Design method of geotextile filter layer for enhancing the safety of silt filter
By revising the filter criterion and introducing a dual-index evaluation system, the problem of insufficient safety in the design of geotextile filter layers was solved, and the safety, reliability and economy of silt filter layers were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG GUANGCHUAN ENG CONSULTING CO LTD
- Filing Date
- 2026-04-07
- Publication Date
- 2026-07-03
AI Technical Summary
Existing filter layer design methods fail to effectively consider the tensile strain, normal stress, and long-term clogging factors of geotextiles under actual engineering conditions, resulting in insufficient safety of silty soil filters, and traditional evaluation methods are prone to misjudgment.
A modified reverse filtration criterion was adopted, taking into account the equivalent pore size of geotextiles under tensile strain and the vertical permeability coefficient under long-term load. Combining the gradient ratio and permeability coefficient ratio as dual indicators, the reverse filtration layer materials that meet the conditions were screened through the filter layer matching algorithm and material database, and the long-term clogging risk assessment was carried out.
It significantly improves the safety and reliability of silt filter layers, reduces the risk of permeability degradation, enables reliable identification and accurate screening of clogging risks, and reduces the cost of redundant tests.
Smart Images
Figure CN121983205B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of porous material physical property analysis and geotechnical engineering filter design technology, specifically a geotextile filter layer design method to enhance the safety of silty soil filter. Background Technology
[0002] In geotechnical engineering, porous materials such as geotextiles are often used for filtration and protection of fine-particle soils such as silt. Evaluating the soil retention, permeability, and anti-clogging properties of these porous materials when in contact with the soil is crucial to ensuring their filtration safety.
[0003] Silt particles are fine and uniform, with poor gradation. Improper selection of geotextile filters can easily lead to filter layer clogging and failure, causing seepage damage. Therefore, silt requires stricter requirements in filter layer design compared to other soils to ensure effective geotextile filtration.
[0004] Existing filter layer design methods have the following limitations: First, they typically do not consider the influence of tensile strain on the geotextile in the actual engineering environment on its equivalent pore size; second, the selected geotextile permeability coefficients are mostly conventional vertical permeability coefficients, failing to adopt vertical permeability coefficients under loads that better reflect actual conditions, and neglecting the influence of normal stress and thickness changes caused by compression creep during long-term service on the vertical permeability coefficient; third, in terms of anti-clogging evaluation, they mostly rely on the gradient ratio obtained from clogging tests, but this index is difficult to distinguish between clogging of geotextiles and soil itself, easily leading to misjudgments, and the gradient ratio limit for silty soil is still controversial, resulting in insufficient accuracy and reliability of this evaluation method.
[0005] Therefore, it is necessary to establish a design method for geotextile filter layers suitable for silty soil filtration. This method should be able to better reflect the influence of factors such as tensile strain, normal stress and long-term clogging on the filtration effect of geotextiles under actual engineering conditions, so as to conduct a safe and reliable analysis and evaluation of the long-term filtration performance of geotextiles in actual engineering environments.
[0006] Therefore, a design method for geotextile filter layers to enhance the safety of silty soil filtration is proposed. Summary of the Invention
[0007] The purpose of this invention is to provide a design method for geotextile filter layers that enhances the safety of silt filter layers. This method includes revising the existing filter criteria to establish a set of geotextile filter criteria that can more realistically reflect actual working conditions, and forming a corresponding geotextile filter layer material selection method based on the criteria.
[0008] The reverse filtration criteria established by this method consider the changes in equivalent pore size of geotextiles under tensile strain in actual engineering in terms of soil retention; in terms of permeability, it adopts the vertical permeability coefficient under load that is more in line with actual conditions, and considers the influence of normal stress and thickness changes caused by compression creep during long-term service on the vertical permeability coefficient; in terms of anti-clogging evaluation, it introduces the gradient ratio and permeability coefficient ratio as dual indicators to comprehensively assess the long-term clogging risk of the silt-geotextile system.
[0009] The proposed method for selecting filter layer materials first retrieves candidate materials that meet the conditions from the material database based on the filter layer matching algorithm, and then combines the clogging risk assessment to comprehensively optimize these candidate materials, thereby determining the optimal material for the filter layer.
[0010] The design method provided by this invention effectively solves the problem of insufficient safety in the design of geotextile filter layers under silty soil geological conditions in existing methods.
[0011] To achieve the above objectives, the present invention provides the following technical solution:
[0012] A design method for geotextile filter layers to enhance the safety of silty soil filter layers includes:
[0013] Obtain engineering silt parameters, including characteristic particle size and permeability coefficient; calculate the maximum and minimum values of hydraulic performance parameters of the filter layer material based on the filter layer matching algorithm, including the maximum equivalent pore size under tensile strain of the geotextile and the minimum vertical permeability coefficient under long-term load; analyze actual engineering conditions, retrieve material parameters from the material database, and determine the candidate filter layer materials that meet the conditions according to the filter layer matching algorithm; conduct long-term clogging tests on the candidate filter layer materials to obtain clogging performance evaluation indicators, including gradient ratio and permeability coefficient ratio; establish a clogging risk assessment model to evaluate the anti-clogging performance of the materials; sort the candidate filter layer materials according to their anti-clogging performance, determine the filter layer materials, and generate a geotextile filter layer design scheme.
[0014] Preferably, the filter interface matching algorithm includes:
[0015] The characteristic particle size of the silt and the equivalent pore size of the geotextile filter layer under tensile strain should satisfy the following relationship:
[0016] ;
[0017] in The equivalent pore size of the geotextile under tensile strain; B is the characteristic particle size of silt, and B is the soil retention coefficient: under static or laminar flow conditions, the soil retention coefficient B is selected as a preset value based on the soil type, uniformity coefficient and compaction of the soil being protected; under dynamic water flow conditions, the soil retention coefficient B is determined based on the interaction test between geotextile and soil.
