Soil Permeability Tests - Laboratory and Field Tests
There are laboratory tests - Constant head and Variable head permeability tests and field tests - Pumping out and pumping in tests to determine permeability.
What are the methods for determination of permeability?
• Constant head permeability test.
• Variable head permeability test.
• Pumping out tests.
• Pumping in test.
• If the particle size and specific surface area are known then permeability can be determined.
• From the consolidation data
Constant Head Test
Used to determine the coefficient of permeability in Coarse-grained particles like gravel and sand.
• Initially there will not be any steady condition.
• Wait until to the steady condition to attain.
• Soil sample should be saturated
Falling Permeability Test
Discharge is not a measurable quantity in fine grained soils hence variable head test is used. Representative samples should be taken.
• Water is filled in a stand pipe as time passes the level of water keeps decreasing and that will be measured.
• Sample should be saturated
Pumping out tests
Simulating all the field conditions is difficult at the laboratory hence pumping out test gives much accurate values. Water is pumped out from the well and from that the permeability is calculated.
• Expensive method.
• Reliable values are obtained.
When pumping starts from the well, the flow is not steady, with time the flow becomes steady.
Pumping in tests
Water is pumped into the well.
• Economical to perform.
• Less reliable than the pumping out test