development of new air port at sikkim

24/02/15

Ashish D Gharpure, P.E. 1

Development of New Airport At Pakyong,

Sikkim, India.

Ashish D. Gharpure, P.E. Director & COO Maccaferri Environmental Solutions Pvt. Ltd. Mobile: 9545533002 Email: agharpure@ maccaferri-india.com

[email protected]

Contents Team behind the project. Introduction. Basic scheme adopted as per project owners requirement. Technical, financial, environmental & social aspects considered. Final solutions adopted. Design Aspects. Construction Aspects. Catastrophic seismic event happened at project site in Sept 2011. CSR initiatives by project owner Airport Authority of India (AAI). AASHTO working groups visit to project site in Dec 2011. Awards received.

Behind the project

Team behind the project

vProject owner : Airport Authority of India, New Delhi.

vContractor: Punj Lloyd Ltd, New Delhi. vDesign Consultant : Mott Mac Donald Pvt Ltd, New Delhi.

vTechnology Partner for retaining & drainage solutions : Maccaferri Environmental Solutions Pvt. Ltd, New Delhi

v Sub Consultant for geotechnical solutions: Genstru Consultants Pvt. Ltd. Mumbai.

vDesign Approval: Indian Institute of Technology, Mumbai.

Introduction

About Sikkim & need for project Sikkim is a landlocked state strategically located with long international border. Connectivity only by road (NH 31A), frequently subjected to land slides during rains. Sikkim has many scenic spots, high altitude lakes, rare flowers, orchids, world

renowned monasteries with great tourism potential. Nearest rail head - Siliguri (W.B.) , 120 Km from Gangtok. Nearest Airport - Bagdogra 125 Km from Gangtok. Considering Socio-economic and strategic

considerations, a new airport was planned.

24/02/15

Ashish D Gharpure, P.E. 2

Airport site (distant view showing longitudinal profile of existing ground conditions)

Runway planned

NORTH

Airport site (close view showing transverse profile of existing ground conditions)

Project Requirements Planned Location Pakyong, 30 km from Gangtok (capital of state of Sikkim) Design Aircraft - ATR 72 type (50 seater) Runway strip- 1700 x30 m Apron - 106 x 76 (Two Bays) Terminal building 100 Pax Other facilities - fire station, control tower , car park and other facilities

required for a civil airport Cost of project 62 million USD

Master Plan of Sikkim Airport Project

Criteria for final solution

Criteria for final solution

Technical Considerations o Foundation soil type o Seismicity of region o Drainage networks

Financial Considerations o Direct cost o Speed of construction

Environmental Considerations o Carbon Footprint Emission o Balancing Cutting & Filling o Afforestation

Social Considerations o Job opportunities for local people o Channelization of surface & sub-surface water

24/02/15

Ashish D Gharpure, P.E. 3

Technical considerations foundation soil type Foundation Soil Type : Avg. 5m thick clayey sand underlain by mica schist (BH 08 & 09)

Virtual absence of firm rock foundation

The existing sub soil type necessitated the need for flexible type of retaining structures that will impart relatively less pressure by better distribution and absorb the immediate settlements within the construction period. For this reason, any rigid type of structures were not feasible.

Technical considerations Seismicity of region o Sikkim airport Project lies in seismic zone IV of India o Ground acceleration coefficient for this region = 0.12g.

o The retaining structure type selected which is as high as 74 m to be highly resilient to withstand the seismic forces.

o The ramifications of failure during a seismic event will be very high due to the presence of house and other establishments close to the proposed retaining wall locations.

Technical considerations Drainage Networks

Drainage is one of the most critical aspect of this project for various reasons. The extensive drainage networks planned includes,

q Channelizing of surface water on the catchment above, & along

cutting slope as well as the jhoras q Channelizing the surface water & jhoras below the runway surface

that exit at bottom through the retaining structures. q Energy dissipaters at exit of channels passing through retaining

structures

The retaining structures should be able to accommodate the drainage structures (preferably concrete culverts) to pass through and exit at downstream side.

