University of Maine Department of Civil and Environmental Engineering, CIE 366 Soil Mechanics Laboratory Falling Head Permeability Date: Group name: Members: * Prepare the sample * 1. Wet the pore stone in the base of the permeameter using a squirt bottle 2. Weigh the permeameter and base. Mp(empty) = g 3. Measure the thickness of soil (height of permeameter) L= cm and the diameter (diameter of permeameter). D= cm 4. Calculate the area (A) A= cm^2 5. Prepare a 2700g (approx) specimen of air dry soil which passes the #4 sieve. 6. Place the soil in the permeameter in 3 equal layers compacting each layer lightly with a tamper. 7. Weigh the permeameter, base, and soil. Mp(full) = g * Determine cross sectional area of burette * 1. Record volume of burette vol = cm^3 2. Measure length of burette (from 0 to 100) length = cm 3. Calculate cross sectional area (a) of burette a= cm^2 * Assemble the test setup * 1. Install the top of the permeameter 2. Attach the line from the burette rack to the base of the permeameter. 3. Attach the line from the tailwater cup to the top of the permeameter. 4. Open the air release valve on the top of the permeameter 5. Close ALL valves on the burette rack - check twice to be sure! (clockwise) 6. Open the "falling" and "perm" valves completely. (counter-clockwise) 7. Open the "water in" valve a little to allow water to flow slowly through the soil. If the water flows out the top of the burette, close the "water in" valve more. 8. While the water is flowing, determine how you will measure head during testing. Establish a datum to measure from (line on burette rack) Measure the height difference (hc) between the datum and the water level in the tailwater cup hc = cm 9. After about 10 minutes, close the "water in" valve, then the "perm." valve. * Run three trials at different head levels * 1. Fill the burette to the top by opening and closing the "water in" valve. 2. Record the height from the datum (ho') 3. Reset the stopwatch. 4. Determine the target height to "fall" to (ht') You will do three different trials each at different ht' levels 5. Start the stopwatch and open the "falling" valve as fast as you can 6. Stop the watch at the pre-determined target height. 7. Close the "falling" valve. 7. Record the height from the datum (ht') * Repeat procedure for a loose sample * 1. Weigh the permeameter and base. Mp(empty) = g 2. Prepare a 2700g (approx) specimen of air dry soil which passes the #4 sieve. 3. Place the soil in the permeameter without compacting it. 4. Weigh the permeameter, base, and soil. Mp(full) = g 5. Continue from "Assemble the test setup" above. * Test data table * raw height readings time corrected height readings perm. Trial ho' ht' t ho ht k =ho'+hc =ht'+hc (cm) (cm) (sec) (cm) (cm) (cm/sec) dense 1 dense 2 dense 3 loose 1 loose 2 loose 3 * Calculations * 1. Compute the void ratio of each specimen. Assume initial water content = 0% and use Specific Gravity = 2.65 2. Compute the average coefficients of permeability from both samples. 3. Compute the coefficients of permeability by both Hazen equations. Coefficients of permeability (k) are usually reported using ONE (1) significant figure. 7. Classify the soil by the Unified method. The soil is the same as the wet sieve lab.