AU2018204590A1 - A subgrade stability reinforcement and filter composite - Google Patents

Abstract

The invention relates to a subgrade stability reinforcement and filter composite, comprising woven fabric and nonwoven fabric, with the woven fabric set on top of the nonwoven fabric; the woven and nonwoven fabric are structurally attached together as an integral composite material using multiple parallel stitch line seams. The subgrade stability reinforcement and filter composite of the present invention can more effectively provide combined application functions of reinforcement, separation, filtration, and drainage; to maintain the subgrade stability of the railways, highways, access roads, airport runways, and other structural load bearing platform applications. The use of multiple parallel stitch line seaming method of the two fabric surfaces can effectively prevent the relative slippage of the woven fabric and nonwoven fabric in whole or in part, reduce construction time and cost, and improve engineering stability and construction.

Description

A SUBGRADE STABILITY REINFORCEMENT AND FILTER COMPOSITE

TECHNICAL FIELD

The present invention relates to the field of geosynthetic materials, particularly relates to a subgrade stability reinforcement and filter composite.

BACKGROUND ART

Geosynthetic materials are synthetic materials used in geotechnical engineering and civil engineering applications. Geosynthetic materials include geotextiles, geogrids, geomattresses, geomats, geonets, etc. Geotextiles are water permeable fabrics that may be produced using weaving technology, with advantages of lightweight, overall structural continuity, easy 0 installation in construction applications and high tensile modulus properties, thus commonly used in subgrade enhancement and separation applications. Geotextiles can be divided into woven geotextiles and nonwoven geotextiles, the former is woven using mono-filament yarns, multi-filament yarns and/or tape yams, and the latter is made using staple fibres or continuous filaments laid onto a webbing surface, then subjected to mechanical entanglement, 5 heat-bonding or chemical bonding process. Geotextiles are commonly used for railways, highways, access roads, airport runways, and other structural load bearing platform subgrade stability improvement applications. Geotextiles can increase the bearing capacity of subgrade and improve construction efficiency; geotextiles can act as a soil filter, preventing intermixing of subgrade soil with basecourse or ballast material under action of rainfall or imposed load, 0 thereby preserving the integrity and strength of basecourse or ballast material over time. Additionally, geotextiles can sustain part of the stresses induced by imposed load, dispersing the stresses over the subgrade soil attached closely to the geotextiles, thereby improving the bearing capacity of the subgrade.

Geosynthetic materials may individually have performance functions such as separation, 25 filtration, reinforcement, protection, barrier or drainage. In practical engineering projects, multiple performance functions are required, resulting in requirement of usage of multiple geosynthetic materials. If multiple geosynthetic materials are simply overlapped with each other, slippage may occur at the interface between the geosynthetic materials, thereby preventing the development of composite performance functions without compromising other 30 safety and stability concerns in design and application. Also, the laying of multiple geosynthetic materials will increase construction time and cost when compared to the laying of a single composite geosynthetic material with multiple performance functions. Composite - 1 2018204590 25 Jun 2018 geosynthetic materials will overcome the above problems. Composite geosynthetic materials combine a variety of geosynthetic materials into a single entity. Multiple individual layers of geosynthetic materials are structurally connected to become a structurally integrated entity.

Compared to single geotextiles, composite geosynthetic materials have multiple performance functions and perform more stable effect.

In the prior art, composite geosynthetic materials are usually made by bonding two or more individual layers of geosynthetic materials through adhesion treatment. Adhesion treatment includes the use of adhesive bonding or heat treatment bonding. However, using adhesive or heat treatment to bond composite geosynthetic materials is complex, and the 0 composite geosynthetic materials tend to become stiff, thus cannot maintain good flexibility and stress resistance.

SUMMARY OF THE INVENTION

In order to solve the above problems, the objective of the present invention is to provide a subgrade stability reinforcement and filter composite.

In order to achieve the above objective, the present invention provides a subgrade stability reinforcement and filter composite, it includes woven fabric and nonwoven fabric, the woven fabric is set on top of the nonwoven fabric; and the woven fabric and the nonwoven fabric are structurally attached together as an integral composite material using multiple parallel stitch line seams.

As can be seen from above, the subgrade stability reinforcement and filter composite is formed by sewing the upper woven fabric and the lower nonwoven fabric. Among them, the woven fabric has high tensile modulus, good creep resistance, and good reinforcement effect on the subgrade. The nonwoven fabric has small opening size, in-plane drainage performance function, high flexibility, and low cost. The woven fabric is set on top of the nonwoven fabric, 25 the woven fabric is in contact with basecourse or ballast material above, able to perform reinforcement and stress alleviation functions, and at the same time the large sized soil particles are filtered; the nonwoven fabric is in contact with the subgrade soil, able to perform filtration of small sized soil particles, while allowing uniform dissipation of pore water pressures. The integral subgrade stability reinforcement and filter composite can more 30 effectively provide combined reinforcement and filtration functions to maintain the subgrade stability of the railways, highways, access roads, airport runways, and other structural load bearing platform applications. The use of multiple parallel stitch line seaming method of the two fabrics can effectively prevent the relative slippage of the woven fabric and the

-22018204590 25 Jun 2018 nonwoven fabric in whole or in part, reducing time and cost when laying the resulting composite, thereby improving engineering and construction stability.

