What laboratory test is used for determining permeability of fine-grained soils?

• A. Falling head permeability test
• B. Pumping test
• C. Constant head permeability test
• D. None of the above

Answer: (A)

The falling head permeability test is suitable for determining the permeability of fine-grained soils, such as silts and clays, where the permeability is relatively low. In this test, a column of water is allowed to drain through a soil sample, and the change in water level over time is measured. This method is particularly useful for fine-grained soils as it minimizes the disturbance of the soil structure and provides accurate results for materials with low hydraulic conductivities.

In contrast, the constant head permeability test is more suited for coarse-grained soils like sands and gravels, where the flow rates are higher. The pumping test is typically applied to assess the hydraulic properties of aquifers, focusing on groundwater flow rather than the permeability of soil samples in a laboratory setting. The choice of the falling head method for fine-grained soils is based on its ability to accurately measure the low flow rates that characterize their permeability behavior.