TS002- Test methods of Geotextiles

Test Methods of Geotextiles

Saurabh Deshmukh

Department of Textile Technology

Veermata Jijabai Technological Institute, Mumbai,India

Abstract:

Geotextiles are thin & strong membrane fabric which is used to reinforce soil & prevent from damage.  It is mostly used for filtration and separation in the road constructions. Geotextile are ideal materials used for Construction & infrastructure like roads, buildings, dams and many more.why need of testing to geotextile material? Because, In order to determine if a geotextile material is suitable for a particular application it must undergo appropriate mechanical testing procedures. The most common forces a geotextile experiences during its application are tensile and puncture. The most common geotextile testing methods are wide widthtensile testing, puncture and puncture resistance testing, and tensile grab testing. Geotextile test specimens are generally simple to make as they are usually just squares or rectangles cut straight from the material. Depending on the test that will be performed on it the sample will be somewhere between two to eight inches wide and four to eight inches long. Geotextiles come in three basic forms: woven, punched, and heat bonded.  and heat bonded. The most common materials to make geotextiles are polypropylene and polyester.

Keywords-Filter fabric, testing standards, scope of accreditation, fibres ,yarn ,fabric ,terminology, significance ,sampling,conditioning and test methods

Introduction:

Geotextiles are a polymers & synthetic made from textile materials named as polyester. The Geotextiles are effectively successful materials to improve road quality. It is divided into following types:

• Geotextile of Woven Fabrics
• Non-woven Fabrics
• Knitted Fabrics

Geotextiles are a permeable geosynthetic comprised solely of textiles. Geotextile materials prevent the erosion of earth and similar substances after the area has been altered due to construction usually pertaining to civil engineering applications such as roads, pavement, bridges, embankments and retaining walls. They allow the passage of water but not soil and other materials.

Products are tested for the following reasons. Products are tested for the following reasons.

• Quality assurance and control
• Quality assurance and control
• Setting and maintaining performance standards
• Investigation of complaints
• Product developments and research

Testing can be classified into two categories:

• Quality testing
• Performance assessment

When to test geotextile? For any project for any civil engineering project the design engineer must check the required specifications of geotextile material without knowing proper specification it is very difficult to select correct geotextile for any specific project. it is important to get the material tested from an independent laboratory, to get correct picture. Because after using geotextile if it fails then not only the geotextile will fail total structure will be collapsed. That is useful to check capabilities of textiles that will be helpful for Roads & highways. Some testing such as Direct shear test, Compressive creep properties, Tensile Creep and Creep Rupture Behavior, Resistance to perforation (Cone drop test), Trapezoid tearing strength, Grab tensile strength and more. 

What based on test are perform?

Testing should  be done by some methods or also known as testing standards. That is some standard set by laboratory, institute or research centre that is given below :

• ASTM  - American Society for Testing of Material- 129 STANDARDS
• ISO  - International Organisation of standardization-  34  STANDARDS
• BIS   -  Bureau of Indian Standards   -17  STANDARDS
• BS    -  Brittish Standard-  8 STANDARDS
• BS EN  - Europian norms- 36 STANDARDS 

ASTM  - American Society for Testing of Material:

ASTM's textile standards provide the specifications and test methods for the physical, mechanical, and chemical properties of textiles, fabrics, and cloths, as well as the natural and artificial fibers that constitute them. The textiles covered by these standards are commonly formed by weaving, knitting, or spinning.

ISO  - International Organisation of standardization:

Today, textiles come from all over the world. They might be formed in one country, dyed in another, and made into finished goods in yet another. To ensure that the same practices are used in this complicated international process, many companies follow agreed-upon standards related to industrial processes and the goods produced by them. These standards are called ISO textile testing standards.

following ISO standards can help to ensure consistent quality of the raw materials being used to make textiles, which in turn improves the final product. Adhering to ISO standards can also help lower operating costs and ensure quality management. Following ISO standards often involves inspection and testing at each stage of a process. For example, raw materials might be tested, then dyed fabrics, and finally finished goods.

                        

BIS-Bureau of Indian Standards:

The Bureau of Indian Standards (BIS) is the national standard organisation of India under the aegis of Ministry of Consumer Affairs, Food & Public Distribution, Govt of India. It was founded on 1st April 1987, replacing the Indian Standards Institute. The Bureau is a body corporate and responsible for formulating national standards. It comprises of members representing the Industry, Consumer Organizations, Scientific & Research Institutes and Professional Bodies, Technical Institutions, Central Ministries, State Governments and Members of Parliament. The Indian Standards are formulated keeping in view national priorities, programmes for industrial development, technological needs, export promotion, consumer welfare, health, safety, etc. So far over 17000 standards have been formulated in different technology areas.

