1. CONFIDENTIAL PRIVATE INFORMATION
International Forum on Life-Cycle
Maintenance and Management
Technologies for Smart Highway System
A Holistic Approach to Road Construction and Environmental Impact,
and the Role of Ecologically Based Techniques in Planning and Design
Authors: Steven B Finnie and Harold T M Insley
• Steven B Finnie
Associate Director, Pavement, Trackbed and Materials Consultancy
URS Scott Wilson Ltd, Nottingham, United Kingdom
• Harold T M Insley
Associate Director, Head of Environmental Services
URS Scott Wilson, Hong Kong
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Contents of Presentation
Theme of paper: Mountain Highways in Developing
Countries
• Halsema Highway Case Study
• Typical Slope Problems
• Design of Remedial Works
• Environmental Aspects
• Examples of other Mountain Road Projects
• Typical Design Features
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Halsema Highway History
• Road at 2,000m elevation and above
• Typical rainfall 2,400mm per year
• Partially paved mountain road damaged
by earthquake and typhoons in1990s
• Richter 7.8 magnitude quake in July 1990
seriously damaged road, and Hyatt Hotel
in Baguio collapsed killing 80 people
• Damage to road not immediately repaired
• Significant typhoons caused major
erosion damage
• Consultants appointed in 1996 for
feasibility study to rehabilitate highway
• World Bank funded
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Major Arterial Highway serving Region
• Halsema Highway runs from Baguio City
to Bontoc to Banaue (rice terraces)
• Baguio City regional capital
• Major vegetable growing area
• Vegetables trucked down to outskirts of
Baguio in small trucks
• Transferred to 10 wheeler trucks or
bigger for transport to Manila (capital
city)
• Construction on first section from La
Trinidad to Mount Data started in 2000
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Feasibility Study, Rehabilitation Design
and Construction Supervision
• 180 km long Halsema Highway links
Philippines summer capital of Baguio with
famous “ Banaue rice terraces” World
Heritage Site considered to be more than
2,000 years old
• Road crosses some of most difficult
topography in South East Asia – main
ridge of Central Cordillera runs
approximately north-south
• Central Cordillera: steep, knife-edged and
underlain by highly fractured, faulted and
weathered materials
• Scott Wilson carried out feasibility study,
design and construction supervision of
geotechnical works
• Scope of services included geotechnical,
geological, bio-engineering, hydrological,
environmental, ecological and social
impact aspects
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Halsema Highway, Philippines
• Rural highway in high rainfall,
seismically active mountainous
area
• Carried out feasibility study for
rehabilitation including
geotechnical, hydrological,
environmental and social impact
investigations
• Although Halsema Highway is a
major road, it is classed as a “low-
cost” road for purposes of this
rehabilitation, which restricted
scope of investigations (i.e. limited
ground investigation) and scope of
rehabilitation work
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Halsema Highway, Philippines
• Landscape very fragile, and highly
susceptible to erosion caused by
intense storm runoff and destabilising
earthquakes
• Programme of aerial photography
carried out
• Followed by field mapping, engineering
geological inspection and the sinking of
boreholes
• Initial Environmental Assessment
carried out
• Innovative bio-engineering designs
needed to stabilise slopes
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One of “Most Dangerous Roads in World”
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Typical Slope Problems
• Failure of slopes on to road (rock falls, debris slides etc)
• Failure of slopes below road Technical Assistance for Risk Assessment and Management D2
282800 in 1997
Leading to loss of road edge
(including wall foundation failure)
• Failure of entire road formation
• Debris flows & slope erosion
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Large Landslide below Highway
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Unstable Slopes above Highway
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“Temporary” Structures to Maintain Access
• After earthquake and typhoons in 1990s
access along highway provided with
mixture of “temporary measures”
including Bailey Bridges, and temporary
diversions
• Photo of crossing of “saddle” where
roadway failed on both sides of highway
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Design of Remedial Measures
Integrated Approach Required
• Geotechnical engineering measures
• Drainage engineering measures and erosion control
• Slope protection and bio-engineering measures
• Environmental protection
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Typical Rehabilitation
Halsema Highway
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Typical Major Rehabilitation
Halsema Highway
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Integration of Bio-Engineering with Geotechnical Design
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Failures and Erosion below Road Bench
Pre-Construction
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Rehabilitation below Road Bench
Works Substantially Complete
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Masonry Wall to Support Road Bench
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Drainage and Stream Protection Measures
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Above Road Retaining Structure
Completion of shotcrete &
construction of above-road
retaining structures
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Environmental Aspects
• Environmental Impacts related
to Heritage Sites and National
Park
• Construction Impacts
• Traffic Related Impacts
• Social Impacts
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Environmental Impacts – Heritage Sites and National Park
• Photo shows rice terraces near Banaue
• Heritage site
• Road also passes through National Park
• World Bank required impacts on Heritage
Site and National Park minimised as far
as practical
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Construction Impacts
• Noise (generated by construction
plant)
• Dust
• Disposal of excavated material
• Excavation of borrow areas
• Water quality impacts, and
erosion
• Social impacts from clearance,
etc.
