SUREACE DRAINS:
Surface drains are provided at both sides of road for flowing of sludge of houses and rain water. Generally sludge water contains water release from bathroom, kitchens and cloth washing etc. so, this water not contains any type of bacteria’s and dirty smells. Surface drains have self cleaning velocity if gradient of drain is good or provided maximum for efficient working the surface drains should fulfill the following requirements:
(i) The inner surface of the drain should be smooth, and this can be achieved by applying plaster to the inner surface.
(ii)
(ii) It should have sufficient
carrying capacity, and should have reasonable free board.
(iii)
(iii) It should be laid on a grade so as to
achieve self cleaning velocity even with \ minimum dry weather flow.
(iv)
(iv) All the joints should be properly and
neatly finished.
(v)
(v) It should be structurally safe and stable.
CONSTRUCTION OF SURFACE DRAIN - The construction of surface drain should be done according to the following stages: Stage
1. Marking the Centre Line of Drain- The centre line of the surface drain is marked on the ground on both sides of the road. The width of the drain is marked by spade. Stage
2. Excavation of Trench- The trench is excavated according to the width and depth. The excavated earth is heaped on one side of excavation leaving sufficient space between the heaps for Planks supplying materials of construction.
Stage 3. Protection of Sides of Trench- Sometimes the construction may not start immediately after the excavation. In that case, the side protection should be done. In loose soil, the side protection is a must but, in hard soil, the side protection can be avoided. The side protection is done by sheet piling with timber planks or iron sheets which may be supported by struts, wooden blocks and timber wedges as shown in Fig.
Stage 4. Preparation of Sub grade -The sub grade is prepared by ramming a layer of sand (about 15 cm). Then a layer of brick bats (15 cm) is laid over the sand layer and rammed perfectly to make the surface compact and leveled.
Stage 5. Construction- Over the compact sub grade a layer of cement concrete (1:3:6) is laid to a thickness of 15 cm. The sides of the drain may be constructed with brick masonry with cement mortar (1:6) or may be constructed with reinforced cement concrete (1:2:4). The inside surface of the drain should be plastered with rich cement mortar and finished with neat cement polish. Curing should be done for 7 days.
Stage 6. Earth Filling - After proper curing,
the hollow spaces on both sides of the drain are filled with excavated earth
and rammed lightly.