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Group 5 1

  2. 2. PROPER DESIGN OF HIGHWAY DRAINAGE SYSTEM INTRODUCTION : HIGHWAY is a term commonly used to refer to a major roads intended for travel by the public between important destinations, such as cities.
  3. 3. <ul><li>In urban areas and highway, a drainage system is a facility to dispose of Two types of water: </li></ul><ul><li>Surface water – rain and snow </li></ul><ul><li>Ground water – can be a problem when a water table is near surface </li></ul>DRAINAGE SYSTEM In geomorphology , a drainage system is the pattern formed by the streams, rivers, and lakes in a particular watershed. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. In agriculture , a drainage system is an intervention to control water logging aiming at soil improvement for agricultural production.
  4. 4. <ul><li>This presentation will discuss the surface water </li></ul>
  5. 5. <ul><li>The Highway Authority has a duty under highways to maintain a safe road network and this duty includes the need to drain the highway to avoid flooding. </li></ul><ul><li>Highway drainage systems : Is the system that installed to capture surface water and Ground water The advantage beyond that is to protect against flooding and protect the fabric of the road. </li></ul><ul><li>The highway drainage system was developed in the late 1980s and into the 90s through a public process. </li></ul>
  6. 6. <ul><li>Appropriate drainage is an important feature of good highway design in terms of ensuring required level of service and value for money is achieved. </li></ul><ul><li>Highway drainage has two major objectives: safety of the road user and long life of the pavement. Speedy removal of surface water will help to ensure safe and comfortable conditions for the road user. </li></ul>
  7. 7. <ul><li>According to the Malaysian standard the Surface drains components include: </li></ul><ul><li>Interceptor drains, </li></ul><ul><li>Roadside drains, </li></ul><ul><li>Embankment toe drains, </li></ul><ul><li>Shoulder drains, </li></ul><ul><li>Bench drains, </li></ul>
  8. 8. BASICS OF DRAINAGE SYSTEM <ul><li>Transverse slopes </li></ul><ul><ul><li>Removes water from pavement surface </li></ul></ul><ul><ul><li>Facilitated by cross-section elements (cross-slope, shoulder slope) </li></ul></ul><ul><li>Longitudinal slopes </li></ul><ul><ul><li>Minimum gradient of alignment to maintain adequate slope in longitudinal channels </li></ul></ul><ul><li>Longitudinal channels </li></ul><ul><ul><li>Ditches along side of road to collect surface water after run-off </li></ul></ul>
  10. 10. BASICS OF DRAINAGE SYSTEM <ul><li>Transverse slopes </li></ul><ul><ul><li>Removes water from pavement surface </li></ul></ul><ul><ul><li>Facilitated by cross-section elements (cross-slope, shoulder slope) </li></ul></ul><ul><li>Longitudinal slopes </li></ul><ul><ul><li>Minimum gradient of alignment to maintain adequate slope in longitudinal channels </li></ul></ul><ul><li>Longitudinal channels </li></ul><ul><ul><li>Ditches along side of road to collect surface water after run-off </li></ul></ul>
  12. 12. BASICS OF DRAINAGE SYSTEM <ul><li>Transverse slopes </li></ul><ul><ul><li>Removes water from pavement surface </li></ul></ul><ul><ul><li>Facilitated by cross-section elements (cross-slope, shoulder slope) </li></ul></ul><ul><li>Longitudinal slopes </li></ul><ul><ul><li>Minimum gradient of alignment to maintain adequate slope in longitudinal channels </li></ul></ul><ul><li>Longitudinal channels </li></ul><ul><ul><li>Ditches along side of road to collect surface water after run-off </li></ul></ul>
  14. 14. <ul><li>Based on these fundamental principles, drainage methods are divided into two categories:- </li></ul><ul><li>First one Separate systems , where the surface and sub-surface are collected and transported in separate pipes. </li></ul><ul><li>and second is Combined systems , where the surface and sub-surface water are collected and transported in the same pipe, </li></ul><ul><li>The most common and active systems are the combined systems, thus this presentation discussed these systems. </li></ul>
  15. 15. Highway drainage combined systems 1. Kerb and Gullies 2. Surface Water Channel 3. Combined Filter Drain(FrenchDrain) 4. Over-the-edge Drainage 5. Drainage Channel Blocks (and Grips) 6. Combined Kerb and Drainage Units 7. Linear Drainage Channels 8. Fin and Narrow Filter Drain (Sub- 9. Edge Drainage for Porous Asphalt surface drainage)
  16. 16. 1.KERB AND GULLIES <ul><li>Road surface drainage by kerbs and gullies is commonly use, particularly in urban and embankment conditions. The function of kerbs is not purely to act as a barrier to retain storm runoff from the road surface. </li></ul>
