles to be screened; x' ij It is the standardized processing result of the original value of the jth evaluation index of the i-th geotextile to be screened.

10. The sand trapping and drainage method according to claim 9, characterized in that: The comprehensive performance score of the geotextile is calculated according to the following formula: In the formula, w j is the weight of the jth evaluation index; γ i is the comprehensive performance score of the i-th geotextile to be screened.

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