Self-repairing warp-knitted spacer high-strength geotextile and preparation method thereof

Abstract

The present invention discloses a self-repairing warp-knitted spaced high-strength geotextile and a preparation method thereof. The self-repairing warp-knitted spaced high-strength geotextile is composed of a surface layer of warp-knitted high-strength geotextile, a spacer yarn layer, and a surface layer of warp-knitted high-strength geotextile arranged in sequence from bottom to top; the surface layer of warp-knitted high-strength geotextile uses high-strength synthetic fiber as raw material; the spacer yarn layer uses core-spun yarn as spacer yarn fiber, connecting the upper and lower surface layers of warp-knitted high-strength geotextiles; the core-spun yarn is composed of an internal high-strength core yarn fiber and an external biological fiber outer covering layer. The present invention has a simple and efficient composition structure. The surface layer of high-strength geotextile provides high mechanical strength and can effectively resist damage from various dynamic and static loads in the use environment; and the special structure of the spacer fabric enables the self-repairing high-strength composite geotextile to have excellent water permeability and anti-filtration functions, can effectively resist infiltration erosion, and is conducive to the biological solidification effect to penetrate deep into the fill.

Description

Technical Field

[0001] The present invention relates to the technical field of geotextiles, and in particular to a self-repairing warp-knitted spaced high-strength geotextile and a preparation method thereof, which can be used to quickly produce a multi-layer reinforced geotextile, and can be used to protect and filter slope projects such as seawalls and riverbanks in water environments, and at the same time utilize bio-solidification technology to perform biological reinforcement on engineering structures. Background Art

[0002] Geotextiles are widely used in a variety of projects such as embankments, foundation pits, and roads, playing an important role in protection, reinforcement, and isolation. In embankment projects such as seawalls and river embankments in water environments, geotextiles not only provide general reinforcement and protection, but also have a filtering (anti-filtration) effect, allowing liquids (such as seawater and groundwater) to pass through the pores of the geotextile while preventing soil particles from being lost.

[0003] With the continuous development of construction projects, slope projects in water environments often require geotextiles with higher mechanical strength, longer service life and self-repairing ability due to the complex chemical and biological environment. These geotextiles are used to better reinforce and protect the projects, and can use the biological solidification process to complete the self-reinforcement of the structure to achieve longer-term use. However, the existing general geotextiles cannot meet the above requirements and have the following shortcomings: 1. Poor mechanical strength, especially poor compressive strength, which is prone to holes, tears and other harmful phenomena when the local force is concentrated or large; 2. Insufficient service life, and less use of components with high life and good environmental tolerance; 3. Lack of self-repairing ability, unable to further reinforce the engineering structure during use, resulting in difficulties in later maintenance; 4. Limited anti-filtration function and limited protection of soil particles.

[0004] Therefore, in order to meet the growing construction requirements, a new type of geotextile with high strength, long life and self-repairing ability is urgently needed to address the problems of insufficient mechanical strength, short service life and no self-repairing ability of general geotextiles. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is to provide a self-repairing warp-knitted spacer high-strength geotextile and a preparation method, which has a simple and efficient composition structure. The surface high-strength geotextile provides higher mechanical strength and can effectively resist the damage of various dynamic and static loads in the use environment; and the special structure of the spacer fabric makes the self-repairing high-strength composite geotextile have excellent water permeability and anti-filtration functions, which can effectively resist infiltration erosion and is conducive to the biological solidification effect to penetrate deep into the fill.

[0007] (2) Technical solution

[0008] The solution adopted by the present invention to solve the above technical problems is a self-repairing warp knitted spaced high-strength geotextile, including a self-repairing warp knitted spaced high-strength geotextile, which is composed of a surface layer of warp knitted high-strength geotextile, a spacer yarn layer and a surface layer of warp knitted high-strength geotextile arranged in sequence from bottom to top;

[0009] The surface layer warp-knitted high-strength geotextile is made of high-strength synthetic fiber as raw material;

[0010] The spacer yarn layer uses core-spun yarn as the spacer yarn fiber to connect the upper and lower surface layers of warp-knitted high-strength geotextiles; the core-spun yarn is composed of internal high-strength core yarn fibers and an external biological fiber outer covering.

[0011] In some embodiments, the high-strength synthetic fibers of the surface warp-knitted high-strength geotextile and the high-strength core yarn fibers of the spacer yarn layer are polypropylene filament fibers, which have a tensile strength of approximately 1000-1500 MPa and a service life of at least 50 years when buried in an application environment such as a bank slope. Most geotextiles use polyester fibers, polyamide fibers, and polypropylene staple fibers, etc., which typically have a tensile strength of 500-800 MPa and a service life of less than 30 years. Therefore, the tensile strength and service life of the self-repairing warp-knitted spacer high-strength geotextile are significantly improved compared to general geotextiles.

