Road Construction & Maintenance Plus Road Survey & Design Training

1. Road Construction & Maintenance Plus Road Survey & Design Training Karma Tenzin Principal Engineer Design Division Department of Roads MoWHS, Thimphu

2. Classification of Road • National Highway • Asian Highway – Phuentshogling-Thimphu (AH48) • Primary National Highway (PNH) • Secondary National Highway (SNH) • Dzongkhag Roads • Farm Roads • Thromde Roads • Access Road

3. Classification of Road 1. National Highway • Asian Highway – Phuentshogling-Thimphu (AH48) The Phuentshogling-Thimphu Highway is designated by the Royal Government as the Asian Highway route No.48 within Bhutan. The design standards for the Asian Highway specified in the Intergovernmental Agreement on the Asian Highway Network are equivalent to the design standards of Primary National Highway (PNH) • Primary National Highway (PNH) PNHs are roads of strategic importance carrying high traffic volume. It should be the shortest possible route between two designated points and provide width for two lanes of traffic.

4. Classification of Road 1. National Highway • Secondary National Highway (SNH) SNHs are those roads that: • connect a Dzongkhag center to a road of equal or higher classification; • provide connectivity between two Dzongkhag centers. It should be the shortest route between two designated points and provide width for two lane traffic. The formation width of SNH will 8.5 m. The existing District Roads will be re-designated as SNHs DoR will be solely responsible for planning and implementation of AH, PNH and SNH. DoR shall also be the authority for development of the national road network with full authority to set technical standards for all classes of roads and bridges, including re-classification of roads, as and when it is necessary to match the socio-economic development of the country. All AHs, PNHs and SNHs shall have necessary safety measures including road signs and guardrails as per the DoR standards.

5. Classification of Road 2. Dzongkhag Roads The Dzongkhag Road will be one that: • connects a Dzongkhag Centre and an Integrated Gewog Centre/Gewog Administration Office; • connects a Dzongkhag Centre and a Dungkhag Centre not otherwise designated as AH, PNH, SNH; • connects a Dungkhag Centre with another Dungkhag Centre within the Dzongkhag not otherwise designated as AH, PNH, SNH; • connects a Dungkhag Centre with a Gewog Centre/Gewog Administration Office; • connects an Integrated Gewog Centre/Centres to an existing road of equal or higher classification. Planning, prioritization and budgeting of the Dzongkhag Roads will be done by respective Dzongkhag Tshogdu

6. Classification of Road 3. Farm Roads • Farm Roads are roads that link farmland areas/villages to an existing road of equal or higher classification to enable the transportation of inputs to the farm and agriculture produce to the market. Like other higher classes of roads, construction of Farm Roads should be inclusive of cost of appropriate bridges. • Prioritization/selection of Farm Roads will be done by the Gewog Tshogde based on the criteria set by the Department of Agriculture (DoA). The design standards for Farm Roads will be set by DoR in consultation with MoA. See Annex-1 for proposed design standards for Farm Roads. Due to the limited capacity of the Gewog Administration, the Dzongkhag Administration will carry out pre-investment studies, geotechnical investigations, survey, design and procurement for Farm Roads with technical backstopping from DoA. Planning, prioritization, budgeting and implementation of Farm Roads will be done by the respective Gewogs with technical backstopping from Dzongkhag Administration/DoA.

7. Classification of Road 4. Access Road • Access Roads are roads listed below Forest Roads, Health Roads, Education Roads, Telecommunications Roads, Power Roads, Private Road, Project Road & Public Road • Design standards for Access Roads Technical backstopping such as provision of design standards and specifications for Access Roads will be provided by DoR in consultation with the concerned agencies. • Design and take off point for access roads shall be approved by the Department of Roads. • Access Roads should be constructed to a minimum of Farm Road standard. Responsibilities for Access Roads Pre-investment studies, geological investigation, survey, design, procurement, construction, and maintenance of Access Roads will be done by the agencies/communities/individuals concerned.

8. Classification of Road 5. Thromde Road • Thromde road means all types of roads located within the municipal boundary not otherwise designated as AH, PNH and SNH. Roads located within the municipal boundaries shall be governed by the rules and regulations of the concerned municipality. Responsibilities for Access Roads • Thromde Roads will be executed either by the Thromde or Dzongkhag Administration wherever relevant including maintenance. Design standards for Thromde Roads will be set by DES in consultation with DoR.

