Porosity and Permeability Lab

1. Porosity and Permeability Lab

2. Background • Have you ever seen the Golden Gate Bridge in California or the Holland Tunnel between New York and New Jersey? • Engineers must first test the porosity and permeability of the soil before they can begin planning a bridge, tunnel, highway, or building

3. Background • Porosity • Amount of empty space in the ground • Permeability • Rate at which water will flow through the empty spaces

4. Purpose • Measure soil porosity • Compare the permeability of different soils

5. Materials • Water • Graduated cylinder • 6 clear, plastic cups • Permanent marker • Metric ruler • Large, medium, and small pebbles (about 1 cup of each)

6. Pre-Lab Questions • Which size pebble will have the most empty space? • Which size pebble will have the least empty space?

7. To Measure Porosity • Measure the height of a clear plastic cup with the ruler. Use the marker to draw a line about 2/3 up the cup. Mark 2 more cups with the same measurement • Fill the first cup to the line with large pebbles and label the cup. • Fill and label the 2nd cup with medium pebbles. • Fill and label the 3rd cup with small pebbles.

8. To Measure Porosity E. Fill the graduated cylinder with 100ml of water. • Slowly pour the water into the first cup. • Stop when the water reaches the rim of the cup. • Record the amount of water left in the graduated cylinder on the Porosity Data Table F. Calculate the amount of empty space in each cup by subtracting the amount of water left in the graduated cylinder from 100ml. G. Repeat steps for remaining 2 cups.

9. Porosity Data Table

10. Measuring Permeability • Materials Needed: • Water • Gravel, sand, and dirt (about 1 cup each) • Funnel • 3 coffee filters • Ring stand • Stopwatch or watch with second hand

11. Pre-Lab Questions • Which substance (gravel, sand, or dirt) will have the most permeability (water will flow through the sample the fastest)? • Which substance (gravel, sand, or dirt) will have the least permeability (water will flow through the sample the slowest)?

12. To Measure Permeability • Line the funnel with a coffee filter and place it in the ring stand. • Place a plastic cup directly below the funnel. • Fill the funnel with gravel. • Fill the graduated cylinder with 100ml of water. Slowly pour the water into the funnel. • Time how long it takes for the water to flow through the gravel into the cup. Stop timing after ten minutes. Record this measurement in the Permeability Data Table.

13. To Measure Permeability • Remove the gravel and the filter. Replace with a new filter. Fill the new filter with sand and repeat steps D and E. • Remove the sand and the filter. Replace with a new filter. Fill the new filter with dirt and repeat steps D and E. • If you want, you can conduct several trials for each rock group, adding more columns to your data table.

14. Permeability Data Table

15. Post-Lab Questions • Was your prediction of which sized pebble had the mostporosity correct? Explain. Why do you think this has the most porosity compared to the others? • Was your prediction of which sized pebble had the leastporosity correct? Explain. Why do you think this has the least porosity compared to the others?

16. Post-Lab Questions • Was your prediction of which soil substance has the mostpermeability correct? Explain. Why do you think this has the most permeability? • Was your prediction of which soil substance has the leastpermeability correct? Explain. Why do you think this has the least permeability?