[0012] The raw materials used for the biological fiber outer covering of the core-spun yarn of the spacer yarn layer are animal fur fibers and plant stem and leaf fibers, and the two are mixed in a ratio of 1:1; the animal fur fibers are mainly processed from poultry feathers and livestock fur, and the plant stem and leaf fibers are mainly processed from straw fibers of crops such as corn and wheat; the gradual decomposition of the biological fiber can provide nitrogen fertilizer and carbon source for the solidification effect of microorganisms for a long time.

[0013] By adopting the above scheme, the surface layer of warp-knitted high-strength geotextile and the high-strength core yarn fiber of the spacer yarn layer provide mechanical strength and service life for the self-repairing warp-knitted spacer high-strength geotextile; the biological fiber outer layer of the spacer yarn layer carries the substances required for biological solidification, which plays a role in reinforcing the geotechnical structures such as backfill and grouting blocks on both sides of the self-repairing warp-knitted spacer high-strength geotextile; the three-dimensional interwoven structure of the spacer yarn layer makes the self-repairing warp-knitted spacer high-strength geotextile have good filtering and anti-filtration functions.

[0014] In some embodiments, the outer surface of the self-repairing warp-knitted spaced high-strength geotextile is covered with a layer of polyvinyl alcohol water-soluble slow-release film with a thickness of about 1 mm.

[0015] By adopting the above scheme, the setting of the polyvinyl alcohol water-soluble slow-release film can prevent the loss of biosolidified substances on the geotextile due to water erosion during the construction period of the self-repairing warp-knitted spacer high-strength geotextile applied to seawalls, riverbanks and other slope projects in water environments.

[0016] In some embodiments, the fibers of the surface layer warp-knitted high-strength geotextile and the fibers of the spacer yarn layer are woven together by a Raschel double-needle bed warp knitting machine to form an integral body.

[0017] In some embodiments, the fibers of the surface layer of warp-knitted high-strength geotextile are woven in the warp and weft directions during warp knitting, interwoven with each other to form a square grid structure, and the central pores of the grid structure are uniform and the size is consistent; the spacer yarn fibers of the spacer yarn layer are woven into a spacer structure in an "X"-shaped crossing manner, and the thickness of the finally formed spacer yarn layer is 10 mm; this can ensure that the spacer yarn layer has good anti-lateral displacement ability within the plane.

[0018] In some embodiments, the core-spun yarn in the spacer yarn layer is composited by wrapping a biological fiber outer layer around the high-strength core yarn fiber through a twisting process.

[0019] In some embodiments, the diameter of the high-strength core yarn fiber in the core-spun yarn of the spacer yarn layer is not less than 80% of the fiber diameter of the surface layer warp-knitted high-strength geotextile, which can ensure that the spacer yarn layer still maintains sufficient mechanical strength when the bio-fiber outer covering layer continues to wear out in the later period of use of the geotextile; and the material consumption of the bio-fiber outer covering layer is calculated based on the cross-sectional area, accounting for 30%-40% of the cross-sectional area of ​​the entire core-spun yarn.

[0020] The solution adopted by the present invention to solve the above technical problems is a method for preparing a self-repairing warp-knitted spaced high-strength geotextile, comprising the following steps:

[0021] (I) preparing a core-spun yarn for a spacer yarn layer; using high-strength synthetic fiber filaments as core yarns and laying them on the roving frame of a spinning frame; making short biological fiber yarns from animal fur fibers, plant stem and leaf fibers, etc. and laying them on the roving frame; wrapping the short biological fiber yarns around the outside of the core yarn and spinning them into core-spun yarns through a twisting process;

[0022] (II) High-strength synthetic fibers and core-spun yarns are introduced into a Raschel double-needle bed warp knitting machine. While warp knitting to form two surface layers of warp-knitted high-strength geotextiles, the core-spun yarns also bind the fibers of the surface layers of warp-knitted high-strength geotextiles, connecting the two surface layers and forming a spacer yarn layer. The spacing between the two needle beds can be flexibly adjusted to control the knitting thickness of the geotextile.

[0023] (III) preparing a mixed solution of Bacillus pasteurianus, urea and calcium chloride, immersing the sewn self-repairing warp-knitted high-strength geotextile in the mixed solution for a period of time, and then taking it out to dry.

