11. Laboratory Measurement of Permeability
The chapter discusses the laboratory measurement of permeability in soils, focused on constant and falling head permeameters suitable for coarse and fine-grained soils, respectively. It introduces the continuity equation for analyzing flow in soils and illustrates the application of Darcy's law to derive flow equations in isotropic materials, culminating in the Laplace equation for two-dimensional steady-state flow. Additionally, the chapter touches upon more complex three-dimensional flow scenarios.
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What we have learnt
- Constant head permeameters are ideal for measuring permeability in coarse-grained soils.
- Falling head permeameters are suited for fine-grained soils with varying hydraulic gradients over time.
- The Laplace equation governs two-dimensional steady-state flow in isotropic materials.
Key Concepts
- -- Constant Head Permeameter
- A device used for measuring the permeability of coarse-grained soils by maintaining a steady total head drop across a soil sample.
- -- Falling Head Permeameter
- A measuring instrument recommended for fine-grained soils that allows the total head in a standpipe to fall and measures the hydraulic gradient over time.
- -- Continuity Equation
- An expression that represents the conservation of mass principle for water flow in porous media, combining inputs and outputs through a defined volume.
- -- Darcy's Law
- A fundamental equation that relates the flow rate through a porous material to the hydraulic gradient and the material's permeability.
- -- Laplace Equation
- A second-order partial differential equation that describes the flow of fluids in a steady state through isotropic materials.
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