Reinforcing method and device combining flood drainage and slope supporting of spoil site

Abstract

The invention discloses a reinforcing method and device combining flood drainage and slope supporting of a spoil site. The method comprises the steps that S1, the stratum lithology composition, physical and mechanical property parameters, hydro meteorological conditions, the spoil volume of the spoil site and the spoil height of the spoil site in a mountainous area are determined; s2, intelligently analyzing the flood of the mountainous area spoil field drainage basin through machine learning forecast to obtain a designed flood peak flow; s3, the filling slope design is combined with a flood drainage box culvert, a wall toe bottom plate is arranged on the inner side of the flood drainage box culvert, a cantilever type retaining wall is formed, and the length and thickness of a wall heel plate of a slope toe section are designed and determined; and S4, the upper middle portion of the spoil slope is supported through slope making and a reinforced retaining wall, the slope ratio ranges from 1: 1 to 1: 0.5, the geogrid length ranges from 5.0 m to 20.0 m, the vertical distance ranges from 0.5 m, and the device is achieved based on the method. The method has the advantages of being multifunctional, low in manufacturing cost, rapid in construction, safe and stable, and solves the comprehensive flood drainage and protection problems of the large spoil site slope in the complex mountainous area.

Description

Technical Field

[0001] The invention relates to the field of spoil field slopes, and in particular to a spoil field flood discharge and slope support combined reinforcement method and device. Background Art

[0002] At present, more and more major projects are expanding into the hilly and mountainous areas around cities, which will inevitably produce a large amount of abandoned soil and slag. Especially for highway and railway projects, a large number of abandoned soil sites must be set up to meet the needs of engineering construction.

[0003] Due to the influence of topography, mountain climate and ecological environment, as well as the special properties of the dump itself, such as looseness, unconsolidation, poor sorting and non-saturation, it is easy to become unstable under conditions such as rainfall, and even cause a chain of disasters, causing huge losses to people’s lives and property.

[0004] Most of the abandoned soil dumps are located in gullies in mountainous areas. The main engineering geological problems are the stability of the abandoned soil dump slopes and the flood control and drainage problems in the gullies. At present, the slope support project and the flood drainage project are basically designed independently, and supervised and reviewed by different government management departments, resulting in high project costs, conflicts, unreasonable design, complicated post-design, long construction period and unsatisfactory control effect. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method and device for reinforcing a spoil site by combining flood discharge with slope support.

[0006] A method for reinforcing a spoil site by combining flood drainage with slope support, comprising the following steps:

[0007] S1: Determine the stratum lithology composition, physical and mechanical property parameters, hydrological and meteorological conditions, volume and height of the dumping site in the mountainous area;

[0008] S2: Conduct in-depth mining and correlation analysis of data, and use machine learning to predict floods in the mountainous area to intelligently analyze the flood peak flow and design flood discharge culverts;

[0009] The data include hydrological observation data, historical flood survey data, rainstorm and flood characteristics;

[0010] S3: Slope stability analysis is conducted on the geotechnical data of the spoil site. The fill slope design is combined with the flood discharge box culvert. A wall toe bottom plate is set inside the flood discharge box culvert to form a cantilever retaining wall. The length and thickness of the wall heel plate at the slope foot section are determined by design.

[0011] The geotechnical data of the spoil site include the material composition of the spoil site, the mechanical properties of the rock and soil, and the height of the spoil slope;

[0012] S4: For the middle and upper part of the abandoned soil slope, slope reduction + reinforced retaining wall support is adopted, with a slope ratio of 1:1 to 1:0.5, a geogrid length of 5.0 to 20.0 m, and a vertical spacing of 0.5 m.

[0013] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S1 comprises the following sub-steps:

[0014] S11: Use comprehensive means to determine the drainage area F of the spoil dump, the length of the gully L, the average slope of the river J, the rainfall H1, the physical and mechanical parameters of the rock and soil mass, and the volume and height of the spoil dump;

[0015] The comprehensive means include engineering surveying, engineering geological mapping, drilling, trenching, field testing, and indoor testing.

