Question

The most suitable test for measuring the permeability of clayey soils in the laboratory is ___________.
 

• A. Constant head test
• B. Pumping out test
• C. Hydrometer test
• D. Falling head test

Hint:

Use the falling head test for fine-grained soils (clays and silts), and the constant head test for coarse-grained soils (sands and gravels).

Answer 1

The Correct Option is D

Clayey soils have very low permeability due to their fine-grained structure. The constant head test is generally suitable for coarse-grained soils like sand and gravel, which allow faster water flow. On the other hand, the falling head test is better suited for fine-grained soils like clay because it can more accurately measure the slow rate of flow through such soils.
In the falling head test, the rate at which the water level falls in a standpipe is monitored, allowing precise calculation of permeability even in low-permeability soils.
Hence, the falling head test is most appropriate for laboratory measurement of permeability in clayey soils.