Porosity and Permeability Lab

*Problem: A) Which of the group's soils has the greatest porosity? & B) Which of the group's soils has the greatest permeability?

Research: Groundwater originates as surface water, melting snow, or rain that infiltrates down into the ground. Groundwater accumulates in either sediments or bedrock and flows slowly through the subsurface. A layer of sediment or rock that yields sufficient water for human use is called an aquifer. Good, producing aquifers have two distinct qualities: they are porous and permeable.

Porosity: Porosity is the percentage of a body of sediment or rock that consists of open spaces, called pores. Porosity determines the amount of water that sediments or rocks can hold. Thee are many kinds of pores – ranging from pores in sediments, to pores in volcanic rocks, to cavities in soluble rocks, to fractures in any rock. And many of these pores can be filled to differing degrees by cement. The porosity is expressed as a percentage of the total volume of material:

( % Porosity = Volume of pore space in ml / total volume of sediment in ml) x 100)

Permeability: Permeability is the ability of soil, sediment, or rock to transmit fluid. Material with low porosity is likely to have low permeability as well, but porosity does not necessarily mean high permeability. In order for pores to contribute to permeability, they must be (a) interconnected, and (b) not so small that they restrict flow. For example, clay commonly has high porosity, but clay grains are so broad in proportion to their microscopic size that the molecular force between clay particles and water restricts the flow. The permeability of aquifers is usually expressed as a velocity in meters/day.

(Permeability = distance traveled in cm / elapsed time in sec).

Description of your soils: Observe your soil for the following qualities. Color, darkness, particle size, mixed particle sizes

*Hypotheses: Please make your H1 hypothesis. You really don't need a null hypothesis because we are not going to do statistics on this data.

Porosity

A) H1:

Permeability

B) H1:

**Experiment:

**Materials: list all materials you are instructed or choose to use

**Procedure: Design 2 procedures to test your hypotheses. Watch your instructor show you how to measure porosity and then write a porosity procedure. Then watch your instructor measure permeability, then you write a permeability procedure.

**Data:

Qualitative Soil Data:

Soil
Color
Darkness
Relative Particle Sizes
1
     
2
     
3
     
4
     

Porosity Data Table:

Soil
(A)
Volume (ml)
of water
(B)
Volume (ml)
of Sediment
(A / B)* 100
% Porosity
(C)
Volume (ml) of
water drained
from soil
% Water Retained
((A - C) / A) * 100
1
         
2
         
3
         
4
         

 

Soil
A
Height of Soil
Column (cm)
B
Time elapsed from pouring
until reaching the Bottom (sec)
A / B
Permeability
(cm / sec)
1
     
2
     
3
     
4
     

**Graphs: Please make two separate graphs of the averages of the two sets of data.

Discussion: Please writeup a formal discussion of your results (all 5 paragraphs).

* write this section both in your lab notebook and formal lab writeup
** write this section only in your lab notebook