9. Road Features • Asian Highway (AH) & Primary National Highway (PNH)

10. Road Features 2. Secondary National Highway (SNH)

11. Road Features 3. Dzongkhag Roads (DR)

12. Road Features 4. Farm Roads (FR)

13. Road Features 5. Access Roads (AR) (Minimum Requirement)

14. Road Features 6. Thromde Roads

15. General Stages of Road Planning Survey & Design is required mainly to address the following points; not necessarily limited to: • Cost Optimization • Fairly accurate cost estimation • To decrease time of construction so that benefit to the road user is achieved earlier than expected. • Attach engineering attributes and geometrics such as stability, gradient, water management, curvature, super elevation, width, structures etc. • Comfort and aesthetic realization • Employment generation and environment protection etc

16. General Stages of Road Planning Some of the governing principles that are required to be considered during desk top study are: • The alignment should take into account all the control points and should be shortest and economical. • Marshy areas, steep terrain, landslide, unstable hill features etc should be avoided. Stereographic use of aerial photographs are recommended. • Need of connecting important villages and towns • Bridge site locations

17. General Stages of Road Planning Map study is carried out using available topographical map and now a days using google earth from internet. 2 or 3 alternative alignments are marked on the topo map between two known points i.e takeoff and terminal points. The gradient of the alignment in the map is maintained by the distance of crossing point between one contour to another contour. It is determined by the simple equation; X =

18. General Stages of Road Planning Example Contour interval = 40m Gradient required = 5% (0.05) Scale of the map = 1/50000 Distance X = (40/0.050)*1/50000 = 0.016m = 1.6cm Therefore, the second contour will be crossed at the distance of 1.6cm from first contour which will give 5% slope / gradient

19. General Stages of Road Planning Example

20. General Stages of Road Planning Example

21. General Stages of Road Planning In Feasibility Study the following must be included: • Team from the head office in Thimphu • Team Leader – Design Engineer • Surveyor – Who will be involved in doing the survey • Geo-Tech Engineer • Bridge Engineer • Engineer from the concerned Dzongkhag Administrative • Environmental Officer from the concerned Dzongkhag Administrative • Forest Officer from the concerned Dzongkhag Administrative/Park • Engineer from the concerned Regional Office, DoR • Representative from the concerned Gewog.

22. General Stages of Road Planning Feasibility Study Report • In conjunction with ground reconnaissance survey, other assessment such as social assessment, environmental assessment, geotechnical assessment etc. are also carried out. Based on the information collected during the ground reconnaissance survey, a report should be prepared. • The report should include all relevant information including a map/plan showing alternative alignments with their rough cost estimates. The report should discuss advantageous and disadvantageous of different alternatives to help the selection of most suitable alignment. The feasibility team should put up their recommendations based on their judgment and knowledge.

23. General Stages of Road Planning Alignment fixing survey (Ghat Tracing survey) • Based on the feasibility study report, the authority will approve one suitable alignment. This alignment which is approved for adoption will have to be transferred to the ground. This is done by fixing the wooden pegs at an interval of 20m with the help of clinometers or abney level and measuring tape. It is suppose to be an approximate center line having a gradient that is given in the feasibility report. • Each alignment peg should contain the information such as chainage and gradient. This phase of survey, though simple is considered to be very important. It should be usually carried out by experienced survey engineer or civil engineer. Once this phase of survey is completed, change of alignment in future is very difficult. • During this phase of survey, the data recorded are: Exact length of road, number of cross drainages required, number of hairpin bends introduced, gradient adopted, soil classification, bridge points and its span etc. A brief report shall be submitted where concern authority will instruct to carry on with further survey works which is called detail survey.

24. General Stages of Road Planning Detail Survey using Total Station • Detail survey which is also known as topographic survey will commence immediately using total station instrument. Collection of topographic data is carried out along the proposed road corridor in combination with traverse survey. In order to attain the line of sight any obstructions such as bushes and small trees should be cleared. • The corridor of about 50m ie 30m towards hill side and 20m towards valley side of centerline should be made visible to the survey instrument. The data that are collected during detail survey phase are : All topographic features such as gullies, ridge, natural surface, change of grade, any man made features, cliff, boundary pillars, fence, cultivated land, Ghattracing pegs, prominent trees etc. • For future references at least 2 nos. of traverse stations per km of alignment shall be made permanent. This type of survey is very time consuming but unavoidable and without which geometric design is not possible. This type of survey demand use of other associated equipment such as computer, generators if electricity is not available. The data that is collected during such detail survey is downloaded to the computer using appropriate software and then handed over to design engineers.

