Question

Q21. Causeways may be classified as
O (A) Flush Causeway
O (B) Low level causeway
O (C) High level causeway
(D) All of the above​

Answer 1

Your answer is (B) Low level causeway.

Answer 2

Answer:

The Correct answer is Option  D

Explanation:

• A causeway is a track, road, or railway that runs along the top of an embankment and crosses "a low, or damp region, or body of water." It can be built from earth, masonry, wood, or concrete. The Sweet Track on the Somerset Levels, England, is one of the earliest known wooden causeways, dating from the Neolithic period. [2] Timber causeways are also known as boardwalks and bridges. A causeway can, of course, be combined with one or more bridges at its centre. For example, the 15-mile-long King Fahd Bahrain Causeway.
• If the culverts are located in the centre of the causeway, the high-velocity water jets that emerge from these culverts will generate extensive scour along the edges of the culverts. This means that while planning causeways, the culverts should be uniformly dispersed along the length of the construction. The water moves as it passes across the causeway. The sand is moved forward by the forward roller, which is illustrated on the right. The rear roller steepens the sand surface on the left side until it collapses. Unless sufficient protection measures are adopted, this impact exposes the foundation very soon.
• Two trenches are excavated along the causeway's upstream and downstream margins. If an overflow of 50 cm over the roadway is projected, the trench on the downstream side should be at least 1.50 metres deep . A appropriate bed for the culverts is created between these ditches using a well-graded gravel material. It is suggested that a 7.5 cm concrete floor be installed. This floor should be indented to fit the culvert's form, so that it is equally supported. Following the installation of the culverts, the head walls are built up to the road level, and the area between the head walls is backfilled with a well-graded stony/gravelly material.
• Causeways are classified into three types: (1) non-vented causeways, (2) vented causeways, (3) high level causeways, and (4) low level submerged bridges.

Reference  Link

• https://brainly.in/question/10220041