Flow Net Soil -
The equations of steady groundwater flow to flow net is a graphical solution.
A flow net consists of two sets of lines which must always be orthogonal (perpendicular to each other): flow lines, which show the direction of groundwater flow, and equipotentials (lines of constant head), which show the distribution of potential energy. Flow nets are usually constructed through trial-and-error sketching.
1. Flow lines and equal potential lines intersect each other at 90 degrees.
2. The areas bounded by the flow lines and equal potential lines form approximate
squares.
3. Flow nets must satisfy the boundary conditions of flow field.
4. Quantity of water flowing through each flow channel is the same.
5. The potential drop in any two consecutive equal potential lines is same/constant.
6. Flow lines and equal potential lines are smooth curves.
7. Flow lines do show refraction at the interface between two soils having different coefficient of permeability.
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Flow Net Properties of flow net - |
Characteristics of flow net -
(1) Flow lines and equipotential lines cut each other at right angles i.e. they are mutually orthogonal.
(2) There should be an approximate square in each field and one should able to draw circle in each well constructed field.
(3) In a homogenous soil, every transition in the shapes of the two types of curves will be smooth, being either elliptical or parabolic in shape.
(4) The discharge through each flow is same.
(5) Between two successive equipotential lines, there is same potential drop.
Application of Flow Net -
(1) Determination of seepage:
For the seepage through a flow net for isotropic condition .
Total Discharge, q=kh [Nf/Nd]
where,
k=co-efficient of permeability
H =head causing flow
Nf=Total numbers of flow channels
Nd=Total numbers of potential drops.
(ii) Determination of seepage pressures:
The change in the effective pressure due to flow of water is known as seepage pressure. The seepage pressure at any point can be determined by
Ps = H.Yw
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