25. General Stages of Road Planning Detail Road Design • Geometric design is carried out based on the detail survey data collected earlier. The parameters that are considered in geometric design are: Classification of Road, Design Speed, Horizontal Alignment, Formation & Cross Section, Sight Distance, Super elevation, Vertical Alignment, Gradient etc. Geometric design is carried out using computer software such as MXROAD, Geocomp etc. The designer is required to visit the site for verification of his/her preliminary design before the finalizing the design. • Necessary drawings and set out data are produced. Drawings include Plan, longitudinal section, cross section to the required scale. Cross sections are generally taken at 20m interval for straight sections and more close for curve sections. Set out data such as station set out, centerline set out, batter set out, earthwork quantities etc are produced. • Environment friendly road construction technique to be adopted in the geometric design through optimization of cut and fill involved in the earthworks. Environment friendly road design aptly demonstrates that a slight shift of the centerline to the valley side can result in substantial reduction of earthworks and height of hill side cut

26. Road Design

27. Road Design

28. Road Design

29. Drawings (Plan & L-Section)

30. Drawing (Cross Section)

31. General Stages of Road Planning Setting out the alignment (Batter Pegging) • The purpose of set out survey is to lay out the final centerline of the road based on the centerline fixed in the design office. Two main operations involved in this survey is fixing centerline and batter pegs to guide the construction team. Both the pegs are fixed at 20m interval with information such as chainage, gradient, cut and fill etc. are written on it. All such pegs should be protected. See drawing in next slide.

32. Pavement Design • Design of pavement for roads, whether in plains or hills follow the same basic principles like: • Soil properties • Traffic parameters • And also climatic conditions

33. Type of Pavement • Rigid Pavement • Flexible Pavement • Composite Pavement

34. Rigid Pavement

35. Flexible Pavement

36. Composite Pavement

37. Typical Pavement Layers

38. Advantages of Flexible Pavement • Adjusts to limited differential settlement • Easily, quickly constructed and repaired • Additional thickness can be added • Quieter smoother (Generally)

39. Disadvantages of Flexible Pavement • Properties may change over time as pavement ages • Generally shorter service life before first rehabilitation • May experiences moisture problems

40. Pavement Design (Flexible) • Design procedure Based on the performance of existing designs and using analytical approach, simple design charts and a catalogue of pavement designs are added in the IRC code. The pavement designs are given for subgrade CBR values ranging from 2% to 10% and design traffic ranging from 1 msa to 150 msa for an average annual pavement temperature of 35 C. Using the following simple input parameters, appropriate designs could be chosen for the given traffic and soil strength: • Design traffic in terms of cumulative number of standard axles; and • CBR value of subgrade.

41. Pavement Design (Flexible) • Design traffic The method considers traffic in terms of the cumulative number of standard axles (8 Tons) to be carried by the pavement during the design life. This requires the following information: • Initial traffic in terms of CVPD (Commercial Vehicle per day) • Traffic growth rate during the design life • Design life in number of years • Vehicle damage factor (VDF) • Distribution of commercial traffic over the carriage way.

42. Pavement Design (Flexible) • Initial traffic Initial traffic is determined in terms of commercial vehicles per day (CVPD). For the structural design of the pavement only commercial vehicles are considered assuming laden weight of three tonnes or more and their axle loading will be considered. Estimate of the initial daily average traffic flow for any road should normally be based on 7-day 24-hour classified traffic counts (ADT). In case of new roads, traffic estimates can be made on the basis of potential land use and traffic on existing routes in the area. • Traffic growth rate Traffic growth rates can be estimated • by studying the past trends of traffic growth, and • by establishing econometric models. If adequate data is not available, it is recommended that an average annual growth rate of 7.5 percent may be adopted. • Design life For the purpose of the pavement design, the design life is defined in terms of the cumulative number of standard axles that can be carried before strengthening of the pavement is necessary. It is recommended that pavements for arterial roads like PNH, SNH should be designed for a life of 15 years and other categories of roads for 10 years.

