“ In engineering practices, difficulties through soils are almost exclusively not due to soils themselves but to water contained in their voids. On a planet without any water there would have been no need for Soil Mechanics “

(Karl Terzaghi,1939)

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So it can easily be said “no water no Soil Mechanics”

Water inhibit itself at different place in mysterious ways

Harmful accumulation of water is a great concern

Most of problems are due to uncontrolled seepage

Consequences of uncontrolled seepage are disastrous

i) Drainage failure caused by PIPING :Caused by the passage for piping including large pores in natural gravel, conglomerate, open jointed bed rocks, crackscaused by crustal movement.(e.g Fontella Dam, Teton Dam ,Baldwin Hill Reservoir, St. Francis Dam)ii) Drainage failure caused by Uncontrolled Saturation & Seepage Forces :Soaking under water reduces cohesion and a slight change in condition affect stability (Earth Slope Failures, vulnerabilityLiquefaction under shocks , Pavement failures )

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Drainage failure caused by PIPING & by Uncontrolled Saturation by understanding fully a simple Physical property called “PERMEABILITY”

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Permeability is facility with which water flows through soil.

Soil is permeable due to the existence of voids between soil grains that are interconnected and allow flow from points of higher potentials towards points of lower potentials (energy).

APPLICATIONS Design of pumping systems for dewatering of

excavations. Estimating of seepage losses through and under

earth dams. Stability analyses of earth dams Stability of earth retaining structures. Design of clay liners and cut off walls.

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1• Depends on:– Fluid viscosity,– Pore-size distribution,– Grain-size distribution,– Void ratio,– Roughness of mineral particles,– Degree of soil saturation,– Temperature.• Absolute permeabilityµ – viscosity of water

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1Darcy’s law v = ki, is true for laminar flow through thevoid spaces. Several studies have been made toinvestigate the range over which Darcy’s law is valid. Acriterion for investigating the range can be furnished bythe Reynolds number. For flow through soils, Reynoldsnumber Rn can be given by the relation:

For laminar flow conditions in soils, experimental results show