SEMINAR_070629553535535653553535355.pptx

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1. PREPARED BY: SAYAN SAHA 3 RD YEAR DIPLOMA CIVIL ENGINEERING TRIPURA INSTITUTE OF TECHNOLOGY TRIPURA INSTITUTE OF TECHNOLOGY, NARSINGARH   A PRESENTATION ON DRAINAGE SYSTEM

2. INTRODUCTION ONE OF THE MAJOR REASONS OF DETERIORATION OF ROADS IS RAIN WATER. DURING RAINFALL, PART OF WATER FLOWS ON GROUND SURFACE AND PART OF IT PERCOLATES THROUGH SOIL MASS UNTIL IT REACHES THE GROUND WATER BELOW WATER TABLE. DUE TO PERCOLATION OF WATER IN HIGHWAY PAVEMENT MOISTURE CONTENT OF SOIL INCREASES WHICH REDUCE THE BEARING CAPACITY OF THE SOIL. THUS STABILITY OF HIGHWAY IS REDUCED. DRAINAGE OF THE HIGHWAY IS THE PROCESS OF REMOVING AND CONTROLLING SURPLUS WATER ON THE SURFACE AND SUB SOIL WATER IN SUB SURFACE WITH IN THE RIGHT WAY.

3. THE DRAINAGE SYSTEM DRAINAGE- A drainage system in urban and industrial areas is a facility to dispose off the liquid waste.

4. WHY DO WE NEED A DRAINAGE SYSTEM? IT CONTAINS HARMFUL BACTERIA: These can causediseases and it hence becomes a health hazard. IT CONTAINS SUSPENDED SOLIDS AND CHEMICALS: These affect the environment. IT STINKS: If we release waste water directly into the environment, things get smelly very fast.

5. DRAINAGE PROCESS Drainage process consist of collection of waste water then processing it and then disposal of this processed water. Waste water is collected from wash basin, kitchen sink, bathroom and toilet. Whenever you take a bath or wash your hands or utensils from there the drainage part starts as how it travels from your home to the treatment system and finally to the sea. Waste water from wash basin, kitchen sink and bathroom is drained through a pipe from your home to gully chamber.

6. TYPES OF DRAINAGE SYSTEMS COMBINED SYSTEMS: This uses a single drain to convey both foul water from sanitary appliances and rainwater from roofs and other surfaces to a shared sewer. The system is economical to install, but the processing costs at the sewage treatment plant are high.

7. SEPARATE SYSTEM This has foul water from the sanitary appliances conveyed in a foul water drain to a foul water sewer. The rainwater from roofs and other surfaces is conveyed in a surfacewater drain into a surface water sewer. This system is relatively expensive to install.

8. CONVENTIONAL WASTE WATER TREATMENT SYSTEMS SEPTIC TANKS CESPOOL SOAK PITS

9. SEPTIC TANK The septic tank is a key component of the septic system, a small treatment system. It is a watertight chamber made of:

10. WORKING OF A SEPTIC TANK Wastewater flows from the home to the septic tank through the sewer pipe. The septic tank treats the wastewater naturally by holding it in the tank long enough for solids and liquids to separate. Anaerobic decomposition of settled sludge occurs in the closed tank. Three processes are involved: Sedimentation Digestion tank Storage of digested sludge

11. CESPOOL An underground hole or container for holding liquid waste (such as sewage) from a building A cesspit, or CESPOOL, it is either used to describe an underground holding tank (sealed at the bottom) or a soak pit (not sealed at the bottom). It can be used for the temporary collection and storage of feces, excreta or faecal sludge as part of an on- site sanitation system and has some similarities with septic tanks or with soak pits. Traditionally, it was a deep cylindrical chamber dug into the earth, having approximate dimensions of 1 metre diameter and 2-3 metres depth. Their appearance was similar to that of a hand-dug water well.

12. A CESPOOL is purely holding tank without an outlet. There is no outlet to treat or discharge the sewage and the CESPOOL is the simple tank holding tank to collect and store wastage. Depending on the size of the tank, the property and the number of occupants, the cesspit can fill up quickly and needs to be emptied regularly, at monthly, quarterly or annual intervals as required. The Cesspit will usually be discreetly buried underground with a single manhole cover for access by the waste collection team.

