What does shear strength determine regarding soil?

Shear strength is a critical property of soil that gauges how well it can withstand shear stresses without failing or deforming. This characteristic is essential in various aspects of civil engineering, such as in the stability of slopes, the design of foundations, and the analysis of retaining structures.

When a shear stress is applied to a soil mass, the soil's resistance to that stress is directly related to its shear strength. This property dictates the maximum shear force the soil can resist before it begins to deform or fail, making it a fundamental aspect of soil behavior when loaded.

Understanding shear strength helps engineers design structures that will not collapse under shear forces, ensuring safety and durability. Conditions like the soil's composition, the presence of water, and the stress history all influence shear strength, but the primary role of measuring shear strength is to determine the soil's resistance to deformation caused by shear stresses.

The other options do not align with the specific definition and importance of shear strength: compressibility pertains to volume changes under load, maximum load differs in its context to overall bearing capacity, and moisture content relates to the water within the soil, which influences various soil properties but is not a direct measure of shear strength.