Question

Which of the following is preferred for filtration function of geotextile?

• A. Jute nonwoven
• B. Cotton knitted
• C. Polypropylene nonwoven
• D. Wool knitted

Hint:

• Geotextile filtration function Allow water passage, retain soil particles.
• Key requirements Appropriate permeability, pore size, and long-term durability (resistance to rot, chemicals, UV).
• Natural fibers (jute, cotton, wool) Generally biodegradable, not suitable for long-term buried applications where sustained performance is needed.
• Synthetic fibers (polypropylene, polyester) Resistant to biodegradation, good chemical resistance, durable. Widely used in geotextiles.
• Nonwoven fabric structure Often preferred for filtration geotextiles due to its good permeability and ability to be engineered for specific pore characteristics.

Answer 1

The Correct Option is C

1. What is a Geotextile?

Geotextiles are permeable fabrics used in civil engineering and construction projects. They are primarily employed for functions like:

• Filtration
• Drainage
• Separation
• Reinforcement
• Protection

2. Filtration Function in Geotextiles:

For filtration, a geotextile must:

• Allow water to pass through
• Retain soil particles (prevent clogging or soil erosion)
• Be durable, chemically inert, and resistant to biological degradation

3. Evaluating the Options:

Option	Material Type	Suitability for Filtration
Jute nonwoven	Natural, biodegradable	Not durable; degrades over time
Cotton knitted	Natural, flexible	Poor filtration, lacks durability in soil
Polypropylene nonwoven	Synthetic, durable, high strength	Excellent for filtration
Wool knitted	Natural, soft, absorbent	Not suitable; bio-degradable and low mechanical strength

Why Polypropylene Nonwoven?

• Hydrophobic (doesn’t absorb water, but lets it pass)
• Chemically inert (resistant to soil chemicals)
• High tensile strength and stability
• Long-lasting (doesn’t rot or degrade easily)
• Widely used in geotextile applications including roadbeds, landfills, drainage systems

Final Answer:

(3) Polypropylene nonwoven — It is the most suitable and preferred material for the filtration function of geotextiles.