A Brief Description of the Permeability Test
PERMIABILITY TEST AIM OF THE EXPERIMENT: To determine the coefficient of permeability of a given soil sample by Variable head permeability test. APPARATUS REQUIRED: a) Special: i. Jodhpur permeameter frame consisting of sand pipe graduated scale, rubber tubing connected to permeameter mould. Permeameter mould. Accessories of permeameter mould including the cover, base, detachable collar, porous stones, dummy plate etc. Round filter paper. Dynamic compaction device.
ii. iii.
iv. v.
b) General: i. ii. iii. iv. THEORY:Permeability is defined as the property of porous material which permits the passage or seepage of water through its interconnected voids. The coefficient of permeability is finding out following method. a) Laboratory method: i. ii. Variable head test. Constant head test. Stop watch. De-aired water. IS 4.75 mm sieve Grease.
b) Field method: i. ii. Pumping out test. Pumping in test.
c) Indirect test: i. Computation from grain size or specific surface.
ii. iii.
Horizontal capillarity test. Consolidation test data.
The derivation of the coefficient of permeability is based on the assumption of the validity of the Darcy’s law to the flow of water in soil. The term coefficient of permeability implies the velocity of flow of water through the soil under unit hydraulic gradient, and consequently has the same units as that of velocity. A. Variable head test: The variable head test is used for fine grained soils like silts and silty clays.
For the Variable head test the following formula is applicable:
Where, k = Coefficient of permeability at To C (cm/sec). a = Cross Sectional area of stand pipe (cm2). L = Length of soil specimen (cm) A = Cross-sectional area of soil sample inside the mould (cm2)
t = (t1 – t2) = Time interval for the head to fall from h1 to h2. h1 = Initial head of water at time t1 in the pipe, measured above the outlet. h2 = Final head of water at time t2 in the pipe, measured above the outlet.
B. Constant
ii. iii.
iv. v.
b) General: i. ii. iii. iv. THEORY:Permeability is defined as the property of porous material which permits the passage or seepage of water through its interconnected voids. The coefficient of permeability is finding out following method. a) Laboratory method: i. ii. Variable head test. Constant head test. Stop watch. De-aired water. IS 4.75 mm sieve Grease.
b) Field method: i. ii. Pumping out test. Pumping in test.
c) Indirect test: i. Computation from grain size or specific surface.
ii. iii.
Horizontal capillarity test. Consolidation test data.
The derivation of the coefficient of permeability is based on the assumption of the validity of the Darcy’s law to the flow of water in soil. The term coefficient of permeability implies the velocity of flow of water through the soil under unit hydraulic gradient, and consequently has the same units as that of velocity. A. Variable head test: The variable head test is used for fine grained soils like silts and silty clays.
For the Variable head test the following formula is applicable:
Where, k = Coefficient of permeability at To C (cm/sec). a = Cross Sectional area of stand pipe (cm2). L = Length of soil specimen (cm) A = Cross-sectional area of soil sample inside the mould (cm2)
t = (t1 – t2) = Time interval for the head to fall from h1 to h2. h1 = Initial head of water at time t1 in the pipe, measured above the outlet. h2 = Final head of water at time t2 in the pipe, measured above the outlet.
B. Constant