geological challenges & ecological effects of highway construction

Geological Challenges &

Ecological Effects of Highway

Construction

PREPARED BY GROUP -1MEMBERS :ABHINAV ANAND [120104001]ABHISHEK ARORA [120104002]AJAY SINGH MEENA [120104003]AKASH YADAV [120104004]AKSHAY JAIN [120104005]

Introduction

India has a road network of over 42,36,000 km, the third largest road network in the world. However qualitatively India’s roads are a mix of modern highways and narrow , unpaved roads.

Major modern highways that connect cities in populous developed and developing countries usually incorporate features intended to enhance the road's capacity, efficiency, and safety to various degrees.

Engineering Geology of rock slopes in Highway

Construction Rock slopes form part of the components in

many highway or roadway construction in hilly terrain. The key question with regard to rock slope can have serious consequences. The stability of a particular rock slope is governed by three main engineering geologic factors namely-

Lithology Structure Weathering Grade

Slope failure

Lithology Refers to rock type. Different rock types have different material

properties and behaviour. For example, granitic rocks differ from shales and schist.

In case of granitic rocks joints control the stability of rock slope at a particular location. On the other hand bedding planes control the stability of cut slopes in case of shales and sandstones.

Similarly, in phyllites and schist which are foliated, the foliations would be the controlling features.

Structures Geological Structures include a host of features

such as joints, faults ,bedding planes ,foliations ,folds ,etc.

They represent breaks/discontinuities or weaknesses in the rock mass.

Detailed mapping of various major joint sets in cut slopes is required for slope stability assessments and follow-up stabilization measures.

Weathering Grade Intense chemical weathering reduces rocks into much

weaker soil like material, resulting in thick soil mantles over bedrock formations.

Superimposed on the lithology and structures, the weathering effects can be predominant in controlling the behaviour of resultant rock mass. For example-In a typical granitic weathering profile, while the grades I to II zones generally have tight joints, the grade III zone just below the rockhead or soil-rock interface often has wide, open sheet/exfoliation joints which are prone to sliding. These sheet joints are formed by stress relief during the weathering process, and tend to run sub parallel to the rockhead, with great tendency to daylight in the cut slope.

Survey of rock slopes In the construction of rock slopes along a

highway, an initial survey along the highway alignment would be necessary to determine the rock types that would be traversed by the highway.

The use of geological maps coupled with surface geologic mapping and site investigation data would be useful.

During the construction stage, close monitoring of the rocks excavated and especially mapping of geological structures would be needed for every cut slope for the assessment and identification of potential instability problems.

Post-failure investigation of rock slopes is also necessary.

Case Study: NH-52(A)

NH-52(A) is a spur route of NH-52 connecting the Itanagar with Brahmaputra valley in Assam, India. It is the principal road communication to the hilly state capital complex, Itanagar.

Presently, the NH-52(A) is a 2-lane width Indian national highway traverses a total distance of 57.7 km out of which 15 km is in plains of Assam near Gohpur and rest 42.7 km is in hilly terrains of AP, built in two phases. Phase-I comprises the part from Bandardowa to Itanagar(31.2 km) which was planned and built during 1988-90. Phase-II which was built during 1992-94 (11.5 km) consist of the rest part from Itanagar to Gohpur.

Case Study: NH-52(A)

Of the many critical sections of NH-52(A) pavement, the highest grade of critically suffering pavement section of NH-52(A) is the Karshingsa area which is geologically termed as sinking zone. The Karshingsa section of about 1 km length generates severe flow type landslides almost every year and experiences of instability.

Geology of Hilly Terrains of NH-52(A)

The part of NH-52(A) from Bandardowa up to Itanagar-Chimpu area (except Mowb-II hillock area in Itanagar) via Naharlagun-Papu Nallah area along Pachim river is composed of quaternary formation bearing weak subsoil and soft rock layers (Bayan, 2004.b), for which it generates more engineering problems. On the other hand, the rest part up to Gohpur area is composed of siwalik group of formation exposed at surface. Hence, it reveals better geotechnical properties and generates fewer problems.


From geological point of view in general, the NH-52(A) as a whole passes over those areas which are situated within the main plate boundary fault between Eurasian and Indian plates and the main thrust fault of Himalayan hill ranges. As a whole the base rock formation of the area principally falls under Quaternary group of rock formation.