[0018] The permeability coefficient of the silt and the vertical permeability coefficient of the geotextile filter layer under long-term load should satisfy the following relationship:
[0019] ;
[0020] in is the vertical permeability coefficient of the geotextile under long-term load; A is the preset safety factor. The value is the permeability coefficient of the soil being protected.
[0021] Preferably, the step of searching and determining candidate materials for the filter layer that meet the conditions in the material database specifically includes:
[0022] A database of material performance parameters for filter layers is established by collecting existing material performance parameters and testing material performance parameters. The material database stores various specifications of filter layer materials and their corresponding performance parameters, including the equivalent pore size of geotextile under tensile strain conditions, the thickness of geotextile under 2 kPa pressure, the vertical permeability coefficient of geotextile under load, and the compressive creep thickness of geotextile under design normal stress and design life.
[0023] The type and level of tensile strain experienced by the filter layer in the actual engineering environment were analyzed, and the equivalent pore size of the geotextile under tensile strain conditions was obtained by calling the material database.
[0024] Analyze the long-term normal stress acting on the filter layer; based on the long-term normal stress and the engineering design life, call the material database to obtain the thickness of the geotextile under 2 kPa pressure, the vertical permeability coefficient of the geotextile under load, and the compression creep thickness of the geotextile under the design normal stress and design life; calculate the vertical permeability coefficient of the geotextile under long-term load and store it in the material database.
[0025] The maximum equivalent pore size under tensile strain and the minimum vertical permeability coefficient under long-term load are used as search criteria.
[0026] The material database is traversed, and the equivalent pore size under tensile strain conditions and the vertical permeability coefficient under long-term load for each material in the database are compared with the search criteria. Materials whose equivalent pore size under tensile strain conditions is smaller than the maximum value of the equivalent pore size and whose vertical permeability coefficient under long-term load is greater than the minimum value of the vertical permeability coefficient are selected.
[0027] All the selected materials are combined into a list as candidate materials for the filter layer.
[0028] Preferably, the step of calculating the vertical permeability coefficient of the geotextile under long-term load specifically includes:
[0029] Use the long-term normal stress and the engineering design life as query conditions;
[0030] Based on the query conditions, the thickness of the geotextile under 2 kPa pressure and the compression creep thickness of the geotextile that match the query conditions are searched and retrieved in the material property database, and the thickness compression creep reduction factor is calculated.
[0031] Based on the environmental conditions of engineering applications, the reduction coefficients of geotextile permeability index are retrieved from the material performance database, including the reduction coefficients caused by siltation, creep-induced reduction coefficients of fabric porosity, reduction coefficients caused by adjacent soil material squeezing into fabric porosity, chemical siltation reduction coefficients, and biological siltation reduction coefficients. The total reduction coefficient of geotextile permeability index is then calculated.
[0032] Calculate the long-term performance reduction factor of geotextiles;
[0033] Based on the long-term normal stress of the filter layer, the vertical permeability coefficient of the geotextile under load is retrieved from the material database.
[0034] Calculate the vertical permeability coefficient of geotextiles under long-term load.
[0035] The relevant calculation formula is as follows:
[0036] ;
[0037] in is the vertical permeability coefficient of the geotextile under long-term load; C is the long-term performance reduction factor of the geotextile. This represents the vertical permeability coefficient of the geotextile under the corresponding load. The thickness compression creep reduction factor of the geotextile; This is the total reduction factor for the permeability index of geotextiles; The compression creep thickness of the geotextile under the design normal stress and design life; The thickness of the geotextile under a pressure of 2 kPa; The reduction factor for geotextiles due to siltation; The reduction factor for the decrease in fabric porosity due to creep; The reduction factor caused by adjacent soil material squeezing into the fabric pores; This is the chemical sludge reduction factor; This is the bioclogging reduction factor.
[0038] Preferably, the step of conducting long-term clogging tests to obtain the clogging performance indicators of the filter layer material specifically includes:
[0039] Conduct long-term clogging tests; determine the gradient ratio (GR) according to the SL235-2012 standard; calculate the permeability coefficient ratio using the following formula:
[0040] ;
[0041] Where KR is the permeability coefficient ratio; The permeability coefficient is the combined permeability coefficient of the geotextile and the soil material 25 mm above it.
[0042] Preferably, the establishment of a clogging risk assessment model to evaluate the anti-clogging performance of materials specifically includes:
[0043] The gradient ratio and permeability coefficient ratio are used as indicators for assessing clogging risk; a threshold for judging clogging status is set; the clogging risk assessment indicators are compared with the clogging status judgment threshold to determine the clogging risk level; a quantitative scoring standard is set for the clogging risk level; the weights of the clogging risk assessment indicators are set; and the clogging resistance performance score of the material is calculated using a weighted scoring method.
[0044] Preferably, the step of comparing the siltation risk assessment index with the siltation state discrimination threshold to determine the siltation risk level specifically includes:
[0045] The gradient ratio is compared with a first preset threshold. If the gradient ratio is less than the first preset threshold, the gradient ratio clogging risk level is determined to be low risk. If the gradient ratio is not less than the first preset threshold, it is compared with a second preset threshold, where the second preset threshold is greater than the first preset threshold. If the gradient ratio is greater than the second preset threshold, the gradient ratio clogging risk level is determined to be high risk. If the gradient ratio is between the first preset threshold and the second preset threshold, the gradient ratio clogging risk level is determined to be medium risk.
