Geotextile / Geomembrane

Geotextiles are permeable fabrics used in geotechnical engineering for separation, filtration, drainage, reinforcement, and erosion control. Made from polypropylene, polyester, or polyethylene fibres, geotextiles are typically supplied in rolls and applied at the interface between soil layers or beneath pavements. Indian Standard IS 14986:2001 + IS 14252 + IS 14253 cover geotextile specifications for road and railway applications. Major Indian geotextile suppliers: Geofabrics, TYPAR, GeoBoard, Maccaferri.

Main geotextile types: (1) Woven — high tensile strength, used for separation and reinforcement. (2) Non-woven — random-fibre arrangement, good filtration properties; used for drainage and erosion control. (3) Knitted — combines stretch and strength. (4) Composite — multi-layer with different functions. Functions: (a) Separation — preventing mixing of soil layers (e.g., sub-base from soft subgrade). (b) Filtration — allowing water to pass while preventing soil migration. (c) Drainage — providing flow path for water in retaining walls and embankments. (d) Reinforcement — increasing soil's tensile capacity (reinforced earth walls per IS 14458). (e) Erosion control — preventing surface erosion on slopes.

Applications in Indian civil engineering: (1) Highway sub-grade separation — IRC 37 mandates geotextile separation when subgrade CBR is below 5% to prevent migration of sub-base material into the weak subgrade. (2) Reinforced earth walls (RE walls) — geotextile or geogrid reinforcement at 0.5-1.0 m vertical spacing; common on Indian highway embankments and bridge approaches. (3) Drainage behind retaining walls and basement walls. (4) Filter beds in drainage and sewage applications. (5) Erosion control on highway embankments and slope-stabilised areas. The most-overlooked aspect of Indian geotextile use: improper installation. Geotextiles must be laid with proper overlap (minimum 300 mm), without wrinkles, and free of damage from heavy machinery. Inadequate installation causes geotextile failure within 1-3 years; proper installation ensures 50+ year service life.