Which two tests can be used to measure the soil coefficient of permeability, "k"?

The measurement of soil permeability, denoted as "k," is crucial for understanding how water will flow through soil, which plays a significant role in geotechnical engineering and environmental assessments. The correct option involves both the constant head test and the falling head test, which are standardized methods for determining the permeability of granular soils and cohesive soils, respectively.

The constant head test is typically employed for permeable soils, such as coarse sands and gravels, where water can flow freely through the soil sample under a constant hydraulic head. This test maintains a steady water level, allowing for the measurement of flow rates to calculate the permeability coefficient.

On the other hand, the falling head test is more suited for less permeable soils, such as silts or clays, where flow is slower and water will not flow rapidly enough to maintain a constant head effectively. In this test, the water level in a standpipe falls over time, and the rate of drop is measured to determine the permeability coefficient.

These two tests complement each other and are widely accepted in the field for accurately determining the soil's hydraulic properties.

The other options involve tests that are not designed for measuring permeability directly or do not complement each other effectively. The compaction test measures the density and moisture