A preferred technical solution is that the woven fabric is a twill fabric.

As can be seen from above, the woven fabric of the present invention adopts a twill woven fabric, the twill woven fabric has good wrinkle resistance and strength, the yarns are arranged tightly, the gap between warp and weft yams is small, and in addition three dimensional voids are formed between adjacent yams in the direction perpendicular to fabric surface, resulting in high cross plane permeability for effective dissipation of subgrade pore pressures, resulting in more effective subgrade stability reinforcement and separation 0 performance.

A preferred technical solution is that the woven fabric is a polypropylene yam woven fabric.

As can be seen from above, the woven fabric of the present invention adopts a polypropylene yarn woven fabric. The polypropylene yam woven fabric has high tensile 5 modulus, good abrasion resistance, good chemical degradation resistance and good biodegradation resistance properties, remain stable in both wet and dry conditions, and can perform consistently the role of effective subgrade stability reinforcement performance.

A preferred technical solution is that the nonwoven fabric is a polypropylene nonwoven fabric.

As can be seen from above, the nonwoven fabric of the present invention adopts a polypropylene nonwoven fabric; the polypropylene nonwoven fabric has elasticity, good chemical degradation resistance and good biodegradation resistance properties, good cross plane and in plane permeabilities for effective dissipation of subgrade pore water pressures, and small opening size to provide the filtration application function and prevent migration and 25 transfer of small sized soil particles across the polypropylene nonwoven fabric.

A preferred technical solution is that the multiple parallel stitch line seams is aligned in the warp direction of the woven fabric.

As can be seen from above, in order to facilitate the fabrication of the subgrade stability reinforcement and filter composite, warp aligned multiple parallel stitch line seams can result 30 in continuous multiple parallel stitch line seaming over long rolls of fabrics.

A preferred technical solution is that the interval spacing between two adjacent parallel stitch line seams may be fixed or varied.

-3 2018204590 25 Jun 2018

As can be seen from above, the interval spacing between two adjacent parallel stitch line seams may be fixed or varied. According to the engineering design and construction requirements, the interval spacing between two adjacent parallel stitch line seams can be appropriately selected and adjusted.

A preferred technical solution is that the interval spacing between two adjacent parallel stitch line seams can vary from 5 cm to 100 cm.

As can be seen from above, the interval spacing between two adjacent parallel stitch line seams can be adjusted. Considering the structural bonding requirements between the woven and nonwoven fabrics and cost, stitch line seams spacing can be optimized. The interval 0 spacing between two adjacent parallel stitch line seams can be as narrow as 5 cm to as wide as 100 cm. Of course, under some special application, the interval spacing can be narrower than 5 cm or wider than 100 cm.

BRIEF DESCRIPTION OF THE DRAWING

Fig.l is schematic structural view of an embodiment of the present invention.

The present invention will be further described with reference to the drawing and embodiment.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Fig.l, the subgrade stability reinforcement and filter composite includes a woven fabric 11 as an upper layer fabric and a nonwoven fabric 12 as a lower layer fabric, the 0 woven fabric 11 and the nonwoven fabric 12 is subject to multiple parallel stitch line seaming to result in multiple parallel stitch line seams 13.

In the present embodiment, the woven fabric 11 is a twill woven fabric. The woven fabric 11 has high tensile modulus, good abrasion resistance, good chemical degradation resistance and good biodegradation resistance properties, remain size-stable in both wet and 25 dry conditions, and can perform consistently the role of effective subgrade stability reinforcement and separation performance. In addition, three dimensional voids are formed between adjacent yarns in the direction perpendicular to fabric surface, and the voids are small, resulting in high cross plane permeability for effective dissipation of subgrade pore pressures, resulting in more effective subgrade stability reinforcement and separation 30 performance.

In the present embodiment, the nonwoven fabric 12 is a polypropylene nonwoven fabric having good filtration and water permeability properties.

-42018204590 25 Jun 2018

In the present embodiment, the interval spacing between two adjacent parallel stitch line seams 13 is fixed, selected from 5 cm to 100 cm, preferably 20 cm. The uniform spacing between two adjacent parallel stitch line seams 13 can prevent slippage between woven fabric 11 and nonwoven fabric 12 for subgrade reinforcement application. A spacing of 20 cm is 5 sufficient for railways and highways subgrade reinforcement. Of course, the interval spacing between two adjacent stitch line seams 13 can be varied, i.e. the interval spacing between two adjacent stitch line seams 13 do not have a fixed value.

