How do you find the phreatic line?
To determine the phreatic line following procedure is followed:
- AB is the upstream face.
- To locate the directrix of the parabola, use the principle that any point on the parabola is equidistant from the focus as well as from the directrix.
- The last point G on the parabola will lie midway between F and H.
What are the characteristics of phreatic line?
Phreatic line is also known as the seepage line or saturation line. It is defined as an imaginary line within the dam section, below which there is positive hydrostatic pressure, and above there is negative hydrostatic pressure in the dam section.
What is meant by phreatic line?
The top flow line of a saturated soil mass below which seepage takes place, is called the Phreatic line. This line separates a saturated soil mass from an unsaturated soil mass. It is not an equipotential line, but a flow line. For an earthen dam, the phreatic line approximately assumes the shape of a parabola.
How do dams prevent phreatic lines?
When the dam embankment is homogeneous or when the downstream zone is of questionable permeability, a horizontal drainage blanket is provided to keep the phreatic line well within the dam body, to allow adequate embankment and foundation drainage, and to eliminate piping from the foundation and the embankment.
What is a phreatic line how do you draw it to estimate seepage through an earth dam?
The phreatic Line or seepage line is defined as the line within a dam section flow which they are positive hydrostatic pressure in the dam the hydrostag phreatic line graphically: AB is upstream face let it horizontal projection be L. On The Water surface measure a distance BC = 0.32.
What is the pressure along phreatic line?
The top flow line of a saturated soil mass below which seepage takes place, is called the Phreatic line. The hydrostatic pressure on the Phreatic line within a dam section is equal to atmospheric pressure. This line separates a saturated soil mass from an unsaturated soil mass.
What does phreatic mean in English?
1 : of, relating to, or being groundwater. 2 : of, relating to, or being an explosion caused by steam derived from groundwater.
What is downstream slope of earthen dam to keep phreatic line within body of dam?
What is the pressure along the phreatic line Mcq?
Solution: the phreatic line or seepage line is the line within a dam section below which there are hydrostatic pressures in the dam . the hydrostatic pressure below on the phreatic line itself is atmospheric.
How long did the phreatic eruption last?
It can last less than a day to several months. An example of a strong plinian eruption was the 1991 Pinatubo explosion in Zambales, which is also known as the second-largest volcanic eruption of the 20th century.
What is another word for phreatic?
Find another word for phreatic. In this page you can discover 11 synonyms, antonyms, idiomatic expressions, and related words for phreatic, like: vadose, flowstone, streamway, doline, gour, stal, , clean-washed, bouldery, aven and gours.
How is the slope safety factor calculated from phreatic line?
Based on the obtained phreatic line, the expression of normal stress on the sliding surface of the slope under the hydrodynamic forces is deduced, and a global analysis method to solve the slope safety factor under hydrodynamic force is proposed.
Where does the phreatic line meet the slope?
The focus of the parabola is at F(Fig. 26.3), the lowest point of the slope. However, in practice the phreatic line must emerge to meet the downstream slope tangentially at N. The portion NF is called discharge face which always remains wet. The portion LN is the correction a by which the parabola is to be shifted downwards.
Which is the solution of the phreatic surface?
The hydraulic gradient i is equal to the slope of the free surface and is constant with depth (Dupuit’s theory), the resulting solution of the phreatic surface is parabola. In some sections a little divergence from a regular parabola is required particularly at the surfaces of entry and discharge of the line of seepage.
Is the phreatic line of seepage a parabola?
It has been noticed from experiments that the line of seepage assumes more or less the shape of a parabola. The hydraulic gradient i is equal to the slope of the free surface and is constant with depth (Dupuit’s theory), the resulting solution of the phreatic surface is parabola.