[0024] In some embodiments, after step (III) is completed, the polyvinyl alcohol coating liquid is sprayed on the surface of the self-repairing high-strength composite geotextile using a coating machine to form a layer of polyvinyl alcohol water-soluble slow-release film.

[0025] (3) Beneficial effects

[0026] Compared with the prior art, the present invention designs a self-repairing warp-knitted high-strength geotextile and its preparation method.

[0027] (1) The present invention has a simple and efficient composition structure. The surface high-strength geotextile provides high mechanical strength and can effectively resist damage from various dynamic and static loads in the use environment. In addition, the special structure of the spacer fabric makes the self-repairing high-strength composite geotextile have excellent water permeability and anti-filtration functions, which can effectively resist infiltration erosion and facilitate the biological solidification effect to penetrate deep into the fill.

[0028] (2) The long-life material selected in the present invention can better adapt to the water environment in which the embankment project is located, has good tolerance to the weak alkalinity of the environment, has a longer service life than ordinary geotextiles, and achieves long-term reliable protection;

[0029] (3) The present invention has a unique self-repairing ability. During use, the biological fibers on the outside of the core-spun yarn can gradually decompose, providing nitrogen fertilizer and carbon source for the long-term curing effect of microorganisms. The biological curing reaction can further reinforce the geotechnical structure protected by the geotextile, bond soil particles and repair cracks on the structure, further improving the life and reliability of the engineering structure, saving maintenance costs, and having high economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 This is a schematic structural diagram of a self-repairing warp-knitted spaced high-strength geotextile according to the present invention;

[0032] Figure 2 This is a schematic cross-sectional view of the core-spun yarn structure of the spacer yarn layer of the present invention.

[0033] The names of the components corresponding to the various reference numerals in the figure are: 1. Surface warp-knitted high-strength geotextile; 2. Spacer yarn layer; 2-1. High-strength core yarn fiber; 2-2. Biofiber outer layer; 3. Polyvinyl alcohol water-soluble sustained-release film. DETAILED DESCRIPTION

[0034] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0037] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0038] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0039] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0040] The following describes the technical solutions provided by various embodiments of the present application in conjunction with the accompanying drawings.

[0041] like Figure 1-Figure 2 As shown, the present invention provides a self-repairing warp knitted spacer high-strength geotextile, including a self-repairing warp knitted spacer high-strength geotextile, the self-repairing warp knitted spacer high-strength geotextile is composed of a surface warp knitted high-strength geotextile 1, a spacer yarn layer 2 and a surface warp knitted high-strength geotextile 1 arranged in sequence from bottom to top; the surface warp knitted high-strength geotextile 1 uses high-strength synthetic fiber as raw material; the spacer yarn layer 2 uses core-spun yarn as spacer yarn fiber, connecting the upper and lower surface warp knitted high-strength geotextiles 1; the core-spun yarn is composed of an internal high-strength core yarn fiber 2-1 and an external biological fiber outer layer 2-2. In some embodiments, the high-strength synthetic fibers of the surface warp-knitted high-strength geotextile 1 and the high-strength core yarn fibers 2-1 of the spacer yarn layer 2 are made of polypropylene filament fibers, which have a tensile strength of 1000-1500 MPa and a buried service life of at least 50 years in application environments such as embankment slopes. The tensile strength of polyester fibers, polyamide fibers, and polypropylene staple fibers used in most geotextiles is usually between 500-800 MPa, and the service life is less than 30 years. Therefore, the tensile strength and service life of the self-repairing warp-knitted spacer high-strength geotextile are greatly improved compared with general geotextiles; the raw materials used for the biological fiber outer layer 2-2 of the core yarn of the spacer yarn layer 2 are animal fur fibers and plant stem and leaf fibers, and the two are mixed in a 1:1 ratio; animal fur fibers are mainly processed from poultry feathers and livestock fur, and plant stem and leaf fibers are mainly processed from straw fibers of crops such as corn and wheat; the gradual decomposition of the biological fiber can provide nitrogen fertilizer and carbon source for the solidification effect of microorganisms for a long time. By adopting the above scheme, the surface layer warp knitted high-strength geotextile 1 and the high-strength core yarn fiber 2-1 of the spacer yarn layer 2 provide mechanical strength and service life for the self-repairing warp knitted spacer high-strength geotextile; the biological fiber outer layer 2-2 of the spacer yarn layer 2 carries the substances required for biological solidification, which plays a role in reinforcing the geotechnical structures such as backfill, grouting blocks and other geotechnical structures on both sides of the self-repairing warp knitted spacer high-strength geotextile; the three-dimensional interwoven structure of the spacer yarn layer 2 makes the self-repairing warp knitted spacer high-strength geotextile have good filtering and anti-filtration functions.