13. SOAK PITS A layer of sand and fine gravel should be spread across the bottom to help disperse the flow. The soak pit should be between 1.5 and 4m deep, but never less than 1.5m above the ground water table.

14. WHAT IS HIGHWAY DRAINAGE HIGHWAY DRAINAGE IS AN ESSENTIALPART OF HIGHWAY DESIGN AND CONSTRUCTION WHICH REMOVE THE SURPLUS WATER IN THE HIGHWAY LIMITS AND DISPOSE IT. ROAD WAY DRAINAGE IS MAINLY DUE TO SURFACE RUNOFF FROM ADJACENT AREA PRECIPITATION OF RAIN AND MOISTURE RISING IF CAPILLARITY FROM THE GROUND WATER TABLE. REMOVAL AND DIVERSION OF SURFACE WATER FROM ROAD WAY AND ADJOINING LAND IS KNOWN AS SURFACE DRAINAGE. REMOVAL OF EXCESS SUB SOIL WATER FROM THE SUBGRADE IS TERMED AS SUB SURFACE DRAINAGE.

15. IMPORTANCE OF HIGHWAY DRAINAGE TO PREVENT SUBGRADE FAILURE: EXCESS MOISTURE REDUCING THE STABILITY OF PAVERNENT WHICH LEADS TO SUBGRADE FAILURE. TO PREVENT REDUCTION IN STRENGTH OF PAVEMENT MATERIAL: THE STRENGTH OF PAVEMENT MATERIAL LIKE STABILIZED SOIL AND WBM (WATER BOUND MACADAM) IS REDUCED. TO PREVENT FROST ACTION: IN FLEXIBLE PAVEMENT THE FORMATION OF WAVES AND CORRUGATION TAKES PLACE DUE TO POOR DRAINAGE. TO PREVENT PAVEMENT EDGE: EXCESS WATER ON PAVEMENT EDGE CAUSE CONSIDERABLE DAMAGE.

16. PREVENT SLOPE FAILURE: EXCESS MOISTURE CAUSES INCREASE IN WEIGHT AND THUS INCREASES IN STRESS AND SIMULTANEOUSLY REDUCTION IN STRENGTH OF SOIL MASS WHICH RESULT INTO FAILURE OF EARTH SLOPES AND EMBANKMENT FOUNDATIONS. PREVENT EROSION OF SOIL: DUE TO SURFACE WATER, EROSION OF SOIL FROM TOP OF ROAD AND SLOPE OF EMBANKMENT. DECREASE VOLUME CHANGES: VOLUME OF SUBGRADE IS CHANGED ESPECIALLY IN CLAYEY SOILS DUE TO VARIATION IN MOISTURE CONTENT. THIS SOMETIMES LEADS TO PAVEMENT FAILURE.

17. Under the surface drainage, water is to be collected in longitudinal drains and then disposed of at the nearest stream, valley or water course. Surface water is removed from surface of road by providing cross slope to the road surface. The road surface is also made impervious to prevent the water entering the subgrade. The recommended ranges of cross slopes for different types of pavement are as per Table-1. SURFACE DRAINAGE

18. SURFACE DRAINAGE METHODS For rural highways on embankments, runoff from the roadway should be allowed to flow evenly over the side slopes and then spread over the adjacent terrain. This method, however, can sometimes adversely impact surrounding land, such as farms. In such instances the drainage should be collected, for example, in longitudinal ditches and then conveyed to a nearby watercourse. When a highway is located in a cut, runoff may be collected in shallow side ditches.

19. INLETS These are parts of a drainage system that receive runoff at grade and permit the water to flow downward into underground storm drains. Inlets should be capable of passing design floods without clogging with debris. The entrance to inlets should be protected with a grating set flush with the surface of gutters or medians, so as not to be a hazard to vehicles. There are several types of inlets. A drop inlet is a box-type structure that is located in pipe segments of a storm-water collection system and into which storm water enters from the top..

