The strength of soil is mainly described by its:
Try it first: pick an option, then read the explanation.
Correct answer: C. shear strength
Asked in SSC JE 30/10/2020 (Morning)
Detailed Explanation
Soil is a collection of particles, not a solid block. It has almost no tensile strength, and when it fails under foundations, in slopes or behind retaining walls, part of it slides along a surface relative to the rest.
Why “shear strength” Is Correct
Because failure in soils is a sliding (shear) failure, their strength is described by shear strength: the maximum shear stress the soil can resist on a plane, τ = c + σ tan φ.
Why the Other Options Are Wrong
- A. torsional strength: Torsional strength is a property of shafts and members, not a soil design parameter.
- B. tensile strength: Soils have negligible tensile strength; it is usually ignored.
- D. compressive strength: Compressive strength (qu) is measured for clays, but it is just a way to find their shear strength (cu = qu/2).
Key Point
Bearing capacity, slope stability and earth pressure all depend on soil shear strength.
Key Concepts for Students
- Shear strength comes from cohesion and friction.
- It depends on effective stress, drainage and stress history.
- Measured by direct shear, triaxial, UCS and vane tests.
Practice more: this is question 27 in Shear Strength of Soils MCQs – Part 2. Try the whole set and check every answer instantly.