[0042] In some embodiments, the outer surface of the self-repairing warp-knitted high-strength geotextile is covered with a 1mm thick layer of polyvinyl alcohol water-soluble slow-release film 3. This arrangement prevents the loss of biosolidified materials from the geotextile due to erosion during the construction period of the self-repairing warp-knitted high-strength geotextile, which is applied to slope projects in aquatic environments such as seawalls and riverbanks.

[0043] In some embodiments, the fibers of the surface layer warp-knitted high-strength geotextile 1 and the fibers of the spacer yarn layer 2 are woven together by a Raschel double-needle bed warp knitting machine to form an integral body. In some embodiments, the fibers of the surface layer warp-knitted high-strength geotextile 1 are woven in a warp and weft interlaced manner during warp knitting, interweaving to form a square grid structure, and the central pores of the grid structure are uniform and of consistent size; the spacer yarn fibers of the spacer yarn layer 2 are woven into a spacer structure in an "X"-shaped crossing manner, and the thickness of the spacer yarn layer 2 finally formed is 10 mm; this can ensure that the spacer yarn layer 2 has good anti-lateral displacement capability within the plane. In some embodiments, the core-spun yarn in the spacer yarn layer 2 is composited with a biological fiber outer layer 2-2 wrapped around the outside of the high-strength core yarn fiber 2-1 through a twisting process.

[0044] In some embodiments, the diameter of the high-strength core yarn fiber 2-1 in the core-spun yarn of the spacer yarn layer 2 is 80% of the fiber diameter of the surface warp-knitted high-strength geotextile 1, which can ensure that when the bio-fiber outer covering 2-2 is continuously worn out in the later period of use of the geotextile, the spacer yarn layer 2 still maintains sufficient mechanical strength; and the material consumption of the bio-fiber outer covering 2-2 is calculated based on the cross-sectional area, accounting for 40% of the cross-sectional area of ​​the entire core-spun yarn.

[0045] The present invention provides a method for preparing a self-repairing warp-knitted spaced high-strength geotextile, comprising the following steps:

[0046] (I) preparing a core-spun yarn for the spacer yarn layer 2; selecting polypropylene filament fiber as a high-strength core yarn fiber 2-1 as the material for the inner core yarn, laying it on the roving frame of the spinning frame; making biofiber staple fibers such as poultry feathers, livestock fur, and crop straw fibers into the material for the biofiber outer layer 2-2, laying it on the roving frame; wrapping the biofiber staple fibers around the outside of the core yarn, and spinning it into the core-spun yarn through a twisting process;

[0047] (II) Polypropylene filament fiber is selected as a high-strength synthetic fiber as the material of the surface warp-knitted high-strength geotextile 1, and the polypropylene filament fiber and the core-spun yarn are introduced into a Raschel double needle bed warp knitting machine. While the two surface warp-knitted high-strength geotextiles 1 are formed by warp knitting, the core-spun yarn also binds the fibers of the surface warp-knitted high-strength geotextile 1, connecting the two surface layers and forming a spacer yarn layer 2; the spacing between the two needle beds is adjusted, and the woven thickness of the obtained self-repairing warp-knitted spacer high-strength geotextile is 10 mm;

[0048] (III) preparing a mixed solution of Bacillus pasteurianus, urea and calcium chloride, immersing the sewn self-repairing warp-knitted high-strength geotextile in the mixed solution for a period of time, and then taking it out and drying it;

[0049] (IV) Using a coating machine, the polyvinyl alcohol coating liquid is sprayed on the surface of the self-repairing warp-knitted spacer high-strength geotextile to form a layer of polyvinyl alcohol water-soluble slow-release film 3 with a film thickness of 1 mm.

[0050] The mixed solution has the following proportions: the mixed solution comprises a binder and a bacterial solution, which are mixed in a volume ratio of 1:1; the binder is a mixture of 1 mol / L urea solution and 1 mol / L calcium chloride solution in a ratio of 1:1; the bacterial solution uses Bacillus pasteurianus bacterial solution with a concentration of OD600 = 1.0.

