5th sem ppt [ch2] (1)transportation engg. .pptx

Transportation engineering

1. Highway alignment/Location and Survey 1

2. 2 Contents Requirements of an ideal alignment Factors considered for alignment of a new highway Engineering surveys- Map study, Reconnaissance, Preliminary surveys, Final location and detailed survey Preparation of survey report

3. 3 Highway Alignment The position or the layout of the centre line of the highway on the ground is called the alignment. It includes both horizontal and vertical alignment It includes the straight path, the deviations and horizontal curves Improper alignment would result Construction cost Maintenance cost Vehicle operation cost Accident rate

4. 4 Requirements of ideal Highway Alignment Short Easy Safe Economical Short: The highway alignment between two terminal stations should be short and as far as possible be straight, but due to some practical consideration deviation may be needed. Easy: The alignment should be easy to construct and maintain. It should be easy for operation of vehicles. So to the maximum extend easy gradient and curves should be provided. Safe: It should be safe both from the construction and operating point of view especially at slopes, embankment and cutting. It should have safe geometric features. Economical: The alignment can be considered economical only if the initial cost, maintenance cost and vehicle operating cost are minimum.

5. 5 Factors controlling alignment The various factors which control the highway alignment in general are: Obligatory points Traffic Geometric design Economics Other consideration

6. 6 Factors controlling alignment The various factors which control the highway alignment in general are;: Obligatory points

7. 7 Factors controlling alignment The various factors which control the highway alignment in general are;: Obligatory points Points through the alignment should pass Chosen bridge site Intermidiate town to be accessed between the termini A mountain pass etc Points through the alignment should not pass Areas requiring costly structure Highly developed expensive areas Cultural or religious places Hilly terrain where there is a possibility of land slides etc

8. 8 Factors controlling alignment The various factors which control the highway alignment in general are;: Geometric feautres Facilitate easy grade and curvature Enable ruling gradient in most sections Avoid sudden changes in sight distance especially near crossing Avoid sharp horizontal curves Avoid road intersection near bend or at the top or bottom of a hill. Traffic The road alignment should be decided based on requirements of road traffic The alignment should be according to the traffic amount and traffic pattern No of lanes= traffic volume / traffic capacity

9. 9 Factors controlling alignment The various factors which control the highway alignment in general are; economics Initial cost of construction of the road Regular and periodic maintenance cost of the road Vehicle operating cost in future years Other consideration Drainage consideration: Hydrological factors: rain fall/ water table/high flood level Political consideration: if a foreign territory comes across a straight alignment will necessitate deviation of horizontal alignment around the foreign land Monotony:   For a flat terrain it is possible to provide a straight alignment, but it will be monotonous for driving. Hence a slight bend may be provided after a few kilometers of straight road to keep the driver alert by breaking the monotony.

10. 10 Special consideration for hilly areas Some of the special considerations for highway alignment through a hilly terrain is discussed below. Stability of hill side 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 filling for road constructions give way to steepening of slopes which in turn will affect 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 different from those in flat 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. Ineffective rise and fall : Efforts should be made to keep the ineffective rise and excessive fall minimum.

11. 11 Special consideration for hilly areas

12. 12 Engineering Surveys for Highway locations Before a highway alignment is finalized in highway project, the engineering survey are to be carried out. The various stages of engineering surveys are Map study (Provisional alignment Identification) Reconnaissance survey Preliminary survey Final location and detailed surveys MAP STUDY From the map alternative routes can be suggested in the office, if the topographic map of that area is available. The probable alignment can be located on the map from the fallowing details available on the map. Avoiding valleys, ponds or lake Avoiding bend of river If road has to cross a row of hills, possibility of crossing through mountain pass. • Map study gives a rough guidance of the routes to be further surveyed in the field

13. 13 RECONNAISSANCE SURVEY To confirm features indicated on map. To examine the general character of the area in field for deciding the most feasible routes for detailed studies. A survey party may inspect along the proposed alternative routes of the map in the field with very simple instrument like abney level, tangent clinometer, barometer etc.... to collect additional details. Details to be collected from alternative routes during this survey are, Valleys, ponds, lakes, marshy land, hill, permanent structure and other obstruction. Value of gradient, length of gradient and radius of curve. Number and type of cross drainage structures. High Flood Level (HFL) Soil Characteristics. Geological features. source of construction materials- stone quarries, water sources. • Prepare a report on merits and demerits of different alternative routs. • As a result a few alternate alignments may be chosen for further study based on practical considerations observed at the site. Engineering Surveys for Highway locations

14. 14 Preliminary survey Objective of preliminary survey are: To survey the various alternative alignments proposed after the reconnaissance and to collect all the necessary physical information and detail of topography, drainage and soil. To compare the different proposals in view of the requirements of the good alignment. To estimate quantity of earthwork materials and other construction aspect and to workout the cost of the alternate proposals. Methods of preliminary survey: Conventional approach- survey party carries out surveys using the required field equipment, taking measurement, collecting topographical and other data and carrying out soil survey. Procedure of the conventional methods of preliminary survey: Primary traverse Topographical pressure Levelling work Drainage studies and hydrological studies Soil survey Material survey Traffic studies Engineering Surveys for Highway locations

15. 15 Final location and detailed survey • The alignment finalized at the design office after the preliminary survey is to be first located on the field by establishing the centre line. Location survey: Transferring the alignment on to ground. This is done by transit theodolite. Major and minor control points are established on the ground and centre pegs are driven, checking the geometric design requirements. Centre line stacks are driven at suitable intervals, say 50m interval in plane and rolling terrains and 20m in hilly terrain. Temporary bench marks are fixed at intervals of about 250m and at all drainage and under pass structure. Earthwork calculations and drainage details are to be workout from the level books. Cross sectional levels are taken at intervals of 50-100m in Plane terrain, 50-75m in Rolling terrain, 50m in built-up area, 20m in Hill terrain. Detail soil survey is to be carried out. CBR value of the soils along the alignment may be determined for design of pavement. The data during detailed survey should be elaborate and complete for preparing detailed plans, design and estimates of project Engineering Surveys for Highway locations

16. 16 Final location and detailed survey • The alignment finalized at the design office after the preliminary survey is to be first located on the field by establishing the centre line. Location survey: Transferring the alignment on to ground. This is done by transit theodolite. Major and minor control points are established on the ground and centre pegs are driven, checking the geometric design requirements. Centre line stacks are driven at suitable intervals, say 50m interval in plane and rolling terrains and 20m in hilly terrain. Temporary bench marks are fixed at intervals of about 250m and at all drainage and under pass structure. Earthwork calculations and drainage details are to be workout from the level books. Cross sectional levels are taken at intervals of 50-100m in Plane terrain, 50-75m in Rolling terrain, 50m in built-up area, 20m in Hill terrain. Detail soil survey is to be carried out. CBR value of the soils along the alignment may be determined for design of pavement. The data during detailed survey should be elaborate and complete for preparing detailed plans, design and estimates of project Engineering Surveys for Highway locations

17. 17 Engineering Surveys for Highway locations Drawing and Report  Key map  Index map  Preliminary survey plans  Detailed plan and longitudinal section  Detailed cross section  Land acquisition plans  Drawings of cross drainage and other retaining structures  Drawings of road intersections  Land plans showing quarries etc