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Engineering vs index properties; index tests

Short answer

Engineering properties are needed directly for design and depend on stress state; index properties identify and classify soil and depend on composition. Coarse-grained tests include sieve analysis, specific gravity, and relative density. Fine-grained tests include hydrometer analysis, Atterberg limits, consistency, and activity.

How do the engineering properties of soil differ from index properties? Mention different index tests done for coarse and fine grained soils.

Difference

Engineering propertiesIndex properties
Needed directly for design (strength, settlement, flow)Used for identification and classification
Examples: cc, ϕ\phi, kk, CcC_c, cvc_vExamples: ww, GG, ee, grain size, wLw_L, wPw_P
Complex and costly tests, undisturbed samplesSimple, cheap tests, disturbed samples often enough
Depend on the structure and stress stateDepend mostly on composition

Index tests

  • Coarse-grained soils: sieve analysis (grain size distribution, CuC_u, CcC_c), specific gravity, relative density (maximum and minimum density), in-situ density, water content, particle shape.
  • Fine-grained soils: hydrometer/pipette analysis, Atterberg limits (liquid limit, plastic limit, shrinkage limit), plasticity index, consistency index, activity, sensitivity, and field tests (dilatancy, dry strength, toughness).

✓ Answer checked by Claude Opus 5.5 (high effort)

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