[0016] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S2 comprises the following sub-steps:

[0017] S21: Calculate the flood flow in the spoil dump area. The rainstorm reasoning formula is:

[0018]

[0019] Where Q represents the maximum flow rate in m 3 / s; ψ represents the peak runoff coefficient; S represents the rainstorm intensity, the unit is mm / h;

[0020] τ represents the flow time of the basin, in h; F represents the basin area, in km 2 ; n represents the rainstorm formula index;

[0021] S22: Compare and calibrate historical flood survey data with theoretical calculation results and correct calibration parameters:

[0022] The verification parameters include but are not limited to flood flow Q and maximum rainfall H;

[0023] S23: Extract flood flow related factors and use the correlation relationship to regard water level analysis as a multi-input, single-output linear dynamic system. The formula is:

[0024]

[0025] Among them, H down (t) represents the output of the system at time t, uj(ti) represents the input of the jth influencing factor at time ti, ε t represents the random error term;

[0026] Among them, α k represents the model parameters, k = 1, 2, ... K, K represents the number of model parameters; bij represents model parameters, i = 1, 2, ..., N(j), j = 1, 2, ..., M, M represents the number of other factors, and N(j) represents the number of model parameter factors;

[0027] S24: Use the stepwise regression method to maximize the predictive ability with the least number of variables, remove variables from the model one by one from most to least until there are no variables that can be removed, and select the model by comparing the errors calculated on the reserved samples. Use the regularization term in the form of L2 norm through the ridge regression method. The formula is:

[0028] min||xw-y|| 2 +z2||w|| 2

[0029] Among them, x and y represent variables, w represents weight, z2 represents the squared deviation factor in the form of L2 norm, and min represents the minimum value;

[0030] S25: The Lasso method uses a regularization term in the form of the L1 norm, the formula is: and

[0031] min||xw-y|| 2 +z1||w||

[0032] Among them, z1 represents the squared deviation factor in L1 norm form;

[0033] S26: The elastic net method uses both L1 and L2 regularization to obtain the properties of both ridge regression and Lasso methods. The formula is:

[0034] min||xw-y|| 2 +z1||w‖+z2||w|| 2

[0035] S27: The L-curve method takes the inflection point of the curve transition interval and the regularization parameter corresponding to the inflection point as the optimal regularization parameter to obtain the flood flow parameter of the spoil field area;

[0036] The inflection point is the point where the curvature is maximum.

[0037] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S3 comprises the following sub-steps:

[0038] S31: Calculate the soil pressure acting on the back of the wall and determine the distance from the bottom of the wall. The formula is:

[0039] E=0.5×γ×H 2 ×K a

[0040] E x=E×cos(β)

[0041] E y =E×sin(β)

[0042]

[0043] Among them, E represents the earth pressure acting on the back of the wall, the point of action is 1 / 3 of the height from the bottom of the wall, and the direction forms an angle β with the horizontal plane;

[0044] K a represents the active earth pressure coefficient, γ represents the gravity, and H represents the height of the retaining wall;

[0045] S32: Anti-sliding stability verification, the formula is:

[0046]

[0047] Among them, Kc represents the stability coefficient, f′ represents the friction angle of rock and soil, ∑G represents gravity, c′ represents cohesion, A represents the area of ​​the retaining wall base surface, and ∑H represents the sliding force;

[0048] S33: Anti-overturning stability verification, the formula is:

[0049]

[0050] Among them, Ko represents the anti-overturning stability coefficient, ∑MV anti-overturning moment, and ∑MH represents the overturning moment;

[0051] S34: Verification of foundation bearing capacity, the formula is:

[0052]

[0053] Among them, Pmax represents the maximum bearing capacity of the foundation, Pmin represents the minimum bearing capacity of the foundation, ∑M represents the moment value acting on the bottom surface of the foundation, and W represents the resistance moment of the bottom surface of the foundation;

[0054] S35: Determine the length and thickness of the wall heel plate at the toe of the slope through the values ​​of soil pressure, anti-sliding stability verification, anti-overturning stability verification, and foundation bearing capacity verification.