[0046] The permeability ratio is compared with a first preset threshold. If the permeability ratio is less than the first preset threshold, the permeability ratio clogging risk level is determined to be high-risk. If the permeability ratio is not less than the first preset threshold, it is compared with a second preset threshold. If the second preset threshold is greater than the first preset threshold, the permeability ratio clogging risk level is determined to be low-risk. If the permeability ratio is between the first and second preset thresholds, the permeability ratio clogging risk level is determined to be medium-risk.
[0047] Preferably, the step of ranking the candidate filter layer materials according to their anti-clogging performance to determine the filter layer materials includes:
[0048] Based on the clogging risk assessment results, the candidate materials for the filter layer are sorted from high to low according to their anti-clogging performance scores; the candidate material with the highest score is selected as the filter layer material, and the filter layer design scheme is generated and output.
[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0050] 1. This invention abandons the traditional approach of using the conventional vertical permeability coefficient of geotextiles in design. Instead, it innovatively introduces the vertical permeability coefficient of geotextiles under load and the thickness compression creep reduction coefficient, combining these with the clogging reduction coefficient to construct the vertical permeability coefficient of geotextiles under long-term load. This permeability coefficient replaces the conventional vertical permeability coefficient, effectively reducing the attenuation of permeability performance caused by material compression creep and long-term clogging, thereby significantly reducing the risk of filter structure failure. Furthermore, this invention further considers the influence of tensile strain on the equivalent pore size in actual engineering projects, innovatively using the equivalent pore size under geotextile tensile strain instead of the conventional equivalent pore size, effectively preventing seepage deformation caused by the loss of silt particles with water flow.
[0051] 2. This invention establishes a dual-index anti-clogging evaluation system combining gradient ratio and system permeability coefficient ratio. Through cross-validation of "internal pore pressure change" and "overall permeability efficiency," it achieves reliable identification of clogging risks. Simultaneously, it abandons the traditional binary "compliant / non-compliant" judgment mode and innovatively constructs a three-level clogging risk classification evaluation model including "high," "medium," and "low." This model can more sensitively identify potential clogging hazards, providing "double insurance" for engineering material selection and significantly reducing the probability of filter failure under silty soil geological conditions.
[0052] 3. This invention proposes a reliable design method for silt-retaining filters. First, by constructing a filter layer interface matching algorithm and a material database, this method screens filter materials that simultaneously meet the requirements of soil retention and water permeability. Then, combining long-term clogging tests and a clogging risk grading evaluation model, it further screens materials with excellent anti-clogging performance. This method not only efficiently screens technically safe and reliable filter materials but also reduces costs by minimizing redundant tests, offering economic advantages and achieving a leapfrog upgrade in filter layer design from "extensive design" to "precise and reliable design." Attached Figure Description
[0053] Figure 1 This is a schematic diagram of the overall design method for a geotextile filter layer to enhance the safety of silty soil reverse filtration proposed in this invention;
[0054] Figure 2 This is a flowchart of a geotextile filter layer design method for enhancing the safety of silty soil reverse filtration proposed in this invention;
[0055] Figure 3 This invention provides a procedure for calculating the vertical permeability coefficient of geotextiles under long-term load. Detailed Implementation
[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0057] Example 1
[0058] Please see Figures 1 to 3 This invention provides a design method for geotextile filter layers that enhance the safety of silty soil filtration. The technical solution is as follows:
[0059] A design method for geotextile filter layers to enhance the safety of silty soil filter layers, such as Figure 1 - Figure 2 As shown, it includes:
[0060] The process involves: obtaining the characteristic particle size and permeability coefficient of the engineering silt; calculating the maximum equivalent pore size under tensile strain and the minimum vertical permeability coefficient under long-term load on the geotextile in the filter layer based on the filter layer matching algorithm; analyzing actual engineering conditions, obtaining material parameters from the material database, and retrieving and determining candidate filter layer materials that meet the conditions based on the filter layer matching algorithm; conducting long-term clogging tests on the candidate filter layer materials to obtain the gradient ratio and permeability coefficient ratio of the filter layer materials; establishing a clogging risk assessment model to evaluate the anti-clogging performance of the materials; ranking the candidate filter layer materials according to their anti-clogging performance, determining the filter layer materials, and generating a geotextile filter layer design scheme.
[0061] Furthermore, the filter layer matching algorithm includes:
[0062] The characteristic particle size of the silt and the equivalent pore size under tensile strain of the geotextile filter layer should satisfy the following relationship:
[0063] ;
[0064] in The equivalent pore size of the geotextile under tensile strain; B is the characteristic particle size of silt; B is the soil retention coefficient: under static or laminar flow conditions, the soil retention coefficient B is selected as a preset value based on the soil type, uniformity coefficient and compaction of the soil being protected; under dynamic water flow conditions, the soil retention coefficient B is determined based on the interaction test between geotextile and soil.
[0065] The permeability coefficient of the silt and the vertical permeability coefficient of the geotextile filter layer under long-term load should satisfy the following relationship:
[0066] ;
[0067] in is the vertical permeability coefficient of the geotextile under long-term load; A is the preset safety factor. The value is the permeability coefficient of the soil being protected.
[0068] The preset safety factor A ranges from 1 to 10. Specifically, for seepage environments with relatively stable hydraulic conditions, the preset safety factor can be taken as a value close to the lower limit of the range, such as 1 to 3; for complex environments with large hydraulic gradients or dynamic hydraulic loads, to increase safety reserves, the preset safety factor should be taken as a value close to the upper limit of the range, such as 8 to 10. In this way, those skilled in the art can reasonably select the safety factor according to the specific engineering hydrological conditions.
