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Innovative Geotechnical Solutions

Geocells – An Innovative Engineered Solution

Presented by: Shahrokh Bagli, Chief Technology Officer Strata Geosystems (India) Pvt. Ltd.

About Strata

Geocells

Technical Details: Load Support Systems

Technical Details: Flexible Pavements

Case Studies: Flexible Pavements

Technical Details: Slope Protection

Case Studies: Slope Protection:- Highway Embankments

Case Studies: Slope Protection:- Energy

Case Studies: Slope Protection:- Reservoirs

Geocells – an innovative engineered solution

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About STRATA

Strata Geosystems (India) Pvt. Ltd., established in 2004, is a JV with

Strata Systems Inc., USA

Strata Systems Inc., USA has been providing geotechnical solutions

since more 25 years

Strata India has an ISO certified State-of-the-Art plant at Daman,

which manufactures geocells and geogrids

Strata India is the 1st manufacturer of geocells in India

About Us

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1st RS Wall at Uslapur

Milestones

Journey begins Daman, India ISO certification

Landmark project in India , completed 1,00,000 sqm of RS Wall in 6 months Launch of StrataWeb®

Bagged 1st project of StrataWeb®

Bagged 1st project of BEBO®

Bagged single largest RS Wall (Ahmedabad – Vadodara) project of 280,000 sqm

Launch of StrataWeb®

Mfg. facility Completed the landmark project of 1st BEBO® precast arch system

Bagged 1st project for StrataBase Bagged 1st project of concrete structures

Manufactured and sold 25 million sq.m. of StrataGrid™ Turnover crossing 1 billion rupee mark

Manufacturing Facility

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Global Presence

India USA Brazil Ireland

Products & Systems

StrataGrid™ StrataWeb® BEBO®

• Knitted geogrid

• Offers superior

junction integrity and

greater soil

interaction

• 3D honeycomb

shaped cellular

confinement system

• Reinforcement for

improving load

bearing capacity of

weak soils and erosion

control for slope

• Precast concrete arch

system

• Design and

construction of earth

overfilled bridges,

culverts and

underground

structures

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StrataBlock™

• RS Wall with block fascia

• Stabilised by horizontal layers of StrataGrid™

StrataWall™

• RS Wall with panel fascia

• Stabilised by horizontal layers of StrataGrid™

StrataSlope™

• Environmental green solution

• Increases usable land for change of grade application

Strata Systems

Geocells

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• 3-Dimensional permeable, honeycomb like structure

• Made of strips of HDPE polymer, welded staggered

• Used in contact with soil or jointed rock in civil engineering applications

• Perforation – Geocells are perforated to enable passage of water and thus dissipate internally generated pore pressure

Geocells

Geocells folded to facilitate transportation and storage

Expanded geocell panels

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Railways Highways Defence

Landfill Mining Ports and Container

Yards

Energy Reservoirs Real Estate

Solutions for sectors

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Technical Details: Load Support Systems

Geocells for load support

Load Bending Moment

When a load is applied to the surface, bending moments develop within the system

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The load distribution system

• These moments are resisted by the infill which provides strength to the system

• Resistance provided by surrounding cells contributes to the ability of the system to distribute loads

Bending Moment caused by load

Resistance to bending of infilled Geocells

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• Geocells filled with non-plastic material form semi-rigid mats capable of distributing imposed loads over larger area

)f q₀ is the vertical pressure:

Lateral stresses generated equals [k₀ q₀+p /2] within loaded cells

With slightest deflection of geocells, frictional forces are generated along geocell walls

Lateral stresses are also generated in congruent cells as reaction

This increases shear strength of the confined soil

This creates a rigid mattress which distributes load over a larger area

Principles of geocells: Load support

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As per José Avesano Neto �∗ = � − 4 ℎ� � � tan � � � + �∗ + �∗ � is earth pressure coefficient at rest, = − sin∅ � is the friction angle between in-fill and cell wall, considered as = ∅ �∗ is the width of geocell mattress on either side beyond loaded width B over which there

is load spread � is average size of a cell wall, = � + � � and � are dimensions of a single cell

Principles of geocells: Load support

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Technical Details: Flexible Pavements

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Critical Points within pavement crust

A

B

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Typical Alligator Reflective Cracks at surface of Bituminous Concrete due to

excessive horizontal strains at Point A

Rutting due to excessive vertical

strains at Point B

Critical Points within pavement crust

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A

B

Critical points within pavement crust

Two Critical points within the

crust; A and B

Number of load repetitions in

terms of million standard

axles (msa) that cause fatigue

denote the fatigue life of the

pavement.

