What does a soil shear box test measure?

A soil shear box test specifically measures the shear strength of the soil, which is a critical parameter in geotechnical engineering. Shear strength refers to the resistance of soil to shear forces, which can determine how well the soil can support structures and how it behaves under loading conditions, such as when subjected to lateral forces or in slope stability scenarios.

During the test, a soil sample is confined within a box and subjected to shear stress until it fails. The maximum shear stress that the soil can withstand is recorded, and this value is used to assess the soil's strength characteristics. Understanding shear strength is essential for determining the stability of slopes, foundations, and earth structures.

The other options relate to different soil properties. Compressive strength pertains to how much load a material can withstand before failing under compression, while porosity measures the voids within a soil sample that affect its water retention capabilities. Permeability is related to the ability of water to flow through soil, which is vital for drainage and groundwater movement but does not directly indicate the soil's response to shear forces. Thus, while these properties are important, the shear box test is distinctively focused on measuring shear strength, making the identified answer the most relevant.