[0055] A reinforcement device combining flood discharge and slope support for an abandoned soil field, comprising clay, a high-toughness polyester yarn cluster grid, a connecting rod, a gravel filter layer, a seed bag, reinforced concrete, a flood discharge box culvert, a wall heel plate, and a concrete cushion layer;

[0056] The clay is arranged above the high-toughness polyester yarn bundle grid, multiple high-toughness polyester yarn bundle grid layers are connected by connecting rods, gravel filter layers are staggered and stacked on the high-toughness polyester yarn bundle grid, seed bags are arranged on the slope, reinforced concrete is arranged below the high-toughness polyester yarn bundle grid, the drainage box culvert connects the reinforced concrete and the wall heel plate, and the concrete cushion layer is arranged below the drainage box culvert.

[0057] Furthermore, a reinforcement device combining flood drainage and slope support of an abandoned soil site is provided, wherein the clay is used to compact the top of the abandoned soil slope, the seed bag is used to green the surface of the abandoned soil slope by planting soil and grass seeds, and the backfill soil is compacted in layers with a high-toughness polyester yarn bundle grid.

[0058] The beneficial effects of the present invention are: a method and device for reinforcing a spoil dump that combines flood drainage with slope support, which is multifunctional, low-cost, fast in construction, safe and stable, and can address the comprehensive flood drainage and protection problems of the slopes of large spoil dumps in complex mountainous areas; it reduces repeated designs, has a simple management process, can adopt prefabricated construction, speeds up construction, and saves implementation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a schematic diagram of a reinforcement method that combines drainage of spoil dump with slope support.

[0060] Figure 2 The structural diagram of a reinforcement device combining flood discharge from a spoil site with slope support.

[0061] In the figure, 1-clay, 2-high-tenacity polyester yarn cluster grid, 3-connecting rod, 4-gravel filter layer, 5-seed bag, 6-reinforced concrete, 7-flood drainage box culvert, 8-wall heel plate, 9-concrete cushion layer, 10-spoil dump fill. DETAILED DESCRIPTION

[0062] The present invention is further described below, but the protection scope of the present invention is not limited to the following description.

[0063] A method for reinforcing a spoil site by combining flood drainage with slope support, comprising the following steps:

[0064] S1: Determine the stratum lithology composition, physical and mechanical property parameters, hydrological and meteorological conditions, volume and height of the dumping site in the mountainous area;

[0065] S2: Conduct in-depth mining and correlation analysis on data, and conduct intelligent analysis of floods in the mountainous area waste dump basin through machine learning forecasting, obtain the designed peak flow, and design flood discharge box culvert 7;

[0066] The data include hydrological observation data, historical flood survey data, rainstorm and flood characteristics;

[0067] S3: Slope stability analysis is performed on the geotechnical data of the spoil site. The fill slope design is combined with the flood discharge box culvert 7. A wall toe bottom plate is set inside the flood discharge box culvert 7 to form a cantilever retaining wall. The length and thickness of the wall heel plate 8 at the slope foot section are designed and determined;

[0068] The geotechnical data of the spoil site include the material composition of the spoil site, the mechanical properties of the rock and soil, and the height of the spoil slope;

[0069] S4: For the middle and upper part of the abandoned soil slope, slope reduction + reinforced retaining wall support is adopted, with a slope ratio of 1:1 to 1:0.5, a geogrid length of 5.0 to 20.0 m, and a vertical spacing of 0.5 m.

[0070] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S1 comprises the following sub-steps:

[0071] S11: Use comprehensive means to determine the drainage area F of the spoil dump, the length of the gully L, the average slope of the river J, the rainfall H1, the physical and mechanical parameters of the rock and soil mass, and the volume and height of the spoil dump;

[0072] The comprehensive means include engineering surveying, engineering geological mapping, drilling, trenching, field testing, and indoor testing.

