Which property helps engineers evaluate soil's resistance to sliding along planes?

Which property helps engineers evaluate soil's resistance to sliding along planes?

• A. Permeability
• B. Shear strength
• C. Porosity
• D. Density

Answer: (B)

Skinny but essential concept first: a soil’s ability to resist sliding along a plane is determined by its shear strength. This is the maximum shear stress the soil can withstand before a failure surface forms and sliding begins. Shear strength comes from two components: cohesion, which helps soils stick together, and internal friction, which increases resistance as the normal force on the potential slip plane grows. In practice, engineers use the Mohr–Coulomb idea that shear strength equals cohesion plus the normal stress times the tangent of the internal friction angle. Tests like direct shear and triaxial shear measure this property so we can predict where sliding might occur under loads. Permeability describes how easily water moves through the soil and affects pore pressures and seepage-related stability, but not the direct resistance to sliding along a plane. Porosity is about how much void space is present, impacting drainage and storage rather than the slip resistance itself. Density influences overall strength through compaction and packing, but the specific measure used to evaluate resistance to sliding along potential failure planes is shear strength.

Skinny but essential concept first: a soil’s ability to resist sliding along a plane is determined by its shear strength. This is the maximum shear stress the soil can withstand before a failure surface forms and sliding begins. Shear strength comes from two components: cohesion, which helps soils stick together, and internal friction, which increases resistance as the normal force on the potential slip plane grows. In practice, engineers use the Mohr–Coulomb idea that shear strength equals cohesion plus the normal stress times the tangent of the internal friction angle. Tests like direct shear and triaxial shear measure this property so we can predict where sliding might occur under loads.

Permeability describes how easily water moves through the soil and affects pore pressures and seepage-related stability, but not the direct resistance to sliding along a plane. Porosity is about how much void space is present, impacting drainage and storage rather than the slip resistance itself. Density influences overall strength through compaction and packing, but the specific measure used to evaluate resistance to sliding along potential failure planes is shear strength.