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|Title:||Evaluation of the O'Neil Shear-O-Meter for performing constant-volume direct shear tests|
|Authors:||United States. Assistant Secretary of the Army (R & D)|
Gilbert, P. A.
|Keywords:||Direct shear tests|
Undrained shear tests
|Publisher:||Soils and Pavements Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Stability analyses of soil structures require knowledge of the shear strength of the soil in question under the conditions of drainage anticipated during loading in the field. Shear failures in large masses of saturated clay may occur with relatively slow rates of shear movement with no drainage occurring during shear. Large thick clay masses are often encountered in engineering design. Thus there is a need for an apparatus to determine undrained shearing resistance in soils; this need formulates the basis of this study. An undrained strength measurement may be obtained in the triaxial compression test by closing all valves to the soil specimen to ensure no drainage during shear, but the triaxial compression test requires saturation and consolidation, processes which could require weeks to accomplish. The immediate concern of this study was to evaluate the O'Neil Shear-O-Meter, a direct shear apparatus so modified as to perform an undrained strength test by varying the normal stress during shear. O'Neil undrained strength tests may be performed in a very short time compared with the time required for triaxial compression undrained tests. The two tests are compared herein, as well as a comparison of drained strength information, which also can be obtained from the O'Neil test, with the standard drained direct shear. Testing procedures for the shear device and for auxiliary consolidation equipment were developed. An evaluation of the constant-volume direct shear test as performed in the O'Neil Shear-O-Meter is included and a complete description of the equipment and testing procedure given.
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