[0073] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S2 comprises the following sub-steps:

[0074] S21: Calculate the flood flow in the spoil dump area. The rainstorm reasoning formula is:

[0075]

[0076] Where Q represents the maximum flow rate in m 3 / s; ψ represents the peak runoff coefficient; S represents the rainstorm intensity, the unit is mm / h;

[0077] τ represents the flow time of the basin, in h; F represents the basin area, in km 2 ; n represents the rainstorm formula index;

[0078] S22: Compare and calibrate historical flood survey data with theoretical calculation results and correct calibration parameters:

[0079] The verification parameters include but are not limited to flood flow Q and maximum rainfall H;

[0080] S23: Extract flood flow related factors and use the correlation relationship to regard water level analysis as a multi-input, single-output linear dynamic system. The formula is:

[0081]

[0082] Among them, H down (t) represents the output of the system at time t, uj(ti) represents the input of the jth influencing factor at time ti, ε t represents the random error term;

[0083] Among them, α k represents model parameters, k = 1, 2, ..., K, K represents the number of model parameters; bij represents model parameters, i = 1, 2, ..., N(j), j = 1, 2, ..., M, M represents the number of other factors, and N(j) represents the number of model parameter factors;

[0084] S24: Due to the large number of factors affecting floods and different weights of factors, the stepwise regression method is used to maximize the prediction ability with the least number of variables. Variables are removed from the model one by one from many to few until there are no variables that can be removed. The model is selected by comparing the errors calculated on the reserved samples. The regularization term in the form of L2 norm is used through the ridge regression method. The formula is:

[0085] min||xw-y|| 2 +z2||w|| 2

[0086] Among them, x and y represent variables, w represents weight, z2 represents the squared deviation factor in the form of L2 norm, and min represents the minimum value;

[0087] S25: The Lasso method uses a regularization term in the form of the L1 norm, the formula is: and

[0088] min||xw-y|| 2 +z1||w||

[0089] Among them, z1 represents the squared deviation factor in L1 norm form;

[0090] S26: The elastic net method uses both L1 and L2 regularization to obtain the properties of both ridge regression and Lasso methods. The formula is:

[0091] min||xw-y|| 2 +z1||w||+z2||w|| 2

[0092] S27: The L-curve method takes the inflection point of the curve transition interval and the regularization parameter corresponding to the inflection point as the optimal regularization parameter to obtain the flood flow parameter of the spoil field area;

[0093] The inflection point is the point where the curvature is maximum.

[0094] Furthermore, a method for reinforcing a spoil dump by combining flood drainage with slope support is provided, wherein step S3 comprises the following sub-steps:

[0095] S31: Calculate the soil pressure acting on the back of the wall and determine the distance from the bottom of the wall. The formula is:

[0096] E=0.5×γ×H 2 ×K a

[0097] E x =E×cos(β)

[0098] E y =E×sin(β)

[0099]

[0100] Among them, E represents the earth pressure acting on the back of the wall, the point of action is 1 / 3 of the height from the bottom of the wall, and the direction forms an angle β with the horizontal plane;

[0101] K a represents the active earth pressure coefficient, γ represents the gravity, and H represents the height of the retaining wall;

[0102] S32: Anti-sliding stability verification, the formula is:

[0103]

[0104] Among them, Kc represents the stability coefficient, f′ represents the friction angle of rock and soil, ΣG represents gravity, c′ represents cohesion, A represents the area of ​​the retaining wall base surface, and ΣH represents the sliding force;

[0105] S33: Anti-overturning stability verification, the formula is:

[0106]

[0107] Among them, Ko represents the anti-overturning stability coefficient, ∑MV anti-overturning moment, and ∑MH represents the overturning moment;

[0108] S34: Verification of foundation bearing capacity, the formula is:

[0109]

[0110] Among them, Pmax represents the maximum bearing capacity of the foundation, Pmin represents the minimum bearing capacity of the foundation, ΣM represents the moment value acting on the bottom surface of the foundation, and W represents the resistance moment of the bottom surface of the foundation;

[0111] S35: Determine the length and thickness of the wall heel plate 8 at the toe section of the slope through the values ​​of soil pressure, anti-sliding stability verification, anti-overturning stability verification, and foundation bearing capacity verification.