Financial considerations Direct Cost Flowchart comparing alternative options for construction and their financial cost

RCC Retaining wall / Composite reinforced soil structure

Excavation more for deeper foundation Not much required

Concrete / heavy scaffolding/machineries

Prefabricated material/ local available material

Skilled Manpower Semi Skilled to Unskilled Manpower

30%-50% cheaper than RCC

RCC Retaining wall Composite reinforced soil

structure

Costly and time consuming

RCC Retaining wall / Composite reinforced soil structure

RCC Retaining wall Composite reinforced soil structure

150000 cum of concrete Cement -60000MT Fine aggregate- 150000MT Coarse aggregate-220000MT

Polymer - 2227 MT Local available stones

Steel - 18000 MT Steel - 608 MT

CO2 - 46065 MT

CO2-51300 MT CO2-1733

MT

CO2-2423 MT

CO2 Foot print 97,000 MT

CO2 Foot print 4,200 MT

Thus reducing carbon emission by 93000 MT

Environmental considerations CFP Emission Flowchart comparing alternative options for construction and their carbon footprint

Environmental Considerations Balancing cutting & filling o Being hilly terrain, land is in short supply in Sikkim. o Ecological and land take reasons lead the local state to rule that fill

should never be imported nor exported.

o This required to completely balance cutting & filling to the tightest possible footprint with land take kept as 56 hectares.

o The only way to accomplish this was to build very high Reinforced Soil Retaining structures. Gentler batters would have extended the structures halfway down the fairly populated valley sides.

o The soil reinforced retaining structure should also accommodate the mixture of sedimentary or metamorphic rock or granites, schist gneiss of bigger sizes that comes from excavations.

24/02/15

Ashish D Gharpure, P.E. 4

Environmental considerations Afforestation

o Green field Airport projects, specially in hilly terrains, impacts environment within and beyond the project boundary for various reasons and hence the solutions planned should be environmental friendly.

o One of the main objective being tourism promotion, the entire project area (cutting side, filling side, runway planar region etc) should have maximum greenery.

o The area of afforestation assessed / required by adopting

environmental friendly solutions was 47.7 hectares ( 22.5 ha on retaining structures on cutting side + 3.2 ha on cutting side slope + 22 ha on basic strip)

Environmental Considerations Channelization of surface & sub surface water

Channelizing Jhoras (Water streams) o Sikkim receives very heavy rainfall. Rain water from hills above Airport site also

passes through the site. Given below is the monthly rainfall data in mm. o 11 Nos. Jhoras (local streams) crossing the airport site are a source of water to

the inhabitants at valley side and hence cannot be affected. Channelizing Sub- Surface water

o Airport site is blessed with existing natural water springs which is another source of water to the inhabitants around airport area. Hence channelization of water springs is essential not only for stability of earth retaining structures but also for ensuring water supply to inhabited area around airport.

Environmental Considerations Job Opportunities for local people

o The priority for employment to the affected families to be given

depending on their academic and professional qualification.

o Major job opportunities were anticipated in earth works being unskilled in nature.

o Being the local people (mainly farmers) mostly unskilled in construction works, the solutions chosen should permit the employment of local people.

o The local farmers can work at site only for 40 days cycle and then have to return home for work on their field.

Final solutions

Final Solutions adopted For the technical, environmental, financial & social considerations mentioned

earlier, following solutions were finally adopted,

o Retaining structures on filling side (east): Composite Soil reinforcement System structures (Maccaferri ParaMesh System)

o Cutting side (west): Cutting slope soil finished to its angle of repose protected for erosion by an ECB (erosion control blanket) and a gabion toe wall.

o Drainage along cutting slope: Gabion cascades for channelizing 9 jhoras. A series of catch water drains to divert surface water into these cascades.

o Drainage below runway basic strip area: Longitudinal Concrete drains collecting water from gabions cascades which distributes into 4 concrete box culverts that run below runway basic strip following ground level and exiting through ParaMesh structures.

o Subsurface drainage: A combination of chimney drains (provided for entire length behind the retaining structures on filling side) and perforated pipes.

Courtesy : Adrian Greeman, New Civil Engineer, UK.,

24/02/15

Ashish D Gharpure, P.E. 5

COMPOSITE REINFORCEMENT SYSTEM : WITH GREEN TERRAMESH FOR SLOPED & GREEN FACIA

GTM Facia (welded mesh + Coir mat)

Secondary Reinforcement (GTM mesh tail) ParaLink Geo-

grid as Primary Reinforcement ParaLink Geo-

grid as Primary Reinforcement

Secondary Reinforcement (GTM / TMS mesh tail)

Terramesh Units (as facia and secondary reinforcement)

COMPOSITE REINFORCEMENT SYSTEM : COMBINING BOTH TERRAMESH & GREEN TERRAMESH FACIA

GTM Facia (welded mesh + Coir mat)

Design Aspects What is Composite Soil Reinforcement System?

