Consolidation states and lab simulation: Identify the correct statements about isotropic consolidation, normally consolidated clay, and overconsolidated clay.

Introduction / Context:
Consolidation history governs stiffness, strength, and compressibility of fine-grained soils. Recognizing whether a deposit is normally consolidated (NC) or overconsolidated (OC) is crucial for settlement prediction and undrained shear strength correlations. Lab apparatus can reproduce stress paths to study behavior.

Given Data / Assumptions:

• Triaxial apparatus permits application of isotropic confining pressure.
• Effective stress concept is used throughout.
• Definitions of NC and OC clays follow consolidation history relative to present effective stress.

Concept / Approach:
NC clay: current effective vertical stress equals the historical maximum; void ratio–log sigma′ plots show the current point on the virgin compression line. OC clay: soil has been unloaded from a higher past stress; it lies on the recompression line and exhibits higher stiffness at small strains. In triaxial labs, isotropic consolidation is achieved by equal all-round pressure (sigma1′ = sigma3′ initially).

Step-by-Step Solution:

Verification / Alternative check:
Oedometer curves show a break at the preconsolidation pressure; triaxial tests reproduce NC and OC responses consistent with these definitions.

Why Other Options Are Wrong:

• Any option excluding one of the correct statements would be incomplete.

Common Pitfalls:
Confusing overconsolidation with cementation; misinterpreting preconsolidation pressure from Casagrande construction; ignoring anisotropy in natural deposits even when isotropic lab consolidation is applied.

Final Answer:
All of the above