TOPIC:- HIGHWAY ALIGNMENT IN HILLY AREAS

CIV204

NAME:-HARKAMAL SINGH

REG.NO:-10801881

ROLL.NO:-RB5803B51

CONTENTS

HIGHWAY ALLIGNMENT

REQUIRMENTS

HILL ROADS-ENVIORNMENTAL CONCERNS

DESIGN AND CONSTRUCTION OF HILL ROADS

DRAINAGE

MAJOR ECOLOGICAL PROBLEMS

PROTECTIVE MEASURES AND CONCLUSIONS

REFRENCES

HIGHWAY ALIGNMENT

The position or the layout of the central line of the highway on the ground is called the alignment. Horizontal alignment includes straight and curved paths. Vertical alignment includes level and gradients. Alignment decision is important because a bad alignment will enhance the construction, maintenance and vehicle operatingcosts. Once an alignment is _xed and constructed, it is not easy to change it due to increase in cost of adjoining land and construction of costly structures by the roadside.And

Highway engineering is the process of design and construction of efficient and safe highways and roads. It became prominent in the 20th century and has its roots in the discipline of civil engineering. Standards of highway engineering are continuously being improved. Concepts such as grade, surface texture, sight distance and radii of horizontal bends and vertical slopes in relation to design speed and in addition to road junction design (intersections and interchanges) are all important elements of highway engineering. Most developed nations have extensive highway networks.

We have seen the requirements of an alignment. But it is not always possible to satisfy all these requirements.Hence we have to make a judicial choice considering all the factors.The various factors that control the alignment are as follows:_ Obligatory points: These are the control points governing the highway alignment. These points areclassi_ed into two categories. Points through which it should pass and points through which it should notpass. Some of the examples are:{ bridge site: The bridge can be located only where the river has straight and permanent path and also where the abutment and pier can be strongly founded. The road approach to the bridge should not be curved and skew crossing should be avoided as possible. Thus to locate a bridge the highway alignment may be changed. { mountain: While the alignment passes through a mountain, the various alternatives are to either construct a tunnel or to go round the hills. The suitability of the alternative depends on factors like topography, site conditions and construction and operation cost.{ intermediate town: The alignment may be slightly deviated to connect an intermediate town orvillage nearby.These were some of the obligatory points through which the alignment should pass. Coming to the second category, that is the points through which the alignment should not pass are: { religious places: These have been protected by the law from being acquired for any purpose. Therefore, these points should be avoided while aligning. { very costly structures: Acquiring such structures means heavy compensation which would result in an increase in initial cost. So the alignment may be deviated not to pass through that point.{ lakes/ponds etc: The presence of a lake or pond on the alignment path would also necessitate deviation of the alignment. _ Tra_c: The alignment should suit the tra_c requirements. Based on the origin-destination data of the area, the desire lines should be drawn. The new alignment should be drawn keeping in view the desirelines, tra_c ow pattern etc.

_ Geometric design: Geometric design factors such as gradient, radius of curve, sight distance etc. also govern the alignment of the highway. To keep the radius of curve minimum, it may be required to change the alignment. The alignments should be _nalized such that the obstructions to visibility do not restrict the minimum requirements of sight distance. The design standards vary with the class of road and the terrain and accordingly the highway should be aligned.

REQUIRNMENTS

Special consideration for hilly areas Alignment through hilly areas is slightly di_erent from aligning through a at terrain. For the purpose of e_cient and safe operation of vehicles through a hilly terrain special care should be taken while aligning the highway. Some of the special considerations for highway alignment through a hilly terrain is discussed below.

_ Stability of the slopes: for hilly areas, the road should be aligned through the side of the hill that is Stable . The common problem with hilly areas is that of landslides. Excessive cutting and _lling for road constructions give way to steepening of slopes which in turn will a_ect the stability.

_ Hill side drainage: Adequate drainage facility should be provided across the road. Attempts should be made to align the roads in such a way where the number of cross drainage structures required are minimum.

This will reduce the construction cost._ Special geometric standards: The geometric standards followed in hilly areas are di_erent from those in at terrain. The alignment chosen should enable the ruling gradient to be attained in minimum of the length, minimizing steep gradient, hairpin bends and needless rise and fall. _ Ine_ective rise and fall : E_orts should be made to keep the ine_ective rise and excessive fall minimum.

HILL ROADS – ENVIRONMENTAL CONCERNS

Hills are of great importance to the country. Traditionally, hills have served as the sentinels guarding the country and checking invasion. They are endowed with great forest wealth and a variety of wild life. They are the sources of water in the major river systems of the country, sustaining large population and agricultural activity. The hill regions usually exhibit a variety of climatic, geological and ecological characteristics and because of their unique character, hill roads require special attention in planning, design, construction and maintenance.