[0069] The soil conservation criterion in this invention adopts the equivalent pore size of geotextiles under tensile strain. This is a more stringent and conservative design principle for special soil types such as silt, which lack cohesion, have fine particles, and are internally unstable. This criterion aims to maximize the retention of the silt's skeletal particles, effectively preventing seepage deformation caused by the loss of silt particles with water flow. The equivalent pore size of the geotextile under tensile strain can be obtained by first analyzing the type and level of tensile strain in the actual engineering environment, followed by tensile testing combined with image analysis, or through numerical simulation.
[0070] The permeability criterion in this invention uses the vertical permeability coefficient of geotextiles under long-term load. This is a more realistic and stringent design principle for geotextiles in silty soil environments under the combined effects of load and long-term seepage. This criterion is adopted to maximize the reflection of the adverse effects of material compression creep and long-term clogging on permeability, ensuring that the geotextile has sufficient permeability to allow for the smooth drainage of seepage water. The vertical permeability coefficient of the geotextile under long-term load is obtained by the method provided in this invention.
[0071] Furthermore, the step of retrieving and determining candidate materials for the filter layer that meet the conditions from the material database specifically includes:
[0072] The performance parameters of the filter layer material are obtained by collecting existing material performance parameters and testing material performance parameters, and a material database is established. The material database stores various specifications of various filter layer materials and their corresponding performance parameters, including the equivalent pore size of geotextile under tensile strain conditions, the thickness of geotextile under 2kPa pressure, the vertical permeability coefficient of geotextile under load, the compressive creep thickness of geotextile under design normal stress and design life, and the vertical permeability coefficient of geotextile under long-term load.
[0073] The type and level of tensile strain experienced by the filter layer in the actual engineering environment were analyzed, and the equivalent pore size of the geotextile under tensile strain conditions was obtained by calling the material database.
[0074] Analyze the long-term normal stress acting on the filter layer; based on the long-term normal stress and the engineering design life, call the material database to obtain the thickness of the geotextile under 2 kPa pressure, the vertical permeability coefficient of the geotextile under load, and the compression creep thickness of the geotextile under the design normal stress and design life; calculate the vertical permeability coefficient of the geotextile under long-term load and store it in the material database.
[0075] The maximum equivalent pore size under tensile strain and the minimum vertical permeability coefficient under long-term load are used as search criteria.
[0076] The material database is traversed, and the equivalent pore size under tensile strain conditions and the vertical permeability coefficient under long-term load for each material in the database are compared with the search criteria. Materials whose equivalent pore size under tensile strain conditions is smaller than the maximum value of the equivalent pore size under tensile strain conditions and whose vertical permeability coefficient under long-term load is greater than the minimum value of the vertical permeability coefficient under long-term load are selected.
[0077] All the selected materials are combined into a list as candidate materials for the filter layer.
[0078] To ensure the accuracy and comparability of the search results, the performance parameters stored in the material database of this invention are obtained according to unified testing standards. In this embodiment, the equivalent pore size of all materials under tensile strain conditions is determined by image method; the thickness of all materials under 2 kPa pressure is determined according to GB / T 13761.1; the vertical permeability coefficient of all materials under load is determined according to GB / T 45366; and the compressive creep thickness of all materials under design normal stress and design life is determined according to ISO 25619-1.
[0079] This invention addresses the problem of unreliable material selection caused by inconsistent data sources and testing conditions by establishing a standardized material property database. This method ensures that all material properties are scientifically compared under a unified benchmark, guaranteeing the accuracy of data input from the outset, thereby improving the reliability of automated screening results and the safety of the final design.
[0080] Furthermore, the step of calculating the vertical permeability coefficient of the geotextile under long-term load is as follows: Figure 3 As shown, it specifically includes:
[0081] Use the long-term normal stress and the engineering design life as query conditions;
[0082] Based on the query conditions, the thickness of the geotextile under 2 kPa pressure and the compression creep thickness of the geotextile that match the query conditions are searched and retrieved in the material property database, and the thickness compression creep reduction factor is calculated.
[0083] Based on the environmental conditions of engineering applications, the reduction coefficients of geotextile permeability index are retrieved from the material performance database, including the reduction coefficients caused by siltation, creep-induced reduction coefficients of fabric porosity, reduction coefficients caused by adjacent soil material squeezing into fabric porosity, chemical siltation reduction coefficients, and biological siltation reduction coefficients. The total reduction coefficient of geotextile permeability index is then calculated.
[0084] Calculate the long-term performance reduction factor of geotextiles;
[0085] Based on the long-term normal stress of the filter layer, the vertical permeability coefficient of the geotextile under load is retrieved from the material property database.
[0086] Calculate the vertical permeability coefficient of geotextiles under long-term load;
[0087] The relevant calculation formula is as follows:
[0088] ;
[0089] in is the vertical permeability coefficient of the geotextile under long-term load; C is the long-term performance reduction factor of the geotextile. This represents the vertical permeability coefficient of the geotextile under the corresponding load. The thickness compression creep reduction factor of the geotextile; This is the total reduction factor for the permeability index of geotextiles; The compression creep thickness of the geotextile under the design normal stress and design life; The thickness of the geotextile under a pressure of 2 kPa; The reduction factor for geotextiles due to siltation; The reduction factor for the decrease in fabric porosity due to creep; The reduction factor caused by adjacent soil material squeezing into the fabric pores; This is the chemical sludge reduction factor; This is the bioclogging reduction factor.
[0090] The reduction coefficients for geotextile clogging, creep-induced porosity reduction, adjacent soil material intrusion into the geotextile pores, chemical clogging, and biological clogging, obtained based on environmental conditions for engineering applications, specifically refer to:
[0091] The reduction coefficients for geotextiles caused by siltation and the reduction coefficients caused by adjacent soil material squeezing into the geotextile pores should be selected within the range specified in the standard, depending on the importance of the project (e.g., important project, general project) and the severity of hydraulic conditions; for silty soil environments, considering the higher risk of siltation, a medium-to-high value within the recommended range should be selected.