In the present embodiment, the parallel stitch line seams 13 are aligned in the warp direction of the woven fabric. When the woven fabric 11 is produced, the woven fabric 11 is 0 rolled up on a core in the warp direction to produce a large master roll with long continuous woven fabric 11 length. When preparing subgrade reinforcement and filter composite, a large master roll of the woven fabric 11 and the nonwoven fabric 12 are seamed by the stitch line seams 13, and continuous large scale production can be performed by mechanical device.

To further describe the properties of the subgrade stability reinforcement of the present 5 invention, property comparisons between subgrade stability reinforcement and filter composites (HP380a+nonwoven, H580a+nonwoven) and single woven geotextiles(H380a, HP580a) and a single nonwoven geotextile (nonwoven) are shown in Table 1

Table 1: Properties

Property	Test Method	Unit	nonwoven	HP380a	HP380a + nonwoven	HP580a	HP580a + nonwoven
Tensile modulus at 2% strain in MD	ISO 10319	kN/m	17.5	765	795	1015	1120
Tensile modulus at 2% strain in CD	ISO 10319	kN/m	12	1245	1305	1945	2090
CBR puncture strength	ISO 12236	kN	3.1	7.0	7.9	11.5	12.9
Opening size, 090	ISO 12956	mm	0.05	0.26	0.12	0.25	0.11
Permeability	ISO 11058	cm/s	0.045	0.10	0.19	0.08	0.22

Table 1 shows the technical properties of woven fabric HP380a, woven fabric HP580a, nonwoven fabric, and composites of HP380a and HP580a with nonwoven fabrics. For

-5 2018204590 25 Jun 2018 railways, highways, access roads, airport runways, and other structural load bearing platform subgrade stability improvement applications, tensile modulus at 2% is indicative of the reinforcement ability, wherein the higher the tensile modulus, the better the reinforcement ability; CBR puncture strength is indicative of the ability to resist puncture due to 5 construction stresses, wherein the higher the CBR puncture strength, the better the ability to resist to puncture; Opening size, 090, is indicative of the ability to prevent cross migration of soil particles in a filtration application function, wherein the smaller the opening size, the better the filtration performance with respect to soil particle retention; Permeability is indicative of the ability to allow water flow through in a filtration application function, 0 wherein the larger the permeability, the better the filtration performance with respect to prevention of pore water pressure backlog.

As shown Table 1, the key technical properties of the composites are better than those of the individual woven fabrics or nonwoven fabric using alone.

As can be seen from above, the subgrade stability reinforcement and filter composite of 5 the present invention, through the process of structural integration of the woven fabric and the nonwoven fabric, thereby combining the different application functions of woven fabric and nonwoven fabric within a composite product, can more effectively exhibit and perform the combined application functions of reinforcement, separation, filtration, and drainage, maintain subgrade stability, and improve long term performance and integrity of railways, 0 highways, access roads, airport runways, and other structural load bearing platform applications. The present invention, through systematic seaming, the woven fabric and the nonwoven fabric are prevented from relative slippage in whole or in part, thus the construction time and cost are reduced, and the construction and application stability is improved.

It will be understood that the term “comprise” and any of its derivatives (eg comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

Finally, it is noted that the above-mentioned preferable embodiment of the present invention is not intended to limit the present invention. For a skilled person in the art, the present invention is susceptible to various modifications and changes. Such modifications and

-6changes may relate to the selection of woven fabric, nonwoven fabric and the interval spacing between two adjacent parallel stitch line seams. Any modifications, equivalent replacements, improvements and the like made within the spirit and principle of the present invention shall fall within the scope of protection of the present invention.

2018204590 25 Jun 2018

Claims (7)

1. A subgrade stability reinforcement and filter composite, wherein comprising woven fabric and nonwoven fabric, with the woven fabric set on top of the nonwoven fabric; the woven fabric and the nonwoven fabric are structurally attached together as an integral composite material using multiple parallel stitch line seams.

2. A subgrade stability reinforcement and filter composite according to claim 1, wherein the woven fabric consists of a twill weave.

3. A subgrade stability reinforcement and filter composite according to claim 1, wherein the woven fabric is of the kind woven by polypropylene yarns.

4. A subgrade stability reinforcement and filter composite according to claim 1, wherein the nonwoven fabric is of the kind formed by polypropylene filament yams.

5. A subgrade stability reinforcement and filter composite according to claim 1, wherein the multiple parallel stitch line seams are arranged along the warp direction of the woven fabric.

6. A subgrade stability reinforcement and filter composite according to any one of claims 1 to 5, wherein the interval spacing between two adjacent parallel stitch line seams is fixed or varied.

7. A subgrade stability reinforcement and filter composite according to claim 6, wherein the interval spacing between two adjacent parallel stitch line seams is from 5 cm to 100 cm.