[0112] A reinforcement device combining flood discharge and slope support for an abandoned soil field, comprising clay 1, a high-toughness polyester yarn cluster grid 2, a connecting rod 3, a gravel filter layer 4, a seed bag 5, reinforced concrete 6, a flood discharge box culvert 7, a wall heel plate 8, and a concrete cushion layer 9;

[0113] The clay 1 is arranged above the high-toughness polyester yarn bundle grid 2, multiple high-toughness polyester yarn bundle grids 2 are connected by connecting rods 4, the gravel filter layer 4 is staggered and stacked on the high-toughness polyester yarn bundle grid 2, the seed bag 5 is arranged on the slope, the reinforced concrete 6 is arranged below the high-toughness polyester yarn bundle grid 2, the drainage box culvert 7 connects the reinforced concrete 6 and the wall heel plate 8, and the concrete cushion layer 9 is arranged below the drainage box culvert 7.

[0114] Furthermore, a reinforcement device combining flood drainage and slope support of a spoil site is provided, wherein the clay 1 compacts the top of the spoil slope, the seed bag 5 greens the surface of the spoil slope by planting soil and grass seeds, and the backfill soil is compacted in layers with a high-toughness polyester yarn cluster grid 2, and the device is arranged next to the spoil site fill 10.

[0115] A reinforcement method and device combining flood drainage and slope support for abandoned soil sites is adopted, which has the characteristics of multi-function, low cost, fast construction, safety and stability, and can solve the comprehensive flood drainage and protection problems of the slopes of large abandoned soil sites in complex mountainous areas; it reduces repeated designs, simplifies the management process, and can adopt prefabricated construction to speed up the construction speed and save the implementation period.

[0116] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for reinforcing a spoil site by combining flood drainage with slope support, characterized in that: The following steps are involved: S1: Determine the stratum lithology composition, physical and mechanical property parameters, hydrological and meteorological conditions, volume and height of the dumping site in the mountainous area; S2: Conduct in-depth data mining and correlation analysis, and use machine learning to predict floods in the mountainous area, obtain the designed peak flow, and design flood discharge culverts (7); The data include hydrological observation data, historical flood survey data, rainstorm and flood characteristics; S3: Slope stability analysis is performed on the geotechnical data of the spoil site, and the fill slope design is combined with the flood discharge box culvert (7). A wall toe bottom plate is set inside the flood discharge box culvert (7) to form a cantilever retaining wall. The length and thickness of the wall heel plate (8) at the slope foot section are designed and determined; The geotechnical data of the spoil site include the material composition of the spoil site, the mechanical properties of the rock and soil, and the height of the spoil slope; S4: For the middle and upper part of the abandoned soil slope, slope reduction + reinforced retaining wall support is adopted, with a slope ratio of 1:1 to 1:0.5, a geogrid length of 5.0 to 20.0 m, and a vertical spacing of 0.5 m.

2. The method for reinforcing a spoil dump by combining flood drainage with slope support according to claim 1, characterized in that: The step S1 comprises the following sub-steps: S11: Use comprehensive means to determine the drainage area F of the spoil dump, the length of the gully L, the average slope of the river J, the rainfall H1, the physical and mechanical parameters of the rock and soil mass, and the volume and height of the spoil dump; The comprehensive means include engineering surveying, engineering geological mapping, drilling, trenching, field testing, and indoor testing.