Combines the advantages low strength soil reinforcement provided near to wall / slope facia and high strength soil reinforcement for primary stability. They are named as secondary reinforcement & primary reinforcement respectively.

Secondary reinforcement improves compaction and prevents sloughing

failure near facia. In Sikkim project, Maccaferris Terramesh system and Green Terramesh system were used as secondary reinforcement which also acted as facia.

Primary reinforcement provides the main stability for the structure. Maccaferri s highs strength Geogrid ParaLink of strength up to 800kN/m were used in this project

What is composite soil reinforcement system ?

Typical section with one type of reinforcement (geosynthetic or metallic)

Here, all reinforcements are required to achieve stability

What is composite soil reinforcement system ? Typical section Composite soil reinforcement system

Here, primary geogrids which are less in number provides stability against slip circle failure whereas, secondary reinforcements contributes to face stability alone.

Composite Soil Reinforcement Structure (typical details)

24/02/15

Ashish D Gharpure, P.E. 6

ParaMesh Structures on filling (east side)

Depending on space availability, drainage requirements and priority of constructions, 4 different structures were planned with discontinuity in between, as per below details,

qWall 1 (CH: 280-680) : ParaMesh with Terramesh (TMS) (vertical) facia for

bottom half height and Green Terramesh (GTM) (sloped) facia for upper half height. Bottom vertical facia was due to space limitation and the need to take a concrete culvert though (TMS facia being rigid compared with GTM).

qWall 2 (CH: 1320-1840) : ParaMesh with GTM facia for full height due to space availability.

qWall 3 (CH: 1320-1840) : Similar to wall-1. Max. height section i.e. 74m is present in this wall.

qWall 4 (CH:1840-2120) : Similar to wall-1, except last 40m stretch which is nearly vertical

Solutions at cutting side (west)

q Gabion toe wall + overlying slope finished to corresponding angle of repose

q Slope protected by erosion control blanket made of coir in order to p reven t e ros ion and a l l ow vegetation to grow.

q The erosion control blankets shall be suitably anchored to the finished slope using U pins

q The maximum height of the cutting slope protected this way shall be approximately 111m

DRAINAGE NETWORK Various Drainage Structures adopted are,

qStepped Gabion cascades along Jhora locations (9 nos)

qPCC Catch Water Drains on the graded area on hill

qRCC Longitudinal Drains along the Runway strip (2 nos)

qRCC Box Culverts (4 nos)

qGabion drop structures for energy dissipation at box culvert exit (4 nos)

DRAINAGE NETWORK

Channelization of Jhoras and surface water through gabion cascades & box culverts

TYPICAL 3-D VIEW OF JHORA & CUT SLOPE WATER CHANELISATION THROUGH GABION CASCADES & CATCH WATER DRAINS.

Catch water Drain

Side Wall

Gabion stepped weir With Concrete Capping -50mm

Gabion Retaining wall

Box Culvert Longitudinal Storm Water RCC drain

Catch pit

24/02/15

Ashish D Gharpure, P.E. 7

SECTION OF JUNCTION BETWEEN JHORAS AND BOX CULVERT

Catch water Drain

Side Wall

Gabion stepped weir with 50mm Concrete Capping

Gabion Retaining wall

Box Culvert

Longitudinal Storm Water RCC drain Catch pit

Counter weir

Stilling Basin

Junction of catch water drain with Jhoras/Intercepting Drain

Typical details of RCC culvert & Gabion drop structure exit

Typical detail of sub-surface water channelization through chimney drains and perforated pipes.

Final solutions in summary..

Slope Stabilization

Filling Composite

Reinforced Soil Retaining Structure

Gabion Faced

Sloped Green Face

Drainage

Surface runoff with storm water drains and Box Culverts

Sub surface water through chimney drain and semi

perforated pipes

Cutting Toe Protection +Slope Protection

Design Aspects

Design Aspects

q Design Approval Process Designs were to be approved by IIT Bombay before construction

q Codes / Guidelines considered

BS 8006 : Static Analysis FHWA (AASHTO) : Seismic Analysis

q Design Life : 120 Years

q Software used MacStARS, RESSA, Hand Calculations

q Checks performed

External Stability : Sliding, Overturning, Bearing, Global / overall Internal Stability : Rupture, Pullout, Facia Analysis

q Need for using high strength geogrids

24/02/15

Ashish D Gharpure, P.E. 8

Stability analysis of ParaMesh structures were mainly done using MacStARS software Design of Gabion Toe Walls along Cutting side (west) was done using

Gawacwin software

Design of hydraulic structures : 1. Concrete box culverts 2. Gabion Cascades along cutting side 3. Drainage network along the large area of cutting side to navigate

storm water to gabion cascades 4. Gabion drop structures at box culvert exit for energy dissipation Maccaferri provided conceptual scheme for the above structures which were designed by consultants from Indian Institute of Technology, Mumbai.

