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TruePath Triaxial Cell

Marine Geotechnical Laboratory  /  CRS Consolidation Cell  /  TruePath Triaxial Cell

The triaxial test system provides control for initial consolidation of the sample followed by control of the shear failure. This provides data to evaluate sediment moduli, ratio of horizontal to vertical effective stress under uniaxial strain, and sediment shear strength. The triaxial experiment has five phases:

1. sample selection, trimming, and preparation
2. back pressure saturation
3. consolidation
4. shear
5. unloading and sample breakdown.

Phase 1 requires that a sample be selected and carefully trimmed for the triaxial test. The typical sample has a diameter of 3.5cm and a length of 7cm. The sample is jacketed in a latex membrane and then placed in the triaxial chamber where it is subject to a confining fluid and a pore pressure (Phase 2) to obtain total water saturation. Water saturation is checked by performing a B test during Phase 2. Phase 3 monitors consolidation of the specimen at a prescribed strain rate under uniaxial strain. This allows monitoring of the vertical stress required for the strain rate and the horizontal stress necessary to maintain uniaxial strain. After the desired consolidation is achieved, the shear portion (Phase 4) of the test is initiated until a target strain or stress is achieved. Finally the sample is unloaded and removed from the triaxial chamber (Phase 5) so bulk grain volume can be evaluated.