Understanding the Triaxial Test
The triaxial test is an essential procedure in geotechnical engineering used to determine the mechanical properties of soil. It involves applying various stresses to a cylindrical soil specimen to assess its strength and deformation characteristics under different conditions.
Confining Pressure
- The specimen is surrounded by a confining fluid, typically water or air, which exerts pressure uniformly around it.
- This confining pressure simulates the stresses exerted on soil layers by overlying materials in natural conditions.
Deviator Stress
- Deviator stress is applied along the axis of the specimen, creating a difference between the axial stress and the confining pressure.
- This stress is responsible for inducing shear failure in the soil sample, allowing engineers to assess its strength.
Both A and B: The Correct Answer
- Since the triaxial test involves applying both confining pressure and deviator stress, the correct answer is option 'C'—both A and B.
- By combining these two stress types, the test provides a comprehensive understanding of how soil behaves under realistic loading conditions.
Importance of the Test
- The triaxial test helps in determining key soil parameters such as cohesion, internal friction angle, and shear strength.
- It is crucial for designing foundations, slopes, and other civil engineering structures, ensuring safety and stability.
In summary, the triaxial test is a fundamental method in civil engineering that evaluates soil behavior under combined stresses, making it vital for effective design and construction practices.

In the triaxial test, the soil specimen is subjected to Confining pressure by fluid compression and Deviator stress.