ASTM D2850-15 PDF Download

The ASTM D2850-15 standard provides a method for determining the compressive strength and stress-strain relationships of intact, compacted, or remolded cohesive soils. The test involves subjecting a cylindrical soil specimen to a confining fluid pressure in a triaxial chamber. During the test, no drainage of the specimen is allowed, and the axial loading is applied at a constant rate of axial deformation.

The test method is applicable when the loads are assumed to occur rapidly, without sufficient time for pore-water pressure to dissipate or consolidation to occur. It should be noted that the resulting strength depends on the pressure developed in the pore fluid during loading, and the test does not consider drainage. Therefore, the unconsolidated-undrained shear strength determined using this method is not applicable to cases where loading conditions in the field differ significantly from those used in the test.

The standard also specifies that if the test specimens are 100% saturated, consolidation cannot occur during the test since drainage is not permitted. Hence, specimens with the same water content and void ratio will have approximately the same unconsolidated-undrained shear strength. However, for partially saturated specimens, consolidation can occur during the application of axial load, despite drainage not being permitted. Consequently, the unconsolidated-undrained shear strength of partially saturated specimens will vary with different confining stresses.

The standard provides guidelines for plotting Mohr failure envelopes, which can be used to depict the failure behavior of the tested soils. These failure envelopes will typically be horizontal lines for saturated specimens and curved lines for partially saturated specimens.

It is important to note that the quality of the test results obtained using this standard relies on the competence of the personnel performing the test and the suitability of the equipment and facilities used. Compliance with relevant practices, such as Practice D3740, can help ensure reliable results. However, it is cautioned that compliance with these practices does not guarantee reliable results, as multiple factors influence the accuracy and reliability of test outcomes.