20. STORM SEWERS These are underground pipes that receive the runoff from a roadside inlet for conveyance and discharge into a body of water away from the road. Storm sewers are often sized for anticipated runoff and for pipe capacity determined from the Manning formula. In general, changes in sewer direction are made at inlets, catch basins, or manholes. The manholes should provide maintenance access to sewers at about every 500 ft.

21. OPEN CHANNELS The ditches may be trapezoidal or V-shaped. The trapezoidal ditch has greater capacity for a given depth. Most roadway cross sections, however, include some form of V shaped channel as part of their cross-sectional geometry. In most instances, it is not economical to vary the size of these channels. As a result, this type of channel generally has capacity to spare, since a normal depth must be maintained to drain the pavement subbase courses. When steep grades are present, the possibility of ditch erosion becomes a serious consideration. Erosion can be limited by lining the channel with sod, stone, bituminous or concrete paving, or by providing small check dams at intervals that depend on velocity, type of soil, and depth of flows.

22. CULVERT A culvert is a closed structure for passage of runoff from one open channel to another. One example is a corrugated metal pipe under a roadway. For small culverts, stock sizes of metal pipe may be used.► For larger flows, however, a concrete box or multiple pipes may be needed. If the culvert foundation is not susceptible to erosion, a bridge may be constructed over the waterway (bridge culvert). The section of a culvert passing under a highway should be capable of withstanding the loads induced by traffic passing over the culvert. Since corrugated metal pipes are flexible, they cancarry gravity loads. Reinforced concrete culverts, however, have to support gravity loads without such assistance.

23. EFFECT OF ROAD GEOMETRY ON DRAINAGE Road surfacing materials are traditionally designed to be effectively impermeable, and only a small amount of rainwater should percolate into the pavement layers. It is important that any such water is able to drain through underlying pavement layers and away from the formation. Rainfall which does not permeate the pavement surface must be shed towards the edges of the pavement. Drainage is a basic consideration in the establishment of road geometry and vertical alignments should ensure that: a) outfall levels are achievable and b) subgrade drainage can discharge.

24. SUB-SURFACE DRAINAGE SYSTEM The change in moisture content of soil affects its bearing capacity of soil. The increase inmoisture content of soil reduces its bearing capacity. Thus keeping this point in view, there should not occur any change in moisture content of the subgrade of the road. The change in moisture content of the subgrade is due to fluctuations in the ground water table, seepage flow, percolation of rain water and capillary water. Thus the aim of the sub soil drainage is to prevent changes in the moisture content of the subgrade

25. LITERATURE REVIEW Water films develop on the pavement surface during natural rainfall and tend to increase in thickness along the water drainage or flow path. At the onset of rainfall, the water first occupies the macrotexture on the pavement surface and is contained within the macrotexture of the pavement surface or is drained from the surface through grooves or internal drainage (porous asphalt surfaces). With increasing rainfall, a film of water forms above the macrotexture. The flow of water on the pavement surface under these conditions is referred to as sheet flow; the depth of the sheet flow tends to increase in the direction of the drainage path. The depth of the sheet flow is of critical importance because the depth of this flow controls the skid resistance of the pavement and the tendency for hydroplaning. The vehicle speed at which hydroplaning occurs is inversely proportional to the depth of the sheet flow. The pavement design engineer must be able to identify any points on the pavement where sheet flow is sufficient to cause hydroplaning and must provide alternative or complementary strategies for reducing the depth of the water film thickness. The models identified during this study provide the tools needed to calculate the depth of sheet flow as a function of four general pavement characteristics: pavement geometry, location and capacity of drainage appurtenances, surface texture of the pavement surface, and any internal drainage

26. CONCLUSION Based on above study we can say that drainage system is process of removing and controlling excess surface and sub soil water with in the right way. Drainage system is an important part for design and construction of highway. In surface drainage, surface water is intercepted and diverted to a natural stream. If it is not done the surface water causing erosion. In sub surface water drainage, sub surface water is interrupted and disposed of to safe place.