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CE 3405
Civil Engineering (CE)
Anna University
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UNIT 1 HIGHWAY ENGINEERING
Significance of highway planning
Wide Geographical Coverage provided by roads: Roads can be constructed to penetrate the interior of any region and to connect remote villages. The advantage becomes particularly evident when planning the communication system in hilly regions and sparsely populated areas. Low Capital investment: Roads can be constructed at comparatively lower initial cost than railways. The cost of roads varies with specifications, but even the best road is cheaper than a railway line. Quick and assured deliveries: Time is great value for a wide range of articles; including both perishables and high value is manufactured products. Road transport by its quick deliveries reduces the need for larger inventories and locking up of working capital a great cost. Flexibility: Road transport offers a flexible service, free from fixed schedules. Any number of trucks or buses can be pressed into service quickly to meet sudden demand or withdrawn .Such a flexibility is absent in railways, which operate generally according to fixed schedules. Door-to-door services: Road transport offers door-to-door service, free from transshipments from origin to destination. Railways on the other hand have to depend upon road transport for picking up loads and making deliveries. Simpler packaging: Road transport permits simpler packaging and crating for the protection of goods against breakage. Personalized service: A personal touch is generally present in road transport. The customer is given in individualized attention in various matters. Employment potential: Road transport has a high employment potential. This is an important factor in a country with a large and employment problem. Personalized travel: Travel by private car or motorized two wheeler or even a cycle, satisfies personal pleasures is one of the main reasons for the popularity of personalized travel mode in the developed countries. Short hauls: For short hauls transport is there only economical means if a major project is to be constructed and is the construction materials have to be transported through short distances one turns only to road transport. Safety: One of the serious advantages of road transport is its poor record of safety. Road accidents have become a serious menace, claiming enormous economic loss to the nation. Environmental pollution: Road transport has been one of the major causes for environmental pollution, noise fumes, vibration, loss of aesthetics, ribbon development these are the some ill effects.
Parking problem: Road transport has caused parking problem of serious proportions in city streets. Long hauls: It has been found that most commodity movements are cheaper by road for short hauls up to 300- 350 kms, but beyond this range, the cost advantage lies with the railways. Energy: Road transport consumes greater energy per passenger km and tone km than railways.
History of road development in India
Roads in India perform a variety of roles in achieving speedy economic development. Some of the important aspects are discussed below: Connection to villages India is a country having 590,000 villages, scattered into small habitations and often located in the extreme interior. Thus social uplift, health and education of the village population is aided by roads. Communications in hilly terrain: For the hill states located along the Himalayan range, communication facility is possible only by roads because of the steep terrain involved. Strategic importance: The defense of the northern, north-eastern and western borders of the country is dependent to a large extent on the road system. Helps agricultural development: Roads have fostered quicker agricultural development facilitating movement of modern inputs such as fertilizers and high yielding seeds. Helps dairy development: Since the cattle wealth of the nation is concentrated in innumerable villages and small habitations, the collection and processing of surplus milk only because of roads. Forestry development: The forest wealth of the country is being exploited mainly because of the roads which penetrate in to the thick jungles. Fisheries Development: The Development of the fisheries along the coast line has been rendered possible because of the construction of link roads leading to the coast. Tourism Development: Some of the ancient monuments, religious places, natural parks and sanctuaries are accessible only roads. Tourism, both domestic and international, has been greatly aided by roads serving such as places of interest. Employment: As already stated, roads and road transport provide employment to a large number of people in the country. Since road construction involves labour intensive techniques in India, the large unemployed labor force gets gainful employment. Famine and flood relief: Roads have helped operations pertaining to flood and famine relief. The affected people are frequently employed on road construction to build durable assets. Administrative convenience:
i) The importance of sub grade drainage and compaction were recognized and the sub grade was compacted and was prepared with a cross slope of 1 in 36. ii) Macadam was the first person to suggest the heavy foundation stones are not at all necessary to be placed at the bottom layer of construction. iii) Though the total thickness of construction was less than previous methods. This technique could serve the purpose in a better way. iv) The size of broken stones for the top layer was decided based on the stability under animal drawn vehicles.
Macadam’s method is the first method based on scientific thinking The construction steps are: i) Sub grade is compacted and prepared with a cross slope of 1 in 36 up to a desired width. ii) Broken stones of a strong variety, all passing through 5 cm size sieve were compacted to a uniform thickness of 10cm. iii) The second layer of strong broken stones of size 3 cm was compacted to thickness of 10 cm. iv) The top layer consisted of stones of size less than 2 cm compacted to a thickness of about 5 cm. The cross slope of pavement surface was also 1 in 36.