  17. 17. ADVANTAGES OF THIS SYSTEM : <ul><li>They also provide some structural support during pavement construction and protect footpaths and verges from vehicular overrun. </li></ul><ul><li>They are a safety hazard for high speed vehicles and are generally not suitable for use on trunk roads where speed is unlimited. </li></ul><ul><li>One advantage of kerb and gullies is that its ability to carry road surface runoff to outfall is not dependent upon the longitudinal gradient of the road itself. </li></ul><ul><li>Road gullies will generally discharge to longitudinal carrier pipes, which can be laid to fall independent of the road gradient to meet the required flow capacity. </li></ul>
  18. 18. 2.SURFACE WATER CHANNEL <ul><li>Surface water channels are normally of triangular/trapezoidal concrete section; they provide an economic alternative to edge channels and are the Agency’s preferred edge-drain solution for rural locations (trunk roads and motorways) Long length of channels, devoid of interruptions, can be constructed quickly and fairly inexpensively using slip-form techniques. </li></ul>
  19. 19. <ul><li>They are capable of carrying large volumes of water over long distances and channel outlets can be located at appreciable spacing and to match with watercourses thus avoiding the need for a separate carrier pipe. They are easy to maintain and any long-term problems developing can be detected and monitored by simple visual inspection from the surface. </li></ul>
  20. 20. 3.COMBINED FILTER DRAIN (FRENCH DRAIN) <ul><li>The system commonly described as ‘French drain’ collects road run-offs through the top of the trench and sub-surface run-offs through the trench walls. This system is using an aggregate-filled trench with a perforated or porous pipe at the bottom. </li></ul>
  21. 21. <ul><li>This drainage have been the traditional solution adopted for rural roads for many years and due to the very open texture of the filter material they provide for the rapid removal of rainwater from the road and verge surfaces. </li></ul><ul><li>They have many Problems in this include: (a) stone scatter by vehicle over-runs, (b) surface failures of embankments caused by the extension of sub-base as a drainage layer, and (c) possible softening of foundation due to the drain becoming waterlogged at road foundation level causing long term deterioration. </li></ul>
  22. 22. 4.OVER-THE-EDGE DRAINAGE <ul><li>This method is applicable to embankment conditions where the carriageway surface water is allowed to drain over the edge and down the embankment slope directly into open ditches as appropriate. </li></ul>
  23. 23. <ul><li>Its use is therefore only advocated in situations where the embankments are of low heights, shallow slopes and constructed of good quality granule material. </li></ul><ul><li>Disadvantage of Over-the-edge drainage can cause soil erosion, topsoil slippage, softening of the side slopes and embankment instability. </li></ul>
  24. 24. 5.DRAINAGE CHANNEL BLOCKS (AND GRIPS) <ul><li>These are small channels across the borders, constructed of precast channel blocks in order to allow drainage collected along a kerb channel to drain across the edge into edge side ditches constructed of larger precast channels. </li></ul>
  25. 25. <ul><li>They are not permitted as edge drains nearby hard shoulders, hard strips or carriageways. There is potential maintenance difficulties associated with the use of the system. Settlement of adjacent unpaved surfaces would reduce their effectiveness. </li></ul>
  26. 26. 6.COMBINED KERB AND DRAINAGE UNITS <ul><li>These are special kerb units that allow lateral entry of surface water from the (kerb side) channel either continuously or intermittently into a continuous internal channel bore that acts as a carrier drain. </li></ul>
  27. 27. <ul><li>They are usually constructed of precast concrete units either in one piece or comprised of a top and bottom section which when laid will form a continuous closed internal channel. The part of a unit projecting above road level acts as a kerb and contains a pre-formed hole, which admits water into the internal cavity. Units are typically 400-500mm long and the pre-formed holes thus occur at that spacing. </li></ul>
  28. 28. 7.LINEAR DRAINAGE CHANNELS <ul><li>These channels comprise of a longitudinal sub-surface closed profile hydraulic conduit, constructed of either precast units or in-situ concrete, into which surface water is drained via longitudinal or angled slots situated above the conduit. </li></ul>
