Consolidation state identification: A soil deposit that has not yet fully consolidated under its existing overburden stress is referred to as which type of soil?

Introduction / Context:
Correctly naming the consolidation state helps predict settlements and shear strength. Geotechnical reports frequently distinguish between normally consolidated (NC), overconsolidated (OC), and under-consolidated deposits, each with characteristic behavior under loading.

Given Data / Assumptions:

• “Existing overburden” is the current effective vertical stress in the field.
• “Not fully consolidated” means excess pore pressures have not yet dissipated for the present stress level.
• No special cementation or aging effects are implied.

Concept / Approach:
Under-consolidated soils still contain excess pore pressure from a recent stress increase (e.g., recent fill). They will undergo primary consolidation under the current stress. Normally consolidated soils have the present effective stress equal to the maximum historical value, with no pending consolidation for that state. Overconsolidated soils have experienced higher past effective stress than current and have already consolidated for larger stresses (OCR > 1).

Step-by-Step Solution:

Verification / Alternative check:
Oedometer drainage curves for under-consolidated clays show significant time-dependent settlement under the existing stress state; piezometers indicate elevated u that dissipates.

Why Other Options Are Wrong:

• Pre-consolidated/overconsolidated implies past maximum stress > current, not pending consolidation at current stress.
• Normally consolidated has current = maximum past stress and is already consolidated for that state.

Common Pitfalls:
Confusing “preconsolidated” with “preloading”; mixing up NC vs OC definitions.

Final Answer:
Under-consolidated soil