Classification of roads
Road classification The roads can be classified in many ways. The classification based on speed and accessibility is the most generic one. Note that as the accessibility of road increases, the speed reduces, the roads can be classified as follows in the order of increased accessibility and reduced speeds.
Freeways: Freeways are access-controlled divided highways. Most freeways are four lanes, two lanes each direction, but many freeways widen to incorporate more lanes as they enter urban areas. Access is controlled through the use of interchanges, and the type of interchange depends upon the kind of intersecting road way (rural roads, another freeway etc.) Expressways: They are superior type of highways and are designed for high
speeds (120 km/hr is common), high traffic volume and safety. They are generally provided with grade separations at intersections. Parking, loading and unloading of goods and pedestrian traffic is not allowed on expressways.
Highways: They represent the superior type of roads in the country. Highways are of two types - rural highways and urban highways. Rural highways are those passing through rural areas (villages) and urban highways are those passing through large cities and towns, ie. urban areas.
Arterials: It is a general term denoting a street primarily meant for through traffic usually on a continuous route. They are generally divided highways with fully or partially controlled access. Parking, loading and unloading activities are usually restricted and regulated. Pedestrians are allowed to cross only at intersections/designated pedestrian crossings.
Local streets: A local street is the one which is primarily intended for access to residence, business or abutting property. It does not normally carry large volume of traffic and also it allows unrestricted parking and pedestrian movements.
Collector streets: These are streets intended for collecting and distributing traffic to and from local streets and also for providing access to arterial streets. Normally full access is provided on these streets. There are few parking restrictions except during peak hours.
Figure 1: Speed vs accessibility
In addition to design speed and topography, there are various other factors that affect the geometric design and they are briefly discussed below:
Vehicle: :The dimensions, weight of the axle and operating characteristics of a vehicle influence the design aspects such as width of the pavement, radii of the curve, clearances, parking geometrics etc. A design vehicle which has standard weight, dimensions and operating characteristics are used to establish highway design controls to accommodate vehicles of a designated type. Human: The important human factors that influence geometric design are the , mental and psychological characteristics of the driver and pedestrians like the reaction time. Traffic: It will be uneconomical to design the road for peak traffic flow. Therefore a reasonable value of traffic volume is selected as the design hourly volume which is determined from the various traffic data collected. The geometric design is thus based on this design volume, capacity etc. Environmental: Factors like air pollution, noise pollution etc. should be given due consideration in the geometric design of roads. Economy: The design adopted should be economical as far as possible. It should match with the funds allotted for capital cost and maintenance cost. Others: Geometric design should be such that the aesthetics of the region is not affected.
Nagpur classification
In Nagpur road classification, all roads were classified into five categories as National highways, State highways, Major district roads, Other district roads and village roads. National highways They are main highways running through the length and breadth of India connecting major ports , foreign highways, capitals of large states and large industrial and tourist centers including roads required for strategic movements. It was recommended by Jayakar committee that the National highways should be the frame on which the entire road communication should be based. All the national highways are assigned the respective numbers. For e. the highway connecting Delhi-Ambala-Amritsar is denoted as NH-1 (Delhi- Amritsar), where as a bifurcation of this highway beyond Full under to Srinagar and Uri is denoted as NH-1_A. They are constructed and maintained by CPWD. The total lengths of National highway in the country is 58,112 Kms, and constitute about 2% of total road networks of India and carry 40% of total traffic. State highways They are the arterial roads of a state, connecting up with the national highways of adjacent states, district headquarters and important cities within the state They also serve as main arteries to and from district roads. Total length of all SH in the country is 1, 37,119 Kms. Major district roads Important roads with in a district serving areas of production and markets , connecting those with each other or with the major highways. India has a total of 4, 70,000 Kms of MDR.
Other district roads Roads serving rural areas of production and providing them with outlet to market centers or other important roads like MDR or SH. Village roads They are roads connecting villages or group of villages with each other or to the nearest road of a higher category like ODR or MDR. India has 26,50,000 kms of ODR+VR out of the total 33,15,231 kms of all type of roads. Roads classification criteria Apart from the classification given by the different plans, roads were also classified based on some other criteria. They are given in detail below. Based on usage This classification is based on whether the roads can be used during different seasons of the year. All-weather roads: Those roads which are negotiable during all weathers, except at major river crossings where interruption of traffic is permissible up to a certain extent are called all weather roads. Fair-weather roads: Roads which are negotiable only during fair weather are called fair weather roads. Based on carriage way This classification is based on the type of the carriage way or the road pavement. Paved roads with hards surface : If they are provided with a hard pavement course such roads are called paved roads.(eg: stones, Water bound macadam (WBM), Bituminous macadam (BM), concrete roads) Unpaved roads: Roads which are not provided with a hard course of atleast a WBM layer they is called unpaved roads. Thus earth and gravel roads come under this category.