As per IRC 37:

Point A: Interface between DBM and GB is critical for horizontal tensile strains

causing Reflective Cracking

Point B: Interface between the subgrade and the GB is critical for vertical

strains causing Rutting

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Strains at critical points within pavement crust

Input parameters:

CBR of subgrade

Design msa which reflects

the load, the traffic intensity

and annual growth over life

of pavement

Elastic Moduli (Resilient Moduli) �� of each pavement crust element

and the respective Poisson’s Ratio �

Pavement element thicknesses in iteration

IITPAVE (or KENPAVE) Software used to determine:

Horizontal Tensile Strain at A for standard IRC recommended section

Vertical Subgrade Strain at B for standard IRC recommended section

A

B

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A

B

Pavement crust reinforced with geocell

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B

A

Pavement Crust Reinforced with Geocell

One of the governing aspects in

pavement design is the Elastic

Modulus (Resilient Modulus) �

As per Prof. K. Rajagopal of IIT M (Modulus Improvement Factor for Geocell-

Reinforced Bases – K. Rajagopal et al), placement of geocell in GB layer of the

pavement crust would improve � by the Modulus Improvement Factor MIF

MIF as per Prof. Rajagopal’s Study is 2.75

The new � for the portion of GB with geocells is computed

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B A

Pavement crust reinforced with geocell

At the outset, thickness of the

costliest layer is reduced

Computations repeated using

IITPAVE (or KENPAVE) with

appropriate values of � for

crust components and geocells

Horizontal tensile strain between the DBM and the GB and the vertical

subgrade strain at the top of the subgrade are thus evaluated

These strains are compared with those for the unreinforced section

The new section would be acceptable if the strains are lower than those

evaluated for the unreinforced section

To be noted that thickness of the DBM should not be less than 50mm

Thickness of the BC should not be less than that indicated by IRC: 37 for that

subgrade CBR and msa

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Strength and Life: Improves the overall strength and

enhances the life of the pavement

Economy in Design: Allows thinner pavement

section

Economical Solution: Use of locally available material

and economy in designs reduces consumption of raw

material and reduction in project time

Logistics: Easy transportation owing to its flat and

collapsible structure

Rapid Installation: Proven to be an all weather

installation system with minimal specialised

equipment and labour, particularly for structures to

be constructed in emergency / disaster situations

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Advantages of geocells for pavements

Maintenance: Reduces number of maintenance cycles over the life of structure

Environment Friendly: Lower carbon footprint due to minimal resource requirements and

minimised transportation requirements

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Case Studies: Flexible Pavements

Initial Conditions Kedarnath

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Geocells Being Laid Kedarnath

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Infilled Geocells Kedarnath

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Initial Site PWD Nasik

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Infilling PWD Nasik

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Infilling PWD Nasik

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Finished Road PWD Nasik

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Finished Road PWD Nasik

Original condition State Highway - 30, Karnataka

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Geocells Being Laid State Highway - 30, Karnataka

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Infilling State Highway - 30, Karnataka

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Finished Paved Road State Highway - 30, Karnataka

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Technical Details: Slope Protection

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Problem

Area

Typical slope erosion

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Conventional measures: Disadvantages

Stone Pitching Requires skilled craftsmen

Shortage in supply of stone

Expensive due to long leads

Not suitable for steeper slopes

beyond 1V : 1.5H

Regular maintenance needed

Slow process resulting in project

delays

Exposure to UV results in early

degradation

Poor erosion control in hostile

climatic conditions

Not suitable for steeper slopes

beyond 1V : 2H

Requires vegetation to grow

within a short frame

Mulch Mat

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Geocells: Advantages

Steeper gradients: Suitable for slopes up to 1V : 1H as long

as slope stability is maintained

Economical: Replaces the use of expensive stones and their

transportation with locally available soil fill

Installation: 8- 10 times faster than conventional methods;

easy to transport owing to its flat and collapsible structure

Aesthetics: Supports development of vegetation

Environmental Friendly: Zero quarrying needs and

minimal transportation resulting in lower carbon footprint

Material Durability: Long lasting and resistant to extreme

soil and weather conditions

Manpower: Lower manpower requirement comprising of

unskilled labour

Infilling: Can be in-filled with soil / concrete / gravel

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Geocells for slope protection Recommended by IRC

