GEOSYNTHETICS AND REINFORCED STRUCTURES

Different Types of Geosynthetics and Their Applications

K. Rajagopal, Professor Department of IIT Madras, Chennai e-mail: gopalkr@iitm. ac. in RECAP OF PREVIOUS LECTURE

• Introduction • Historical background • Early applications • Functions of geosynthetics • Types of geosynthetics

Types and Functions of Geosynthetics 2/52 OUTLINE OF 2nd LECTURE

• TYPES of geosynthetics ----CONTINUED • TYPICAL APPLICATIONS

Types and Functions of Geosynthetics 3/52 TYPES OF GEOSYNTHETICS

• • GidGeogrids • Geonets • • Pre-fabricated vertical drains (PVD) • Geosynthetic Liner (GCL) • Gll(3Geocells (3-dfit)d confinement) • Geocomposites & Geo-others

Types and Functions of Geosynthetics 4/52 GEONETS • Geonets are also planar products • Consists of ribs in two directions • Apertures are of diamond shape • Ribs in the two directions are at different planes • Thickness of geonets is larger than that of • Geonets are also referred to as ggpeospacers

Types and Functions of Geosynthetics 5/52 TYPICAL GEONETS

Ribs at two horizontal planes

Types and Functions of Geosynthetics 6/52 GEONET APPLICATIONS

• – ribs act as small check to slow down the surface runoff – decreases erosion potential of water • DiDrainage layers – water flows al ong the geonet because of large thickness

Types and Functions of Geosynthetics 7/52 Boulder net laid on Konkan railway line in Western ghats – functions as guide for loose boulders and vegetation support

Types and Functions of Geosynthetics 8/52 Laying of boulder net

Vegetation growth after two seasons Courtesy: M/s Garware Wall Ropes Ltd., Pune

Types and Functions of Geosynthetics 9/52 Anchor at the top of the slope, 1m deep, 0. 5m wide, filled with soil

Types and Functions of Geosynthetics 10/52 GEOMEMBRANES • Thick impervious sheets • Thickness . 5 mm to 3 mm approximately • To contain liquids and gases

Rough surface te xt ure Smooth – dou ble sided membrane

Types and Functions of Geosynthetics 11/52 APPLICATIONS OF GEOMEMBRANES • lining • lining • lining

Types and Functions of Geosynthetics 12/52 in a landfill

Types and Functions of Geosynthetics 13/52 Canal lining using geomembranes

Concrete lining of surface geomembrane Anchor trench

Types and Functions of Geosynthetics 14/52 Tunnel lining for moisture prottitection

Types and Functions of Geosynthetics 15/52 Pre-fabricated vertical drains to accelera te the pre-consolida tion of soft clay t  f (U %)  cv T v T v 2 d Tv = time factor t = time 2 cv = coefficient of T v d consolidati on t  d = drainage path length U% = degree of consolidation cv Types and Functions of Geosynthetics 16/52 Reducing the flow path length to accelerate rate of consolidation

surcharge fill

Highly permeable drainage medium

Types and Functions of Geosynthetics 17/52 PVDs for pre -consolidation

Corrugated plastic core for drainage L

t

Geotextile filter

Types and Functions of Geosynthetics 18/52 Pore water flows laterally to the wick drains and is Connection carried through the core arrangements for wick drain installation

Types and Functions of Geosynthetics 19/52 Installation of PVDs at a construction site – notice the connection of PVD w ith the anc hor p la te

Types and Functions of Geosynthetics 20/52 PVD be ing pus he d in to the groun d

Types and Functions of Geosynthetics 21/52 General view after installation of PVD’ ssatasite at a site

Types and Functions of Geosynthetics 22/52 Geosynthetic Clay Liners

• Consist of a core of clay sandwiched between layers of thick non- woven • Applied below and above geomembrane layers in • Self-repair mechanism • Bentonite expands when flid leaks through punctured geomembrane – closes the gap

Types and Functions of Geosynthetics 23/52 Geosyyynthetic Clay Liner

Geotextile layers

dry bentonite powder

Types and Functions of Geosynthetics 24/52 GEOCELL – 3d confinement product

Iso-metric view of a geocell layer Plan view showing the mechanism of confinement

Types and Functions of Geosynthetics 25/52 Photograph of an expanded geocell

Types and Functions of Geosynthetics 26/52 Advantages

• Easy to • Any fill material can be used • All roun d con finemen t to so il • Semi-rigid layer (very stiff support) • Spreads loads over a large area • Excellent support even under cyclic loads.