Construction Aspects

Construction Aspects Sequence Planning The construction sequence planned at beginning was,

1. Cutting & filling excluding wall locations 2. Temporary water diversions 3. Walls 1,2,3 & 4 and their backfilling 4. Concrete culverts at required levels from East to West direction 5. Filing side slope protection with ECB 6. Gabion walls for toe slope protection of cutting side 7. Longitudinal drains 8. Cutting side slope protection by using ECB 9. Gabion cascades, catch water drains etc on cutting slope 10. Aerodrome pavement* * Remaining airport facilities like terminal building etc will be a separate contract later.

Priority of Wall Construction

Wall 1 was given top priority as the Terminal building and other necessary infrastructure for Airport were planned near Ch:0 to 600.

The culvert E1 (which passes through wall-1) was taken up

simultaneously to navigate water parallel to wall construction. Wall 2 and Wall 3 (partly) were also taken up as not much

interference was present in terms of habitat like houses etc.

Wall 4 is located adjoining to the Pakyong town and was planned to be taken up on later stage.

24/02/15

Ashish D Gharpure, P.E. 9

Training to AAI (Client) and PLL (Contractor)

Training sessions on the design considerations and construction aspects were periodically conducted by Maccaferri

The construction difficulties and other critical observations are also debated during such sessions.

Training to AAI (Client) and PLL (Contractor) contd

Field Training sessions were periodically conducted by Maccaferri supervision staff.

Pictures for various phases of construction

Screening plant at site to remove boulders from excavated soil before using as structural soil.

Slope cutting / Hard Rock blasting Creating internal road networks for truck movements has been a challenge.

24/02/15

Ashish D Gharpure, P.E. 10

Standard machineries used Excavators, Dumpers, dozers, compactors etc

Concrete box culvert E4 under construction

Placement of initial slope units at space left in front of nearly vertical backfill portion

Placing Geotextile behind TMS Unit

Construction of Chimney drains Culvert E5 under construction and view of Gabion cascade for water energy dissipation

24/02/15

Ashish D Gharpure, P.E. 11

QA Process QA Process..

Temporary diversion of rain water during monsoon periods.. Work disrupted due to heavy monsoon in 2011

Protection works at top of walls during monsoon Managing bend along wall alignment wrt boundary change has been a challenge

24/02/15

Ashish D Gharpure, P.E. 12

Care was taken to optimize Geogrid consumption at wall bends (inward & outward) by reducing overlapping.

Protection of slopes above walls by Coir Erosion Control Blankets

Gabion toe wall at bottom of cutting along west side Slope protection along cutting side using erosion control blanket (ECB)

Vegetation growth on facia and intermediate berms

WALL -1 Ch. 280 to 680

24/02/15

Ashish D Gharpure, P.E. 13

Typical cross section of wall-1 Initial Ground Condition

Grading for Wall Construction

Initial Layers

Initial Layers Wall 1 under construction

24/02/15

Ashish D Gharpure, P.E. 14

Structure completed up to substantial height - 20th Layer in progress

Structure nearing completion Vegetation on berms

Environmental friendliness proven

WALL-2 Ch. 1040 - 1320

Typical cross section of wall-2

Initial Grading

24/02/15

Ashish D Gharpure, P.E. 15

Initial layers of Green Terramesh installed

Greenery coming up during construction

Further Construction of Reinforced slope in progress Rolling of structure fill in progress

Photograph in 2011 (Good amount of vegetation has developed on Green

Terramesh)

Photograph in 2011 (Good amount of vegetation has developed on Green Terramesh)

24/02/15

Ashish D Gharpure, P.E. 16

WALL - 3 Ch. 1320 - 1840

Typical cross section of wall-3 at highest section of the project (CH:1660, Height = 74m)

