Moisture movement is soil and its permeability
Loading ... Civil Engineers Blog

top page

Latest News

top post page

Home Moisture movement is soil and its permeability

Moisture movement is soil and its permeability

Font size

 



Moisture movement is soil and its permeability


As it is known from the scientific facts that ground water in the soil moves inside it if it is exposed to a difference in the water level on both sides of it and through its mass, and this difference in the water level is called hydrostatic pressure. And that the water movement is rapid and noticeable if the soil is sandy, and slow if the soil is silty or clayey cohesive.

As an example of this and a statement of this movement, if we dug at a site for the purpose of implementing foundations for a facility and the drilling extends below the groundwater level at the site as a result, hydrostatic pressure will be generated on the drilling wall, the maximum value of which will be at the level of the drilling bottom.  And this pressure (the weight of the water column is above the bottom level Drilling) It causes the movement of water to flow into the hole from both sides and the bottom of the drilling, as shown in the figure below.


- Soil Permeability.

The speed of water movement in the soil depends on several factors:

- The soil permeability, which is the characteristic that relates to the free movement of water through its grains.

- the amount of Hydraulic gradient, which is the amount of the hydrostatic pressure relative to the distance the water move in the soil.

Thus, the phenomenon of water movement in the soil is expressed by a law known as the Darsy EQ law, which is

V = K * I

Where,

V = the velocity of water in the soil m/s

K = the soil permeability coefficient CM/S

I = Hydraulic gradient

This, given the velocity of water in the soil, it is possible to calculate the amount of water accumulated in a certain area, which is called water discharge

Q = V * A

Q = Discharge in units of length cubed per unit time

V = the velocity of water in the soil

A = Cross sectional area in units of length squared

 - Measuring Soil Permeability.

 We can measure soil permeability by two methods:

- Constant Head Test.

The same relative elevation of the top of the water column (head pressure) remains over the sample throughout the test. It is a valid test for soils with a high rate of flow like sands and gravels, but also some clay soils.


Falling Head Test.

Allows the head to decrease as water infiltrates the sample, diminishing the pressure over the course of the test. Falling head methods are generally limited to fine-grained soils.

 






Labels:
No comments
Post a Comment