Types and Functions of Geosynthetics 27/52 APPLICATIONS

• Erosion control • Steep slopes and retaining walls • SbSub-btbase support • bases • RilRailway t rack s • Container yards

Types and Functions of Geosynthetics 28/52 Use of geocells for construction of unpaved road Factory

SSaptapling t ojoo join PtifdPreparation of ground Stretching of the geocell layer different geocells

Stone aggregate filled in geocell pockets Compaction by a 10 tonne roller

Types and Functions of Geosynthetics 29/52 Geocells used for construction of a steep slope

Types and Functions of Geosynthetics 30/52 Vegetation taking root through geocell pockets

Types and Functions of Geosynthetics 31/52 IITM students standing on a geocell supported soil

Types and Functions of Geosynthetics 32/52 Typical Container yard – heavy loads, usually constructed on soft marine clays near the shore

Types and Functions of Geosynthetics 33/52 Typical mud wave formation in container yards due to heavy ldloads an d ex treme ly so ft subdbgrade so il

Types and Functions of Geosynthetics 34/52 Geotextile separator being laid on the ground surface at a container yard

Types and Functions of Geosynthetics 35/52 Geocell layer laid on the geotextile separator and filled with stone aggregate

Types and Functions of Geosynthetics 36/52 Container yard 3 years after geocell treatment

Types and Functions of Geosynthetics 37/52 Some more pictures of the same yard

Perfectly level surface – minor damaggpe in paver blocks

Types and Functions of Geosynthetics 38/52 Polymeric erosion control mats

Types and Functions of Geosynthetics 39/52 Geocomposites • Com bina tion o f two differen t types of geosynthetics to take advantage of each

Types and Functions of Geosynthetics 40/52 Geo-others • Geodrains • Lightweight fills • Geopipes • Geot extil e b ags & soil encapsu la tion • • Geosynthetic Encased Stone Columns • Many others – left to the imagination of engineers

Types and Functions of Geosynthetics 41/52 Drainage boards for use in Retaining Walls

Types and Functions of Geosynthetics 42/52 Light-weight fill cum drainage medium

Thic k me dium ma de o f po lys tyrene bea ds

43/52 Types and Functions of Geosynthetics Gabions filled with stones

Types and Functions of Geosynthetics 44/52 Gabions filled with bags

SAND FILLED GEOBAGS PLACEMENT OF GEOBAGS

TYING OF ROPE GABIONS FINAL VIEW 45/52 Types and Functions of Geosynthetics Light-weight drainage medium

Made of used rubber tyres and other industrial wastes

Types and Functions of Geosynthetics 46/52 Encased Stone Column enhanced by

Passive pressure + Geosynthetic Additiona l encasement confinement

Stone column

Sectional plan

Types and Functions of Geosynthetics 47/52 Construction of Encased Stone Column

Alexi ew etlt al. (2005)

Types and Functions of Geosynthetics 48/52 Courtesy: Dipl.-Ing. Holger Pohlmann Naue Fasertechnik GmbH & Co. KG

PdPresent study

Types and Functions of Geosynthetics 49/52 Load settlement curve for stone columns encased in non -woven geotextile Pressure (kPa) 0 100 200 300 400 0 ESC - 50 mm ESC - 75 mm 10 ESC - 100 mm OSC - 50 mm OSC - 75 mm 20 OSC - 100 mm t (mm) Clay 30 ttlemen ee S 40

50

Types and Functions of Geosynthetics 50/52 Latest Trends

• • Encased stone columns • Electro Kinetic geosynthetics

Types and Functions of Geosynthetics 51/52 52/52