What does soil shear strength refer to?

Soil shear strength refers specifically to the ability of soil to resist shear failure, which is the critical factor in understanding how soil will behave under various loading conditions. Shear strength is a measure of the internal friction and cohesion of the soil; it determines how much stress the soil can withstand before it begins to fail, primarily due to sliding or shearing along internal failure planes. This property is essential in geotechnical engineering for assessing the stability of slopes, foundations, and retaining structures, as well as in understanding soil behavior under different moisture conditions and loading scenarios.

The other options pertain to different characteristics of soil but do not define shear strength. The weight of the soil is more related to its mass and gravitational forces acting on it. The amount of water in the soil influences other properties but does not directly measure shear strength. The density of soil particles refers to how tightly packed the particles are, which can affect strength but does not encompass the full definition of shear strength itself.