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 operating costs. Once an alignment is fixed 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. Requirements The requirements of an ideal alignment are
The alignment between two terminal stations should be short and as far as possible be straight, but due to some practical considerations deviations may be needed. The alignment should be easy to construct and maintain. It should be easy for the operation of vehicles. So to the maximum extend easy gradients and curves should be provided. It should be safe both from the construction and operating point of view especially at slopes, embankments, and cutting. It should have safe geometric features. The alignment should be economical and it can be considered so only when the initial cost, maintenance cost, and operating cost are minimum.
well as the riding comfort and safety. Of these, pavement surface characteristics affect both of these. Camber, kerbs, and geometry of various cross-sectional elements are important aspects to be considered in this regard. They are explained briefly in this chapter. Camber
Camber or cant is the cross slope provided to raise middle of the road surface in the transverse direction to drain off rain water from road surface. The objectives of providing camber are:
Surface protection especially for gravel and bituminous roads Sub-grade protection by proper drainage Quick drying of pavement which in turn increases safety Too steep slope is undesirable for it will erode the surface. Camber is measured in 1 in n or n% (Eg. 1 in 50 or 2%) and the value depends on the type of pavement surface. The value suggested by IRC for various categories of pavement is given in Table 1. The common types of camber are parabolic, straight, or combination of them (Figure 1)
Figure 1: Different types of camber
Table 1: IRC Value s for ca mber
Surface Heavy Light
type rain rain
Concrete/Bituminous 2 % 1 %
Gravel/WBM 3 % 2 %
Earthen 4 % 3 %
Engineering surveys for alignment
The stages of the engineering surveys are: a) Map study. b) Reconnaissance. c) Preliminary surveys. d) Final location and detailed surveys.
Map study: - *) In the topographic map, to suggest the likely routes of roads. In India topographic maps are available from the survey of India with 15 or 30-meter contour intervals. *) The main feature like rivers, hills, and valleys etc. The probable alignment can be located on the map from the following details available on the map. Alignment avoiding valleys, ponds or lakes When the road has to cross a row of hills, possibility crossing through a mountain pass. Approximate location of bridge site for crossing rivers, avoiding bend of the river. When a road is to be connected between two stations one of the top and the other on the foot of the hill then alternate routes can be suggested keeping in view the permissible alignment. Suppose the scale of the contour map is known, and then the contour intervals it is possible to decide the length of road required between two consecutive contours keeping the gradient within allowable limits. In the fig. Let A and B be two stations to be connected by road. AB is the shortest route (Straight line) APQB is a steep route in which the gradient positively exceeds 1 in 20 as the distance between the contour intervals is only about 200 meter APLMNB is a route with an approximate slope of 1 in 20 whereas APEFGB is an alternate alignment with the same gradient. Thus the map study also is possible to drop a certain route in view of any unavoidable obstructions (or) undesirable ground enroute. Reconnaissance:- The second stage of surveys for highway location is the reconnaissance to examine the general character of the area for deciding the most feasible routes for detailed studies. Some of the details to be collected during reconnaissance are given below: Valleys, ponds, lakes, marshy, land, ridge, hills, permanent structures and other obstructions along the route, which are not available in the map. Approximate values of gradient, length of gradients and radius of curves of alternate alignments. Number and types of cross drainage structures maximum flood level and natural groundwater level along the probable routes. Soil type along the routes from field identification tests and observation of geological features. Sources of construction materials water and location of stone quarries. When the road passes through hilly or mountainous terrain, additional data regarding the geological formation types of rocks, dip of strata, seepage flow etc. Preliminary survey: -
Levels along his final centerline should be taken at all staked points. Levelling work is to great importance as the vertical alignment. A detailed soil survey is carried out to enable drawing of the soil profile. The data during the detailed survey should be elaborate and complete for preparing detailed plans, design and estimates of the project.
Soil suitability analysis
The methodology for locating appropriate sites for each land use activity is guided by the intent to minimize the possible adverse effects of development on the environment and on existing communities, and to emphasize the positive impacts of such development, by locating them in a most suitable location.
This is achieved by examining a number of individual criteria, assigning them relative levels of importance as a whole, and using a mathematical resultant model to identify the most suitable location.