[0092] The reduction factor for the decrease in fabric porosity caused by creep shall be selected according to the level of the long-term normal stress and with reference to the corresponding range in the specification.
[0093] The chemical clogging reduction factor and the biological clogging reduction factor are selected based on the water quality analysis report (such as pH value) and microbial content of the project site, directly corresponding to the application conditions in the standard table.
[0094] This invention, by coupling long-term normal stress, design life, and engineering environment characteristics, introduces the vertical permeability coefficient of geotextile under corresponding loads, the compression creep thickness of geotextile under design normal stress and design life, and combines it with the total reduction factor of geotextile permeability index. This effectively solves the problem of traditional design neglecting the influence of material compression creep and actual environmental loads and siltation on the permeability of materials, achieving accurate prediction of the long-term permeability performance of geotextiles, and significantly improving the drainage safety and reliability of the reverse filtration system throughout its entire life cycle.
[0095] Furthermore, the step of conducting long-term clogging tests to obtain the gradient ratio and permeability coefficient ratio specifically includes:
[0096] Conduct long-term clogging tests; determine the gradient ratio (GR) according to the SL235 standard; the formula for calculating the permeability coefficient ratio is:
[0097] ;
[0098] Where KR is the permeability ratio; The permeability coefficient is the combined permeability coefficient of the geotextile and the soil material 25 mm above it.
[0099] This invention introduces the permeability coefficient ratio as a supplementary evaluation index to the conventional gradient ratio. This index, by calculating the ratio of the composite permeability coefficient of the geotextile and the key soil layer above it to the soil permeability coefficient, directly quantifies the degree of change in drainage performance of the reverse filter system relative to the natural soil. Through dual verification using KR and GR, the limitations of a single index in determining silty fine-particle clogging are effectively avoided, significantly improving the accuracy and reliability of long-term clogging safety assessment of the reverse filter structure.
[0100] Furthermore, the establishment of a clogging risk assessment model to evaluate the anti-clogging performance of materials specifically includes:
[0101] The gradient ratio and permeability coefficient ratio are used as indicators for assessing clogging risk; a threshold for judging clogging status is set; the clogging risk assessment indicators are compared with the clogging status judgment threshold to determine the clogging risk level; a quantitative scoring standard is set for the clogging risk level; the weights of the clogging risk assessment indicators are set; and the clogging resistance performance score of the material is calculated using a weighted scoring method.
[0102] Furthermore, the comparison of the siltation risk assessment index with the siltation state discrimination threshold to determine the siltation risk level specifically includes:
[0103] The gradient ratio is compared with a first preset threshold. If the gradient ratio is less than the first preset threshold, the gradient ratio clogging risk level is determined to be low risk. If the gradient ratio is not less than the first preset threshold, it is compared with a second preset threshold, where the second preset threshold is greater than the first preset threshold. If the gradient ratio is greater than the second preset threshold, the gradient ratio clogging risk level is determined to be high risk. If the gradient ratio is between the first preset threshold and the second preset threshold, the gradient ratio clogging risk level is determined to be medium risk.
[0104] The permeability ratio is compared with a first preset threshold. If the permeability ratio is less than the first preset threshold, the permeability ratio clogging risk level is determined to be high-risk. If the permeability ratio is not less than the first preset threshold, it is compared with a second preset threshold. If the second preset threshold is greater than the first preset threshold, the permeability ratio clogging risk level is determined to be low-risk. If the permeability ratio is between the first and second preset thresholds, the permeability ratio clogging risk level is determined to be medium-risk.
[0105] In this embodiment, the preset threshold for the permeability coefficient ratio is an empirical value calculated by back-calculating from numerous gradient ratio permeability tests on various typical silt samples. Specifically, the first preset threshold for the permeability coefficient ratio is determined as a critical lower limit for the permeability coefficient ratio. When the permeability coefficient ratio is less than this lower limit, it physically corresponds to the geotextile being severely blocked by migrated fine particles, resulting in unacceptable deterioration of its permeability performance. At this point, the system is classified as a high-risk level.
[0106] The second permeability ratio preset threshold is determined as a critical upper limit value for the permeability ratio. When the permeability ratio is greater than this upper limit value, it physically corresponds to the formation of a stable self-reflective filter layer in the system, and the entire soil-geotextile system maintains a much better permeability than the undisturbed soil. At this time, the system is judged to be stable and at a low risk level.
[0107] When the permeability ratio is between the critical lower limit and the upper limit, the system is in a transitional state, and its long-term stability is uncertain, so it is judged to be of medium risk level.
[0108] The gradient ratio preset threshold was also determined based on statistical data from long-term clogging tests on silt-geotextile systems. Specifically:
[0109] The first gradient preset threshold (typically between 1.0 and 1.5, preferably 1.5 in this embodiment) is determined as a "non-clogging safety limit" for the gradient ratio. When the gradient ratio is less than this threshold, it physically corresponds to the absence of a dense, low-permeability layer at the interface between the geotextile and the silt, and the water flow does not generate significant excess head loss when passing through the fabric. This indicates that the silt particles have formed a stable "skeleton-pore" structure on the fabric surface, the loss of fine particles has stabilized, the system is in an ideal self-reverse filtration state, and is judged to be at a low-risk level.
