Selection of suitable type of cross drainage work using chaturvedi and hind meathod
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Answer:
Cross Drainage Work
The following points should be considered while selecting the site of a cross-drainage work:
At the site, the drainage should cross the canal alignment at right angles. Such a site provides good flow conditions and also the cost of the structure is usually a minimum.
The stream at the site should be stable and should have stable banks.
For economical design and construction of foundations, a firm and strong sub-stratum should exit below the bed of the drainage at a reasonable depth.
The site should be such that long and high approaches of the canal are not required.
The length and height of the marginal banks and guide banks for the drainage should be small.
In the case of an aqueduct, sufficient headway should be available between the canal trough and the high flood level of the drainage.
The water table at the site should not be high, because it will create De-watering problems for laying foundations.
As far as possible, the site should be selected d/s of the confluence of two streams, thereby avoiding the necessity of construction of two cross-drainage works.
The possibility of diverting one stream into another stream upstream of the canal crossing should also be considered and adopted, if found feasible and economical.
A cross-drainage work should be combined with a bridge, if required. If necessary, the bridge site can be shifted to the cross-drainage work or vice versa. The cost of the combined structure is usually less. Moreover, the marginal banks and guide banks required for the river training can be used as the approaches for the village roads.