In a triaxial compression test when drainage is allowed during the first stage (i. e. application of cell préssure) only and not during the second stage (i. e. application of deviator stress at constant cell pressure), the test is known as

Explanation:

 Consolidated Undrained Test (CU Test):

• Drainage is allowed during consolidation under cell pressure, so the soil consolidates and reaches equilibrium.

• During shearing, no drainage is allowed, but pore water pressure is measured using transducers.

• Suitable for determining both total and effective stress parameters by analyzing pore pressure development.

• This is the most commonly used triaxial test for cohesive soils, especially in undrained loading conditions like during construction.

Additional InformationConsolidated Undrained Test (CU Test):

• Drainage is allowed during consolidation under cell pressure, so the soil consolidates and reaches equilibrium.

• During shearing, no drainage is allowed, but pore water pressure is measured using transducers.

• Suitable for determining both total and effective stress parameters by analyzing pore pressure development.

• This is the most commonly used triaxial test for cohesive soils, especially in undrained loading conditions like during construction.

 Unconsolidated Undrained Test (UU Test):

• Drainage is not allowed during either consolidation or shearing stages.

• The test is quick and does not require pore pressure measurement.

• Suitable for short-term stability analysis under total stress conditions.

• It gives total shear strength parameters, and no information about effective stress or pore pressure is obtained.

Unconsolidated Drained Test (UD Test):

• Drainage is not allowed during the first stage (consolidation), but allowed during the shearing stage.

• This test is theoretically possible but rarely conducted in practice due to limited applicability.

• It does not represent real field conditions well and is not commonly referenced in design.