[0110] The second gradient preset threshold (typically between 2.5 and 3.0, preferably 3.0 in this embodiment) is determined as a "critical value for severe clogging" of the gradient ratio. When the gradient ratio is greater than this threshold, it physically corresponds to a large number of fine silt particles being embedded inside the fabric pores or forming a thick and dense "mud cake layer" on the fabric surface. At this time, the hydraulic gradient at the interface is significantly higher than the gradient inside the soil, indicating that the drainage channel is severely blocked, which can easily induce pore water pressure accumulation leading to soil softening or structural instability. Therefore, the system is judged to be at a high risk level.
[0111] When the gradient ratio is between the first preset threshold and the second preset threshold, it indicates that there is a certain degree of fine particle accumulation at the system interface. Although the permeability has decreased, it has not completely failed. It belongs to the "slight blockage" or "gradual blockage" stage. It needs to be comprehensively judged in conjunction with the permeability ratio. Therefore, it is judged to be of medium risk level.
[0112] This invention constructs a dual-index clogging classification evaluation system based on gradient ratio and permeability coefficient ratio. By setting clear physical thresholds, it accurately defines the "clogging-free safe zone," "transition zone," and "severe clogging failure zone." This method not only overcomes the limitations of single-index assessment in determining the behavior of complex interfaces in silt soil, but also achieves dynamic identification and refined management of long-term service risks of reverse filtration systems by quantifying the formation of the interface "mud cake layer" and the state of head loss.
[0113] Furthermore, the weighted scoring method for calculating the material's anti-clogging performance score specifically includes:
[0114] The two qualitative indicators, gradient ratio siltation risk level and permeability coefficient ratio siltation risk level, are converted into quantitative risk scores. For example, a "low risk" level is assigned 3 points, a "medium risk" level is assigned 2 points, and a "high risk" level is assigned 1 point.
[0115] To eliminate the influence of dimensions, the continuous variable of the long-term permissible water flow capacity of each candidate material is normalized. For example, its value is mapped to the range of 1 to 3 points, which is the same as the risk score, through a linear transformation.
[0116] Specific weighting coefficients are set to calculate the comprehensive performance score. In this embodiment, based on the current research status of the seepage and clogging mechanism of the silt-geotextile reverse filtration system, the gradient ratio clogging risk level is set as the primary consideration indicator, and the permeability coefficient ratio clogging risk level is set as a secondary consideration indicator. Specifically, a gradient ratio clogging risk level score is assigned. Weighting coefficients Assign a permeability coefficient score to a clogging risk level. Weighting coefficients The formula for calculating the anti-clogging performance score S is:
[0117] ;
[0118] This invention proposes a quantitative selection method for geotextile anti-clogging performance based on multi-dimensional index weighted scoring. By converting qualitative clogging risk levels into quantitative scores, a dual-index clogging classification evaluation model is constructed. This method effectively overcomes the one-sidedness of evaluating clogging solely based on gradient ratios in traditional design, ensuring that the ultimately selected filter material possesses optimal long-term anti-clogging reliability under complex silty soil conditions.
[0119] Furthermore, the process of ranking the candidate filter materials according to their anti-clogging performance and determining the filter material includes:
[0120] Based on the clogging risk assessment results, the candidate materials for the filter layer are sorted from high to low according to their anti-clogging performance scores; the candidate material with the highest score is selected as the filter layer material, and the filter layer design scheme is generated and output.
[0121] This invention comprehensively considers the influence of engineering design life, long-term normal stress, tensile strain, etc. on the equivalent pore size and permeability coefficient of geotextiles. It adopts geotextile hydraulic performance indicators that can more realistically and accurately reflect the actual engineering to evaluate the soil retention and permeability of geotextiles. At the same time, by introducing dual evaluation indicators of gradient ratio and permeability coefficient ratio, a multi-dimensional siltation risk classification model is established, which overcomes the limitations of judging silt siltation with a single indicator, realizes the precise quantitative selection of filter materials, and significantly improves the long-term safety of silt-geotextile filter layers.
[0122] Example 2
[0123] This embodiment uses a coastal seawall reinforcement project as an example to illustrate the specific application of the design method described in this invention.
[0124] Located in a coastal soft soil area, the foundation soil is mainly composed of silty sand and silt, with a high groundwater level that fluctuates frequently due to tides. The project design adopts a geotextile-based reverse filter twisted block slope protection and riprap toe protection structure to prevent the silt particles in the dike body from seeping and deforming under the action of receding tides or wave suction.
[0125] Step 1: Obtain silt parameters and calculate the maximum equivalent pore size under tensile strain and the minimum vertical permeability coefficient under long-term load on the geotextile filter layer.
[0126] The silt was surveyed and sampled at the site, and its characteristic particle size was measured. Permeability coefficient .
[0127] Referring to the table in GB / T 50290-2014, for silty soil in a dynamic water flow environment (tidal), a coefficient B=1.0 was selected to calculate the maximum equivalent pore size of the geotextile filter layer under tensile strain. .
[0128] With coefficient A=10, the minimum vertical permeability coefficient of the geotextile filter layer under long-term load was calculated. .
[0129] Step 2: Analyze the environmental conditions in which the geotextile is used, and access the material database to obtain material performance parameters.
[0130] The engineering design service life is 50 years. The analysis and calculation show that the long-term normal stress of the geotextile in the seawall is about 50 kPa, and the tensile strain on the geotextile is a laterally confined uniaxial tensile strain with a value of about 15%.
[0131] Based on the tensile strain value, a material database was consulted to obtain the equivalent pore size under tensile strain for various materials. .
[0132] Based on the environmental conditions of engineering applications, the reduction coefficient of geotextile permeability index and the reduction coefficient of siltation were obtained with reference to GB / T 50290-2014. The reduction factor for the decrease in fabric porosity due to creep The reduction factor caused by adjacent soil material squeezing into the fabric pores Chemical sludge reduction factor Bioclogging reduction coefficient Taking values of 8, 1.5, 1.2, 1.0, and 4.0 respectively, the total reduction factor is calculated to be 57.6.