India has a long experience of constructing hill roads. Based on the expertise available, the Indian Roads Congress brought out a standard (IRC: 52) on Alignment, Survey and Geometric Design of Hill Roads in 1973, which has been revised twice. The IRC had also organized a Seminar on Hill Roads at Nainital in July, 1985 wherein several Technical Papers from eminent professionals on seven Themes, viz., Survey and alignment of roads in hilly regions; Environmental considerations in selection of alignment of roads in hilly regions; Design of hill roads including retaining structures; Construction and maintenance of hilly roads including use of modem equipment and snow clearance of roads; Landslide problems and road drainage practices and Water crossings in hilly regions were presented and discussed. The Seminar was aimed to focus attention of highway engineers on various problems connected with the selection of alignment and adoption of design standards, construction specifications and maintenance strategies on hill roads, to stress the need to preserve eco-system in the hilly region when constructing roads. Besides Proceedings, some important Papers on design, construction and maintenance of Hill roads, presented during the Seminar have also been published. Another Special Publication, 'IRC:SP:48 Hill Road Manual' was brought out by IRC in 1998 which also covers the issue of ecology and environment.

When aligning new roads, some simple precautions, such as, avoidance of unstable terrain having deep blanket of loose soil and boulders susceptible to seepage and water saturation, selection of mild slopes in preference to steep slopes, avoidance of forest land as far as possible, avoidance of landslide prone locations, selection of alignment causing least disturbance to the natural drainage courses, etc: should be taken into account. Tunnels, though costly, provide eco-friendly solution, besides reducing the travel length.

While designing hill roads, special considerations, such as, balanced cut and fill with a retaining wall, use of reinforced soil to minimize earthwork and provision of adequate erosion control measures should be considered.

During construction, the drainage arrangement should proceed side by side with the earthwork; retaining walls wherever required should be constructed before hill cutting so that cut soil can be used as back fill; cross fall should be on hill side to control runoff over valley side; replantation should be resorted and young plants should be protected by fencing; and use of emulsions should be encouraged to minimize use of wood for heating.

As massive programme of widening the existing roads to 4/6 lanes and providing connectivity to villages have been launched by the Government of India and a large proportion of proposed roads pass through hilly areas, there is an urgent need to provide due consideration for preserving the ecological balance. Cutting of hillsides and felling of forests on hill faces, which are necessary concomitants to any developmental activity, have disturbed such balance and sometimes brought disaster in its wake. Large and rapid developmental activities may cause alarming degradation and depletion of natural resources resulting in ecological imbalances. Therefore, while planning and constructing roads, the conservation of forests and ecological balance should be maintained. Similarly, planning of important roads through potential landslide zones should be avoided.

The Government of Uttaranchal has established a Disaster Mitigation and Management Centre (DMMC) which is preparing a comprehensive database on areas prone to earthquake, landslides, flash floods, road accidents, etc. using remote sensing and GPS techniques to map the landslide zones, etc. which may prove to be helpful in planning of new road alignment and also in mitigating the problem on existing road network. Similarly, soil-nailing techniques are being evolved for control of erosion. Use of gabion walls in place of conventional reinforced concrete or masonry structures also provide eco-friendly solution. Considering its importance and special significance to the State of Uttaranchal a few technical presentations on control of erosion and landslides on hill roads have been planned during the forthcoming mid-term Council meeting of IRC scheduled for the l2th May, 2004 at Nainital. Some of the Technical Papers are published in this issue of Indian Highways for the benefit of IRC members at large.

DESIGN AND CONSTRUCTION OF HILL ROADS

PRECIPICE WORK

If the rock strata slopes downward into the hillside,the rock is permitted to overhang the road forming a half tunnel.blasting is done either from face or from one or both sides.if strata is inclined towards the hill slope,cutting is continued until the inner slope ia at safe angle to prevent slipping.in such a case,blasting and cutting is commenced from top.if the rock is soft or loosely stratified,the cutting is commenced at point on hillside far above ther formation level for obtaining enough batter for inner slope.blowing out the cliff face by firing large mines and then dreesing the slope,is another alternative.in actual consideration,there is graet difficulty in removing rock exactly to the required levels and grade.unless special care is taken,balsting may be slighltly short of requirements or it can be overblasting.during blasting,the drain on hill side is formed.blasted stones are used for retaining walls,backfiiling,high retaining walls and aprons etc.

When boring is not practicable,a light roadway may be carried on timber cradles suspended by means of wire cables from jumpers driven ar the top of the cliff,.the bearer of the cradle should tilt upwards;otherwise when the cradle draws away from the face of the cliff;the surface will slope outwards and become dangerous.

