STP254: A Method for Adjusting Strain-Rates to Obtain Pore Pressure Measurements in Triaxial Shear Tests

    Ellis, Willard
    Materials Engineer, Bureau of Reclamation, Earth Laboratory Branch, Denver Federal Center, Denver, Colo.

    Holtz, W. G.
    Earth Laboratory Branch, Bureau of Reclamation, Denver Federal Center, Denver, Colo.

    Pages: 16    Published: Jan 1960


    Abstract

    Many triaxial shear tests are performed in the Bureau of Reclamation laboratory on partially saturated soils for embankments and partially saturated to saturated soils for foundation design purposes. The method of design used requires that the shear values obtained be based on effective stresses which exist within the shear specimens during the test, rather than stresses which are applied to the exterior of the specimens. This method, therefore, requires that accurate pore-fluid pressure measurements be made during the shear tests, so that the effective stresses can be determined. The pore pressures are usually measured through special end plates when conducting the tests for project works. In using the method, it is necessary that the rate of testing be adjusted so that equalization of pore pressures throughout the specimens are obtained. This paper presents a procedure for establishing the maximum rate of axial strain compatible with accurate pore pressure measurements. The procedure is based upon establishing a continuous relationship of the pattern between the pore pressures computed from volume changes and the pore pressures measured during the test.


    Paper ID: STP44305S

    Committee/Subcommittee: D18.05

    DOI: 10.1520/STP44305S


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