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Soil Physics 2010

Outline. Announcements Aeration Permeability Relative permeability Air permeability. Soil Physics 2010. Announcements. Review session Friday, 11:00 – 1:00 Homework 5 due now Exam II on Friday, April 2 Remember I’ll be gone most of next week. Soil Physics 2010. And now Delise,

Lucy
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Soil Physics 2010

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  1. Outline • Announcements • Aeration • Permeability • Relative permeability • Air permeability Soil Physics 2010

  2. Announcements • Review session Friday, 11:00 – 1:00 • Homework 5 due now • Exam II on Friday, April 2 • Remember I’ll be gone most of next week Soil Physics 2010

  3. And now Delise, on the topic of Aeration Soil Physics 2010

  4. Aeration mechanisms • Advection (also called convection, mass movement, mass flow) • Diffusion • We’ll look at advection today, and start diffusion on Friday. Soil Physics 2010

  5. Advection Darcy’s law is about advection (or mass flow): Mass moved (flux density) Potential gradient Proportionality coefficient Soil Physics 2010

  6. Now replace the water with molasses (keep the same soil, same potential gradient) Same flux? Same potential gradient Same proportionality coefficient? • Ks has 2 parts: • Soil properties • Fluid properties Soil Physics 2010

  7. Parts of Darcy’s Ks Soil property: Permeability k L2 Fluid property: Fluidity f L-1 T-1 Fluidity is often given as r g/h: r fluid density g gravitational acceleration h fluid viscosity Soil Physics 2010

  8. What’s with the L2? Permeability k L2 The actual length L that is squared for a soil’s permeability is quite small. It is usually interpreted as the soil’s effective pore diameter. Soil Physics 2010

  9. Back to water, molasses, etc. Soil permeability fluidity The soil’s permeability does not depend on the fluid’s properties. So permeability can also describe the flow of air Soil Physics 2010

  10. Relative permeability kr Big pores Little pores 1 Air permeability of dry soil = Water permeability of saturated soil kr 0 0 Sw 1 1 Sa 0 Soil Physics 2010

  11. Relative permeability 1 Petroleum engineers, and some geologists, use these “relperm” plots kr 0 0 Sw 1 1 Sa 0 Soil Physics 2010

  12. Air permeability ka air entry value h 0 1 No air flow until soil has dried to the air entry value. This is like qr for hydraulic conductivity: K(qr) = 0 ka 0 0 Sw 1 1 Sa 0 Soil Physics 2010

  13. Measuring air permeability Soil Physics 2010

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