[0133] Access the materials database to obtain the vertical permeability coefficient of geotextiles of various materials under corresponding loads. Compression creep thickness of geotextile under design normal stress and design life The thickness of geotextile under 2 kPa pressure Calculate the long-term performance reduction factor C for various materials, and then obtain the vertical permeability coefficient of various geotextiles under long-term load. The obtained material performance parameters are shown in Table 1. This embodiment only lists some of the material data.
[0134] Table 1 Material Performance Parameters
[0135]
[0136] Step 3: Search the materials database and identify suitable filter layer materials that meet the requirements.
[0137] Based on the filter layer matching algorithm, a search is conducted in the material database to determine the material that meets the requirements. and Materials were selected as candidate materials. After searching, materials A, D, E, and 12 other materials were identified as candidate materials.
[0138] Step 4: Conduct long-term siltation tests
[0139] Considering the long-term clogging test time and cost, this embodiment selects three materials, A, D and E, to conduct a long-term clogging test. The test is carried out according to the method specified in SL 235-2012. The gradient ratio GR and the permeability ratio KR are measured. The test results are shown in Table 2.
[0140] Table 2 Results of alternative long-term clogging tests
[0141]
[0142] Step 4: Establish a clogging risk assessment model and evaluate the anti-clogging performance of the material.
[0143] Based on statistical data from long-term clogging tests of silt-geotextile systems and relevant research findings, thresholds for gradient ratio and permeability ratio were set. In this embodiment, the first and second thresholds for gradient ratio were set to 1.5 and 3, respectively, and the first and second thresholds for permeability ratio were set to 0.3 and 0.6, respectively.
[0144] The gradient ratio and permeability coefficient ratio are compared with the clogging status judgment threshold to output the clogging risk level of the filter layer. The clogging risk level judgment results of the alternative materials are shown in Table 3.
[0145] Table 3 Results of the assessment of siltation risk level of alternative materials
[0146]
[0147] The gradient ratio siltation risk level and the permeability coefficient ratio siltation risk level indicators are converted into quantitative risk level scores. In this embodiment, a "low risk" level is assigned 3 points, a "medium risk" level is assigned 2 points, and a "high risk" level is assigned 1 point.
[0148] Based on the current research status of the seepage and clogging mechanism of the silt-geotextile reverse filtration system, the gradient ratio clogging risk level is set as the primary consideration, while the permeability coefficient ratio clogging risk level is set as a secondary consideration. A score is assigned to the gradient ratio clogging risk level. Weighting coefficients Assign a permeability coefficient score to a clogging risk level. Weighting coefficients The formula for calculating the anti-clogging performance score S is:
[0149] ;
[0150] The calculation results of the anti-clogging comprehensive performance score S are shown in Table 4.
[0151] Table 4 Calculation Results of Anti-clogging Performance Score
[0152]
[0153] Step 6: Rank the candidate filter materials according to their anti-clogging performance to determine the filter material.
[0154] Based on the material anti-clogging performance scores in the order of D, E, and A, material D, with the highest anti-clogging performance score, was selected as the filter layer material.
[0155] Based on this, the final design scheme recommends using material D as the filter layer material for the seawall project. This design method is based on the service environment of geotextiles under the silty soil geological conditions of the seawall project. It scientifically selects filter layer materials, significantly improving their anti-siltation ability while meeting the requirements of soil conservation and permeability, and ensuring the long-term stability and effectiveness of the filter function of the seawall within its design service life.
[0156] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method of designing a geotextile filter layer for enhancing the safety of a silt filter, characterized in that, include: Obtain engineering silt parameters, including characteristic particle size and permeability coefficient of silt; Based on the filter layer matching algorithm, the maximum and minimum values of hydraulic performance parameters of the filter layer material are calculated, including the maximum value of the equivalent pore size under tensile strain of the filter layer geotextile and the minimum value of the vertical permeability coefficient under long-term load. The filter layer matching algorithm includes: The characteristic particle size of the silt and the equivalent pore size of the geotextile filter layer under tensile strain should satisfy the following relationship: ； wherein is the equivalent pore size under tensile strain of the geotextile; is the characteristic grain size of the silt; B is the soil conservation coefficient: under static water or laminar flow conditions, the soil conservation coefficient B is selected as a preset value according to the soil type, the non-uniformity coefficient and the compactness of the protected soil; under dynamic water flow conditions, the soil conservation coefficient B is determined according to the interaction test between the geotextile and the soil; The permeability coefficient of the silt and the vertical permeability coefficient of the geotextile filter layer under long-term load should satisfy the following relationship: ； in is the vertical permeability coefficient of the geotextile under long-term load; A is the preset safety factor. The permeability coefficient of the soil being protected; Analyze actual engineering conditions, retrieve material parameters from the material database, and use the filter layer matching algorithm to search and determine candidate materials for the reverse filter layer that meet the conditions. Conduct long-term clogging tests on the candidate materials for the reverse filter layer to obtain the clogging performance indicators of the reverse filter layer materials, including gradient ratio and permeability coefficient ratio. The steps for retrieving and identifying suitable filter layer materials from the materials database include: The performance parameters of the filter layer material are obtained by collecting existing material performance parameters and experimentally determining the material performance parameters, and the material database is established. The material database stores various specifications of various filter layer materials and their corresponding performance parameters, including the equivalent pore size of geotextile under tensile strain, the thickness of geotextile under 2kPa pressure, the vertical permeability coefficient of geotextile under load, the compression creep thickness of geotextile under design normal stress and design life, and the vertical permeability coefficient of geotextile under long-term load. The type and level of tensile strain experienced by the filter layer in the actual engineering environment were analyzed, and the equivalent pore size of the geotextile under tensile strain conditions was obtained by calling the material