AASHTO T 296:10(2020) Standard Method of Test for Unconsolidated, Undrained Compressive Strength of Cohesive Soils in Triaxial Compression

AASHTO T 296:10(2020) Standard Method of Test for Unconsolidated, Undrained Compressive Strength of Cohesive Soils in Triaxial Compression.
3. TERMINOLOGY
3.1. Definitions—The definitions of terms used in this test method shall be in accordance with ASTM D653 or D2487.
3.2. Description of Terms Sped/Ic to This Standard:
3.2.1. future—the stress condition at failure for a test specimen. Failure is often taken to correspond to the maximum principal stress difference (maximum deviator stress) attained or the principal stress difference (deviator stress) at 1 5 percent axial strain, whichever is obtained first during the performance of a test. Depending on soil behavior and field application, other suitable failure criteria may be defined, such as the principal stress difference (deviator stress) at a selected axial strain other than 15 percent.
TERMINOLOGY
Definitions—The definitions of terms used in this test method shall be in accordance with ASTM D653 or D2487.
3.2. Description Terms Specific to This Standard:
3.2.1. fiuilure—the stress condition at failure for a test specimen. Failure is often taken to correspond to the maximum principal stress difference (maximum deviator stress) attained or the principal stress difference (deviator stress) at 15 percent axial strain, whichever is obtained first during the performance of a test. Depending on soil behavior and field application, other suitable failure criteria may be defined, such as the principal stress difference (deviator stress) at a selected axial strain other than 15 percent.
3.2.2. principal stress difjèrence (deviator stress)—the difference in magnitude between the major principal stress and minor principal stress; in a triaxial compression test, the stress due to the axial load that is applied in excess of the confining pressure.
3.2.3. total stress, a- -the total force per unit area acting within a soil mass. It is the sum of neutral and effective stresses
SIGNIFICANCE AND USE
The strength in this test is measured under undrained conditions and is applicable to field conditions where soils are subjected to a change in stress without time for consolidation to take place (unconsolidated condition), and the field stress conditions are similar to those in the tests.
4.2. The shear strength determined from the test expressed in terms of total stresses or effective stresses is commonly used in embankment stability analyses, earth pressure calculations, and foundation design.
APPARATUS
The requirements for equipment needed to perform satisfactory tests are given in the following sections.
5.2. Axial Loading Device—The axial compression device may be a screw jack driven by an electric motor through a geared transmission, a hydraulic or pneumatic loading device, or any other compression device with sufficient capacity and control to provide the rate of axial strain (loading) described in Section 8.1.4. The rate of advance of the loading device should not deviate by more than ±1 percent from the selected value.AASHTO T 296 pdf download.