Geologically, the selected corridor of the NH-52(A) where Karshingsa is one of the critically important parts between Bandardowa and Itanagar runs almost entirely through the Quaternary Formation/ upper Siwalik, locally known as the Kimin Formation. These rocks have been deposited during Mid-Miocene to Lower-Pleistocene period.


The Formation consist mainly of alternations of conglomerates known as pseudo-conglomerate, soft and massive sand rock/ sandstone, and silty clay beds.

The beds strike NW - SE and gently dip towards NE. Three sets of joints exist in these rocks. Besides the Upper Siwalik rocks, Quaternary deposits and terraces also occur at some places. The Main Boundary Thrust passes on its north and in the south is the Plate boundary fault (i.e. the Himalayan Foothill Thrust) between Indian Plate and Eurasian Plate.

Geology of Hilly Areas of NH-52(A)

Pseudo-Conglomerates are the prominent rock unit exposed along the national highway. These rocks are easily erasable because of poor cementation and pronounced weathering. The thickness of pseudo-conglomeritic bends varies from 1.2 – 15 m and that of sandstones is 0.6 – 10 m on the uphill side above road level. However, it is seen that the waste materials reveals out of various pattern of landslides are comprises of Colluvium subsoil layers only. The figure shows geological map of Capital Complex Covering the Study Area NH-52(A)

Solutions The concept of skirted retaining wall together with road

foundation system for hilly roads is targeted to hold structural soil by confining them within a hard thin circular structural layer made of concrete or PVC materials, and place them in a pattern of honey comb cell.

For drainage outlet section of hilly road, the skirted wall in the toe side is normally extended down to the required design depth below road level, such that it can rest on an almost flat ground in such structure the other three side of the skirted wall provides excessive retaining as well as lateral strength.

Impacts of Highway Construction on Soil &

Geology The con struc tion and oper a tion of the trunk

road net work can also have an impact on the func tion of soil and geo log i cal prop er ties of an area.

These impacts may arise through the phys i cal removal or impor ta tion of soils and rocks or the com paction and seal ing of the ground dur ing con struc tion. Impacts may also be caused dur ing the oper a tion of the road by the effects of air borne pol lu tion and spray.

Environmental Impacts of Highways

Air Quality Water Pollution Noise Habitat Fragmentation

Air Quality Negative Impacts

Air pollution from fossil (and some biofuel) powered vehicles can occur wherever vehicles are used and are of particular concern in congested city street conditions. Emissions include particulate emissions like NOx,volatile organic compounds, Carbon monoxide etc.

Road dust kicked up by vehicles may trigger allergic reactions. Carbon dioxide is a major greenhouse gas and motor vehicle emissions are an important contributor to the growth of CO2 concentrations in the atmosphere and therefore to global warming.

Air Quality

Positive Impacts The construction of new roads which divert traffic from built-up

areas can deliver improved air quality to the areas relieved of a significant amount of traffic. The Environmental and Social Impact Assessment Study carried out for the development of the Tirana Outer Ring Road estimated that it would result in improved air quality in Tirana city centre.

For Example : A new section of road being built near Hindhead, UK, to replace a four-mile section of the A3 road is expected by the government to deliver huge environmental benefits to the area including the removal of daily congestion, the elimination of air pollution in Hindhead caused by the congestion, and the removal of an existing road which crosses the environmentally sensitive Devil's Punchbowl area of outstanding natural beauty.

Water Pollution

Urban runoff from roads and other impervious surfaces is a major source of water pollution. Rainwater and snowmelt running off of roads tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants. Road runoff is a major source of nickel, copper, zinc, cadmium, lead and polycyclic aromatic hydrocarbons (PAHs), which are created as combustion byproducts of gasoline and other fossil fuels.

De-icing chemicals and sand can run off into roadsides, contaminate groundwater and pollute surface waters. Road salts (primarily chlorides of sodium, calcium or magnesium) can be toxic to sensitive plants and animals.Sand can alter stream bed environments, causing stress for the plants and animals that live there.

Noise

Road noise can be a nuisance if it impinges on population centres, especially for roads at higher operating speeds, near intersections and on uphill sections. Noise health effects can be expected in such locations from road systems used by large numbers of motor vehicles.

