The trenching will be done after the fixing of alignment, jungle clearance and chalk powder marking .
The width of the trench is normally Dia of pipe plus 1 meter i.e. each side 500 mm clearance will be allowed for pipe laying.
The depth will be normally 1.2 meter more than the pipe diameter i.e. the cushion will be kept 1.2 meter from the ground level.
The length of the pipe either 12 meter or 6 meter is to be marked the weld pit for every joint to facilitate the joint welding of adjacent pipes.
The depth of weld pit will be 400 mm below the bottom of trench so that the bottom welding is to be done properly.
The actual length of the pipe to be laid will be taken the measurement to make weld pit to avoid the offset of the weld pit.
The trapezoid trench will be taken if the soil condition is loose or collapsible. Sufficient taper will be formed to avoid further collapse during the laying of pipe.
Ensure the underground utilities likeTelephone cable, power cable, water line and UGD drain line before starting the excavation.
Ensure any culvert and water passing area the pipe line to be laid below that level and if possible concreting and encasing will be done properly.
In the alignment the precaution to be taken over head electrical line during excavation and backfilling. So skilled operators to be engaged for the excavators.
The excavated soil will be placed in right place so that the laying will not be disturbed and the same soil will be used for the backfilling.
The hard [rock blasting will be done if necessary the control blasting may be done for the safer side and the pre measurement as well as the post measurement will be taken and recorded.
If the soil is not suitable for back filling it is to be shifted by engaging tippers during excavation itself and it has to be dumped nearby area so that we can avoid reshifting of soil.
The place will be levelled during excavation for carrying pipe in to the trench i.e. the land should be kept motor able for crane and vehicle movement.
The chain ages and levels are to be marked base on the bench mark so that we can analyses the location of fixing testing dummies and suitable air valves and scour valves during laying itself.
The excavation for particular length, i.e. 3 or 4 pipes then the laying is to be started and the backfilling also to be done after necessary welding test and joint coating. etc.
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