RETAINING WALLS

These walls are most important structure in hill road construction to provide adequate staibility to the roadways and to the slope.retainig walls are constructed on the valley side of the roadway and also on the cut hill side to prevent land slide towards the roadway.

DRAINAGE

Road Geometrics Longitudinal Gradient

Flatter slopes both longitudinal and transverse slow down the flow of rain water

over the oadway and decrease the drainage capacity.

For better internal drainage of pavement layers, especially of granular material,

a slight longitudinal gradient is most preferable.

A minimum longitudinal drainage gradient is most preferable

A minimum longitudinal drainage gradient of 0.3% is adequate.

Pavement Cross Slope/ Camber

In geometric design pavement cross-fall or camber could be made to slope

either on one side or on both sides with a crown in the middle of the road

pavement.

On hill roads preference generally is to drain the carriageway water towards the

hill side particularly where the road banking is susceptible to erosion so that the

drain on the roadway could carry away the discharge safely to proper outfall.

Camber should not be less than 1 in 40.

Shoulder Drainage

The effective method of maintaining the shoulders is to have paved or hard

shoulders instead of earth shoulders

A common defect in some of the road is occurrence of shoulders at levels higher than pavement surface. In such situations, during rain - the water on road

surface does not find a free outlet and accumulates on top of it. Such defect where shoulder blocks the drainage should be rectified.

MAJOR ECOLOGICAL PROBLEMS There are a large number of ecological problems associated with road construction in hilly tribal areas, some of these can be summarized as below:

i) Deforestation: The association between deforestation and slope instability has been a subject of considerable research. Deforestation brings about erosion and soil movement is generally accepted, but opinions differ on its impact. So far as "Creeping" slopes are concerned, greater creep velocities are found in slopes covered by trees in the region of Queenland (Australia) than in slopes merely covered by grass in region of rain forests (Brown and Shen, 1975). Prandini et al. (1977) reported that deforestation leads to loss of mechanical strength imparted by rock system. Reinforcing power of roots is also demonstrated by the results of in situ block shear tests, which show that shear strength increases with increase in root density. At higher altitudes top green layer is very thin and takes hundreds of years to come. A large number of trees along the roadsides are falling down due to road construction. Improper road construction results in soil erosion that may lead to uprooting of large trees and degeneration of lower plants. This way it leads to serious ecological imbalances affecting adversely run-off factors, temperature gradient, surface radiation etc. Due to loss of vegetation, the velocity of run-off also increases that results in soil erosion, hence of soil-fertility.

ii) Disturbance of geological strata:Operations like blasting excavation, chipping of mountain slopes to come to desired accessibility, are involved during road construction in hill areas. These operations creates geological disturbance in the mountain body. The blasting operations set dynamic forces causing the movements of slip zones, cracks, fissures and weak planes. The geological havoc caused due to road construction in Kinnaur District in before us. The chronic problems of landslides at Tranda, Chaurah and Kadhra dhank are a few examples.

iii) Hill face disturbance: Natural inclination of hill face is disturbed by road cutting operation. Down hill movement of the land slides material and disposal of

excavated mass from road construction degrade and deface the nature. Growth of vegetation is affected by the loss of topsoil that causes ecological imbalances.

iv) Drainage pattern interruption: Velocity of run-off at the down hills increases to a very large extent due to construction of bridges and culverts on the road as well as due to cutting for getting proper communication systems. This leads to eroding of banks and is a threat to the existence of trees and vegetation on the hill slopes. Sometimes lakes are formed by accumulation of debris from the excavated material and land slides. Such lakes formed force the water to flow through some other way destroying the side by flora e.g. at Nallah on NH = 22, bridge was washed away thrice in six years because due to debris river was blocked and a temporary lake was formed. Same story was repeated at Pabbar river in Chhawara valley (Rohroo) in 1992, where a big lake (2 miles) was formed and about ten villages were vacated in order to avoid any loss to human life. This lake formed resulted in a loss of large number natural wealth both flora and fauna. This way natural drainage pattern of the area is disturbed by road construction, which sometimes results in flash floods also.

v) Water resources disturbance: Natural water resources get disturbed due to blasting which is used during road construction activities. Moreover, improper disposal of fuel, lubricants used in the process contaminates the surface and ground water.

vi) Siltation problem: A large quantity of excavated material disposed on the down hill slopes is carried by the river that gets accumulated in the dams and reservoirs and reduce their life-span e.g. siltation rate of Bhakhra Dam reservoir is very large which is due to large scale road construction in Sutlej catchment.

