DRAINAGE CONSTRUCTION PROCEDURE
The following procedure is followed in road drainage construction step by step;
🧨SETTING OUT
The setting out for realignment and new construction shall involve staking of the intended road drainage centerline with pegs (wooden if possible) at 50 meters intervals. The setting out involves the setting out of the entire centerline (horizontal and vertical alignment), chainage reference pegs, cross sections, and the setting out for all the activities.
🧨SITE CLEARING
Site clearance is the first operation in the construction/upgrading/rehabilitation sequence (after the alignment has been set out) and it is the removal from within the proposed road drainage construction width of all bushes, trees, boulders, and organic matter including topsoil.
🧨 EXCAVATION
This can be done by labour-based technology or machine-intensive application. Utilization of machines/equipment like excavators or backhoes can increase the work rate productivity and accuracy.
🧨SPREADING AND COMPACTION
The formation bed of the drainage structure needs to be leveled and compacted properly to the required relative degree of compaction. This can be to 90 -95% Maximum Dry Density as per AASHTO or the selected specification standard in use.
🧨BLINDING
Upon bed leveling and compaction, concrete blinding is done to remove irregularities and offer a good bed for the placement of concrete while minimizing differential settlement. The thickness of blinding concrete is usually 50-75mm depth of C-10 0r C-15 concrete and it’s a mass concrete. The mix ratio for concrete blinding can be obtained by performing a concrete mix design.
🧨FIXING REINFORCEMENT BARS
If the drainage structure is precast, installation becomes the next step. But if it’s insitu cast, steel bars are fixed at this stage. Reinforcement must be fixed in the correct position and care must be taken to keep it in the correct position while concrete is being placed.
🧨MATERIAL FOR FORMWORK
Timber and plywood are commonly used materials for formwork because they can easily be cut and assembled on-site. Another advantage of timber formwork is that it is relatively cheap compared to steel formwork.
🧨CONCRETE CASTING
At this stage, the next activity will be the casting of the concrete structure.
The concrete should have good workability so that it’s easy to place and compact with the available equipment. It should also fulfill the requirements for strength and durability.
Conclusion
When all the steps are followed and keen expertise is deployed during this process, there is a high chance of having a well-durable and functional road drainage structure.
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