Methods used for testing of geotextile material:

• Determination of Mass per unit Area:

This standard explains a method to determine the mass per unit area of all natural geotextile. The mass per unit area is calculated by weighing small square specimens of known dimensions. Ten specimens of 100cm2 are cut from the material in such way that they are representative of the material to be tested. The area and weight of the specimens are determined to an accuracy of 0.5 and 0.1 % respectively.

The mass per unit area of each specimen is calculated using the equation p= (m X 106 ) /a

Where p=mass/unit area in g/m2

m=mass of the specimen in, g

a=the area of the specimen in mm2

The average mass per unit area is calculated.

• Determination of Thickness:

This standard describes a method for the determination of the thickness of geotextiles at specified pressures. The distances between a reference plate on which the specimen rests and a parallel presser-foot applying the given pressure to the specimen is define as the thickness of the geotextiles. A thickness tester apparatus capable of exerting a pressure of 2kPa is used. Test specimen shall be cut from the material from positions evenly distributed over the full width and length of the sample. The specimen is placed between the surfaces of the reference plate and pressure foot of the thickness tester. The presserfoot is load gentle over the specimen by applying a pressure of 2±0.01 kPa. The gauge reading is noted after 30 seconds. Remove the pressure and the specimen. The procedure is repeated for at least ten specimens. The average of all the readings is reported as the thickness of the geotextile. The thickness is expressed in mm to an accuracy of 1% for geotextiles thickness over 0.05mm and to the nearest 0.001mm for thickness not exceeding 0.05mm.

• Determination of Percentage of Swell:

This standard prescribes method for determination of the percentage of swell in water of geo textiles after it has been immersed in water for 24 hours. Ten specimens of size 100mmx100mm are used for the test. The thickness of each specimens is noted on thickness tester and recorded as the initial thickness ti to the nearest 0.01mm. Now place the specimen between the two No.17 gauge wire mesh screens that have been soaked in water for a minimum of one hour .The screen corners are connected loosely to hold the test specimen in place. The test specimen is immersed in deionized water for 24 hours. After the soaking period, the specimen is removed from the assembly after allowing the water to drain of. The thickness of the drain specimen is measured as tf. The percentage thickness change or swell is calculated as,

Percentage thickness change=100(tf - ti)/ ti

The procedure is repeated for 10 specimens.

• Determination of Water Absorption Capacity:

This standard describes the method for determination of the water absorption capacity of geotextiles. A galvanized screen and pans are used for this method. Three specimens measuring 200mm x 200mm are prepared and weight the nearest 0.1g. Each specimen is placed on a tared 230mm x 230mm galvanized wire screen. Another tared screen having similar dimension is placed over the specimen. Now both screen and specimen is placed in a 76mm deep pan containing water at about 75mm deep. The specimen is allowed to soak for 24 hours. After the soaking period the specimen and the screens are allowed to drain for 10 minute and then weighed to the nearest 0.1g. The amount of water held by the specimen is calculated by subtracting the sum of the weights of the weighing pan, screens and dry specimens from the total weight. The absorptive capacity is a ratio of the water held by the specimen to the weight of the original dry specimen.

• CBR Puncture:

To eliminate the high degree of variability from the Mullen Burst (3786) and Pin Puncture (4833) test methods, Static (CBR) Puncture Strength (ASTM D 6241) was developed to replace them. CBR stands for California Bearing Ratio, a soil strength test that was adapted for this geotextile test. CBR Puncture is an index of puncture resistance that measures the force required to push a flat ended plunger through a geotextile. A 150 mm geotextile sample is secured between two steel rings. Instead of an 8 mm diameter probe with a beveled edge (Pin Puncture 4833); this test utilizes a 50mm diameter, flat-ended probe (plunger) that is pushed slowly through the geotextile. The relatively large size of the plunger provides a multidirectional force on the geotextile and simulates big stones pressed onto a geotextile laying a relatively soft sub-base.

