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The drained test is also known as ___________
Direct shear test
Slow test
Vane shear test
Quick test
Slow test
The drained test, often referred to as the Consolidated-Drained (CD) test, is called the 'slow test' because it is conducted at a very slow rate of strain to ensure that excess pore water pressure generated during the test is completely dissipated. This allow the effective stress to be equal to the total stress applied throughout the loading process.
The drained test, often referred to as the Consolidated-Drained (CD) test, is called the 'slow test' because it is conducted at a very slow rate of strain to ensure that excess pore water pressure generated during the test is completely dissipated. This allow the effective stress to be equal to the total stress applied throughout the loading process.
╧Д=cтА▓+╧ГтА▓tan(╧ХтА▓) тАФ Shear strength in terms of effective stress for drained condition
╬Фu=0 тАФ Characteristic condition for drained tests
During the shearing phase, the load is applied at a rate slow enough to prevent any buildup of excess pore water pressure (╬Фu=0). This ensures that the soil remains in a state of consolidation throughout the test, making the drainage valve open at all times. This setup allows the measurement of shear strength parameters in terms of effective stresses (╧ГтА▓).
The test is ideal for permeable soils like sands or for long-term stability analysis of clay slopes.
The test is performed in two stages: consolidation followed by slow shearing.
The failure plane is well-defined as the effective stress parameters are constant.
Because of the slow strain rate, it can take several days to complete a single test on low-permeability soils.
Measures effective stress parameters (c', ╧ХтА▓)directly.
Eliminates pore pressure effects, providing stable results for long-term design.
Time-consuming for cohesive soils (clays) due to low permeability.
Higher testing cost compared to quick (unconsolidated-undrained) tests.
Long-term stability analysis of earth dams and embankments.
Foundation design on sandy soils where drainage is rapid.
Quick test refers to the Unconsolidated-Undrained (UU) test, where no drainage is permitted.
Vane shear test is a field test used primarily for measuring the undrained shear strength of soft clays.
Direct shear test is a common laboratory method to determine the shear strength parameters of soil.
B is correct тАФ The drained test is known as a 'slow test' because the shearing rate is kept slow to ensure full dissipation of excess pore water pressure.
Always remember the 'slow' label for drained tests because it implies waiting for consolidationтАФan essential concept for long-term stability analysis in Geotechnical Engineering.