What does the intersection point of the Mohr-Coulomb failure envelope with the shear stress axis represent in soil mechanics? 

Explanation:

Mohr-Coulomb Failure Envelope in Soil Mechanics

In soil mechanics, the Mohr-Coulomb failure envelope is a graphical representation of the shear strength of soils. It is defined by the equation:

τ = c + σ tan(φ)

where:

• τ = shear stress

• σ = normal stress

• c = cohesion of the soil

• φ = angle of internal friction of the soil

The intersection point of the Mohr-Coulomb failure envelope with the shear stress axis (τ-axis) is significant:

1. Option 1: The angle of internal friction of the soil

   This option is incorrect because the angle of internal friction (φ) is related to the slope of the failure envelope, not its intersection with the shear stress axis.

2. Option 2: The maximum shear stress the soil can withstand before failure

   This option is incorrect because the maximum shear stress the soil can withstand before failure depends on both the cohesion and the normal stress, not just the intersection point.

3. Option 3: The cohesion of the soil

   This option is correct. The intersection point of the Mohr-Coulomb failure envelope with the shear stress axis represents the cohesion (c) of the soil. This is because when the normal stress (σ) is zero, the shear stress (τ) at failure is equal to the cohesion (c).

4. Option 4: The maximum normal stress the soil can withstand before failure

   This option is incorrect because the maximum normal stress the soil can withstand before failure is not related to the intersection point with the shear stress axis.