In the direct shear test conducted on soils, a proving ring is used to:
- Ameasure the magnitude of shear loadCorrect
- Bmeasure vertical strain
- Cmeasure horizontal strain
- Dmeasure horizontal stress
Solution
Concept
In the direct shear test, a proving ring measures the horizontal shear force on the sample.
Formula
Shear load = proving ring dial reading × ring constant; τ = shear load / A
Step-by-step solution
1. The shear box is pushed horizontally to shear the soil. 2. The resisting shear force acts on the proving ring and deforms it. 3. The dial gauge on the ring reads this deformation. 4. Dial reading × ring constant gives the shear load. So the answer is A.
Explanation
A proving ring is a steel ring that deforms in proportion to the load on it. In the direct shear test, it gives the shear force. Strains and movements are measured by separate dial gauges.
Why the other options are wrong
B: Vertical movement is measured by a separate vertical dial gauge. C: Horizontal movement is measured by a horizontal dial gauge. D: Stress is not measured directly. It is calculated as load divided by area.
Shortcut
Proving ring = load measuring device.
Common mistake
Mixing up the proving ring (load) with the dial gauges (displacement).
Correct answer: A) measure the magnitude of shear load