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Shear strength tests (lab and field)

Short answer

Lab tests include direct shear, triaxial (UU, CU, CD), unconfined compression, vane, ring shear. Field tests: vane, SPT, CPT, pressuremeter, plate load. Sands: direct shear, CD triaxial, SPT/CPT. Soft clays: UU, UCS, vane. Stiff clays: UU/CU. Long-term clay: CD/CU with pore pressure.

List out / name the laboratory and field tests for determining the shear strength parameters of the soil. Also state which tests are appropriate for which type of soil.

Laboratory tests

  1. Direct shear test (shear box).
  2. Triaxial compression test: unconsolidated undrained (UU), consolidated undrained (CU) with or without pore pressure measurement, and consolidated drained (CD).
  3. Unconfined compression test (UCS).
  4. Laboratory vane shear test.
  5. Ring shear test (for residual strength).

Field tests

  1. Field (in-situ) vane shear test.
  2. Standard Penetration Test (SPT).
  3. Cone Penetration Test (CPT / static cone).
  4. Pressuremeter test.
  5. Plate load test.

Suitable tests for each soil

Soil typeAppropriate tests
Clean sand and gravel (cohesionless)Direct shear; CD triaxial; SPT and CPT in the field (undisturbed samples are hard to get)
Soft to medium saturated clayUU triaxial, UCS, laboratory and field vane shear
Stiff or fissured clayUU and CU triaxial; UCS not reliable if fissured
Clay with long-term (drained) loadingCD or CU with pore pressure measurement (effective stress parameters)
Silts and silty sandsDirect shear (drained); CU triaxial
Residual strength of clay (slope failures)Ring shear; reversal direct shear

✓ Answer checked by Claude Opus 5.5 (high effort)

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