Question

Which of the following factors will REDUCE the chances of landslide failure?

• A. Increase in shear stress
• B. Increase in water content of pore spaces
• C. Increase in angle of internal friction
• D. Increase in cohesion of soil grains

Hint:

The angle of internal friction and cohesion of soil grains are key factors that determine the stability of slopes. Higher friction and cohesion enhance slope stability and reduce the risk of landslides.

Answer 1

The Correct Option is C, D

Step 1: Understanding the mechanics of landslides.
Landslides occur when the driving forces (like gravity and water pressure) exceed the resisting forces (like friction and cohesion). The following factors influence this balance:

- Increase in shear stress: This increases the driving force, making failure more likely. ❌
- Increase in water content: Water in pore spaces reduces cohesion and increases pore pressure, thereby reducing resisting strength. ❌
- Increase in angle of internal friction (φ): This improves the resisting strength of soil by increasing shear strength, thereby reducing failure chances. ✅
- Increase in cohesion of soil grains (c): Cohesion directly increases the resisting forces, which prevents failure. ✅

Step 2: Conclusion
✅ Correct Options: (C) Increase in angle of internal friction, and (D) Increase in cohesion of soil grains
❌ Incorrect Options: (A) Increase in shear stress, and (B) Increase in water content of pore spaces