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MEKANIKA TANAH I

MEKANIKA TANAH I. PERTEMUAN II PERMEABILITAS TANAH. Oleh : Arwan Apriyono. PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED TAHUN 2011. I NTRODUCTION. What is permeability?.

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MEKANIKA TANAH I

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  1. MEKANIKA TANAH I PERTEMUAN II PERMEABILITAS TANAH Oleh : ArwanApriyono PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED TAHUN 2011

  2. INTRODUCTION What is permeability? A measure of how easily a fluid (e.g., water) can pass through a porous medium (e.g., soils) water Loose soil - easy to flow - high permeability Dense soil - difficult to flow - low permeability

  3. INTRODUCTION HukumdalamKonsepPermebilitas Hukum Bernoulli (Aliran Gas danFluida) Hukum Darcy (Aliran Air pada Media Porous)

  4. fluid particle z datum Bernoulli’s Equation The energy of a fluid particle is made of: 1. Kinetic energy - due to velocity 2. Strain energy - due to pressure 3. Potential energy - due to elevation(z) with respect to a datum

  5. Bernoulli’s Equation Expressing energy in unit of length: Total head = Velocity head + Pressure head + Elevation head

  6. 0 Bernoulli’s Equation For flow through soils, velocity (and thus velocity head) is very small. Therefore, Velocity head + Total head = Pressure head + Elevation head Total head = Pressure head + Elevation head

  7. NOTES  Pressure head = pore water pressure/w At any point within the flow regime:  Elevation head = height above the selected datum

  8. water B A • NOTES If flow is from A to B, total head is higher at A than at B. Energy is dissipated in overcoming the soil resistance and hence is the head loss.

  9. water B A length AB, along the stream line Hydraulic gradient (i) between A and B is the total head loss per unit length.

  10. Darcy’s Law Velocity (v) of flow is proportional to the hydraulic gradient (i) – Darcy (1856) v = ki Permeability • or hydraulic conductivity • unit of velocity (cm/s)

  11. 10-6 10-3 100 clays silts sands gravels Coarse Fines Permeability Values (cm/s)

  12. INTRODUCTION CONSTANT HEAD (TINGGI KONSTAN) • SUITABLE FOR SANDY SOIL, SAND OR GRAVEL WHICH HAVE BIG VOID RATIO VALUE • BASIC EQUATION :

  13. EXAMPLE 1 q = 1 ft3/hr Question : Find the permeability coefficient of sand in ft/min

  14. TERIMA KASIH

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