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Geocells for slope protection: Recommended by MoRTH

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Geocell for slope protection

Concrete Infill

Vegetative Infill

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Design procedure

Locational analysis and selection of infill

• Geocells ensure retainment of the soil slope against erosions with cover of infilled geocells

• Two types of geocell infills for slope protection : • Plain cement concrete (PCC) • Soil

• Choice between the two depends on several factors including:

• Slope application (Slopes adjacent to water bodies need PCC infill) • Climatic conditions • Maintenance requirements • Aesthetics

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Locational analysis and selection of infill

• PCC Infill • PCC is used where:

• Climatic conditions are not conducive to vegetation • Location is subject to heavy rainfall • Right type of soil for vegetation is not available

• Soil Infill

• Selected where climatic conditions are conducive to vegetation without much effort

• Soil conducive to vegetation is available • Aesthetic requirements

Design procedure

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Resolution of Driving Force

Design procedure

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Down-slope driving force

Resolution of Driving Force • Tendency of geocell system is to slide down

• Driving force due to

• weight of geocell • weight of infill • Topping • Slope surcharge if any

Design procedure

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Interface resistance mechanism

• Developed by: • Spikes holding the geocell walls

• Friction between geocell infill and

slope soil

• If geocells overlay geogrids, then inter-connection between geocells and the underlying geogrids

For the stability of the slope, Interface Resisting Force > Driving Force

Design procedure

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Resistance from spikes

• Resistance generated by spikes contributes to stability of the geocell system along the slope

• Spacing of spikes and depths to which these are driven are dependent on: • slope geometry • geocell size • weight of infilling

• Generally spikes are closely spaced at the

crest and toe of slope

Design procedure

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Crest / Shoulder Resistance Anchors

• Crest / Shoulder resistance mobilised by embedment in suitable trench

• To be designed considering net of driving force and resisting force

• Dimensions of the trench to be designed as per Net Sliding Factor (NSF).

Design procedure

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Toe Resistance

• Toe to be designed to resist some net downward force due to slackness

• May be buried in trench

• Trench back-filled with gravel and cobble, which would also serve as toe drain

• Backfill material also to be designed to prevent scour

Design procedure

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Choice of infill

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PCC infill is recommended when:

climatic conditions are not conducive to vegetation

location is subject to heavy rainfall

right type of soil suitable for vegetation is not available

Soil infill is recommended when:

climatic conditions are conducive to vegetation without

much effort

soil conducive to vegetation is available

horticultural maintenance is possible

aesthetic and mandatory green requirements

Gravel infill is recommended when:

the right size of gravel is easily available

it is essential that hydrostatic pressures are not allowed

to build up at all

aesthetics is not an issue

Case Studies: Slope Protection Highway Embankments

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Bogibeel Bridge Approach on NH 37 Assam

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Bogibeel Bridge Approach on NH 37 Assam

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Original Condition NH- 202, Andhra Pradesh

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StrataWeb™ – Slope protection

Geocells Laid NH- 202, Andhra Pradesh

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StrataWeb™ – Slope protection

Finished slope NH- 202, Andhra Pradesh

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Case Studies: Energy

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Original Condition ONGC Plant, Uran

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StrataWeb™ – Slope protection

Geocells laid out ONGC Plant, Uran

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Corporate Presentation

Partially vegetated slope ONGC Plant, Uran

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Finished slope ONGC Plant, Uran

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Geocells laid Suzlon, Gujarat

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Case Studies: Reservoirs

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StrataWeb™ – Slope protection

Original Condition ARS, Chennai

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StrataWeb™ – Slope protection

Geocells laid out ARS, Chennai

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StrataWeb™ – Slope protection

Final Site ARS, Chennai

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