vii) Destruction to flora and fauna:Wild life gets disturbed due to blasting, hauling of machineries, shriveling sound of road rollers and noise of moving vehicles on the up-gradient. Destruction of key habitats such as resting sites, hollow trees, feeding and breeding grounds occurs due to road constructions. Some of the flora and fauna gets destroyed out right due to intrusion into forest for road construction.

viii) Pollution: Tremendous pollution is created due to accumulation of debris down hill. Moreover, heating of bitumen through hot mix plants produces a large number of air pollutants like oxides of sulphur, nitrogen and carbon. Long chain aliphatic hydrocarbons and aromatic compounds are also the byproducts of this heating process, which are having carcinogenic property (Cancer producing) and special precautions must be taken for protecting the labourers working under such conditions on the road construction site. Surrounding temperature gets increased and atmospheric humidity is lowered due to movements of machineries and vehicles, altering the physiological processes of the plants and thereby affecting their growth pattern. The alterations in the surrounding conditions causes interference of micro-organism life in the soil.

ix) Destruction of medicinal wealth:In the hill areas of Himachal Pradesh out of 3000 species of identifies plants, over 500 species possess various kinds of medicinal properties. Hundreds of plants have ethno botanical importance. There are about 150 species of aromatic plants used in different kinds of cosmetics and having different medicinal properties. But due to improper planning in road construction and processes involved during road construction, the natural wealth gets destroyed costing crores of rupees in spite of protecting the atmosphere from pollution.

PROTECTIVE MEASURES In order to maintain balance between the road construction activities and environment certain protective measures have to be taken. Some of these measures are as follows: i) Environment impact assessment: Before starting the road construction operation, environmentalists must be consulted in order to avoid any ecological imbalance.

ii) Geological investigation: A geologist must be incorporated in the road construction work. Blasting and chipping of mountain slopes must be done under his instructions in order to avoid any geological havoc.

iii) State of wildlife: During the road construction loss to flora and fauna must be minimum. It should not be disturbed. An environmentalist must be consulted prior to road construction work.

iv) Avoidance of unstable and fissureal zones:Roads should not be constructed in lose soil and where erosion chances are more. In such cases the help of a soil Engineer must be taken, before starting any such activities.

v) Least disturbance to natural streams and gradients:Natural face of the hill must be least disturbed while constructing the roads. Only the required land must be used for the purpose.

vi) Restriction on reserve forests: Road construction activities must be minimum on reserve forests in order to avoid any disturbance to natural wealth. This will help in maintaining the ecological balance.

vii) Judicial way of doing work: While cutting and disposing the debris special care must be taken so that there is no soil erosion and loss to flora and fauna.

viii) Minimum blasting operations: Blasting practice during road construction must be to the minimum extent in order to avoid any dynamic forces causing movements of slip zones, cracks, fissures and weak planes.

ix) Half tunneling must be restored:In case of vertical rocky slopes half-tunneling must be restored.

x) Ropeway technique: In case of less densely thick population ropeway must be installed instead of going for road construction. This will provide protection to soil erosion, wild life and environment.

xi) Suitable drainage system: Along the entire side of the road, a suitable drainage system must be provided so as to avoid any flash flood, soil erosion, damage to vegetation etc.

xii) Restoration of natural springs and waterways:Natural springs and water resources must not be disturbed during road construction process, otherwise it will be a great challenge to the nature.

xii) Rebuilding of environment:

a) On suitable points, places must be provided that may act as scenic spots to the users. b) Programme of social forestry must be taken upto the root level. The wastelands must be garlanded with trees, and valuable herbs and shrubs. The best example of social forestry is found in china where even single inch of wasteland is not left without plantation. Debris obtained during road cuttings must be accumulated at some appropriate place and plantation must be done on the same. This plantation will help in retaining the natural environment. c) Plantation must be done along the banks of rivers, nallaha etc. in order to avoid any further cutting of soil and to protect the water reservoirs and dams from more siltation. d) Small water tanks along with the proper drainage system must be

constructed along the roadsides in order to protect both flora and fauna. Roadsides must be planted at war-level so as to give the best example of afforestation.

CONCLUSION Although road construction in hilly areas causes a huge damage to both flora and fauna in spite of having adverse effect on environment, but without proper communication facilities, it is not possible to explore the valuable wealth of such areas. So a balance must be struck between the road construction and environment in order to minimize the ecological imbalance. Certain scientific measures must be taken into account while constructing the roads in hills. The balance between the two will lead to the prosperity of the region and no hazard to environment will occur.

REFRENCES

http://gbpihed.gov.in/envis/HTML/vol82/vo82-kaith.htm

http://www.nbmcw.com/articles/roads/472-salient-drainage-design-aspects-for-roads-a-highways.html

Text book

http://en.wikipedia.org/wiki/Canol_Road