43. Pavement Design (Flexible) • Vehicle Damage Factor Introduction to Transportation Engineering 28.3 Tom V. Mathew and K V Krishna Rao CHAPTER 28. IRC METHOD OF DESIGN OF FLEXIBLE PAVEMENTS NPTEL May 3, 2007 The vehicle damage factor (VDF) is a multiplier for converting the number of commercial vehicles of different axle loads and axle configurations to the number of standard axle-load repetitions. It is defined as equivalent number of standard axles per commercial vehicle. The VDF varies with the axle configuration, axle loading, terrain, type of road, and from region to region. The axle load equivalency factors are used to convert different axle load repetitions into equivalent standard axle load repetitions. For these equivalency factors refer IRC:37 2001. The exact VDF values are arrived after extensive field surveys. • Vehicle distribution A realistic assessment of distribution of commercial traffic by direction and by lane is necessary as it directly affects the total equivalent standard axle load application used in the design. Until reliable data is available, the following distribution may be assumed. • Single lane roads: Traffic tends to be more channelized on single roads than two lane roads and to allow for this concentration of wheel load repetitions, the design should be based on total number of commercial vehicles in both directions. • Two-lane single carriageway roads: The design should be based on 75 % of the commercial vehicles in both directions.

44. Pavement Thickness

45. Pavement Design (Flexible) • Pavement composition • Sub-base • Sub-base materials comprise natural sand, gravel, laterite, brick metal, crushed stone or combinations thereof meeting the prescribed grading and physical requirements. The sub-base material should have a minimum CBR of 20 % and 30 % for traffic upto 2 msa and traffic exceeding 2 msa respectively. Sub-base usually consist of granular or WBM and the thickness should not be less than 150 mm for design traffic less than 10 msa and 200 mm for design traffic of 1:0 msa and above. • Base • The recommended designs are for unbounded granular bases which comprise conventional water bound macadam Introduction to Transportation Engineering 28.4 Tom V. Mathew and K V Krishna Rao CHAPTER 28. IRC METHOD OF DESIGN OF FLEXIBLE PAVEMENTS NPTEL May 3, 2007 (WBM) or wet mix macadam (WMM) or equivalent confirming to MOST specifications. The materials should be of good quality with minimum thickness of 225 mm for traffic up to 2 msa an 150 mm for traffic exceeding 2 msa. • Bituminous surfacing • The surfacing consists of a wearing course or a binder course plus wearing course. The most commonly used wearing courses are surface dressing, open graded premix carpet, mix seal surfacing, semi-dense bituminous concrete and bituminous concrete. For binder course, MOST specifies, it is desirable to use bituminous macadam (BM) for traffic upto o 5 msa and dense bituminous macadam (DBM) for traffic more than 5 msa.

46. Pavement Design (Flexible) • Numerical example • Design the pavement for construction of a new bypass with the following data: • Two lane carriage way • Initial traffic in the year of completion of construction = 400 CVPD (sum of both directions) • Traffic growth rate = 7.5 % • Design life = 15 years • Vehicle damage factor based on axle load survey = 2.5 standard axle per commercial vehicle • Design CBR of subgrade soil = 4%. Solution • Distribution factor = 0.75 = 7200000 = 7.2 msa • Total pavement thickness for CBR 4% and traffic 7.2 msa from our Chart = 525 mm + 200 mm SR • Pavement composition can be obtained by interpolation from Pavement Thickness chart. (a) Bituminous surfacing = 40 mm AC + 60 mm DBM (b) Base course = 200 mm WWM (c) sub-base = 225 mm GSB (d) Soil replacement of 200 mm

50. Road Maintenance WHY IS MAINTENANCE IMPORTANT? • Roads are among the most important public assets in many countries. Road improvements bring immediate and sometimes dramatic benefits to road users through improved access to hospitals, schools, and markets; improved comfort, speed, and safety; and lower vehicle operating costs. For these benefits to be sustained, road improvements must be followed by a well-planned program of maintenance. Without regular maintenance, roads can rapidly fall into disrepair, preventing realization of the longer term impacts of road improvements on development, such as increased agricultural production and growth in school enrollment. • Postponing road maintenance results in high direct and indirect costs. If road defects are repaired promptly, the cost is usually modest. If defects are neglected, an entire road section may fail completely, requiring full reconstruction at three times or more the cost, on average, of maintenance costs. • Delayed maintenance has indirect costs as well. Neglected roads steadily become more difficult to use, resulting in increased vehicle operating costs (more frequent repairs, more fuel use) and a reluctance by transport operators to use the roads. This imposes a heavy burden on the economy: as passenger and freight services are curtailed, there is a consequent loss of economic and social development opportunities.