Introduction
Permeability also known as hydraulic conductivity is the ability of the soil to allow the water to pass through it with ease. The characteristic property of soil is useful in calculation of the seepage in the dams and under sheet pile walls. It also helps in determining the rate of seepage through the facilities for storing waste water such as landfills and fish ponds. Moreover, the rate of settlement of clayey soils can also be established. The determination of hydraulic conductivity of soils can be performed using several methods. The method of constant head is used to determine the hydraulic conductivity of coarse grained materials while the falling head method is used to determine the permeability of fine grained soils. In this report, the Dancy law will be utilized in the experiment.
( Hayashi, Masaki & Quinton, 258)
Materials
Permeameter
Graduated cylinder
Graduated cylinder
Calipers
Measuring tape or yard stick
Largemouth funnel
Large spoon
Paint brush
Tamper
2.5 inch porous stones (2)
Timing device
8 inch evaporating dish
Water
Vacuum source
Air source
Procedure
The soil to be used that was used in the experiment gravel. The porous stone is placed at the bottom of the permeameter by tilting slightly to avoid damaging the stone. The soil is then placed in the permeameter to a level of within two inches from the top of the chamber. The gravel is then tampered gently by leveling it in place using a temper. This is followed by placing the second porous stone on top of the gravel sample. The black ledge on top of the chamber is cleaned using a paint brush. This is done by making sure that there are no particles on either side of the chamber.
The spring is then attached to the bottom of the cap and placed on the chamber making sure that the pressure is applied to the porous stone. This pressure will prevent the movement of the material. This is followed by tightening the screws at equal proportions. The switch is perpendicular to the direction of flow when the valve is closed. One end of the hose is then attached to the upper inflow valve and the other to the vacuum source but the valve should be closed. The head funnel is then place at a desired height and the hose is attached to the outflow valve at the bottom. The constant head funnel is then filled with water and the bottom valve is opened to allow the chamber to fill with water. The constant head funnel is filled and the vacuum is turned on and the inflow valve is carefully opened to remove air from the chamber. The vacuum chamber is closed when the water appears in the vacuum tube. The bottom valve is closed and the constant head hose is removed and is attached to the top of the inflow valve. The second hose is then attached to the bottom outflow valve and the constant head funnel is filled with water ensuring no air bubble s are inside the chamber. The brass bleed valve is used to work out the air bubbles( Hayashi, Masaki & Quinton, 260)
The water in the funnel is kept at constant water level for the duration of the test. The outflow valve is opened and water allowed to flow into the sink. The 250 ml graduated cylinder is used to collect the volume for some time when the flow is steady
Results
The results recorded was a variation of time with the rate of flow. In each case these values and other parameters of length of the hose, cross-sectional area and the change in hydraulic head were used in determination of the hydraulic conductivity of the soil. These results are shown in the appendix section.
Discussion
Work Cited
Hayashi, Masaki, and William L. Quinton. "A Constant-head Well Permeameter Method for Measuring Field-saturated Hydraulic Conductivity above an Impermeable Layer." Canadian Journal of Soil Science Can. J. Soil. Sci. 84.3 (2004): 255-64. Web.
Appendix
Readings
USACE EM _1110-2-1906 Appendix VII [3]
ASTM D2434 [14]
ASTM D5856 [15]
Equation of hydraulic conductivity.
k= QLAth
Where,
Q = volume of water collected.
A= area of the sample perpendicular to the flow
L = length of water that travelled from the source
t=time taken to collect the volume of water
h=change in hydraulic head from top of the funnel to the bottom outflow valve
Results
Data