By adopting this site suitability method, it is possible to systematically identify the criteria considered, clearly document the relative importance of one criterion over another, analyze the net outcome using a Geographic Information System, and then possibly revisit the mathematical relationships in this “decision model”.
By revising the relative importance to identified criteria based upon the particular land use under consideration, it is possible to generate “suitability maps” for each individual land use, and then generate a final composite land use that is based on a best possible collective suitability of multiple land uses.
To achieve this, all the criteria are assigned a “rank” denoting their relative levels of importance within the suitability study. These ranks are assigned as numeric values ranging from 1 to 10, with 1 reflecting a low level of importance and 10 reflecting a high level of importance. For example, within the criteria of road networks, national highways would have a different level of influence on the suitability for a particular land use, as compared with local roads. Further, the distance from each of these features would further modify the relative suitability of a land use based on the proximity to a particular type of road.
Criteria for Site Suitability Analysis: The decision criteria for site selection are examined for assigning relative ranks and individual feature weights based on the land use type for which suitability is being examined. For benefit of analysis, the criteria under consideration in this paper activity are organized as:
Critical Criteria: Criteria that will be very significant in the site selection of the identified land use and will act as key drivers in the selection of the geographic location. These criteria can be clustered into a single decision model and the outcome collectively reviewed. These criteria have a strong influence in the final suitability.
Additional Criteria: Criteria that will have to be examined one at a time to carefully assess its relationship with the proposed land use activity. These criteria have a positive influence in the final suitability.
Constrained Criteria: These criteria impose strong negative opportunities in the selection of areas for the identified land use. Consequently, they inform of us of where the particular land use under consideration should not be located. These criteria serve to limit or exclude areas from the final suitability.
GIS Site Suitability Analysis Model: We were developed a tourism site suitability analysis model in ArcGIS - 9.3, which is shown in Figure -
Cross sectional elements
Kerbs Kerbs indicate the boundary between the carriage way and the shoulder or islands or footpaths. Different types of kerbs are
Bus-bays
Bus bays are provided by recessing the kerbs for bus stops. They are provided so that they do not obstruct the movement of vehicles in the carriage way. They should be at least 75 meters away from the intersection so that the traffic near the intersections is not affected by the bus-bay.
Service roads Service roads or frontage roads give access to access controlled highways like freeways and expressways. They run parallel to the highway and will be usually isolated by a separator and access to the highway will be provided only at selected points. These roads are provided to avoid congestion in the expressways and also the speed of the traffic in those lanes is not reduced.
Drainage
The pavement surface should be absolutely impermeable to prevent seepage of water into the pavement layers. Further, both the geometry and texture of pavement surface should help in draining out the water from the surface in less time.
Footpath Footpaths are exclusive right of way to pedestrians, especially in urban areas. They are provided for the safety of the pedestrians when both the pedestrian traffic and vehicular traffic is high. Minimum width is 1 meter and may be increased based on the traffic. The footpath should be either as smooth as the pavement or more smoother than that to induce the pedestrian to use the footpath.
Right of way
Right of way (ROW) or land width is the width of land acquired for the road, along its alignment. It should be adequate to accommodate all the cross-sectional elements of the highway and may reasonably provide for future development. To prevent ribbon development along highways, control lines and building lines may be provided. Control line is a line which represents the nearest limits of future uncontrolled building activity in relation to a road. Building line represents a line on either side of the road, between which and the road no building activity is permitted at all. The right of way width is governed by:
Width of formation: It depends on the category of the highway and width of roadway and road margins. Height of embankment or depth of cutting: It is governed by the topography and the vertical alignment. Side slopes of embankment or cutting: It depends on the height of the slope, soil type etc. Drainage system and their size which depends on rainfall, topography etc. Sight distance considerations: On curves etc. there is restriction to the visibility on the inner side of the curve due to the presence of some obstructions like building structures etc. Reserve land for future widening: Some land has to be acquired in advance
Table 2: Design speed in as per IRC (ruling and minimum) Type Plain Rolling Hilly Steep NS&SH 100-80 80-65 50-40 40-
MDR 80-65 65-50 40-30 30- ODR 65-50 50-40 30-25 25-
VR 50-40 40-35 25-20 25-
anticipating future developments like widening of the road.
Table 1: No
right of way for open areas Road Roadway width in m classification Plain and Mountainous and
rolling terrain steep terrain Open areas NH/SH 45 24
MDR 25 18 ODR 15 15 VR 12 9 Built-up areas
NH/SH 3020 MDR 20 15 ODR 15 12
VR 10 9
CE 3405
Course: Civil Engineering (CE)
University: Anna University
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