3. The method for reinforcing a spoil dump by combining flood drainage with slope support according to claim 2, characterized in that: The step S2 comprises the following sub-steps: S21: Calculate the flood flow in the spoil dump area. The rainstorm reasoning formula is: Where Q represents the maximum flow rate in m 3 / s; ψ represents the peak runoff coefficient; S represents the rainstorm intensity, the unit is mm / h; τ represents the flow time of the basin, in h; F represents the basin area, in km 2 ; n represents the rainstorm formula index; S22: Compare and calibrate historical flood survey data with theoretical calculation results and correct calibration parameters: The verification parameters include but are not limited to flood flow Q and maximum rainfall H; S23: Extract flood flow related factors and use the correlation relationship to regard water level analysis as a multi-input, single-output linear dynamic system. The formula is: Among them, H down (t) represents the output of the system at time t, uj(ti) represents the input of the jth influencing factor at time ti, ε t represents the random error term; Among them, α k represents model parameters, k = 1, 2, ..., K, K represents the number of model parameters; bij represents model parameters, i = 1, 2, ..., N(j), j = 1, 2, ..., M, M represents the number of other factors, and N(j) represents the number of model parameter factors; S24: Use the stepwise regression method to maximize the predictive ability with the least number of variables, remove variables from the model one by one from most to least until there are no variables that can be removed, and select the model by comparing the errors calculated on the reserved samples. Use the regularization term in the form of L2 norm through the ridge regression method. The formula is: min||xw-y|| 2 +z2||w|| 2 Among them, x and y represent variables, w represents weight, z2 represents the squared deviation factor in the form of L2 norm, and min represents the minimum value; S25: The Lasso method uses a regularization term in the form of the L1 norm, the formula is: and min||xw-y|| 2 +z1||w|| Among them, z1 represents the squared deviation factor in L1 norm form; S26: The elastic net method uses both L1 and L2 regularization to obtain the properties of both ridge regression and Lasso methods. The formula is: min||xw-y|| 2 +z1||w||+z2||w|| 2 S27: The L-curve method takes the inflection point of the curve transition interval and the regularization parameter corresponding to the inflection point as the optimal regularization parameter to obtain the flood flow parameter of the spoil field area; The inflection point is the point where the curvature is maximum.

4. The method for reinforcing a spoil dump by combining flood drainage with slope support according to claim 2, characterized in that: The step S3 comprises the following sub-steps: S31: Calculate the soil pressure acting on the back of the wall and determine the distance from the bottom of the wall. The formula is: E=0.5×γ×H 2 ×K a E x =E×cos(β) E y =E×sin(β) Among them, E represents the earth pressure acting on the back of the wall, the point of action is 1 / 3 of the height from the bottom of the wall, and the direction forms an angle β with the horizontal plane; K a represents the active earth pressure coefficient, γ represents the gravity, and H represents the height of the retaining wall; S32: Anti-sliding stability verification, the formula is: Among them, Kc represents the stability coefficient, f′ represents the friction angle of rock and soil, ∑G represents gravity, c′ represents cohesion, A represents the area of ​​the retaining wall base surface, and ∑H represents the sliding force; S33: Anti-overturning stability verification, the formula is: Among them, Ko represents the anti-overturning stability coefficient, ∑MV anti-overturning moment, and ∑MH represents the overturning moment; S34: Verification of foundation bearing capacity, the formula is: Among them, Pmax represents the maximum bearing capacity of the foundation, Pmin represents the minimum bearing capacity of the foundation, ∑M represents the moment value acting on the bottom surface of the foundation, and W represents the resistance moment of the bottom surface of the foundation; S35: Determine the length and thickness of the wall heel plate (8) at the toe of the slope according to the values ​​of soil pressure, anti-sliding stability verification, anti-overturning stability verification and foundation bearing capacity verification.

5. A spoil dump flood discharge and slope support combined reinforcement device, based on the spoil dump flood discharge and slope support combined reinforcement method according to any one of claims 1 to 4, characterized in that: It comprises clay (1), a high-tenacity polyester yarn cluster grid (2), a connecting rod (3), a gravel filter layer (4), a seed bag (5), reinforced concrete (6), a flood discharge box culvert (7), a wall heel plate (8), and a concrete cushion layer (9); The clay (1) is arranged above the high-tenacity polyester yarn bundle grid (2), a plurality of high-tenacity polyester yarn bundle grids (2) are connected between layers via connecting rods (4), a gravel filter layer (4) is staggered and stacked on the high-tenacity polyester yarn bundle grid (2), a seed bag (5) is arranged on the slope, a reinforced concrete (6) is arranged below the high-tenacity polyester yarn bundle grid (2), a flood discharge box culvert (7) connects the reinforced concrete (6) and the wall heel plate (8), and a concrete cushion layer (9) is arranged below the flood discharge box culvert (7).

6. The device for combining flood discharge and slope support for spoil dump according to claim 5 is characterized in that: The clay (1) is used to compact the top of the abandoned soil slope, the seed bag (5) is used to green the surface of the abandoned soil slope by planting soil and adding grass seeds, and the backfill soil is layered and compacted into the high-toughness polyester yarn cluster grid (2).

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