database. Analyze the long-term normal stress acting on the filter layer; based on the long-term normal stress and the engineering design life, call the material database to obtain the thickness of the geotextile under 2 kPa pressure, the vertical permeability coefficient of the geotextile under load, and the compression creep thickness of the geotextile under the design normal stress and design life; calculate the vertical permeability coefficient of the geotextile under long-term load and store it in the material database. The maximum equivalent pore size under tensile strain and the minimum vertical permeability coefficient under long-term load are used as search criteria. The material database is traversed, and the equivalent pore size under tensile strain conditions and the vertical permeability coefficient under long-term load for each material in the database are compared with the search criteria. Materials whose equivalent pore size under tensile strain conditions is smaller than the maximum value of the equivalent pore size under tensile strain conditions and whose vertical permeability coefficient under long-term load is greater than the minimum value of the vertical permeability coefficient under long-term load are selected. All the selected materials are combined into a list as candidate materials for the filter layer; The steps for calculating the vertical permeability coefficient of geotextiles under long-term load specifically include: Use the long-term normal stress and the engineering design life as query conditions; Based on the query conditions, the thickness of geotextiles under 2 kPa pressure and the compression creep thickness of geotextiles under design normal stress and design life are searched and retrieved in the material database to match the query conditions, and the thickness compression creep reduction factor is calculated. Based on the environmental conditions of engineering applications, the reduction coefficients of geotextile permeability index are retrieved from the material database, including the reduction coefficients caused by siltation, creep-induced reduction coefficients of fabric porosity, reduction coefficients caused by adjacent soil material squeezing into fabric porosity, chemical siltation reduction coefficients, and biological siltation reduction coefficients. The total reduction coefficient of geotextile permeability index is then calculated. The long-term performance reduction factor of the geotextile was calculated. Based on the long-term normal stress of the filter layer, the vertical permeability coefficient of the geotextile under load is retrieved from the material database. The vertical permeability coefficient of the geotextile under long-term load was calculated. The calculation formula is as follows: ; in is the vertical permeability coefficient of the geotextile under long-term load; C is the long-term performance reduction factor of the geotextile. This represents the vertical permeability coefficient of the geotextile under the corresponding load. The thickness compression creep reduction factor of the geotextile; This is the total reduction factor for the permeability index of geotextiles; The compression creep thickness of the geotextile under the design normal stress and design life; The thickness of the geotextile under a pressure of 2 kPa; The reduction factor for geotextiles due to siltation; The reduction factor for the decrease in fabric porosity due to creep; The reduction factor caused by adjacent soil material squeezing into the fabric pores; This is the chemical sludge reduction factor; This is the biofouling reduction factor; Establish a clogging risk assessment model to evaluate the clogging resistance performance of materials; rank the candidate materials for the filter layer according to their clogging resistance performance, determine the filter layer materials, and generate a geotextile filter layer design scheme.
2. The geotextile filter layer design method for enhancing the safety of silty soil filter according to claim 1, characterized in that, The steps for conducting long-term clogging tests to obtain the clogging performance indicators of the filter layer material specifically include: Conduct long-term clogging tests; determine the gradient ratio according to SL235-2012 standard. Calculate the permeability coefficient The calculation formula is as follows: ; in The ratio of permeability coefficients; The permeability coefficient is the combined permeability coefficient of the geotextile and the soil material 25 mm above it.
3. The geotextile filter layer design method for enhancing the safety of silty soil filter according to claim 1, characterized in that, Establish a clogging risk assessment model to evaluate the anti-clogging performance of materials, specifically including: The gradient ratio and permeability coefficient ratio are used as indicators for assessing clogging risk; a threshold for judging clogging status is set; the clogging risk assessment indicators are compared with the clogging status judgment threshold to determine the clogging risk level; a quantitative scoring standard is set for the clogging risk level; the weights of the clogging risk assessment indicators are set; and the clogging resistance performance score of the material is calculated using a weighted scoring method.
4. The geotextile filter layer design method for enhancing the safety of silty soil filter according to claim 3, characterized in that, The siltation risk level is determined by comparing the aforementioned siltation risk assessment indicators with the siltation state discrimination threshold, specifically including: The gradient ratio is compared with a first preset threshold. If the gradient ratio is less than the first preset threshold, the gradient ratio clogging risk level is determined to be low risk. If the gradient ratio is not less than the first preset threshold, it is compared with a second preset threshold, where the second preset threshold is greater than the first preset threshold. If the gradient ratio is greater than the second preset threshold, the gradient ratio clogging risk level is determined to be high risk. If the gradient ratio is between the first preset threshold and the second preset threshold, the gradient ratio clogging risk level is determined to be medium risk. The permeability ratio is compared with a first preset threshold. If the permeability ratio is less than the first preset threshold, the permeability ratio clogging risk level is determined to be high-risk. If the permeability ratio is not less than the first preset threshold, it is compared with a second preset threshold. If the second preset threshold is greater than the first preset threshold, the permeability ratio clogging risk level is determined to be low-risk. If the permeability ratio is between the first and second preset thresholds, the permeability ratio clogging risk level is determined to be medium-risk.
5. The geotextile filter layer design method for enhancing the safety of silty soil filtration according to claim 1, characterized in that, The process of ranking candidate filter materials according to their anti-clogging performance to determine the filter material includes: Based on the clogging risk assessment results, the candidate materials for the filter layer are sorted from high to low according to their anti-clogging performance scores; the candidate material with the highest score is selected as the filter layer material, and the filter layer design scheme is generated and output.