• Impact of construction on traffic
using road
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Traffic Related Impacts
• Improved road surface, previously
unpaved, now concrete pavement,
results in increased vehicle speeds
• Increased speeds result in greater
potential for accidents involving
excessive speeds
• Accidents as a result of “blind” corners,
pedestrians on roads, boulders from
slopes above causing obstacle on road,
fog banks
• Mountain road creates opportunity for
major accidents with vehicles crashing
off road, and causing many fatalities
(especially buses)
• Limited budget for road side barrier but
small up stand wall included
• Road humps to reduce speed
• Increased axle loads
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Social Impact Assessment
• Clearance of encroachments into
road reserve
• Some acquisition of agricultural
land for minor alignment
improvements
• Socio-Economic Surveys carried
out
• Resettlement Action Plan prepared
• Community engagement
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Examples of Other Mountain Road Projects
• Nepal: Prithvi Highway
• Nepal: Third Road Improvement Project
• Tajikistan: Shagon-Zigar Road
• Bhutan: Road Network Study
• Ethiopia: Koombolcha – Mekane Salem – Gundewien
Road
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Prithvi Highway, Nepal
Flood Damage Assessment, Study Report, Design of
Remedial Works and Supervision
• Geotechnical examination,
inventory of flood damage
• Recommendations for and
prioritisation of reinstatement
and further erosion protection
works
• Remedial, reinstatement, and
protection measures
• Design/supervision/ contract
management services for
damage repair, contract
management and supervision
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Third Road Improvement Project, Nepal
Improvement and Rehabilitation of Rural
Roads
• Improvement and rehabilitation
of 350km of rural access road to
bitumen standard in mountainous
and flat terrain
• Economic screening study
• Typical design details, and
design checks
• Procurement and construction
supervision
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Shagon-Zigar Road, Tajikistan
Feasibility, Design, Supervision
• Situated along border with Afghanistan,
alignment through foothills of Pamirs and
bordered by Pyanj River to east
• Alignment traverses extremely rugged,
mountainous terrain
• Challenges to engineering team included
rockfall from natural slopes, extreme
topography and weather conditions and
sensitive ground conditions disturbed by
pre-contract blasting and seismic activity
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Road Network Study, Bhutan
Technical Assistance Project to Prepare Prioritised Road
Improvement Programme
• Survey and analysis of typical slope
stability problems
• Slope maintenance manual
• Economic evaluation of proposed
improvements
• Environmental Impact Assessment
of proposed improvements
• Road improvement strategies
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Kombolcha – Mekane Salem – Gundewien Road, Ethiopia
Remote Sensing, Engineering Geological Mapping, Ground
Investigation, Design Review (including redesign) and
Construction Supervision
• Construction of 136 km new gravel road,
with dense base macadam on steep
gradients, and simultaneous construction
of 2 new bridges over River Nile and
tributary, Difarsa River
• Geotechnical services included detailed
aerial photograph interpretation, field
engineering geological and
geomorphological mapping, reference
condition mapping, landscape evolution
modelling, ground investigation and
outline design of slope works.
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Typical Design Features
• Bio-engineering
• Gabion Wall
• Combined Masonry and Gabion Wall
• Reinforced Earth Wall
• Reinforced Concrete Grid Wall
• Surface Reinforcement
• Buttress Wall
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Bio-Engineering Slope Protection
Bio-engineering is the use of
vegetation, either alone or in
conjunction with civil
engineering structures, to
reduce slope instability and
erosion on slopes.
4 main groups of techniques are
available:
Grass line planting
Brush layering etc
Shrub, tree and bamboo
planting
Composite techniques
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Bio-engineering
• Low construction cost
• Low maintenance cost
• Visually preferable
• Contributes to local economy
• Species selection is key:
• Hardy
• High rainfall and drought resistant
• Extensive use of grasses
• Bamboo and Shrub species with strong root network
• Pine trees
• Pilot trials
• Indigenous and imported species
• Local expertise utilised
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Gabion Wall
Above Road: Gabion Wall in Nepal
Below Road: Gabion Wall
in Ethiopia
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Combined Masonry and Gabion Wall
Construction Substantially Complete
Pre-Construction
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Reinforced Earth Wall
Under
construction
(Ethiopia)
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Reinforced Earth Wall
Completed
wall (Ethiopia)
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Reinforced Concrete Grid Wall
Reinforced Concrete Grid Wall comprising
Reinforced Concrete Members with Mortared
Masonry Panels on Halsema Highway
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Surface Reinforcement
“Plastering” a thin
concrete layer over
decomposed rock
slope in Laos
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