  29. 29. <ul><li>The top of the system will be flush with the adjacent surface from which surface water is drained. Precast units may be of concrete, glass reinforced concrete, polymer resins or similar materials. In-situ construction is usually of concrete using slip-form techniques. Although precast units in small sections of this type have been commercially available for many years, the construction of larger sections by slip-forming techniques is an innovative breakthrough in highway application. </li></ul>
  30. 30. 8.FIN AND NARROW FILTER DRAIN (SUB-SURFACE DRAINAGE) <ul><li>These are intended to be the normal methods of sub-surface drainage on motorways and trunk roads usually installed longitudinally along the lower edges of road pavements. </li></ul>
  31. 31. <ul><li>They act as low capacity filter drains to remove and keep out water from the road structure in order to ensure that the road structure does not fail prematurely by softening of the sub-grade. They also prevent ingress of water from verge areas adjacent to the pavement. </li></ul><ul><li>The system although very efficient and simple in its detail. Some major difficulties were reported, particularly with narrow trenching and back filling when it was first introduced some ten years ago. </li></ul>
  32. 32. 9. EDGE DRAINAGE FOR POROUS ASPHALT <ul><li>The use of porous asphalt on roads is primarily for the purpose of noise reduction but it has the added advantage of spray reduction, which enhances road safety. The open texture of porous asphalt with interconnecting voids which act as a drainage layer underneath the road surface makes it necessary to have a special edge detail for positive drainage. </li></ul>
  33. 34. INADEQUATE DRAINAGE <ul><li>Damage to highway structures </li></ul><ul><li>Loss of capacity </li></ul><ul><li>Visibility problems with spray and loss of retroreflectivity </li></ul><ul><li>Safety problems, reduced friction and hydroplaning </li></ul>Garber & Hoel, 2002
  34. 35. IMPROVEMENTS TO DRAINAGE SYSTEMS <ul><li>Improvements to drainage systems comprise: </li></ul><ul><li>New water features, such as ponds, ditches and lagoons. These should be designed not only to fulfil their required function but also to be sensitive to the local landscape and have ecological benefits. </li></ul><ul><li>New structures such as bridges, culverts, outfalls and headwalls. </li></ul><ul><li>These should also be carefully located in the landscape, be well designed and built out of appropriate materials. </li></ul>
  35. 36. MAINTENANCE OF DRAINAGE SYSTEMS <ul><li>This is an ongoing duty of the Highway Authority and the maintenance program must balance different needs: </li></ul><ul><ul><li>In areas where there are local drainage problems, work may need to be carried out in drier conditions when access is easier </li></ul></ul><ul><ul><li>Maintenance of a system must not cause pollution elsewhere. Waste from drains, gullies and kerb offlet cleaning must be disposed of in an appropriate manner </li></ul></ul><ul><ul><li>Maintenance must be carried out when it causes least impact on local wildlife, avoiding annual breeding and plant growing seasons </li></ul></ul>
  36. 37. <ul><ul><li>Vegetation which obstructs a watercourse may require specialised pruning or removal. Coppicing, for example of willows, may be more effective than total removal as the root growth can help bind river banks together. </li></ul></ul><ul><ul><li>If erosion is occurring to the watercourse then bioengineering solutions should be investigated such as the use of willow faggots or spiles, biodegradable matting and planting tree cuttings or marginal species, e.g. flag iris. </li></ul></ul><ul><ul><li>There will often be ecological benefits to retaining open ditches which could otherwise be culverted. Their value should be properly assessed prior to any blocking off or culverting. </li></ul></ul><ul><ul><li>The Land Drainage Act 1991 requires a licence to be obtained </li></ul></ul><ul><ul><li>prior to filling in or culverting a watercourse. </li></ul></ul>
  37. 38. REFERENCES <ul><li>Manual of Contract Documents for Highway Works – Volumes 1, 2 & 3, HMSO Publication, May 1998 </li></ul><ul><li>Design Manual for Roads and Bridges Volume 4a, HMSO Publication </li></ul><ul><li>Trunk Road Maintenance Manual, Volumes 1 & 2, HMSO Publication </li></ul><ul><li>Standard specification for road works-MALAYSIA </li></ul><ul><li>AbsoluteAstronomy (2009), Indian highways, </li></ul>
  38. 39. <ul><li>Babylon dictionary(2009), Babylon Ltd, </li></ul>
  39. 40. THE END