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The curve obtained by plotting the normal and shear stress is called as _
MohrтАЩs envelope
Coulomb envelope
Strength envelope
Stress envelope
Strength envelope
The curve obtained by plotting the relationship between the shear stress (╧Д) at failure and the corresponding normal stress (╧ГnтАЛ) for a soil sample under different loading conditions is known as the Strength Envelope or Failure Envelope. This curve represents the limiting shear stress a soil can withstand for a given normal stress, defining the failure criterion of the material.
The curve obtained by plotting the relationship between the shear stress (╧Д) at failure and the corresponding normal stress (╧ГnтАЛ) for a soil sample under different loading conditions is known as the Strength Envelope or Failure Envelope. This curve represents the limiting shear stress a soil can withstand for a given normal stress, defining the failure criterion of the material.
╧Д=c+╧ГnтАЛtan(╧Х) тАФ The Mohr-Coulomb failure criterion where c is cohesion, ╧ГnтАЛ is normal stress, and ╧Х is the angle of internal friction.
According to the Mohr-Coulomb failure theory, soil shear strength is a linear or non-linear function of the normal stress acting on the failure plane. By conducting multiple triaxial or direct shear tests at different confining pressures, several Mohr's circles are generated; the line tangent to these circles represents the strength envelope. The slope of this line indicates the angle of internal friction (╧Х), and the intercept on the shear axis indicates the cohesion (c).
The strength envelope provides the fundamental shear strength parameters (c and ╧Х).
It separates the stable region (below the line) from the unstable failure region (above the line).
In purely cohesive soils, the envelope is horizontal, representing an undrained shear strength.
For granular soils (sands), the envelope typically passes through the origin (c=0).
Predicts shear failure in soil slopes and foundations.
Essential for designing retaining walls and earth structures.
Linear approximation may not hold true for very high confining pressures (curved envelope).
Parameter determination is highly dependent on testing conditions (drained vs. undrained).
Slope stability analysis.
Bearing capacity calculations for shallow foundations.
Earth pressure calculations.
Mohr's envelope is a specific type of strength envelope constructed using Mohr's circles.
Option A is technically a component used to derive the envelope, not the envelope itself.
The terms 'Coulomb envelope' and 'Strength envelope' are often used interchangeably in soil mechanics literature.
C is correct тАФ The curve formed by the tangent to Mohr's circles at failure is known as the strength envelope, which defines the relationship between shear stress and normal stress at failure.
Always remember that c and ╧Х are not fundamental soil constants but parameters that depend heavily on the drainage conditions during testing.