Rupture surface terminology at critical angle of shearing The slip developed at the critical angle of shearing resistance in soil mechanics is generally referred to as:

Introduction / Context:
In earth pressure and slope stability, failure tends to occur along a surface inclined at or related to the material’s angle of shearing resistance. Different texts use slightly different terms for the same physical feature—recognising that equivalence avoids confusion in design communication.

Given Data / Assumptions:

• Classical earth pressure and slope stability contexts (Rankine/Coulomb).
• Homogeneous soil and a representative failure surface.
• Terminological variants used in literature.

Concept / Approach:

The locus/plane along which relative displacement localises at limiting equilibrium is variously called the rupture plane, slip plane, or by annotated lines in construction (e.g., δ₁-line in some texts). Despite naming differences, the engineering meaning is the same: it is the surface where shear stress reaches shear strength.

Step-by-Step Solution:

Verification / Alternative check:

Mohr–Coulomb failure representations predict a family of candidate planes; at limit equilibrium the mobilised one is the rupture/slip plane.

Why Other Options Are Wrong:

Picking any single term ignores accepted synonyms; “failure circle” describes a graphical construct in Mohr’s plane, not the physical plane in the soil mass.

Common Pitfalls:

Assuming δ (wall friction angle) equals the soil friction angle; confusing graphical Mohr circle with physical slip plane.

Final Answer:

All of the above.