• Permittivity:

Permittivity is the mechanism by which water moves through the fabric. The permittivity test measures the quantity of water which can pass through a geotextile perpendicular to the surface of the geotextile. The permittivity may be measured either in a constant head or falling head test, although constant head testing is more common due to the high flow rates through geotextiles which make it is difficult to obtain readings of head change versus time in the falling head test. In the constant head test, a head of 50 mm water is maintained on the geotextile throughout the test. The quantity of flow is measured versus time. In the falling head test, a column of water is allowed to flow through the geotextile and reading of head changes versus time is taken. The flow rate of water through the geotextile needs to be slow enough to obtain accurate readings.

The Bombay Textile Research Association:

The Bombay Textile Research Association (BTRA) was registered by members of the Millowners' Association, Bombay, under the Societies Registration Act, XXI of 1860 on 21st April 1954, with nine mill companies contributing to the Memorandum and Articles of Association. In the past 25 years many applications of geosynthetics have proved their value in civil engineering projects and this new class of material has added entirely a new dimension to the world of geotechnical engineering. Geosynthetic materials like Geotextiles, Geogrids, Geonets, Geocell, and Geomembranes are used in various civil engineering activities especially in highway engineering to facilitate construction, ensure better performance of the structure and reduce maintenance. To know the performance of these products, performance evaluation is to be done & to meet the requirements, quality has to be maintained.

The standard is not directly concerned with the actual properties or design of product but with gaureenting that the product is always manufactured in the same way, to the same specifications, that no substandard raw material used in the production and that any rejects do not find their way into the output. The concerns of the standard are really with good organizational practice and it involves complete documentation of the whole process together with internal and external checks to ensure that everything is being run according to these written instructions.

Testing staff having skill in sample preparation, handling of test equipments, knowledge of quality system and test standards. Experience in testing of similar products & various tests will have better influence on quality of testing. The staffs are trained time to time for various tests, quality control systems and interpretation of results. Calibration of test equipments is done periodically ( every year ). Quality audit is carried out by NABL every year. The Laboratory implements new or revised test.

Common Tests of Geotextile:

• Mass : gms per meter square
• Thickness at specified pressure
• Tensile strength : Strip / Grab / Wide Width
• Tear Strength : Trapezoid
• Water Permeability : Vertical / Horizontal
• Apparent Opening Size : Sieving method
• Puncture Resistance : CBR / Index / Cone

It is pertinent to mention that BTRA is the first institute in India and probably only the third institute outside USA to get this coveted accreditation. What this means to the geosynthetics producers and users is that they can get the products tested in BTRA with utmost confidence that the accuracy of the results are as good as any other GAI-LAP accredited laboratories. They can get the tests done in India, thus saving time and money without compromising on the quality of the results.

Result and Disscusion:

Considering environmental impact, geotextiles should be collected from the project site. The test which we normally do in isolation that may not be suitable for most of the geotextile testing. So, we have to get the sample collected from the exact site and then the sample should be tested in the laboratory. Now there are standards for collection of test specimens. (Refer Slide Time: 13:26) So, this standards are ASTM D4354 which is standard practice for sampling of geo synthetics for testing, then ISO 554 which is specifying the standard atmosphere for conditioning and or testing specifications ISO 9862 Geotextile sampling and preparation of test specimen. So, during production and construction time, test specimens are collected at specified interval. The number of specimens to be collected for testing is given in the concerned standard. So, we have to collect the specimen from the site.

So, there are two different types of test which are conducted on geotextiles. One is called index testing or in isolation test, which actually test in the laboratory condition. So, only the tests are performed on geotextile next is that its called performance test what is that? The performance test are performed along with site specified soil and conditions. So, index test will only give an idea and comparative value between the geotextiles which is good or which is bad comparatively, but the better geotextiles as per index test may not perform well in performance test. Because in performance test we have to test along with the site specified soil and site specified condition. So, there are different types of tests conducted on geotextile materials, these are physical testing, mechanical test, hydraulic test, endurance test degradation test. So, we were discuss each and every methods.

Conclusion:

• test methods are a means to understand the product
• test results give a true picture of the product
• test results are dependable when conducted exactly as per the standard
• methods for testing of geotextile materials is important for determine the properties of geotextile materials. The properties are affected on construction in where use of materialthat’s mean a testing should done best way and without any errors. Hence these paper describe the all information for testing of geotextile.

References:

• Geotextiles - TestResources
• www.technotex.gov.in › TES...PPT
• Web results
• TEST METHODS FOR GEOTEXTILES
• https://www.astm.org › Standards
• ASTM D4595 - 17 Standard Test Method for Tensile Properties of Geotextiles by
•  https://nptel.ac.in › Lecture-8PDF
• Web results
• Testing of Geosynthetics - Nptel