Initial grading

Wall under construction

Wall under construction

Wall under construction

24/02/15

Ashish D Gharpure, P.E. 17

Wall under construction Wall under construction (recent photo taken in May 2012)

WALL - 4 Ch. 1840 - 2120

Typical cross section of wall - 4

Initial Grading Preparation of bed

24/02/15

Ashish D Gharpure, P.E. 18

Construction of initial layers and progress

Construction of Initial layers and progress

WALL 4 constraints. Houses in front of wall. Wall up to 16th layer completed

Wall up to 16th layer completed View of RCC box culvert exit & Gabion drop structure

24/02/15

Ashish D Gharpure, P.E. 19

View of RCC box culvert exit & Gabion drop structure

Catastrophic seismic event happened in Sikkim

The magnitude of the recent earthquake that happened in Sikkim on Sept 18th 2011 was 6.9. At least 111 people were killed in the earthquake, majority from Sikkim. While most of the infrastructures were damaged partially / completely, the ParaMesh structures withstood this catastrophic event successfully without any damage, which proves its seismic resilience that was considered at planning stage. Moreover, back analysis revealed that the magnitude of seismic event occurred was more than the design magnitude and still the structures were intact.

Recent Seismic event in Sikkim

As per above table, the peak ground acceleration (PGA) for the seismic event of 6.9 (in Richter scale) = 0.354. The h can be calculated as = 0.5xPGA = 0.175g ParaMesh structures were designed for an h =0.12 !!

Recent Seismic event in Sikkim...... Backcalculation for horizontal seismic coefficient (h)

Richter Magnitude, PGA, and Duration Richter Magnitude PGA (g) Dura5on (seconds)

5.0 0.09 2 5.5 0.15 6 6.0 0.22 12 6.5 0.29 18 7.0 0.37 24 7.5 0.45 30 8.0 0.50 34 8.5 0.50 37

CSR Initiatives by project owner AAI

Corporate Social Responsibility Initiatives by project owner AAI Along with Airport Construction works many social welfare works

taken up at Pakyong. These were focused mainly on areas affected by project

implementation. 1. Health Construction of New

Health Centre at Pakyong Quarterly Health Check-up

camps

24/02/15

Ashish D Gharpure, P.E. 20

Corporate Social Responsibility Initiatives by project owner AAI 2. Rural Water Supply Scheme for Lossing & Dikling Village Natural Source tapped Village Covered- Lossing, Dikling Population Covered : 660 people

Inauguration of Water Supply Scheme

Corporate Social Responsibility Initiatives by project owner AAI 3. Environmental Protection 1000 nos of trees planted at airport Site

Inauguration of tree plantation

Visit of AASHTO representatives to project site

AASHTO Working groups visit to project site

Maccaferri recently hosted Dov Leshchinsky (Geotechnical Professor from University of Delaware), Jim Collin (geotechnical specialist from the USA) and Adrian Greeman, a London based international journalist at the Sikkim site.

The purpose of this investment is to spread the word about Maccaferris technical prowess and its capability in these cutting edge structures.

Furthermore, the involvement of the American guests was to challenge the AASHTO design methodology which restricts the spacing of geogrids within these types of structures. Following this leg of the trip, the tour then moved to Albania to view our huge structures there as well.

Awards

Awards received

2011: In Dec 2011, Sikkim Projects owner Airport Authority of India received the award of Environmental Excellence in Corporate Social Responsibility from the Green Tech Foundation, a respected NGO based in New Delhi.

2012: Maccaferri won the prestigious award at the Ground Engineering geotechnical awards ceremony, held in London on Friday 4th May under the category International Project of the year. The other finalist and their projects for this category were,

1. AECOM Asia co, Resorts World Sentosa Singapore 2. Coffey Geotechnics, Ballina Bypass Alliance 3. Drainage Services Department, AECOM & Leighton-John Holland, Lai Chi

Kok Drainage Tunnel, Hong Kong 4. Fugro Geotechnics, Arkona-Becken Sudost Offshore Wind Farm 5. Mott MacDonald, National Radioactive Waste Repository, Btaapti 6. Parsons Brinckerhoff, Setting the Foundation for Adelaide's Rail Revitalisation

24/02/15

Ashish D Gharpure, P.E. 21

Thank You

Q & A? Discussions?

Ashish D. Gharpure, P.E. Director & COO Maccaferri Environmental Solutions Pvt. Ltd. Mobile: 9545533002 Email: agharpure@ maccaferri-india.com

[email protected]