[0051] The following is a specific application scenario of the self-repairing warp knitted spaced high-strength geotextile of the above embodiment, but it is not limited to this: the self-repairing warp knitted spaced high-strength geotextile is transported from the factory to the roadbed construction site, and after the slope area to be paved is leveled, the self-repairing warp knitted spaced high-strength geotextile is laid in the area; during the construction process, generally, at least 10 cm of overlap is required between each two pieces of MICP double-sided self-repairing geotextile; after the laying is completed, a gravel cushion layer is laid on the geotextile, and other geotechnical structures such as cast-in-place blocks are built; during construction, the polyvinyl alcohol water-soluble slow-release film slowly dissolves to temporarily prevent water from eroding the geotextile. After completion, the film is basically dissolved, and water penetrates into the geotextile, triggering a microbial curing (MICP) reaction, and reinforcing the geotechnical structures on both sides of the geotextile. The same and similar parts between the various embodiments in this specification can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0052] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a self-repairing warp-knitted spaced high-strength geotextile, characterized by: The following steps are involved: (I) preparing the core-spun yarn of the spacer yarn layer (2); using high-strength synthetic fiber filaments as the core yarn and laying them on the roving frame of the spinning frame; making animal fur fibers and plant stem and leaf fibers into biofiber short yarns and laying them on the roving frame; The core yarn is wrapped with short biofiber yarn and spun into core-spun yarn through twisting process; (II) High-strength synthetic fibers and core-spun yarns are introduced into a Raschel double needle bed warp knitting machine. While warp knitting to form two surface layers of warp-knitted high-strength geotextiles (1), the core-spun yarns also bind the fibers of the surface layers of warp-knitted high-strength geotextiles (1), connecting the two surface layers and forming a spacer yarn layer (2). The spacing between the two needle beds can be flexibly adjusted to control the knitting thickness of the geotextile. (III) preparing a mixed solution of Bacillus pasteurianus, urea and calcium chloride, immersing the sewn self-repairing warp-knitted high-strength geotextile in the mixed solution for a period of time, and then taking it out and drying it.

2. The method for preparing the self-repairing warp-knitted spaced high-strength geotextile according to claim 1, characterized in that: After the step (III) is completed, the polyvinyl alcohol coating liquid is sprayed on the surface of the self-repairing high-strength composite geotextile using a coating machine to form a layer of polyvinyl alcohol water-soluble slow-release film (3).

3. A self-repairing warp knitted spaced high-strength geotextile made by the preparation method of any one of claims 1-2, comprising a self-repairing warp knitted spaced high-strength geotextile, characterized in that: The self-repairing warp-knitted spacer high-strength geotextile is composed of a surface warp-knitted high-strength geotextile (1), a spacer yarn layer (2), and a surface warp-knitted high-strength geotextile (1) arranged in sequence from bottom to top; The surface layer warp-knitted high-strength geotextile (1) is made of high-strength synthetic fiber as raw material; The spacer yarn layer (2) uses core-spun yarn as the spacer yarn fiber to connect the upper and lower surface layers of warp-knitted high-strength geotextile (1); the core-spun yarn is composed of internal high-strength core yarn fibers (2-1) and an external biological fiber outer layer (2-2).

4. The self-repairing warp-knitted high-strength spacer geotextile according to claim 3, characterized in that: The outer surface of the self-repairing warp-knitted spacer high-strength geotextile is covered with a layer of polyvinyl alcohol water-soluble slow-release film (3).

5. The self-repairing warp-knitted high-strength spacer geotextile according to claim 3, characterized in that: The fibers of the surface warp-knitted high-strength geotextile (1) and the fibers of the spacer yarn layer (2) are knitted together by a Raschel double-needle bed warp knitting machine to form an integral body.

6. The self-repairing warp-knitted high-strength spacer geotextile according to claim 3, characterized in that: The fibers of the surface layer warp-knitted high-strength geotextile (1) are woven in a warp and weft interlaced manner during warp knitting, interweaving to form a square grid structure, and the central pores of the grid structure are uniform and of consistent size; the spacer yarn fibers of the spacer yarn layer (2) are woven into the spacer structure in an "X"-shaped cross pattern.

7. The self-repairing warp-knitted high-strength spacer geotextile according to claim 3, characterized in that: The core-spun yarn in the spacer yarn layer (2) is composited by wrapping a biological fiber outer layer (2-2) around the outside of a high-strength core yarn fiber (2-1) through a twisting process.

8. The self-repairing warp-knitted high-strength spacer geotextile according to claim 3, characterized in that: In the core-spun yarn of the spacer yarn layer (2), the diameter of the high-strength core yarn fiber (2-1) is not less than 80% of the fiber diameter of the surface warp-knitted high-strength geotextile (1); and the material usage of the biofiber outer layer (2-2) is calculated based on the cross-sectional area and accounts for 30%-40% of the cross-sectional area of ​​the entire core-spun yarn.

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