Speed bumps, which are usually deployed in built-up areas, can increase noise pollution. Especially if large vehicles use the road and particularly at night.

Habitat Fragmentation

Roads can act as barriers or filters to animal movement and lead to habitat fragmentation.Many species will not cross the open space created by a road due to the threat of predation and roads also cause increased animal mortality from traffic.This barrier effect can prevent species from migrating and recolonising areas where the species has gone locally extinct as well as restricting access to seasonally available or widely scattered resources.

Habitat fragmentation may also divide large continuous populations into smaller more isolated populations.These smaller populations are more vulnerable to genetic drift, inbreeding depression and an increased risk of population decline and extinction.

Habitat Fragmentation

Need of Green Highways for Sustainable Development

Development of road infrastructure is currently being given high priority by the government of India to meet the requirement of growing travel demand and to help the faster growth of economic activity. Most of these roads have bituminous surface at the top constructed using naturally available road aggregates and bitumen, a petroleum product, which being mixed at high temperature to produce hot mix asphalt (HMA).

By this process there has been a faster depletion of road aggregates and also increase in emission of gases in to the atmosphere causing environmental pollution. Use of low emission bitumen (green bitumen materials) and milling and re-use of material collected from old existing pavement, recycled asphalt pavement (RAP), to build green highways will be the most promising alternative to the current practice to achieve sustainability in road construction.

Benefits of Concrete Pavements over Asphalt pavements

Reduced Lighting Requirement

because of the more reflective nature of concrete pavements, a specified luminance level can be achieved with fewer high-output lighting fixtures and standards. Ultimately, this translates to lower costs and lower energy consumption over time.


Reduced Vehicle Fuel Consumption and Emissions


Heat Island Mitigation The energy of sunlight that is not reflected off pavement surfaces is converted into thermal energy that increases the pavement’s temperature. This, in turn,increase the temperature of the air around the pavement. In urban areas, the higher air temperature occurs as a result of pavements and other surfaces absorbing the sun’s heat.

Key Areas for the Development of a Green

Highway

Watershed Driven Storm Water Management

Recycle, Reuse

and Renewable

Conservationand EcosystemManagement

Lifecycle Energy and EmissionsReduction

Overall Societal Benefits


Recycle, Reuse

and Renewable

Conservationand EcosystemManagement

Lifecycle Energy and EmissionsReduction



Stormwater is rainwater and melted snow that runs off streets, lawns, and other sites. When stormwater is absorbed into the ground, it is filtered and ultimately replenishes aquifers or flows into streams and rivers. In developed areas, however, impervious surfaces such as pavement and roofs prevent precipitation from naturally soaking into the ground. Instead, the water runs rapidly into storm drains, sewer systems, and drainage ditches and can cause:

Downstream flooding Stream bank erosion


Increased turbidity (muddiness created by stirred up sediment) from erosion

Habitat destruction Changes in the stream flow hydrograph (a graph

that displays the flow rate of a stream over a period of time)

Contaminated streams, rivers, and coastal water. Technologies used are bioretaintion, pervious

pavement shoulders, environmentally friendly concrete, forest buffers, wildlife crossings, restored and storm water wetlands, etc.


Pervious concrete has the potential to provide an environmentally sensitive product for specific applications. Currently, the most common uses of pervious concrete are parking lots, low traffic pavements, and pedestrian walkways.

Energy & Emissions Reduction

Given projected cement production, using 50% fly ash can save the equivalent energy in 6.4 billion gallons of gas annually.

2.9 billion gallons of gas was wasted due to vehicles in congestion in 2007.

Recycle, Reuse and Use Renewable

Conservation of natural minerals and reduction of waste during construction and maintenance of highways.

Recycle is a process and Reuse is practice.

Industrial By-products can be recycled and used as highway construction materials like fly ash, blast furnace slag, foundry sand, etc.

Conservation and Ecosystem Management The impacts of highway construction are

division and displacement of natural habitat. Solutions Provide animal crossing structures. Maintaining natural flows of streams, rivers.


Highways are tied to the quality of life in a particular area.

Highways have an important economic role.

A Future for the Nations Infrastructure

Green construction has been implemented in the structural market successfully.

We need innovative ways to solve environmental issues while maintaining a strong infrastructure

THANK YOU