首页 / 官方藏书 / River and Canal Engineering, the characteristics of open flowing streams, and the principles and methods to be followed in dealing with them. / 4. Arrangements at Bifurcations.—At a bifurcation, as where a branch takes off from a canal, it is possible to reduce the quantity of rolled material entering the canal by raising its bed or constructing a weir or “sill” in its head. This arrangement may have great effect in excluding boulders, shingle, or gravel. As regards rolled sand, it has much less effect than might be expected (Chap. IV., Art. 2). If the canal is reduced in width (fig. 5) there will be eddies below the bed level of the branch. They will stir up the sand and some of it will enter the branch. If the canal is not reduced in width, eddies will be produced in the surface water, and they will affect the bed.

4. Arrangements at Bifurcations.—At a bifurcation, as where a branch takes off from a canal, it is possible to reduce the quantity of rolled material entering the canal by raising its bed or constructing a weir or “sill” in its head. This arrangement may have great effect in excluding boulders, shingle, or gravel. As regards rolled sand, it has much less effect than might be expected (Chap. IV., Art. 2). If the canal is reduced in width (fig. 5) there will be eddies below the bed level of the branch. They will stir up the sand and some of it will enter the branch. If the canal is not reduced in width, eddies will be produced in the surface water, and they will affect the bed.

River and Canal Engineering, the characteristics of open flowing streams, and the principles and methods to be followed in dealing with them. · E. S. Bellasis · 第 2 / 8 章