Test: Groundwater- 2 - Civil Engineering (CE) MCQ

The coefficient of transmissibility T is equals the field of co-efficient of permeability K multiplied by the aquifer thickness b:
T = b k.

Based on the assumption proposed by Dupuit’s theory, the velocity of flow is proportional to the tangent of the hydraulic agent instead of its sine.

Since the flow of water is not horizontal near wall and the flow no longer remains laminar. Thus, Darcy’s law equation is not valid near the well face.

The geological formations which are porous and contain a good amount of water but does not yield water freely to wells due to its lesser permeability is called aquitard. The water yield from such a formation is insignificant. Sandy clay is an example of the aquitard.

The geological formations which are porous but have no permeability are termed as an aquiclude. Water cannot be extracted from such formations. A clay layer is an example of aquiclude.

The geological formations which are both porous and permeable hence sufficient quantity of water can be extracted from them. Aquifers vary in depth and thickness and in general, confined and non-confined aquifers are two main categories of the aquifer.

The geological formations which are very dense and contain no water in voids and are neither porous nor permeable are termed as aquifuge. Granite rock is an example of aquifuge.

When the saturated formations are drained under the action of gravity drainage, the volume of water drained is less than the volume of void space. The water contained in these voids cannot be drained out by force of gravity. The water which is always retained by these interstices due to molecular attraction is called pellicular water.

Yield is the volume of groundwater extracted by gravity drainage from a saturated water-bearing material. It is known as the specific yield when it is expressed as the ratio of the volume of the total material drained.
Specific Yield = (Volume of the water obtained by gravity drainage/ total volume of drained material) x 100.

Field capacity can be expressed as the percentage of the total volume of the material drained. Specific retention or field capacity is given as –
F.C = volume of water held against gravity drainage/total volume of the material drained x 100
The summation of Specific yield and field capacity is equal to the porosity.